Study On The Effect Of Different Environmental Temperatures On Wheat Yield During Reproductive Transition Period

Wheat is a kind of overwintering crop,especially the winter wheat,requires experiencing a period of low temperature to flowering and bearing,which is known as vernalization.The main cultivate pattern of wheat broadcast in our country is in the winter,wheat remains vegetative stage before winter.Different wheat varieties demands differently of low-temperature vernalization,so they transfer to reproductive stage disparately.We need to determine the optimal sowing time for specific varieties and planting areas to avoid wheat flowering in winter.However,it is a widespread problem to study the mechanisms of organ development and gene expression regulation which causes the differences of yield.We seeded 11 wheat varieties with different vernalization needs in stages,inspected the reproduction transition process,investigated the change of the yield and heading date,research the changes in gene expression and hormone levels during the reproductive transition period under temperature control environment,after different temperature treatments to analyze the regulation mechanism of suitable sowing time of wheat.The results are as follows:1.The diversity of sowing date causes significantly different in reproductive transition time but little difference in flowering time while late sowing conditions affected the performance of multiple agronomic traits among several wheat varieties.We broadcasted 11 wheat varieties included winter,semi-winter and spring varieties,which sown in mid-October and early November.The difference in flowering time of the same variety was about a week while the difference in reproductive transition time more than 50 days.At the same time,plant height,tiller numbers,panicle characters and yield of most varieties decreased after late sowing.Some varieties,such as Yannong 1212,showed no significant difference in tiller number and panicle characters between different sowing dates,which showed better late sowing resistance.2.Low temperature treatment after reproductive transition can improve the performance of yield performance.Ji Mai 325,which performed greatly affection by staging sowing,was treated with low temperature at different stages included vegetative stage and after reproductive transition,and the group without low temperature treatment was used as control group.The number of grains per panicle increased by 15.2%,the number of tillers increased by 36.9% and the grain weight decreased by 1.9%.Similar phenomena were observed in other materials such as Zhengmai 9023,Sinong 979 and Jimai 322.This indicated that different sowing dates caused the reproductive transition time differently,especially the long period of low temperature after reproductive transition was conducive to the increase of yield.3.Low temperature conditions significantly changed the gene expression network of young spikes.The expression profile of young spike samples with the same growth stage were analyzed,included without vernalization(V0),low temperature vernalization during vegetative growth stage(V)and low temperature treatment after reproductive transition(Vs).The results showed that a total of 4912 Vs genes were differentially expressed relative to V,of which 3867 were up-regulated and 1045 were down-regulated,and the up-regulated differential genes were significantly more than down-regulated ones.A total of 969 genes were differentially expressed in V compared with V0,among which 488 genes were up-regulated and481 genes were down-regulated.Among the 4103 differentially expressed genes,3583 Vs genes were up-regulated relative to V0,and the remaining 520 were down-regulated relative to V0.Therefore,the gene expression pattern of spike was significantly changed by low temperature treatment after reproductive transition.4.Low temperature treatment after reproductive transition affected hormone metabolic pathways: The above RNA-seq data showed that a large number of genes related to carbohydrate,lipid metabolic pathways and hormone signal transduction were differentially expressed.The results showed that the contents of auxin,abscisic acid,salicylic acid and jasmonic acid were different,with the changes of gene expression and hormone content,we isolated a group of candidate genes which may change expression levels and affect hormone metabolism in spike after low temperature treatment.To summarize,our study combined different sowing stages in the field and low temperature treatments at different stages to identify the main reasons for the distinction in final yield performance,including differences in reproductive transformation time and the temperature of young spike development after reproductive transformation.Combining gene expression and hormone content analysis,it reveals that the low-temperature environment after reproductive transformation alters the spike development process by affecting hormone content and metabolism.This study provides a developmental biology perspective for the formulation of cultivation measures and the improvement of yield.