Ricardo Gonçalves Silva

Evaluation of Top-Cross Popcorn Hybrids Using Mixed Linear Model Methodology

The market for popcorn (Zea mays L.) has been continuously growing in Brazil fact has required the development of cultivars adapted to local environmental conditions. For this reason, the analytical objectives of this study were to evaluate top-cross popcorn hybrids in relation to popping expansion and grain yield in three different ecogeographic regions of Brazil, in order to estimate variance components using Restricted Maximum Likelihood (REML) and predict breeding values using Best Linear Unbiased Prediction (BLUP). Genetic evaluation considered a linear model with heterogeneous residual (environmental) variances. The Restricted Likelihood Ratio Test (RLRT) evidenced significant differences (p < 0.01) for the genotypic effect. Grain yield showed a moderate heritable trait (h2 = 0.26-0.39). A higher additive genetic control was evidenced for popping expansion (h2 = 0.58-0.85). Genetic correlations and Spearman coefficient between both traits were negative, indicating that selection based on grain yield would have a negative effect on popping expansion. The top-cross hybrids showed an adequate grain yield, whereas the quality of the popcorn was lower than commercial standards.

Inbreeding depression and genetic components for popping expansion and other traits in Brazilian populations of popcorn

E. Arnhold, J.M.S. Viana, F. Mora, G.V. Miranda, and R.G. Silva. 2010. Inbreeding depression and genetic components in Brazilian populations of popcorn. Cien. Inv. Agr. 37(3):125-132. The aim of the study was to assess inbreeding depression and determine genetic components in landrace populations of popcorn. Six Brazilian popcorn landraces: Amarelo, Beija-Flor, Branco, Rosa-claro, Roxo and Vicosa, were subjected to self-pollination. Experiments with S0 populations and their selfing populations (S1) were conducted in a randomized complete block design. The estimates of inbreeding depression varied from 1.2% (popping expansion) to 79% (grain yield). The gene action was predominantly additive for plant height, ear height and hundred-grain-weight. The dominance genetic effects were important for index of prolificacy and grain yield. The genetic effect of popping expansion was bidirectional with null dominance and a predominance of additive gene effects. Based on these results, it was possible to identify popcorn populations suitable to extract inbred lines, develop hybrids and use in population improvement. The present study also confirmed that popping expansion is a trait that can be improved efficiently by recurrent selection programs of popcorn.

ESTIMATIVAS DE PARÂMETROS GENÉTICOS DA PRODUÇÃO DE GRÃOS DAS POPULAÇÕES DE MILHO UFVM 100 E UFVM 200, SUMETIDAS A DÉFICIT HÍDRICO DAS POPULAÇÕES DE MILHO UFVM 100 E UFVM 200, SUMETIDAS A DÉFICIT HÍDRICO

The large-scale production of Baculovirus to control fall armyworm, Spodoptera frugiperda, presents many limitations. The most important limiting factor is that the baculovirus, which infects fall armyworm, causes liquefaction of the integument immediately after death. This disruption of the integument difficultates the large scale production because dead insect must be frozen before being harvested. This fact implies in high lab work need, increasing the cost of the biopesticide. This problem was overcome by the discovery of a new baculovirus nucleopolyhedrovirus (NPV) isolate in Cascavel/PR, that doesn’t cause liquefaction of the integument (isolate 6NR) immediately after the insect death. This is an extremely important factor in a large-scale baculovirus production. In addition, mortality caused by isolate 6NR on 6-day-old-larvae was above 93% (SEM=0.7%), the average weight dead larva was 116.21 mg (SEM=22.9), the larval equivalent and weight equivalent/ha were 15.04 g (SEM=1.2) and 140.32 larvae (SEM=20.1), respectively.