Alternativas para obtenção de híbridos intervarietais de milho

Abstract

Sowing in the second crop extends from January to the end of March, however, it should be carried out as early as possible, given that weather conditions, especially rainfall, sharply reduce from March onwards, thus increasing the risk of cultivation. of corn in succession to soybean. In this sense, producers have chosen to allocate less investment in this modality of rainfed cultivation, minimizing the economic risks with the use of lower cost seeds. Among the lowest cost seed options is the use of intervarietal hybrids (HI). In view of the above, the objective was to evaluate alternatives for obtaining the parents aiming at the production of intervarietal hybrids, based on information from the reciprocal recurrent selection program involving populations A and B or C and D. Four populations were used to carry out the work in Hardy-Weinberg equilibrium. In 2018, the four fields A, B, C and D were obtained. At the time of flowering, prolific plants were identified and from each plant S1 and FS progenies were obtained. In the second crop of 2019, the FS progenies were evaluated in two locations: Lavras and Nazareno -MG. After joint analysis of grain yield data from FS progenies, from both populations, AxB and CxD, the 20 best were identified. The intercrossing was performed simultaneously, obtaining the intrapopulation and interpopulation populations. In obtaining the parents (intrapopulation) the different proportions of inbred progenies (1, 2, 5, 10, 15 and 20) were considered. Simultaneously, the pairs of plants from the different populations (A, B, C and D) were intercrossed to obtain the HI's. In the 2020/21 harvest, the hybrid evaluation experiments were implemented. The six intervarietal hybrids (HI) obtained from each population were evaluated in contiguous AB and CD experiments, using common controls. Ten treatments were evaluated in a complete randomized block design with three replications in four environments: Lavras, Nazareno, Ijaci and Lambari-MG. Data from each location of the AB and CD populations were subjected to combined analysis. Other experiments were carried out in the same season, with 18 treatments, in order to obtain an estimate of heterosis: six HI's and the 12 parents obtained according to the number of inbred progenies involved in obtaining the parents. It was found that the estimates of genetic variance among the Full Sib (FS) progenies were significant, indicating the existence of variability among the progenies and the possibility of success with selection; Although no significant difference was observed between the HI's, there was a tendency for the HI with a smaller number of parents to present a better performance, including some of them with productivity equivalent to commercial HS widely cultivated in the region; The heterosis estimates, manifested in each HI, were higher when a smaller number of progenies was used to constitute the parent population of the hybrid; The association of SRR programs and obtaining HI's is promising because simultaneously it is possible to obtain new HI's superior to the pre-existing ones and to continue the SRR aiming at improving the heterosis between populations.