Heterosis and genetic distance in intervarietal corn hybrids

Abstract: The objective of this work was to evaluate the performance of intervarietal corn (Zea mays) hybrids with topcross crosses between landrace populations, and to confirm whether genetic dissimilarity between populations is correlated with the heterosis of the intervarietal hybrids in the field. Nine topcross hybrids were evaluated with their tester 'BRS Planalto', and the following landrace populations were used as parents: Argentino Branco, Dente de Ouro, Amarelão, Criolão, Caiano Rajado, Branco Oito Carreiras, Branco Roxo Índio, Cateto Branco, and Argentino Amarelo. The tester 'BRS Planalto' and the topcross hybrids Branco Oito Carreiras x 'BRS Planalto' and Criolão x 'BRS Planalto' showed higher per se potential for grain yield. The topcross hybrid Branco Oito Carreiras x 'BRS Planalto' showed a better performance for number of grains per row, grain weight, and ear diameter, whereas Criolão x 'BRS Planalto' displayed a better performance for the number of grains per row and ear length. Greater estimates of genetic distance did not necessarily result in greater heterosis values and were exclusively correlated with grain ear length. Therefore, it is not possible to predict the effects of high heterosis on grain yield, based on the genetic distance between the populations involved in the crosses.

摘要：本研究旨在评估以地方品种群体为亲本开展顶交（topcross）所获得的玉米（Zea mays）品种间杂交组合的表现，并验证群体间遗传差异与田间品种间杂交种的杂种优势（heterosis）是否存在相关性。本试验共评价了9个以测验种（tester）'BRS Planalto'为共同父本的顶交杂交组合，所用地方品种亲本包括：Argentino Branco、Dente de Ouro、Amarelão、Criolão、Caiano Rajado、Branco Oito Carreiras、Branco Roxo Índio、Cateto Branco以及Argentino Amarelo。测验种'BRS Planalto'以及顶交组合Branco Oito Carreiras × 'BRS Planalto'、Criolão × 'BRS Planalto'自身具备较高的籽粒产量潜力。其中，顶交组合Branco Oito Carreiras × 'BRS Planalto'在每行粒数、粒重及穗径性状上表现更优，而Criolão × 'BRS Planalto'则在每行粒数和穗长性状上表现更佳。群体间遗传距离越大，并不必然对应更高的杂种优势值，且仅与穗长相关。因此，无法仅依据杂交组合所涉及的群体间遗传距离，预测其强杂种优势对籽粒产量的效应。