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, Amarelao, Criolao, Caiano Rajado, Branco Oito Carreiras, Branco Roxo Indio, Cateto Branco, and Argentino Amarelo. The tester 'BRS Planalto' and the topcross hybrids Branco Oito Carreiras x 'BRS Planalto' and Criolao 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 Criolao 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.