Studies On The Biological Characteristics And Chemical Control Of Roegneria Kamoji Ohwi

Roegneria kamoji Ohwi is an emerging weed of wheat fields in the Yangtze Delta Region,China.The damaging range has been expanding,and some areas have evolved into dominant weeds.In this dissertation,the seed setting,seed dormancy and seed germination were preliminary studied to understand the biological characteristics.In greenhouse experiments,the plant height,total stem number and fresh weight were studied to understand the competitive relationship between R.kamoji and wheat.The preliminary study on chemical control of the weed was also conducted by laboratory screening bioassay.1.At maturity,the plant height was 121.5 cm,the panicle length was 24.3 cm,the number of grains per panicle was 78.2,and the 1000-grain weight was 5.34 g.Gibberellin and potassium nitrate treatment could overcome seed dormancy;the optimum temperature for seed germination is 25?/15?(day/night),requiring no light.Additionally,seed germination was sensitive to water potential stress,while drought stress inhibits germination.The seed showed a certain tolerance to salinity,while high salinity inhibits germination.The pH showed no significant effect on seed germination,and the seed germination was more than 75%under the pH value ranges between 4 and 10.The seed emergence rate significantly decreased with the increase of sowing depth.Seed absorbency was good and storage under flooding condition was conducive to maintaining seed vigor.2.The growth and development process of R.kamoji and wheat were similar.The growth trend of plant height,total stem number and fresh weight per plant was approximately same.R.kamoji entered rapid growth period 3 weeks later than wheat.Under greenhouse conditions,the plant height of wheat before maturity was higher than that of R.kamoji while at harvest,the plant height of R.kamoji was higher than wheat.The total stem number per plant of R.kamoji was higher than wheat during whole growth period,and the fresh weight of aboveground part was higher than wheat.During harvest at 27th week,the plant height,total stem number and fresh weight of aboveground were 86.5 cm,2 and 19.88 g,respectively.R.kamoji reduced wheat yield by influencing wheat yield components,which revealed the significant impacts on the number of spikes per unit area,followed by the number of grains per spike,but no significant impact on the 1000-grain weight of wheat.With the increased density of R.kamoji,the aboveground fresh weight of wheat decreased significantly,and the competition between them could be clearly observed.3.The control effects of nine herbicides at the 3-7 leaf stage were not ideal,and R.kamoji was generally resistant to the common herbicides.The control effect is relatively good at the 3-leaf stage.The seeds of R.kamoji were sensitive to mesosulfuron-methyl and pyroxsulam,but not sensitive to flucarbazone-sodium.Further,the seedlings of R.kamoji at the 3-4 leaf stage showed resistance to three ALS inhibitory herbicides.The combined effects of mesosulfuron-methyl and flucarbazone-sodium,carfentrazone-ethyl and clodinafop-propargyl were additive and antagonistic respectively.Moreover,when the combined dose of MCPA-Na and diflufenican reached the recommended dose,the comprehensive control effect was 95.7%,which was suitable for the control and removal of weed communities of R.kamoji as the dominant species.