科研之友
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摘要
The diversity and genetics of tassel branch numbers (TBN) in maize (Zea mays L.) were evaluated in a series of five studies. Diversity was assessed in races and inbreds and genetics assessed in diallels, generation mean analyses (GMAs), nearisogenic lines (NILs), and recombinant inbred lines (RILs). High diversity characterized 215 tropical maize races that averaged 27.0 +/- 3.27 TBN and 80 modern inbreds that averaged 14.8 +/- 1.45 TBN. There was a close correlation between TBN values and husk numbers (r = 0.674). Both were much higher in tropical lowlands than in highlands. Correlations of the native elevations of races were r = -0.465 for TBN and r = -0.732 for husk numbers. Reduced tassel size and branch numbers have been viewed as advantages for grain yield, but this could also be attributed to the correlation with husk numbers. The related genetic controls of meristematic activity in tassel and ear are implicated. Heritability studies included an eight-entry diallel, five sets of progenies for GMA analysis, three sets of RILs, and evaluation of 169 NILs of inbred Hi27. A new mutant Brta (branched tassel) on Chromosome 2 was identified that doubled branch numbers. Inbred TBNs were highly correlated with means of their hybrids (r = 0.918); mean square ratios of general combining ability (GCA) to specific combining ability (SCA) averaged 11.2; and heritability values were high (h = 67%) with negligible dominance and epistasis effects. Midparent heterosis for TBN was high (32%). Variances and means were highly correlated (r = 0.677) and CVs low (average 10.4%). The RIL segregations were interpreted on the basis of three or four quantitative trait loci (QTLs) biased by highvariance -mean correlations. Inheritance of TBN is concluded to involve additive polygenic systems that could involve many loci in the genus Zea. Reducing TBN in tropical maize offers little challenge to breeders, but seems of doubtful value.
- 出版日期2015-2
