Mapping of simple sequence repeats SSRS and marker assisted introgression of quantitative trait loci QTLS for stay green in sorghum SorghumbicolorI L Moench

Abstract

With the objective of increasing the marker density in the linkage map of the stay-green newlinemapping population, ninety four individuals from N13 x E36-1 sorghum recombinant inbred population newlinewere genotyped with 78 EST-SSR makers and 55 markers (70%) gave reliable and scorable newlineamplification. The genotypic data from these markers was integrated with the genotypic data of 164 newlinepreviously mapped RFLP, AFLP, RAPD and SSR markers to produce the genetic maps. The genetic newlinemap constructed has a total length of 2838 cM. The number of EST-SSR markers mapped per linkage newlinegroup ranged from 2 (linkage group H) to 9 (linkage group F). Some of the markers such as Xisep0841, newlineXisep0733, and Xisep0938 mapped in the stay-green QTL regions making them good candidate newlinemarkers to be used in fine mapping of the QTLs and marker-assisted selection of the stay-green trait. newlineIn a marker-assisted backcrossing programme, four stable stay-green QTLs (StgB, Stg1, Stg3 newlineand Stg4) were selected to be transferred from the stay-green donor parent (B35) to the senescent newlinerecurrent parent (R16). After two additional marker-assisted backcrossing and two selfing generations, newlinefour backcross families with single (Stg1, Stg3, Sg4 and StgB) and five backcross families with double newlineputative QTLs (Stg1+Stg3, Stg1+Stg4, Stg3+Stg4, Stg3+StgB and Stg4+StgB) have been selected. newlinePreviously generated, early generation stay-green introgression lines (BC2F2/BC1F3) were newlineevaluated for their agronomic and stay-green related characters under well watered and water-stress newlineconditions both in field (in the post rainy season) and greenhouse condition for two seasons. Among the newlineintrogression lines, RSG 04001/RSG 05001 was found to be the most promising line both in terms of its newlinegrain yield and stay-green related characters. newlineBesides high % green leaf area, the stay-green genotypes had high chlorophyll content and newlineleaf nitrogen concentration compared with the senescent lines showing the relationships among these newlinetraits. The correlations of relative grain yield to relative % GLA in the s