Heterose e distâncias genéticas moleculares para a produção de grãos em soja

Abstract

ResumoEm soja, tem sido relatada a ocorrência de heterose para a produção de grãos, e embora a utilização de cultivares híbridas não seja ainda uma realidade nesta espécie, o conhecimento da heterose é importante para uma pré-seleção de cruzamentos, visto que cruzamentos mais heteróticos estão associados a uma maior divergência entre os genitores. Entretanto, a obtenção de sementes F 1 em quantidade suficiente para a avaliação experimental em parcelas é muito difícil e, assim, outros indicadores da ocorrência da heterose poderiam ser muito úteis. Objetivou-se, neste trabalho a avaliação da heterose para a produção de grãos em soja e as suas relações com as distâncias genéticas (DG), obtidas com o marcador molecular AFLP. Seis híbridos F 1 oriundos de cruzamentos com diferentes distâncias genéticas (DG) e os respectivos genitores foram avaliados em experimentos com quatro repetições, empregando o delineamento em blocos ao acaso. Foi observada uma grande variação entre os cruzamentos quanto às heteroses, isso é, de 6,29 a 56,50% em relação à média dos genitores ( mg h ) e de -0,34 a 51,30% em relação ao genitor superior ( gs h ). As correlações entre as distâncias genéticas (DG) e as heteroses foram elevadas (r = 0,83 e 0,60, respectivamente, para mg h e gs h ), indicando que as distâncias genéticas podem ser utilizadas como indicativas de cruzamentos mais divergentes e, consequentemente, como um dos auxiliares na seleção de genitores mais divergentes em soja. Termos para indexação:Glycine max, heterose, distância genética, marcadores AFLP. AbstractHeterosis has been reported for grain yield in soybeans, and despite the fact that hybrid cultivars have not been used yet, the knowledge of heterosis magnitude is very important for a previous selection of crosses, since heterosis is related to parental divergence. However, the obtention of enough F 1 seeds for experimental evaluation in plots is a time-consuming task, and thus, other indicators of the occurrence of heterosis could be very useful. The objective of this work was to evaluate heterosis and its relationship with AFLP molecular genetic distance (DG). Six F 1 hybrids, derived from parents with different levels of genetic distances (DG) and their respective parents, were evaluated in completely randomized block designs, with four replications. Heterosis estimates were very different among different crosses, varying from 6.29 to 56.50% for mid-parent heterosis ( mg h ) and from -0.34 to 51.30% for high-parent heterosis ( gs h ). Besides, the correlation between heterosis and genetic distances (DG) were very high (0.83 and 0.60, respectively, for mg h and gs h ), which indicates that DG can be used as indicative of more divergent crosses, and thus, as one criterion for selection of more divergent parents.

Epistatic effects on grain yield of soybean [Glycine max (L.) Merrill]

“…The experimental precision of the experiments at both locations was satisfactory, with coefficients of experimental variation (CV%) for GY (Table 1) similar to those reported in the literature for the same plot size used in this study (Barona et al 2009, Colombari-Filho et al 2010). The overall mean was 144.1 g plot -1 for Location1 and 203.4 g plot -1 for Location 2, which is the reason for the higher CV% at Location 1 (32.3%) than at Location 2 (23.6%), since the mean squares of the error of both locations were similar.…”

Identification of potential soybean crosses for grain yield in the F2 generation

“…When heterosis is present for quantitative traits such as seed yield, it may indicate that the parents contrast sufficiently so that the diversity between the parents can be captured in a transgressive recombinant progeny (Taliercio et al, 2017). In the F1 generation, Colombari Filho et al (2010) found heterosis ranging from 6 to 57 %. Chaudhary and Singh (1974) also found values above 68 %.…”

Genetic variability among cashew hybrids and prediction of superior combinations based on agronomic performance

“…The expansion of the genetic base is a constant concern in plant breeding, since a narrow genetic base can threaten future genetic gains by selection and increase the potential risk of genetic vulnerability of crops (Carvalho et al, 2008). Thus, the evaluation of genetic distances among elite genotypes, based on the detection of polymorphisms by molecular markers, can generate important information with a view to the broadening of genetic variability by crosses (Colombari Filho et al, 2010). This information is useful for the choice of parents and their combinations to increase heterozygosity and heterotic effect on progenies and, consequently, raise the probability of identifying transgressive genotypes (Dutra Filho et al, 2013).…”