Allozyme polymorphism and relationships to quantitative traits: diversity of 10 local varieties
--Z.X. Zhang, Y.L. Zheng, J.S. Li and J.L. Liu

The North Carolina II mating design was used to evaluate the genetic variation of 10 local varieties (Lanhuazao, Wuxiumi13, Wuxiyumi14, Roulihuang, Xiaomeihuang, Zhuxiyumi, Yinxinhuang, Jingzihuang, Qiyunhuong and Hongtianhua) collected from the Three Gorges area, and four exotic synthetics (BSSSC9, Lancaster, Suwon2, and Meihuang9). The results showed there was abundant additive genetic variability within local varieties. The estimation of combining ability revealed that the value of GCA effects on studied traits was significantly different among the fourteen materials. Lanhuazao, Xiaomeihuang, Zhuxiyumi, Wuxiyumi14 and Roulihuang had positive GCA effects in yield and its component factors. BSSSC9 and Meihuang9 also showed higher GCA effects in most of the quantitative traits, and were exotic elite germplasm. Ten local varieties and four exotic populations were assayed for allozyme variations at 16 enzyme marker loci. Extensive allozyme variability was observed in all materials studied. No locus was monomorphic over all materials. Each of the loci adh1, amy1, cox2, cox3, e1, e8, got1, got2, mdh2, px4, sod1, and sod4 expressed two allozymes. Both acp1 and mdh1 had three allozymes present, and acp4 had four allozymes present. Within local varieties and exotic populations, 1.17 and 1.79 alleles per locus were present, respectively. Got2-6 was present in the local varieties but was not discovered in exotic populations; E8+4.5, Mdh2+5.5 and Sod1+B were observed in four exotic populations but were not observed in local varieties. The proportion of polymorphic loci of local varieties ranged from 50% to 68.75%, the mean value was 63.13%, and the average expected heterozygosity was 0.1919. MRD (Modified Rogers' Distance) based on 16 loci revealed the genetic differences among local varieties (0.148 - 0.391) and between local varieties and exotic populations (0.110 - 0.444). Based on combining ability, heterotic patterns and allozyme variation of the ten local varieties, a suggestion about how to form the basic population which could be used for population improvement has been brought forward. The correlation coefficient between MRD based on per se isozyme loci and quantitative traits of hybrids showed that a chromosome fragment near acp4 and adh1 on 1L is associated with yield per plant directly or indirectly. But there were no relationships between MRD based on 16 allozyme loci and SCA, and between SGD (Specific Genetic Distance) and SCA of yield and other quantitative traits. The results indicated allozyme marker loci were of limited usefulness in predicting heterosis in maize.

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