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Various pests, such as those in the order Lepidoptera, frequently feed on young maize (Zea mays) plants and pose a significant threat to plant development and survival. To manage this problem, maize generates a wide variety of responses to attack by pests, from activation of wound-response pathways to the release of volatile compounds. Mp708, an inbred line resistant to feeding by the larvae of the fall armyworm (Spodoptera frugiperda J.E. Smith Lepidoptera: Noctuidae), has been developed through traditional breeding methods, but its underlying mechanisms of resistance are still not completely understood. Mp708 has been shown to have a moderately high constitutive expression of jasmonic acid (JA) before infestation by fall armyworm. However, Tx601, a genotype susceptible to feeding by fall armyworm, activates JA pathway only in response to feeding, suggesting that Mp708 is "primed" to respond swiftly to an attack. Current research indicates that fall armyworm show a lack of preference to feeding on Mp708, leading to the hypothesis that volatiles constitutively released by the plant may also play an important role in its resistance. Analysis of volatiles released by Mp708 and Tx601 in the presence and absence of fall armyworm larvae identified (E)-β-caryophyllene, a terpenoid associated with resistance, released constitutively in Mp708. Fall armyworm fed samples of both Mp7O8 and Tx601 showed high transcript number of tps23, the gene responsible for the synthesis of (E)-β-caryophyllene. In addition, fall armyworm larvae show a preference for Tx601 whorl tissue over Mp708 tissue, and the dosage of Tx601 whorl with (E)-β-caryophyilene repels the fall armyworm. [ABSTRACT FROM AUTHOR]

A maize synthetic population was improved for resistance to the Mediterranean corn borer (MCB, Sesamia nonagrioides) while maintaining yield. The objectives of this research were to investigate whether yield and yield stability of the maize synthetic population named EPS12 were affected by selection for MCB resistance; also to determine which genotypic and environmental covariates could explain the genotype (G), environment (E) and genotype × environment (GE) effects for yield under corn borer infestation. Plants from three cycles of selection and their testcrosses to three inbred testers (A639, B93 and EP42) were evaluated at two locations in 2 years, under MCB and European corn borer infestations. After selection EPS12 was a more stable genotype. Hybrids derived from crosses between B93 and inbreds obtained from the initial cycles of selection could be recommended for cultivation in northern Spain. The yield of crosses between cycles of selection and testers increased when there were fewer days with temperatures >25°C and higher mean maximum temperatures. Differences in yield among these genotypes were mostly explained by resistance to corn borer attack. In general, among EPS12-derived materials, genetic characteristics that contribute to increased grain yield were also responsible for increased abiotic stress tolerance. [ABSTRACT FROM AUTHOR]

Sesamia nonagrioides causes high yield losses in maize in northwestern Spain. Therefore, a recurrent selection programme to improve resistance against this pest has been carried out in a maize synthetic population. The main purposes of this investigation were to determine which are the main components of genetic variance for stem tunnelling and yield under infestation, to determine the variance remaining after selection, and, finally, to establish the genetic relationship between traits used as selection criteria and other ear resistance and agronomic traits. A North Carolina Design I mating system was used. Individual analyses by year were carried out and additive variance was identified as the only significant component of the genetic variance for stem tunnel length while a dominant variance was significant for yield. Those variances have decreased due to selection, but not significantly. Selection could continue for more cycles as there is enough variance. Additive genetic correlation coefficients between tunnel length and yield could not be determined. Thereafter, we propose three different methodologies of the selection to determine the relationship between resistance and yield under infestation. [ABSTRACT FROM AUTHOR]

Our knowledge of the genetics of resistance to the pink stem borer ( Sesamia nonagrioides) in maize ( Zea mays) is restricted to a few crosses among maize inbreds. The objectives of this study were to enlarge our understanding of the genetics of traits related to damage by pink stem borer and yield under infestation and to use generation means analyses to compare per se and testcross performance for detecting epistatic effects. All generations, either per se or crossed to testers, were evaluated in a 10 × 10 triple lattice design under artificial infestation with S. nonagrioides in 2005 and 2006. Most traits fit an additive–dominance model; but evidence for epistasis for resistance and yield under infestation was shown. Epistasis, in general, did not appear to play an important role in the inheritance of yield under pink stem borer infestation. However, the epistasis contribution to maize yield performance could be important in some outstanding crosses such as EP42 × A637. Testcross generation means revealed epistatic effects undetected by the generation means analysis, but neither method was able to eliminate dominance effects that could prevail over epistatic effects. [ABSTRACT FROM AUTHOR]

Abstract: In northwestern Spain, the grounded whole kernel of flint maize (Zea mays L.) landraces is traditionally used for making bread and other bakery products. We have identified some local varieties appropriate for traditional bakery. Thus far, evaluations have been made under low corn borer pressure, but to know their ability to compete for yield and quality in a wider area, evaluations should be done under higher corn borer, specifically targeting Sesamia nonagrioides (Lepidoptera: Noctuidae) and Ostrinia nubilalis (Lepidoptera: Crambidae) pressure. Therefore, the objectives of this study were to explore the stem and ear resistance to corn borer attack of maize landraces already evaluated for yield, kernel, and bread tasting qualities under organic farming conditions and to know possible relationships among yield, quality and corn borer damage traits. No significant correlation coefficients were detected between yield and quality-related traits. Therefore, simultaneous progress for yield and quality could be made. Many varieties providing high yield and kernel density under high insect pressure were similar to the ones selected by the same characteristics under low insect pressure in a previous study. However, under high insect pressure, varieties with less stem and shank damage by S. nonagrioides are recommended for reducing losses and the risk of kernel contamination with fumonisins. Among the late varieties, Bianco Perla would be the most appropriate to obtain high yield along with reduced stem damage by S. nonagrioides and reduced risk of fumonisin contamination. In areas with shorter growing season, EPS12 (T) C3 and Rebordanes would be the most suitable varieties for obtaining high-quality flours under high insect pressure. [Copyright &y& Elsevier]

Popcorn adapted to Spanish conditions could be an interesting and profitable alternative to field corn. However, little is known about breeding popcorn germplasm for adaptation to Spain. Sesamia nonagrioides Lefèvbre is the main insect pest affecting popcorn quality and yield under Spanish growing conditions. The objectives of the study were the search for sources of resistance to & nonagrioides among popcorn germplasm and to study the genetics of the resistance to S. nonagrioides attack. Eight breeding populations along with a five-inbred line diallel and two popcorn commercial checks were evaluated under S. nonagrioides infestation in 2 yr. Significant differences were found among general combining ability (GCA) effects for days to silking, & nonagrioides tunnel length, general appearance of the ear, kernel moisture, and yield. Specific combining ability (SCA) effects were found to be significant for yield and ear damage. Therefore, heterotic patterns among popcorn materials should be taken into account to generate new popcorn hybrids that are not only more productive but also have higher kernel quality. Breeding popcorn populations BSP4APC0 and PSPW1C1 could be base germplasms in a breeding program for obtaining parental inbreds of healthy kernel popcorn hybrids. New inbred lines could be generated from the cross BP1 × BP2 that would have improved GCA and SCA effects for S. nonagrioides resistance when crossed to South American inbreds. [ABSTRACT FROM AUTHOR]