| Rice is one of the major food crop which feeds more than half of the world's population.However,the increasing risk of lodging has prominently affected the total grain yield of rice to serious levels in major growing areas.Hence,structural characterization of the rice culm is imperative for deeper understanding about the mechanisms of lodging and has practical implications for improving rice cultivars without intensive losses in yield.Present experiment was designed to explore the relationship between different morphological and culm traits related to stem strength during 2014 and 2015,followed by QTL analysis in the RIL population(F13-14)derived from the cross of two indica rice Huahui3(HH3)and Zhongguoxiangdao(ZGX).Significant differences for almost all of the traits were observed across two seasons(2014 and 2015).Correlation coefficients revealed that plant height(PH),plant weight(PW),diameter of 2nd internode(ID 2nd),diameter of the 3rd internode(ID 3rd),breaking strength of the 3rd internode(Brf 3rd),panicle length(PnL),panicle weight(PnW),flag leaf length(Fg L)and leaf area(L.A)showed consistent relationship in both years.Breaking forces of 2nd and 3rd internodes significantly associated with their diameter and weight at P<0.01.Total plant weight also exhibited positive contribution towards diameter of 2nd and 3rd interModes during 2015.Based on these findings,it is asserted that breaking strength of the lower plant part can be advanced by increased diameter,weight of basal internodes(2nd and 3rd)and total plant weight.Genotypic effects of culm physical attributes were determined by identifying their putative QTLs in the RIL population.A total of 65 QTLs were detected in two seasons affecting the different traits with 9 major clusters at chromosomes 2,3,4,6,8b and 10.The QTL cluster 7(C7)at chromosome 8b,showed the pleotropic effect as the QTLs for major traits related to culm strength including IL 2nd,ID 2nd,ID 3rd,PW and HD were spotted in the interval RM310 and RM547.Likewise,QTL cluster 9(C9)at chromosome 10 also indicated the pleotropic effect for the diameter and weight of 2nd internode at the base.Whilst,C2 and C6 corresponded to the QTLs regions associated with breaking strength of basal internodes(qBrf2-6-1,qBrf3-6-1)and IL3rd,respectively.Of the 22 genomic regions related to total PH and its components,16 QTLs showing major effect were associated with the length of internodes.In addition to these 16 QTL regions,22 QTLs related to physical strength of the basal internodes were suggested to participate towards higher levels of culm lodging resistance(LR)in rice.The presence of allelic differences in the mapping population at such scale implies that stem strength of the rice(indica)can be improved readily by combining favorable QTL alleles affecting breaking strength,diameter and length of basal internodes in addition to their weight. |
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