Selection for hard endosperm, Tryptophan content and yield contributing traits in F3:4 QPM families

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College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal
The present investigation was undertaken for selection of QPM inbred lines with hard endosperm and high tryptophan content in a set of 60 F 3:4 QPM families shortlisted from four QPM crosses V341 X V 373, CML 165 X V 373, CML 161 X V 341and CML 161 X V 373. A total of 681 cobs harvested from sib matings within different families were screened for opacity and sixty lines with index scores of 2 and 3 (hard endosperm) and high seed index value was further selected for determining tryptophan content using Hopkins-Cole reaction. The % tryptophan was found to range from amaximum of 0.095% to a minimum of 0.020%. Twenty two lines with tryptophan % inthe range of 0.095% to 0.073% could be identified. Differences in tryptophan content between normal and QPM lines were significant. High genetic gain and realized heritability could be recorded for % tryptophan increase in most of these twenty two lines studied. These lines were further charcterized at the DNA level along with dive low QPM and two normal maize genotypes using twenty o2 specific reported SSR markers. Distinct polymorphism was observed between the normal and a majority QPM inbred lines with respect to all the three gene specific SSR markers phi 057, phi 112 and umc 1066 validating the identity of the lines. Cluster analysis using Unweighted Neighbour Joining based on allelic data grouped the lines into three major clusters.QPM lines with high % tryptophan grouped into Clusters I and II while QPM lines with low % tryptophan grouped into Cluster III. The genetic distance based on dissimilarity matrix ranged from a minimum of 0.10 to a maximum of 0. 47. The polymorphism information content (PIC) ranged from 0.19 to 0.65 with an average of 0.44. Yield/plant calculated for the different families as total kernel weight (g) was the most variable traits and ranged from 88 to 28 g for the twenty two high QPM families. Based on these studies, QPM lines with more than 0.090% tryptophan can be shortlisted for further use to initiate a hybrid breeding programme for QPM.