Phalaris minor (little seed canary grass) is vastly occurring weed in winter crops, while it is abundant in the areas producing wheat which are the fields of Pakistan, India, Nepal and Bangladesh (Singh, 2007)
What is Phalaris minor dangerous for plant life?
The seeds of Phalaris minor are abundantly present in upper layer of soil up to 5.0 cm and the number of seeds reduced as we go to the deeper layer (Om et al., 2002). According to Franke et al., (2002) seeds of little seed canary grass were comparatively same in upper 10 cm layer of soil in no tillage and traditional tillage practices. It is because of regular tillage practices and only rice cultivation in puddled soil.
According to Yadav (2002) the germination tendency of Phalaris minor at 6.0 pH was highest but there were remarkable decrease in germination in higher and lower pH than 6. However there was zero germination at 3.0, 9.0 and 10.0 pH. The dormancy period in Phalaris minor was lower than 2 months in normal field circumstances because the seeds obtained in soil of infected field survive till the last of May revealed about 80 to 96 percent germination (Om et al., 2004).
Significance of Phalaris minor and other weeds
Weeds are actual enemy of crops, the weeds inhibits the functions of plants and also effect the growth and development. Almost 34% reduction in the crop yield is due to the weeds in various crops cultivated in whole world. The reduction in yield is greater than the yield loss due to the weed as compared to the other invaders in these crops. Adequate weed control is required to avoid the highest reductions of crop yield because of the weed intensity. Variety in weed control measures enables the reduction of developing resistance in weeds. Allelopathy is now days also being used as an important measure to control weeds, it can significantly apply to fight against the difficulties caused by the evolving pollution and the property of resistance in weeds (Jabran et al., 2015).
Among various weeds which effect the wheat crop, Phalaris minor Retz. (Little seed canary grass) exists as an alarming problem for a healthier wheat and good yield. This fast growing weed in winter crops is now discovered in almost sixty countries of world (Travlos, 2012). This weed is most influential in wheat crops of many countries (Pakistan, Bangladesh, India, Iran and Nepal). It is becoming a crucial issue in Rice and Wheat crops in Asian cities (Hussain et al., 2015). The loss in wheat yield because of canary minor ranges in 25 to 50% of the total (Chhokar and Sharma, 2008).
A severe parasitism in 2000 to 3000 plants of crop per meter square can be a cause of whole crop destruction (Chhokar et al., 2006). The infection in 40 plants per meter square can decrease the growth and yield of crop specially wheat up to 28 to 34% (Hussain et al., 2015). Phalaris minor is similar to wheat plants in physical characteristic, so it is difficult to control in early stages, which became a cause of more growth weed and it also became even difficult to kill by biological methods (Abbas et al., 2016a; Abbas et al., 2016b).
During studying the issue about the crop loss by arising problem of Phalaris minor because of the evolution of resistance property in herbicide, in the Editorial of Indian Society of Weed Science Newsletter a few lines are written in these words, ‘‘It also focuses over hollowness in our research for we know very little about the biology and ecology of Phalaris minor the weed which has been with us for over three decades’’ (Anon, 2000). The genetically inherent capability of a weed to thrive and develop even after the application of a specific quantity of herbicide, which is usually hazardous for a non-resistant type (Heap, 2000).
In expensive and capital consuming agricultural practices worldwide, cultivators scarcely manages the weeds in an active way to control or stop weeds before germination this process us usually delayed by them. Usually the growers only manages the weeds proactively when the weeds became resistant towards applied herbicides, otherwise the weed management and control by chemical is considered to be most effective way to control weeds. The herbicide resistance in various varieties of weeds is due to the application of same group of herbicides is the premium reason for the amendments in weeds management techniques and selection of the cropping routine that lessen the evolving resistance in weeds. The efficiency and selection of chemical and integrated techniques and methods for the pre-germination and after germination control of weeds having resistant property were evaluated. Techniques involve the system of cropping, sequence, chemicals, dose applied, mode of action of herbicides and the extent of herbicide resistance in crops. Zero chemical weed control methods Non-herbicide weed-management practices or the application of herbicide prior to the germination in field, use of any rarely used herbicide and alternative cropping system are a few reasons for reducing the increasing herbicide resistance in weeds. It will surely help to reduce the capital loss crop due to herbicide resistant weeds (Beckie, 2006).
Elevating resistance in herbicides
The herbicide resistance is becoming a serious issue in whole world, it is becoming mandatory for farmers to evaluate the resistance of weeds and understand the way to manage the resistance. Researchers have discovered various resistance determining methods for multiple herbicides and varieties of weeds. The producers require instant results while the researchers are fighting with the difficulties arising due to the huge verities of samples and rapidly increasing resistance of herbicides. Researchers developed Quick tests and performing them, these Quick tests are developed to tackle the need but the classical testing is still the part of culture. The latest techniques include molecular techniques. While the traditional whole-plant assay tests for resistance evaluation is performed despite of a lengthy procedure, various quick tests have kickbacks such that they are specific for any weed or herbicide resistance. The progressing research in the biology of weeds and gene study aids the improvement in collection of samples and testing techniques. Hence, there is continues improvement and diversification in resistance evaluation methods, that can stuns the unexperienced researchers, the study was done to support the field workers of weed sciences to settle the problems which are becoming the barrier in determining the resistance of herbicide in weeds. From field detection, collection of samples, selection of herbicides, tests the herbicides, analysis of data and finally the implementation. More over the study specifically defines the protocols for collecting plant for resistance confirmation assays, describes suitable summaries on the anatomical and mathematical methods for managing and performing dose-response experiment and describes possible methods for quick confirmation of resistance, also containing the molecular-based assays. The techniques for confirmation of resistance usually require to be changed a little to become fit for a specific herbicide or weed under test. Hence the main necessities and also the procedures and conclusions of DNA-based assays are alternative to each other. Finally, the resistance in weeds testing results also the conclusions from the research should be applicable, practical and based of scientific techniques (Burgos, 2013).
Herbicide resistance in weeds is a main issue crop and herbicide cycle is not present or very less used. While there are yet some real possibilities for the deduction of selection pressure in resistance populations. Alternate use of herbicides, combination of herbicides, alternation of crops and other agricultural techniques like early sowing of crop, good varieties and higher rate of seeds can give crop the ability to fight with weeds (Cavan et al., 2000). Phalaris minor is the terrible problem of the wheat .it create the competition with wheat for nutrition of soil, fertilizer, area and in other aspects, although many researcher done many research on the Phalaris minor by using Isoprotroun, fenoxaprop-p-methyl, diclofop- methyl, clodinafop propargyl, pinoxaden, iodosulfuron + mesosulfuron and other herbicide used for control the Phalaris minor, they used the these herbicide single way and the also used in mixture form ,but now the Phalaris minor got resistance against these herbicide. one of the best approach to the resistance of the weed against the herbicide is the RISQ resistance in seasonal quick method this method is specially used against the grasses species like the Phalaris minor, in RISQ classical method, seed assay, seedling assay, leaf assay and other approach are include in the RISQ. Seed assay and seedling assay was the best way to check the resistance of Phalaris minor this was used to check the resistance and saved the loss of yield of wheat because for this approach required less days to the resistance of weed and best herbicide used for kill the weed .in seed assay and seedling assay appropriate dose fenoxaprop p methyl find out for Phalaris minor.
Significance of Wheat
Phalaris minor is considerably very hazardous and problematic weeds of wheat cropping system in Pakistan. There are certain features like structural resemblances with the wheat plant, capability to resist tillering practices, yield of more than one seeds on a plant, seed dropping at early stages and lengthy period of dormancy in seed and resistance to harsh environment made this weed harmful for wheat crop and it is very hard to control this weed (Rammoorthy and subbain, 2006; Walia, 2006; Yasin and Iqbal, 2011) because of its increasing competition against wheat crop. The deduction of yield in wheat crop ranges from 25 to 50% and its depends upon the growth intensity of Phalaris minor, the time of germination in field, duration of competition against weed, cultivation practices and environmental conditions (Chhokar and Sharma, 2008). Highly germination of this weed in crop of weed from 2000 to 3000 m-2 may lead to total yield loss in wheat crop (Chhoker et al., 2006).
Chemical are the most efficient and worldwide used way to suppress weeds in the crops of wheat, significantly the weeds like Phalaris minor because of their structural resemblance and their capability of competition with wheat plant. Hence, the occurrence of Phalaris minor is rapidly increasing as compared to the wide leaved species of weeds (Singh, 2007).
A study conducted by Beckie et al., (2004) in Alberta to evaluate the resistant property of a few herbicides in wild oat weather resistance is affected by the growing practices or not. Samples were gathered from 33 fields of different growers in 1997 and in 1998 and 1999, 31 fields of different growers were selected for wild oat seeds collection. The collected samples of seeds were tested for resistance towards two acetyl-CoA carboxylase (ACCase) inhibitor, these two types were ALS (Aceto-Lactate Synthase) inhibitor Triallate which is Thiocarbamate herbicide. Also a survey was done and opinion poll was done with each farmer. Results prove that these resistant properties in weeds were produced due to the absence of crop rotation by different varieties. Including this resistance towards ALS inhibitor in wild oats was linked with the application of herbicide having same mode of action. The study concluded that tillage on exact time and crop rotation will reduce this resistance in weeds. It is discovered in 1999 in South Africa that the Phalaris minor colony is resistant towards ACCase-Inhibiting herbicide which were Clodinafop and diclofop. But these types of resistant weeds are destroyed by Iodosulfuron (Smit and Cairns, 2000).
Resistance against Photosystem II-inhibiting weedicides which is Isoproturon in firstly observed in Phalaris minor in 1992, at that time this weed was expanded in various regions of India about millions of hectare. Phalaris minor when genetically studied proved that this self-evolutionary resistance is due to this uninterrupted use of Isoproturon and zero crop rotation. It is observed that the types of Phalaris minors which are resistant to Isoproturon are also resistant towards Diclofop, however they are not resistant to Chlortoluron having same working mechanism like Isoproturon. Selection of Fenoxaprop against resistant varieties were proved very effective in 1997 and cause increase in yield of crop. But the weed management cost was relatively greater. After this treatment the weed was eradicated from rice fields but transferred to other crops in which Isoproturon was applied from many years because of its less cost. Proper management, selection of good quality variety, tillage on adequate time and perfect optimization of herbicide dosage will surely destroy Phalaris minor having resistant properties (Singh, 2007).
Pieterse and Kellerman, (2002) investigated that various types of Phalaris minor in western region of South Africa found to be resistant toward Clodinafop, Diclofop, Haloxyfop, Quizalofop-P, Iodosulfuron and Mesosulfuron. Multiple varieties which are collected found resistant weather single, cross and multiple against ACCase and Aceto-Lactate synthase inhibiting weedicides. Resistance against Propaquizafop and Sulfosulfuron has also been discovered in South Africa. Kyser and DiTomaso, (2006) reported that in Imperial Valley California the Phalaris minor in a field detected to resistant toward Sethoxydim, Clethodim and Fluazifop-P. As reported by Tamayo and Martinez-Carrillo, (2002) some selected biotypes in Yaqui Valley, Mexico found to be resistant against Tralkoxydim however not against Diclofop and Clodinafop.
Hence, the Herbicide do not work alone and should be used consecutively with various weed managing practices such as no tillage (Malik et al., 2002), Resistant varieties of crops (Chauhan et al., 2001), sowing on proper time, rotation of crops and adequate spraying method (Miller and Ballinder, 2001). In 1999-2000 the wheat production increased in Haryana, Punjab and Uttar Pradesh due the use of alternative herbicide fenoxaprop, sulfosuefuron ,clodinafop, and tralkoxydim these four herbicide effectively control Phalaris minor and increased production of wheat, while the used of isoproturon in 1994-95 in wheat field the production decreased and the cost ratio 1:6 new herbicide cost was low as compare to isoproturon but it’s not sure these new herbicide was not sure it would be always good for the p minor due the possibilities of cross resistance and multiple resistance (Yadav et al., 2002).
There were many reasons for the spreading of Phalaris minor in different parts of country after the report of herbicide resistance in rice and wheat zone Malik, (2003) made outline for the spreading of Phalaris minor as followed:
- Little seed canary grass spread farm to farm due to the water contamination which passed in canals in canal irrigation system, sometime due to flooding the Phalaris minor seed spread, farm machinery, equipment and other things were the sources of weed transport from different parts of the country and sometime the seed was spread due to wheat straw exchange.
- The second reason was for the spreading the Phalaris minor and other weeds seeds were mechanical thresher which involve combination of wheat seed and weed seed and in sowing time it spread from one area to other area of country.
Mool Chand et al., (2002) investigated 13 different species of weeds including Phalaris minor were reported in wheat shipped from Australia in 1996 to 1998 for people consumption. It makes the government to apply strict rules termed as seed laws and plant quarantine.
Medica, from Greek: μηδική (πόα) Median (grass) was not significantly killed by the herbicide 2, 4-D Metsulfuron-Methyl by the dose of 4 g ha-1 (Singh et al., 2002), while same as bitter dock, broad-leaved dock, (Balyan and Malik, 2000). Kurchania et al., (2000) lamb’s quarters, melde, goosefoot, manure weed were effectively controlled by the metsulfuron at 4 g ha-1 but this herbicide was not effective for the Phalaris minor. Yaduraju and Das, (2002) effectively controlled floral weeds and Phalaris minor in wheat crop by use of Metsulfuron at 4 G + isoproturon at 1000 g ha-1(Singh and Singh, 2002).
In 1997-98 rice wheat the wheat production was effectively good due the use of alternative herbicide which were Clodinafop (Topic, 15% WP) at 60 g ha-1, Fenoxaprop (Puma Super, 10% EC) at 120 g ha-1, Sulfosulfuron (Leader, 75% WP) at 25 g ha-1 and Ttralkoxydim (Grasp, 10% EC) at 350 g ha-1,they were used instead of isoproturon. These herbicides showed excellent results 30-35 days after sowing (DAS) against the Phalaris minor (Brar et al., 2002).
Latest three Herbicides (ClodinaFop, Sulfosulfuron and Fenoxaprop) now being approved and suggested for managing of Isoproturon-Resistant varieties of Phalaris minor in wheat crops. Although the guidance about all of these herbicides have lots of dilemmas at the process of resistance is completely related to metabolism of weed (Singh et al., 1998). As described by Hari et al., (2003) that 15 to 25 percent of seeds of Phalaris minor are destroyed by burning the wheat residues or straws in field after cultivation while the left seeds are not as efficient for causing any harm to crop. The impact of heat on Phalaris minor seeds in upper and lower layer of soil can be observed in detail in puddled and non-puddled soils. In Pantnagar it was reported that the seeds of Phalris minor were more scattered in field of wheat after combine harvesting as compared to the manual harvesting of wheat crop. Wheat straws are burnt after combine harvesting which cause a loss of 67.7% of Phalaris minor seeds while the left seeds are totally unable to grow.
The germination rate of Phalaris minor seeds collected from a manually harvested field is comparatively higher which 91.2% than that of was acquired from combine harvested field which was 86.1%. Hence it was concluded that the process of burning of wheat field residues in wheat aids to deduce the strength and number of seeds in field (Yadav, 2002).
The Clodinafop is very efficient and helpful for the growers for killing the Phalaris minor varieties which are resistant to Isoproturon. Clodinafop and Sulfosulfuron have been effective against the germination of Phalaris minor especially in wheat field; however the wide leave biotypes are not controlled by the application of Clodinafop (Majumdar et al., 2002). Antagonistic resistance by Phalaris minor to Clodinafop and Fenoxaprop-P-ethyl had been proven. However their individual impacts were good as by the study done in pots by growing resistant variety of Phalaris minor (Bhullar et al., 2002; Mahajan and Brar, 2001).
According to Yadav et al., (2002) the Clodinafop, Sulfosulfuron, Fenoxaprop and Tralkoxydim have been impartially functional on the resistant as well as wild biotypes of Phalaris minor. Phalaris minor should be removed by application of herbicide at 2 to 3 leaf phase, which is usually achieved 30 to 35 days after sowing of crop. However occasionally because of less moisture and delayed irrigation Phalaris minor did not grow or not achieved to 2 to 3 leaf phase even after 30 to 35 days of sowing. Hence under these conditions cultivators suggested to must wait and spray any other alternative herbicide when the Phalaris minor germinate and reached to 2 to 3 leaf phase.
For the removal of high density resistant weed population in wheat crop Metasulfuron at the rate of 4g per hectare and 2, 4-D Na at the rate of 500g per hectare should be sprayed after the alternative herbicide (Yadav et al., 2002). For wide leaved weeds Triasulfuron applied at the rate of 20g per hectare however in case of complex grassy weed in wheat combination of Triasulfuron plus Clodinafop, Fenoxaprop, Sulfosulfuron or Tralkoxydim is very efficient (Yadav et al., 2004a). However, the application of Metribuzin on wheat crop is very harmful (Yadav et al., 2004; Singh et al., 2004).
As proposed by Zand et al., (2007) the two herbicides naming Aryloxy Phenoxy Propionate (APP) and Cyclo Hexane Dione (CHD) hinders Acetyl-CoA carboxylase and is being usually applied to suppress the grassy weed species, like Wild oats and Phalaris minor. While Pinoxaden is recently recommended herbicide of grassy weeds, which is linked with the family of Phenolpyrazolines herbicides and also retards the chemical action of Acetyl-CoA carboxylase and production of lipid. Application of Pinoxaden caused retardation in grassy weed growth.
The expanding dependency on herbicides acting on specific action sites like Acetolactate (ALS) and Acetyl-CoA carboxylase (ACCase) hinderers are actually increasing the risk of resistance. Hence the resistant weed varieties are increasing continuously (Heap, 2012). As recorded in Europe, the situation of resistance in weeds is emerging rapidly in Mediterranean areas, in that place the huge variety of resistant weeds, weedicides and cultivation areas are included (Sattin, 2005; Travlos et al., 2012). Various Phalaris minor colonies are being appeared to have developed resistance against ACCase inhibitor weedicides and also in a few situations, cross or multiple resistance models (Afentouli and Georgoulas, 2002; Heap, 2012).
The field testing of Phalaris minor elevation with the application of various herbicides Clodinafop and Fenoxaprop, exhibits remarkably lesser Phalaris minor elevation to become resistant toward Clodinafop and Fenoxaprop comparatively with Diclofop. Relatively close differences are also been seen in various countries (Chhokar et al., 2008; Om et al., 2004).
While adopting the genetically modified plant cultivation has elevated drastically within past three years and recently up to 52 million hectares of genetically modified crops were cultivated in whole world. Roughly about 41 million hectares of genetically modified crops cultivated shows resistant properties against herbicides, they contains approximately 33.3 million hectares of soya-bean resistant to herbicide. About 77% of genetically modified wheat, corn, cotton and soya-bean were estimated in 2001. Whereas, beet root, wheat and 14 other crops like them had genetically modified herbicide resistant varieties that are publically accessible in future time. There are a lot of hazards connected with the development of genetically modified crops which are resistant to herbicides, having issues with grain destruction, spreading and admittance crops that have herbicide resistant properties, adoption in market and elevated dependence on the use of herbicide for weeds destruction. After that the problems are depicted in the presence of population of weed, the development of resistance against herbicide in weeds and crops which are also resistant to herbicides becoming very common. One more hazard is the effect on ecology by cultural weed control techniques against herbicide resistant weeds population. Asiatic dayflower (Commelina cumminus L) common lambs quarters (Chenopodium album L) and wild buckwheat (Polygonum convolvulus L) have discovered to be expanding chiefly in many cultivation regions because of the traditional and specific assortment techniques become a reason of the increment of herbicides resistant populations be increasing in prominence in some agroecosystems due to the simple and significant selection pressure brought to bear by herbicide‐resistant crops and is related to the utilization of herbicide. Eventually, development of resistant property in weed communities is because of the crops that are resistant to herbicides having been observed in many cases. For example weed having resistance toward herbicides comprises of horseweed (Conyza canadensis (L) Cronq) shows resistance towards N-(phosphonomethyl) glycine (glyphosate) (Owen and Zelaya, 2005).
Herbicides acting on weed’s acetyl coenzyme A carboxylase (ACC) are very efficient grassy weed killer. The rigorous use of these types of herbicides in whole world had been a reason of the development of resistance in various weed varieties. The biochemical and biological study is the reason for evaluating the mode of action of herbicide and the choice of crops towards ACC-inhibiting herbicides. In present years, In recent few years, explanation about tri dimensional molecule of ACC inhibitors while identity of 5 amino acid decreases during the ACC carboxyl transferase demesne which are crucial determining factor for the sensibility of herbicide and throw light on the reason of ACC-based herbicides to which the weeds show resistance. Whereas the metabolic basis of ACC-inhibiting herbicides is very commonly known, however this sort of resistant is apparently very generally known. The resistance towards ACC-inhibiting herbicide usually depends upon the number of gene mutations. All of this is with insufficient data about the genetic variations that are the cause of developing resistance in weeds. The development of resistant property against ACC-inhibiting herbicides is un-definable. The researchers are trying to develop the techniques to reduce the scattering of resistance in weeds in near future. Due to this reason, it is mandatory to elevate the knowledge about the developing biochemical resistance which is increasing rigorously, however it is very laborious to understand the mode of action of herbicides and resistance of weeds toward them (Delye, 2005).
Alternation of herbicides and combinations of herbicides are extensively suggested to control the resistance against herbicides. While there are very few researches that can explain that how actually these mode of actions impacted the resistance selection in weeds. A study for four years was performed in western Canada from 2004 to 2007 to evaluate the impact alternation of herbicides and various combination that act as an Acetolactate synthase (ALS) inhibitor, broadleaf weeds are resistant towards this herbicides. All trials performed comprises of ALS-inhibitor herbicide, Ethametsulfuron is implemented in combination with bromoxynil/MCPA composed herbicides (photosystem-II inhibitor/synthetic auxin), or alternatively with the non-ALS inhibitor on an ALS-inhibitor application rate of 0, 25, 50, 75, and 100% (that is zero to combinations, correspondingly) during the period of four years. The stock of seeds in storage at the initiation of trails comprises of about 5% seeds resistant towards Ethametsulfuron. However the control of weeds was reduced a little, the extent of resistance was increased significantly after applying ALS-inhibitor only ones. While at the finishing time of the trials, the status of resistant properties in seed storage is geared by the seeds at risk, the level of resistance increased from 29% to 85% in seedlings after a single application. The status of resistance in seed storage after the treatment of mixture after four year trial was compared to the zero treated or weed containing trail having 0% ALS-inhibitor. The conclusions of the above study defines that how quickly ALS-inhibitor resistance could developed by the repeatedly application of herbicides with same mode of actions also help the growers to understand the disease and weed knowledge. The study also revealed that the combinations of herbicides work even better to cope with the development of resistance in weeds against herbicides of same mode of actions (Beckie and Reboud, 2009).
The International Survey of Herbicide-Resistant Weeds outlined 388 unique probes (species x site of action) having resistant property worldwide, contain 210 different species. Weeds had become resistant towards 21 out of 25 present mode of action of herbicides and also to 152 various herbicides. The ALS inhibiting herbicides are highly vulnerable to resistance and 126 species of weeds found resistant towards them, afterward 69 species discovered resistant towards Triazines and 42 species were detected to have resistance towards ACCase inhibiting herbicides. Resistance against herbicides in weeds were firstly detected in USA and Europe in the 1970s and early 1980s, it was because of the regular application of atrazine and simazine in wheat crops. Farmers were attracted towards ALS and ACCase inhibiting herbicides in the 1980s and 1990s to control the Triazine resistance in weeds and for glyphosate-resistant crops in the mid-1990s for some reasons to control ALS inhibitor, ACCase inhibitor, and triazine-resistant weeds. The glyphosate alone was applied repeatedly on large fields on glyphosate-resistant crops which lead to a rapid elevation in the development of resistance in weeds against glyphosate, weeds having glyphosate resistance were discovered in 23 different species in 18 countries and now it became the main topic of research in herbicide resistance. But still it is less damaging than the weeds which are resistant towards ALS inhibitor and ACCase inhibitor herbicides. Lolium rigidum is the weed having highest capability of resistance against herbicide in the whole world (12 countries, 11 sites of action, 9 cropping rules, over 2 million hectares) after that Amaranthus palmeri, Conyza canadensis, Phalaris minor, Avena fatua and Amaranthus tuberculatus. In the recent years the weed resistance became the cause of devaluation of various herbicides and various unconventional herbicides are developed with modes of actions that define the extraordinary hazard to sustained weed management in agricultural crops. The development of latest herbicide with new mode of actions and latest crops that are resistant to herbicides should take part in weed control in upcoming time. While the farmers should implement the integrated weed management that consumes all economical weed killing methods (Heap, 2014).
Extensive resistance against herbicide in Phalaris minor is a chief restriction towards the development of wheat crop. Development and promotion of an integrated weed management program is crucial. Field trials were conducted in Faisalabad, Punjab, Pakistan during the winter of 2014-2015 and 2015-2016 to evaluate the effectiveness of herbicide mixtures on herbicide-resistant P. minor (resistant to fenoxaprop-P-ethyl) in wheat sown at 11.25- and 22.50-cm rows. Tank mixtures of clodinafop–propargyl + metribuzin, pinoxaden + sulfosulfuron, pinoxaden + metribuzin, and sulfosulfuron + clodinafop-propargyl at 75% and 100% of label dose/s provided effective control of Phalaris minor. The herbicide mixtures performed better in 11.25-cm rows than in 22.50-cm spacing of wheat. Narrow row spacing (11.25-cm) reduced the number of seeds per spike and the dry shoot biomass (33-38%) of Phalaris minor relative to the wider row spacing. Wheat growth and yield (up to 32%) were improved by herbicide mixtures in both growing seasons, and such an effect was more pronounced at the narrow row spacing. Narrowing spacing not only compensated for 25% less herbicide input but also increased wheat grain yield by 6% more than suggested spacing. Therefore, narrow row spacing and herbicide mixtures can help tackle herbicide-resistant Phalaris minor in wheat fields (Yadav et al., 2018).
In Iran last two decades used of aryloxyphenoxy propionates against the Phalaris minor, Phalaris minor got the resistance due to the inhibiting herbicide ACCase enzyme repeatedly use.wheat and baraly was the major crop of iran but consistently use of aryloxyphenoxy propionates was not affected on Phalaris minor, due to change in the enzyme ACCase, the pharalis minor not afected by the (APP), a way Dose–response assays conducted to check the resistance in the (AR and MR4) Phalaris minor populations against the clodinafop propargy, diclofop‐methyl and fenoxaprop‐P ethyl. The Phalaris minor got resistant due the mutation the enzyme of ACCase enzyme, this mutation occured due the change in encoding enzyme ACCase insensitivity responce against the herbicide. Molecular studies conducted which told in MR4 and AR , Asp‐2078‐Gly and Trp‐2027‐Cys respectively, are the responsible for the resistance of Phalaris minor against APP herbicides, this thing was reported elsewhere that the Phalaris minor biotype got the resistance. These resistance occurred due to the use of DEN and DIM herbicide against the Phalaris minor, this seem this resistance occurred due to lack of plant rotation and continue use of same herbicide which act on the target site of the herbs and herbs got the resistance against this kind of DEN and DIM herbicide. For this purpose addition management practices necessary for the prevent ACCase inhibiting herbicides which cause the ineffective over worldwide (Gherekhloo et al., 2012).
Investigations were carried out to evaluate the accumulative impact of planting scheme and herbicides the growth and yield of Phalaris minor in rice and wheat cropping system. The wheat cultivated on flat field have remarkably less dry matter accumulation of Phalaris minor comparatively the bed cultivation technique and flat field cultivation with 22.5 cm row distance which on an average, increased grain yield by 12% when compared with the bed sowing method and also flat sowing at 22.5 cm row spacing. Clodinafop and sulfosulfuron with their suggested doses effectively controlled Phalaris minor and elevated the yield of grain comparatively the weed containing trail (control). Application of clodinafop at the rate of 60 g ha−1 on flat field cultivated closely spaced (15.0 cm) crop decreased the dry matter of Phalaris minor to the extent of 16.7% when compared with the bed planted crop (Walia et al., 2003).
It is noted significantly less dry matter collection by Phalaris minor, whereas PAR interception (%) and effective tillers were higher as compared to November 10 and 25 sown crops, hence early sown crop increased grain yield by 15.3 and 24.4%, respectively. Among wheat cultivars, PBW 154, PBW 343 and WH 542 smothered Phalaris minor more effectively as compared to PDW 233 and WH 283 cultivars. Though TL 1210 smothered Phalaris minor effectively due to its tall growing habits but it yielded less due to its low tillering capacity. These studies further envisage that combination of early sowing (October 25) with quick growing variety (PBW 154 or PBW 343 or WH 542) provided significantly higher smothering potential against Phalaris minor (virk et al., 2003).
In 1998, field populations of weeds like Phalaris minor observed to have resistance against chlorsulfuron had gathered and analyzed for resistant capability through the Quick-Test technique. This evaluation effectively exposed chlorsulfuron-resistant communities of weed. Complete dose–response experimentations with the off springs from these communities assured the resistance in them and confirmed the application of the Quick-Test in case of dicot species. Afterwards in 1999, randomly a survey was established to implement this test to judge the level of resistance against chlorsulfuron in wild radish populations. This survey was conducted in more than 200 fields in the northern, central, and eastern wheat cropping regions in Western Australia. Weeds had been gathered from the fields of wheat from 133 fields. The Quick-Test technique had been performed to analyze the weeds applied with the Acetolactate synthase (ALS)-inhibiting herbicide chlorsulfuron. Eventually, 21% of the irregularly gathered weeds were resulted towards chlorsulfuron (Walsh et al., 2001).
The study here defines the complete procedure for analyzing the resistance towards post‐emergence Acetolactate synthase and acetyl CoA carboxylase herbicides in grassy weeds. The technique depends upon weeds that had been collected from grower’s fields and transferred for analysis to a central laboratory. The weed seedlings are placed in the agar comprising different doses of herbicides and seedling still alive are observed 10 days and then compared with the vulnerable and resistant results. The analysis had been performed in greenhouse; growth cabinet and phytotron on Lolium spp. seedlings were tested at 1–3 leaf stage and showed results in very less of false positives and negatives of resistance. Depending on the various already established target site and non‐target site of resistance in Lolium spp. communities and three generally applied herbicides, clodinafop‐propargyl, pinoxaden and iodosulfuron + mesosulfuron, we recorded that the conclusions by the agar‐based seedling assay are perfectly related with classical whole‐plant pot tests technique. The technique had been efficiently implemented to Lolium spp. seedlings gathered from two UK fields in 2009 and concluded as a proved moveable to other grass weeds. As it is sprayed very soon in the season, it gives a chance for forecasting herbicide efficiency before application in field and hence permits for a well-known option of herbicide for successful control of weed. Distinguishing that economical, basic and early season bioassay from the various living ones, we suggest refer to it as the Syngenta ‘Resistance In‐Season Quick’ test (Kaundun et al., 2011).
Identifying test (Syngenta Quick-Test, QT) performed for screening grassy weeds remain alive after the application of herbicides for the determination of resistance in them. Portions of the grassy weeds are planted as a whole in pots and let them grow new leaves and shoots, and then the herbicide is applied. The experiment carried out in greenhouse, resistance of known herbicide-resistant blackgrass biotypes to the aryloxyphenoxypropanoate herbicides CGA 184927 and fenoxaprop-ethyl and to the phenylurea herbicide isoproturon was confirmed by Quick Test. The results obtained were very close to the results obtained from the seeds. So, stiff rye grass collected from the suspected resistant fields in South Australia was preserved and transferred Switzerland for Quick Test screening. Resistant capability was verified in just four weeks, which confirmed that the resistance in weeds is the main cause of decline in crop yield. The other properties of Quick Test on present resistance tests recommended likely fit for in-season testing of surviving weeds and possible and actions taken (Boutsalis, 2001).
The recorded figures were investigated statistically by using CRD factorial analysis of variance (ANOVA) technique at 5% probability level. All pair wise comparison was done by least significance difference (LSD) test (Steel et al., 1997).
Germination Rate (%) in resistant and non-resistant biotypes in seed assay by (RISQ) test.
The values shows the result from the experiment that germination rate was either reduced or not due to the varied levels of herbicide application. As low levels of the herbicide the process of germination is not affected at all and the rate of germination is 100%. The rate of germination decreases as the amount used for the herbicide is increased. From 0.001 to 200 µM no seed were inhibited to grow. All the seeds were germinated at these concentrations of herbicide. A regular decrease in the germination is observed due to increment in the dose from 300 µM to 900 µM at which the rate of germination completely stopped. The quantity of the chemical used determines the rate of germination by affecting the processes with in the seeds causing less or no germination. At low concentrations of medicine used the resistant biotype still shows growth that indicates their ability to withstand their ability against the herbicide.
The graphical representation of the above data indicates the same trend as shown in the table that makes it more obvious that the resistant types of the weeds can resist against the low doses of herbicides where the line shows the maximum graph. Still good growth at elevated quantity makes it obvious that this biotype can withstand the negative environment caused due to the herbicide. At high level of 750 µM the rate of germination is 20 % that indicates the presence of the weed.
Germination rate of the nonresistant biotype is on contrary to the resistant, is seriously affected by the increase in herbicide amount applied. As the herbicide quantity increases, the germination is reduced. At low amounts of the applied herbicide the germination rate is still good but at high concentrations the rate decreases, and reduces at more rates as compared to the resistant biotype, as at 100 µM the reduction in rate of germination is observed, that shows the sensitivity of this biotype to the applied herbicide thus reducing the germination due to having low ability to survive under the applied herbicide. The seed collected from field can thrive several for several days. The similar method had been performed to confirm resistance towards glyphosate and to determine a glyphosate-dose response assay and various treatment on a group of Italian ryegrass (Lolium perenne ssp.) plants (Salas et al., 2012).
Resistance towards glyphosate in ryegrass could be determined through pre-germinating seeds in dose of herbicide containing petri dish, the seed are planted in these dishes and the then glyphosate mixture of various quantities are added in it, then place din incubator for 7 days the length of the coleoptile increases proved the germination and resistance in the weed seeds (Ballot et al., 2009). The similar study revealed that all treatments reduced the growth of Phalaris minor and Avena fatua remarkably comparatively the herbicide free crop, the raised production of wheat is also seen (Ahmad et al., 1995).
Suppression Rate (%) in resistant and non-resistant biotypes in seed assay by (RISQ) test.
Data related suppress rate of the resistant biotype is shown in the table below that elaborates the suppression of the weeds under herbicide application. The data clearly shows that under the influence of low herbicide amounts there was no suppression of the weeds and the growth was not affected at all, but as the rates were increased up to 300 µM and more the suppression was observed and the growth of the weed plants was reduced. As the dose was increased, the damage due to herbicide done was increased but up to a limit when the herbicide amount was not that much to affect so much that plants began to die. At higher amounts of the herbicide the suppress rate is zero showing that there was no germination at all and the weeds died under the influence of the herbicide thus the data shows suppression rate of 0 at 800 µM and above doses. The maximum damage was at the rate of 600 – 750 µM that seriously suppressed the weed plants to grow causing delayed plant growth.
Suppression rate of the resistant biotype of weed is given in this graph showing clearly that the suppress rate was maximum in the range of 550 to 750 µM more than that amount caused the death of the plants eventually declined the suppress rate and is shown in the graph declining line.
The above given data is about the growth of non-resistant biotype being suppressed due to the effect of the herbicide applied during the experiment. The data shows that the non-resistant biotype was much more affected by the herbicide as compared to the resistant biotype even at low concentrations of the applied herbicide. At amounts of 100 µM the suppression due to applied treatment was observed that indicates that the biotype cannot with the harsh conditions of the applied herbicide and the growth of the weed plants is reduced at even a more rate as compared to the resistant biotype. Amounts more than 650 µM caused mortality in non-resistant types that was much more in resistant. Even the damage percentages are more than the resistant types at any of the applied concentration of the treatment. Maximum damage of 40 % was observed in the non-resistant type at the amount of 400 to 500 µM herbicide.
The curve of the graph is the virtual representation of the data clearly pointing the concentrations that were responsible for maximum damage to the non-resistant biotype of Phalaris minor Indicating its sensitiveness towards the applied herbicides. The death of the plants was caused at the rate of 650 µM of the herbicide, after which the line along the axis is the representative of which.
The seedling assay method can be applied on some wide leaf weed types (Walsh et al., 2001). The results show by another study prevalence of resistance to ACCase inhibitors in all organic fields investigated, with an average of 74% of the plants analyzed being resistant. The major part of this resistance is not due to mutations at the gene encoding ACCase, and is likely due to enhanced herbicide metabolism. This situation may be due to gene flows from conventional fields, persistence of resistance from before the fields were converted to organic farming (Clement et al., 2007).
Mortality rate (%) in resistant and non-resistant biotypes in seed assay by (RISQ) test.
When we added 400µM of fenoxaprop p methyl in agar medium the mortality rate was 0% in resistant biotype it means all plants survive. When the concentration of dose increased to 450µM the mortality rate increased to 10% which means out of 100 10 plants didn’t survived. With 500µM there was same result mortality rate is still 10% and with 550µM of fenoxaprop p methyl the in non-resistant biotype immortality rate increased to 30% which means out of 100 plants 30 were not survived after taking respective agar dose. When applied agar medium containing 600µM of fenoxaprop p methyl dose the plants mortality rate reached to 40% means out of 100 plants 40 were not survived. The agar having 650µM of fenoxaprop p methyl showed mortality rate of 60% means that out of 100 plants 60 plants were not survived. By increasing the concentration of the dose up to 700µM the resistant variety showed very high mortality rate i.e., 90% it means only 10% plants could survive.
At concentration of 400µM of agar containing herbicide fenoxaprop p methyl the non-resistant variety of the plants showed mortality rate of 10% it means 10 plants out of 100 didn’t survived after the treatment of agar containing 400µM of fenoxaprop p methyl dose. By increasing dose of fenoxaprop p methyl to 450µM mortality rate increased to 30% from 10% that is 30 plants out of 100 are not survived due to the application of treatment. In case of 500µM of fenoxaprop p methyl the mortality rate increased to 70 that is 70 plants out of 100 are not survived. When the dose concentration increased to 550µM the mortality rate was highest that is 100% means that all plants died by the addition of agar containing 550µM of fenoxaprop p methyl. At concentrations 550µM, 600µM, 650µM, 700µM of fenoxaprop p methyl in agar medium the non-resistant variety showed 100% mortality rate means no one plant was survived. There was no change in mortality rate at 550µM, 600µM, 650µM and 700µM of fenoxaprop p methyl changing concentrations as there were in case of resistant varieties.
Tank combination of fenoxaprop + carfentrazone 120 g/ha in multiple variation evaluated the intensity Phalaris minor treat with only fenoxaprop 120 g/ha. The intensity and dry matter of Phalaris minor reduced with increasing the ratio from 4:1 to 6:1 of fenoxaprop + carfentrazone in both the concentration. Generally, fenoxaprop at the rate of 120 g/ha gave good results and was comparatively better against100 g/ha against Phalaris minor. At the rate of 120 g/ha, the mixture of fenoxaprop + carfentrazone showed better control of Phalaris minor and also in broad leaf weeds. But their mixture at all the variations were similar to each other on a relative dose, specifically 100g/ha. Compatibility of fenoxaprop and carfentrazone as tank mixture in controlling complex weed flora in wheat has been reported by earlier workers as well (Singh and Singh, 2005; Chopra et al., 2008). As in another study Resistant capability was verified in just four weeks, which confirmed that the resistance in weeds is the main cause of decline in crop yield. The other properties of Quick Test on present resistance tests recommended likely fit for in-season testing of surviving weeds and possible and actions taken (Boutsalis, 2001).
Resistance in seasonal quick test method (RISQ) was the best way to check the resistances of weeds especially in grasses weed Phalaris minor. In RISQ Agar based seed assay and seedling based assay was the finest method to find out the resistance in biotypes of Phalaris minor. In seed based assay the optimize dose of Fenoxaprop p methyl against Phalaris minor for non-resistance biotypes was 600 μM under which non-resistance biotype stop to germinate. While the resistance biotype of Phalaris minor stop to germinate at 650μM. In seedling based assay for the non-resistance biotype of Phalaris minor the optimize dose of Fenoxaprop p methyl 500 μM under which new leaves and root growth did not occurs while in resistance biotype of Phalaris minor stop to growth under 700 μM.
Author: Faran Muhammad1, Muhammad Ali Tariq2, 1,2 Department of Agronomy University of Agriculture Faisalabad