ABSTRACT In the present study it is hypothesized that the germplasm of popcorn of tropical regions shows resistance to FAW, and the multivariate analysis can characterize the main traits of this resistance. Thus, the aim of this study was to identify key traits used to select fall armyworm resistance in popcorn by using factor and cluster analyses. Sixteen biological traits were evaluated at larval and pupae stages: total number of armyworm, time larval period, final mass of caterpillars, total mass of caterpillars, mean mass of caterpillars, pupae period, mass of pupae and some indices used to evaluate the food consumed by the caterpillars. Multicollinearity diagnosis, factor and canonical analysis, and the genetic divergence among the genotypes were performed to implement multivariate analysis. The groups were established according to Mojena (1977). After multicollinearity test, only five traits were retained for further analysis. The factor analysis divided the five traits into two factors: the first factor included time larval period, metabolized food and mass of pupae; the second was composed of total number of armyworm and stool mass. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) grouped the eighteen genotypes in three clusters. The present study provides insights of popcorn resistance to fall armyworm, and the multivariate analytical approach used here is directly applicable to any species and set of traits exhibiting correlation.
The objectives of this study were to identify promising popcorn lines and hybrids for genetic resistance to tropical rust (Tr, Physopella zeae) in diallel crosses of nine lines derived from a large part of Brazilian popcorn germplasm and to estimate genetic parameters for Tr resistance. Crosses and checks were tested in a random block design, with artificial inoculations under greenhouse conditions. Plots consisted of a single 14-L pot, with four plants. Tr was measured by severity and area under the disease progress curve. Data was analyzed by Griffing's diallel model, and genetic parameters were estimated. Heritability estimates to Tr resistance was medium. Specific combining ability-SCA had significant effects (P<0.10) for resistance, and was eight to nine times larger than general combining ability-GCA (P>0.10). This indicated the major importance of non additive gene effects. In general, breeding possibilities for resistance was restricted. The line 9 (L7.4) had the most outstanding GCA for resistance to Tr, and hybrids 1×7 and 3×6 had outstanding SCA and were recommended for breeding.
Os objetivos deste estudo foram identificar linhagens e híbridos de milho-pipoca promissores quanto à resistência genética à ferrugem tropical (Ftrop, Physopella zeae) em cruzamentos dialélicos, envolvendo nove linhagens derivadas de uma grande parte do germoplasma brasileiro de milho-pipoca, e estimar parâmetros genéticos envolvendo a resistência à Ftrop. Cruzamentos e testemunhas foram testados em delineamento de blocos ao acaso, sob condições de casa-de-vegetação e inoculação artificial. As parcelas consistiram de um vaso de 14 litros, com quatro plantas. A Ftrop foi avaliada pela severidade e pela área abaixo da curva de progresso da doença. Os dados foram analisados pelo modelo dialélico de Griffing e parâmetros genéticos foram estimados. As estimativas de herdabilidade foram médias. A capacidade específica de combinação-CEC teve efeito significativo (P<0,10) para a resistência e foi oito a nove vezes maior que a capacidade geral de combinação-CGC (P>0,10). Isso indicou que os efeitos gênicos não aditivos foram mais importantes. Em geral, as possibilidades de melhoramento foram restritas. A linhagem 9 (L7.4) teve a mais destacada CGC para a resistência e os híbridos 1×7 e 3×6 tiveram destacada CEC e foram recomendados para melhoramento.