| The yield has been the most important indicator of breeding new varieties of rice.Salt and alkaline stress is a serious adversely affecting the growth and development of rice,and planting rice on salinized land will reduce its production by nearly 30%.Therefore,to study salt and alkaline tolerance based yield related traits in rice,explore the main effect QTL of salt and alkaline tolerance,and analysis of QTL additive,epistatic and the QTL interaction between environmental effects.,which is of great significance to clarify the genetic mechanism of yield-related traits in rice under salt and alkaline stress,meanwhile,it could lay the foundation for saline-alkali soil improvement and salt and alkaline tolerance molecular marker assisted breeding.In this study,180 recombinant inbred line(RIL)population derived from a cross Dongnong 425(DN425)and Changbai 10(CB10),and a genetic linkage map containing 102 SSR markers and 113 In Del markers was constructed.The whole growth period was treated with 6ds·m-1 Na Cl solution as salt stress,Na2CO3 solution(p H=9.0)as alkaline stress and the normal water irrigation as control conditions.The panicle number per plant,panicle length of the main stem,total number of grains per panicle,empty flat grain number,number of grains per panicle,seed setting rate,thousand grain weight and panicle weight per plant were measured under salt,alkaline and control conditions in 2015 and 2016.The additive quantitative trait loci(QTL)analysis was conducted by using the complete interval mapping method(ICIM),the additive and epistatic QTL×environment interaction effects was conducted by using the mixed composite interval mapping method(MCIM).The main results of this study are as follows.1.Yield-related traits of both RIL populations and parents were affected by salt and alkaline stress in 2015 and 2016,the panicle number per plant,panicle length of the main stem,total number of grains per panicle,number of grains per panicle,seed setting rate,thousand grain weight and panicle weight per plant were decreased under the stress condition,the empty flat grain number were increased.Compared with the salt stress,the yield-related traits and their relative traits decreased even more under the alkaline stress,indicating that rice is more sensitive to alkaline stress2.In addition to the spike length of the main stem and the total number of grains per panicle,the remaining yield-related traits did not show significant correlation under the salt and alkaline stress conditions for two years.Indicating that there may be genetic differences in salt tolerance and alkaline tolerance resistance of rice.3.The genetic map was constructed by mapchart,containing 102 SSR markers and 113 In Del markers was constructed based 180 lines of F8 RIL population,all of the markers distributed in 12 chromosomes,covering the rice genome about 2387.33 cM,the average distance between markers is 11.10 c M.4.QTL was performed with LOD=2.5 as the threshold by using the QTLIci Mapping V3.3.A total of 110 additive QTLs were detected,which distributed on chromosomes 1,2,3,4,5,6,7,8,10,11 and 12.q PW11 was repeatedly detected in salt,alkaline and natural environment for two years,q WN3-2 was repeatedly detected under salt and alkaline stress for two years,q PN1-1 was repeatedly detected under both natural and salt stress conditions for two years,q PN11-2 was repeatedly detected only under alkaline stress for two years,q RSS12 was repeatedly detected under both natural and alkaline stress conditions for two years,q PW11 was repeatedly detected in salt,alkaline and natural environment for two years,and q WN3-2 was repeatedly detected in salt and alkaline environment for two years,which are important QTL for controlling yield-related traits under under salt and alkaline stress.q PW11 is a new salt-tolerant QTL with a contribution rate of 7.94%-20.13%.5.The mixed composite interval mapping method(MCIM)was used to the joint location analysis of additive,epistatic×environmental interaction effect of of RIL population by mapping software QTL Network 2.1.A total of 54 the additive QTL×environment interaction effects QTLs were detected,which were distributed on chromosomes 1,2,3,4,5,6,7,8,10,11 and 12.q PN1-1 was repeatedly detected under both natural and salt stress conditions for two years with using the ICIM,46 QTLs including q PN11-2 detected using ICIM were detected simultaneously by MCIM.Some of the genetic overlap of rice yield-related traits under salt stress and alkaline stress,indicating that the genetic mechanism of yield-related traits in rice is not only related to each other but also has differences between salt and alkaline stress.6.Epistatic QTL×environment interaction effects on the yield-related traits of rice was analyzed by using the MCIM in six environments.A total of 25 pairs of additive QTLs were detected,23 pairs of QTLs had environment interaction effects.The epistatic effect and the interaction effect of QTL together affect the genetic expression of yield-related traits. |
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