Popcorn genotypes resistance to fall armyworm

Abstract

The aim of this study was to evaluate popcorn genotypes for resistance to the fall armyworm, Spodoptera frugiperda. The experiment used a completely randomized design with 30 replicates. The popcorn genotypes Aelton, Arzm 05 083, Beija-Flor, Colombiana, Composto Chico, Composto Gaúcha, Márcia, Mateus, Ufvm Barão Viçosa, Vanin, and Viviane were evaluated,along with the common maize variety Zapalote Chico. Newly hatched fall armyworm larvae were individually assessed with regard to biological development and consumption of food. The data were subjected to multivariate analyses of variance and genetic divergence among genotypes was evaluated through the clustering methods of Tocher based on generalized Mahalanobis distances and canonical variable analyses. Seven popcorn genotypes, namely, Aelton, Arzm 05 083, Composto Chico, Composto Gaúcha, Márcia, Mateus, and Viviane,were shown to form a cluster (cluster I) that had antibiosis as the mechanism of resistance to the pest. Cluster I genotypes and the Zapalote Chico genotype could be used for stacking genes for antibiosis and non-preference resistance.

Selection of popcorn genotypes tolerant toSpodoptera frugiperdaand key traits related to the identification of tolerance

“…Multivariate techniques to select traits related to S. frugiperda tolerance in popcorn genotypes were also used by [7, 17] and as in this study, the application of multivariate analysis allowed a significant reduction in the number of traits. This raises the chances of a more effective selection, since the smaller number of traits prevents the effect of interrelationships among them, avoiding redundancy and mistakes in the process of selecting promising genotypes [8].…”

“…The other cultural treatments were applied as required for full crop development, without using any other chemical product, so as not to affect larva growth. The corn leaves used to feed the larvas were collected when the plants were in the eight-leaf (V8) stage, so that all genotypes were evaluated when the plants were in the same developmental stage [6,7,17]. to feed the larvas and the biological parameters were evaluated daily.…”

“…The corn leaves used to feed the larvas were collected when the plants were in the eight-leaf (V8) stage, so that all genotypes were evaluated when the plants were in the same developmental stage [6, 7, 17].…”

“…In view of the concern to reduce or even eliminate insecticide applications and only a few of studies involving S. frugiperda tolerance in popcorn, breeding programs ought to intensify studies to the selection of tolerant popcorn genotypes, as well as to elucidate key traits related to the identification of tolerance [6,7]. Although some traits related to identification of S. frugiperda tolerance, e.g., larval stage duration, final and mean larva weight, consumption rates and leaf area consumed have been studied in maize breeding programs [7], they have not yet been conclusively proven and used as key traits. A likely reason may be that the trials were analyzed based on a univariate and inconclusive approach.…”

“…The high cophenetic correlation coefficient (CCC = 0.93) indicated an optimal fit between the original data and the dissimilarity matrix and high accuracy of the experimental results. The dendrogram shows two main groups, making the discrimination of the tolerance and/or susceptibility of each genotype group possible[1,5,23].The first group contained the variety Zapalote Chico, considered by several authors as tolerant to S. frugiperda[7,13,17], and variety Arachida. The varieties Composto Gaúcho, UEM J1 and Composto Márcia were grouped in the second(Figure 1).…”