Genetic variation in testcrosses of European maize inbreds for resistance to the European corn borer and relations to line per se performance

Abstract

The European com borer (ECB) Ostrinia nubilalis H. is a major pest in World maize Zea mays L. production. Objectives of this study were to (1) investigate the genotypic variance and covariance in testcrosses of European flint and dent inbreds for ECB resistance and agronomic traits, and (2) estimate the correlation between line per se and testcross performance for ECB resistance traits. A total of 16 flint and 24 dent inbreds and their testcrosses with two testers from the opposite germplasm pool were evaluated in four and three German environments, respectively. Using artificial infestation with ECB larvae, resistance was assessed by damage rating of stalks, tunnel length in dissected stalks, and relative yield of infested plots compared with protected plots. Yield losses due to ECB damage in testcross hybrids amounted to 40%. Significant genotypic variances between flint and dent lines and high heritabilities were found for damage rating of stalks for both line per se and testcross performance. Heritabilities were low or intermediate for tunnel length and relative grain yield. Correlations between line per se and testcross performance were tight for the damage rating of stalks and moderate for tunnel length and relative yield in both flint and dent germplasm. For damage rating of stalks, per se performance of lines tested in a few environments can be used to predict their testcross performance. In contrast, assessment of testcross performance for tunnel length and relative yield requires evaluating testcrosses with several testers in multi-environment trials.

Breeding maize as biogas substrate in Central Europe: II. Quantitative-genetic parameters for inbred lines and correlations with testcross performance

“…The very strong estimates of r g (LP, GCA) for DTS (0.97) and DMC (0.94) are in accordance with the preponderance of additive gene action reported to be present for DTS (Buckler et al 2009) and DMC in forage maize (Lübberstedt et al 1997). High estimate of r g (LP, GCA) for PHT (0.80) agrees with earlier results on forage (Kreps et al 1998) and grain maize (Mihaljevic et al 2005). Concentrations of fat, starch, ADF, and ADL, which had estimates of r g (LP, GCA) intermediate to those of DTS and DMY (0.81-0.89), were largely determined by the ear proportion and, therefore, also by DTS.…”

“…Estimates of r g between LP and TP depend on the predominant type of gene action (Hallauer and Miranda 1988;Mihaljevic et al 2005;Smith 1986) and, therefore, vary for different traits. For forage maize, correlations between LP and TP for DMY, days to silking (DTS) and various quality traits ranged from moderate to strong (Argillier et al 1995;Gurrath et al 1991;Kreps et al 1998;Seitz et al 1992). Thus, estimates of r g between LP and TP for novel traits like MFY and MY, which are important for biogas maize, are needed to develop optimum breeding strategies.…”

QTL mapping for European corn borer resistance (Ostrinia nubilalis Hb.), agronomic and forage quality traits of testcross progenies in early-maturing European maize (Zea mays L.) germplasm

“…In a set of 16 European flint and 24 dent lines, correlations between per se and TC performance were high for stalk damage ratings, but low for tunnel length and yield reduction caused by larvae feeding (Kreps et al 1998). In tropical maize the association between per se and TC performance was low for corn borer resistance (Thome et al 1992).…”

“…This tester was selected based on its high level of susceptibility to ECB larvae feeding combined with otherwise good agronomic performance (Schulz et al 1997). In the case of a susceptible tester, specific interactions of the tester and segregating alleles facilitate the detection of new QTL (Kreps et al 1998). In addition, this finding might be due to the low power of QTL detection in the per se and TC evaluations as a result of the relatively small population size (N<210), the low to moderate heritabilities for the evaluated ECB resistance traits, and the fact that per se and TC evaluations were performed in different environments.…”

“…Little information is available on the correlation between line per se and hybrid performance for ECB resistance in temperate maize germplasm. Correlations between per se and TC performance were high for stalk damage ratings, but low for tunnel length and yield reduction caused by ECB larvae feeding (Kreps et al 1998). In tropical maize the association between per se and TC performance was low for corn borer resistance (Thome et al 1992;Groh et al 1998) and the consistency of QTL mapped for per se and TC performance was poor.…”