QTL Mapping Analysis Of Plant Height And Shelling Percentage In Peanut

Peanut(Arachis hypogaea L.) is one of the most important oil crops and is extensively planted worldwide.In peanut breeding programs,it is a primary objective to increase seed yield.As two important agronomic traits,plant height(PH) and shelling percentage(SP) are both closely related to peanut yield.Therefore,clarifying the genetic basis of PH and SP plays a crucial role in developing high yield peanut varieties.However,it is still unclear about the genetic basis of PH and SP on account of their complexity controlled by multiple genes and affected by environmental factors.In the present study,two recombinant inbred lines(RIL) populations were constructed from the crosses of Yuanza 9102×Xuzhou 68-4(YX) and Xuhua13×Zhonghua 6(XZ),respectively.Genetic linkage maps were constructed for the two RIL populations using SSR markers.The phenotyping of PH and SP in YX and XZ populations were conducted in multiple environments,and subsequently phenotypic correlations between two traits were analyzed.QTLs were identified to reveal genetic basis of PH and SP traits.In addition,common markers linked to robust and consistent QTLs in both RIL populations were further mapped into the pseudomolecule of A.duranensis to explore candidate genes.These results would lay a foundation for synergistic genetic improvement of PH and SP traits to develop high yield variety.The main results are as follows.1.The phenotypic data of PH showed continuous normal distribution across all environments in both populations,while phenotypic data of SP showed the same as PH across most of environments besides skewed distribution across individual environment,indicating that PH and SP were both controlled by multiple genes.Both of PH and SP showed stable variation across multiple environments with broad sense heritability(H~2) higher than 0.8,reflecting that PH and SP are both controlled by genetic factors.The results of phenotypic correlation analysis indicated that PH and SP had significant negative correlation in both populations,while phenotypic correlation coefficients were different in both populations due to different genetic background between their corresponding parents.2.The genetic map of YX RIL population contained 830 loci spanning 1386.19cM with an average distance of 1.67cM between two adjacent loci,while the other genetic linkage map of XZ RIL population contained 817 loci spanning 1756.48cM with an average distance of 2.15cM between two adjacent loci.There were 213 common marker loci with better collinearity between the two genetic linkage maps,which could be used as anchor markers to verify stable QTLs determined from the two RIL populations with different background.3.In QTL mapping of PH,thirty-eight QTLs were determined from YX RIL population with 3.99%?26.27% phenotypic variation explained(PVE) across four environments.Of these 38 QTLs,there were 7 major QTLs,and 8 QTLs could be repeatedly detected across at least two environments.Ten QTLs were determined from XZ RIL population with 6.41%?12.03% PVE across three environments.On each linkage group,detected PH QTLs from the two RIL populations were compared to search for stable PH QTLs according to tightly linked common markers.As a result,consensus QTL cqPHA09.d(YX RIL population) and qPHA09.1a(XZ RIL population) distributed on A09 linkage group both possessed two common linked markers Ad09A3779 and AGGS2438,indicating that they were stable QTLs which could be detected from multiple populations and different environments.4.In QTL mapping of SP,sixty-six QTLs were identified with 4.64%?26.27% PVE across four environments from YX RIL population.Of these 66 QTLs,16 QTLs could expain more than 10% of phenotypic variance,and 14 QTLs could be repeatedly detected across no less than two environments.A total of 17 QTLs with 4.99%?23.71% PVE were detected across three environments from XZ RIL population.Of these QTLs,there were 7major QTLs with more than 10%of PVE,and 6 QTLs could be repeatedly detected in no less than two environments.Consensus QTL cqSPA09.a(YX RIL population) and qSPA09.3a(XZ RIL population) were stable QTLs with tightly linked common markers.Likewise,on B10 linkage group,there was a flanking marker AGGS1393 simultaneously linked to two repeatedly detected QTLs,qSPB10.2b and qSPB10.3c(YX RIL population),and to a QTL qSPB10.3b(XZ RIL population) partly affected by PH trait,reflecting that there were stable QTLs that could express in different RIL populations with genetic background and multiple environments.5.In terms of colocalization of PH and SP QTLs,for YX RIL population,consensus PH QTL cqPHA09.a with 19.67%,8.33% and 22.28% PVE and consensus SP QTL cqSPA09.a with 12.95% and 17.44% PVE,the two consensus QTLs co-localized in the A09 chromosome region;for XZ population,qPHA09.3a for PH with 10.63% PVE and qSPA09.3a for SP with 4.99% PVE co-localized in the A09 chromosome region.Conditional QTL mapping results verified that these colocalized QTLs possessed opposite additive effect,revealing that chromosome A09 is rich in pleiotropy genes or tightly linked genes controlling PH and SP traits.6.Two common markers Ad09A3779 and AGGS2438 tightly linked to consensus PH QTL cqPHA09.d in YX population and PH QTL qPHA9.1a in XZ population were mapped into the pseudomolecule A09 of A subgenome(A.duranensis V14167),161putative genes were detected in the 3.4Mb(10231303-13631263bp) physical interval.Of these 161 putative genes,150 genes were well annotated,while 11 genes were unknown.Among all putative genes,50 genes were found with corresponding orthologous transcripts in the transcriptome of the allotetraploid(Arachis hypogaea).The expression pattern of these genes generally could be sorted into two subgroups.The transcripts in one subgroup were mainly abundant in developmental pods,developmental seeds and tips from vegetative shoot and reproductive shoot.The members in the other subgroup were predominantly expressed in roots and nodules or leaves from seedling,main stem and lateral branch.The results showed that the interval of two linked markers Ad09A3779 and AGGS2438 contains multiple genes controlling PH and SP traits.