Correlation Of Grain Main Characters And Fine-Mapping QTL For Starch Concentration In Maize

Maize is the most widely grown crop with great commercial value in China. Grain of maize consists protein, starch, oil,vitamins etc. in which protein account for 10% and starch about 75%.1) Grain protein is the main material for feed product. To investigate the correlation between protein and other components, a F2 population with 367 lines derived from high protein 1481 and low protein 1228 was constructed. Correlation analysis showed that protein concentration is negatively correlated with 100 kernel weight, grain size, oil concentration, especially with starch with R=0.7895.2) Grain starch is a major component to determine maize yield and seed quality. However, the causal genes or loci conferring to variation of starch concentration are not well understood. To evaluate the quantitative trait loci (QTL) associated with starch concentration, data were collected with IBM population (211 lines) from multiple years and locations. Eight potential QTL were detected explaining 3.16%-14.54% of the phenotypic variance. A major QTL (Q9.1) on chromosome 9 was located in the interval ranging 3.6 Mb, containing 204 annotated open reading frames (ORFs). After adding 16 new InDel markers the QTL was narrowed down into 1.5 Mb region containing 97 annotated non-transposon ORFs. In order to validate the target region, a new F3 population was constructed by cross B73 and Mo 17 and two extreme tails of starch concentration were surveyed allele frequency at the QTL region. There were significant differences in allele frequencies of five markers of Q9.1, showing a significant deviation from a 1:1 ratio. After profiling the transcripts of B73 seeds at 0,2,4,6,8,10,12,14,16,18,20,22,24,26,28, 30,32,34,36 and 38 days after pollination,72 expressed genes were detected in the interval. Comparison of gene expression in both parental lines’seeds at 12,16,20,24,30, and 36 days after pollination showed that two candidate transcripts (GRMZM2G174048 and GRMZM5G859017) with the potential to increase starch concentration in maize.