Effect Of Chemical Mutagenesis Agent N-methyl-n-nitrosoure A (MNU) On Oat

Oat(Avena sativa L.)is an annual crop for both grain and forage.At present,there are some problems such as relatively single germplasm resources,few special-purpose varieties,and inability to meet the rapidly developing market demand.The effective way to solve this problem is to create different types of oat germplasm and breed new oat varieties for different uses.In this study,three oat varieties,Everleaf,Longyan No.4 and Baler 2 were used as experimental materials and mutated with 4 concentrations(0%,0.20%,0.25%,0.30%)and 3mutagenic time(8 h,11 h,14 h)of N-methyl-N-nitrosourea(MNU).The germination rate,germination energy,relative lethal rate,root and shoot length were measured,and the optimal semi-lethal treatment for each variety was selected with the relative germination rate of 50.00%as the standard.Then the mutagenesis treatment was conducted with this condition.The seedlings were transplanted to the field,harvested after maturity,and sowed in the field together with the control in the next year.Mutants from M2 generation was screened and their photosynthetic performance was determined to explore the mutagenic effect of MNU on oats.The main research results are as follows:(1)MNU treatment significantly affected the seed germination and seedling growth of oat.The effect of the mutagen concentration was far greater than mutagens time and oat variety.With the increase of the mutagens concentration,the germination potential and germination rate of oat seeds decreased but significantly increased the relative mortality.When the concentration of mutagens increased to 0.30%,the germination rate decreased from 92.67%～98.67% to20.00%～54.75%.Mutants promoted the growth of oat seedlings at low concentration and inhibited them at high concentration.The response of oat varieties was disparate with different treatment.With the increase of treatment time,the germination rate and germination energy decreased by 59.09% and 55.79% of Everleaf varieties,59.23% and 58.07% of Longyan No.4,78.80% and 81.33% of Baler 2 under the high concentration(0.30%),respectively.The optimal semi-lethal treatment combinations of the three varieties were 0.30%/8 h,0.25%/11 h and0.20%/11 h,respectively.(2)Many types of mutants were produced by MNU treatment.Among the M2 variant plants,the leaf variation was the most,including leaf edge yellowing,spiral leaf and leaf cracking,accounting for 46.01% of the total variant plants.Secondly,28 plants of plant height with significantly higher and 6 plants with significantly lower compared to control,which accounted for 15.96% of the total number of variation plants.There are 19 plants heading 8～10 days earlier than the wild type,and 12 plants heading 10～12 days later,accounting for14.55% of the total variation plants.Panicle variation includes long or short panicle,panicle type changing from scattered to bending panicle,spikelet number obviously increased or decreased,which accounts for 11.74% of the total variation plant number.(3)The responses of oat varieties to MNU treatment M2 generation were significantly different.Leaf variant of Everleaf was accounted for 87.76% of the total leaf variant,plant height variant accounted for 67.65%,and panicle variant accounted for 64.00%,showing the best mutagenic effect.The effect of Longyan No.4 was the lowest,and the number of variant plants of each type was less than 3 mutant plants.(4)The photosynthetic characteristics of the variant types with more than 3 mutant plants were analyzed at the filling stage,and it was found that MNU treatment had a significant effect on the photosynthetic performance of M2 generation variants.Except for the yellow edge leaf plants,the SPAD values of the other mutants were higher than the wild type.The SPAD values of the plants with increased spikelets in Baler 2 and Everleaf increased by 8.38% and 9.60%(P<0.05),respectively.Compared with the wild type,the Pn of tall plants of Baler 2 and Everleaf increased by 35.81% and 52.54%,respectively.In addition,the Fv/Fo,Yield and ETR of different mutants were higher than wild type,and there was no significant change in Fv/Fm and q P between the wild type and different variant types,but the q N of the mutant was significantly lower than that of the wild type,with a decreased of more than 10.00% in Baler 2 and 6.67%～28.89% in Everlef,respectively.In conclusion,except the plants with dehiscent leaves and yellow-leaf margin,the photosynthetic performance of the other variant types was higher than that of the wild type.