Combining Ability, Heterosis And Heterotic Patterns Of Tropical, Subtropical And Domestic Maize Germplasm Populations

The study was conducted to analysize combining ability, determine the heterotic grouping and patterns and combining ability of 27 maize(zea.mays L.) populations which were crossed with four domestic maize inbred lines (Dan340, Ye478, Mo 17 and Huangzaosi) in NCII mating design, and out of the 27 maize populations, 14 are tropical and subtropical, and the 13 are domestic populations. The 108 (27×4) testcrosses were planted in Ya'an farm in 2001 and 2002. The 27 populations were clustered into four heterotic groups based on the special combining ability (SCA) with four common testers and heterosis for grain yield, The potential heterotic patterns availble for exotic and domestic population were proposed. The main results were summarized as follows:1 .The study evaluated the major agronomic traits, yields and combining ability of the 27 populations. The results indicated that the 14 tropical and subtropical populations had adaptedto the Ya'an ecological environment, and showed the promising breeding values for important agronomic traits, such as grain yield, standability, they were valuable maize germplasm and could be used to develop the genetic foundation of existing maize germplasm. But the plant is taller, the ear position is a little higher and the rachis is wider for tropical and subtropicalpopulations compared with domestic populations. So,those traits must be focused in the future selection. According to the performance of comprehensive trait, combining ability and heterosis for grain yield in this study, the populations of Suwanl, Pob43, Pob501, Pob32, Pob21 and WBM-C4 were better than others, and possessed the higher utilizing potential.2.The 108 combinations were evaluated by total combining ability (TCA) of grainweight per plant. The results indicated that when breeding to improve parents of combination,it not only considered the general combining ability of special combining ability but their totaleffects, the effects of TCA proved the heterosis of hybridized combination to be better.3.According to the performance of special combining ability and heterosis (relative heterosis) of grain yield, 13 domestic maize populations could be divided into 4 heterotic groups. The first group is Ludahonggu, including Jizong A, Liaoluzong, Zhongzong 3, Dongnong population-C5. The second group is PA, including Yuzong 5. Shanzong 1,Shanzong 3, Zhongzong 14 belong to the third group, Lancaster. Huangzong and WBM-C4belong to the forth group, Sipingtou. In this study^Jinhuanghou and Zhongqun 13 could not be divided into 4 heterotic groups. Compared with then- pedigree, the clustering of heterotic groups is reasonable.4. This paper also studied the clustering of tropical and subtropical maize populations.The results showed that Pob43, Pob501 could be divided into Ludahonggu heterotic group.Stay Green and Pool 19 were divided into Lancaster group. Pob28 and PoM5 had intimategenetic relationship with Sipingtou and Luda Red Cob germplasm. But, in this study, Pob46, Pob69, Pob70, Pob21, Pob32, Pob49, Pob502, Suwanl populations could not be divided into4 domestic heterotic groups.5.Based on the grain yield (contributing character) of all combinations, ten heterotic patterns have been obtained from this study, they are SuwanlxPA, Pob43×PA, Pob32×FA, Pob501×FA, Pob21×PA, Suwanl×Ludahonggu, SuwanlxLan., Pob43×Lan., Pob28×PA, HuangzongxpA.