Conventional resistance of experimental maize lines to corn earworm (Lepidoptera: Noctuidae), fall armyworm (Lepidoptera: Noctuidae), southwestern corn borer (Lepidoptera: Crambidae), and sugarcane borer (Lepidoptera: Crambidae)

Plant resistance is a useful component of integrated pest management for several insects that are economically damaging to maize, Zea mays L. In this study, 15 experimental lines of maize derived from a backcross breeding program were evaluated for resistance to corn earworm, Helicoverpa zea (Boddie); fall armyworm, Spodoptera frugiperda (J. E. Smith); southwestern corn borer, Diatraea grandiosella Dyar; and sugarcane borer, Diatraea saccharalis (F.). Experimental line 100-R-3 was resistant in the field to leaf feeding by fall armyworm and line 116-B-10 was resistant in the field to leaf feeding by fall armyworm and leaf and stalk feeding by southwestern corn borer. When corn earworm larvae were fed field harvested silks from experimental line 81-9-B in the laboratory, their pupal weights were significantly lower than the pupal weights of larvae that were fed silks from the resistant control, Zapalote Chico. Maysin levels lower than those commonly associated with corn earworm resistance were present in the resistant experimental line, 107-8-7, indicating a new basis confers resistance to corn earworm in this line. These resistant experimental lines will provide plant breeders with new sources of resistance to lepidopterous insects for the development of improved maize breeding populations.     

Genetic basis of resistance to fall armyworm (Lepidoptera: Noctuidae) and southwestern corn borer (Lepidoptera: Crambidae) leaf-feeding damage in maize

Leaf-feeding damage by first generation larvae of fall armyworm, Spodopter frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), and southwestern corn borer, Diatraea grandiosella Dyar (Lepidoptera: Crambidae), cause major economic losses each year in maize, Zea mays L. A previous study identified quantitative trait loci (QTL) contributing to reduced leaf-feeding damage by these insects in the maize line Mp704. This study was initiated to identify QTL and their interactions associated with first generation leaf-feeding damage by fall armyworm and southwestern corn borer. QTL associated with fall armyworm and southwestern corn borer resistance in resistant line Mp708 were identified and compared with Mp704. Multiple trait analysis (MTA) of both data sets was then used to identify the most important genetic regions affecting resistance to fall armyworm and southwestern corn borer leaf-feeding damage. Genetic models containing four and seven QTL explained southwestern corn borer and fall armyworm resistance, respectively, in Mp708. Key genomic regions on chromosomes 1, 5, 7, and 9 were identified by MTA in Mp704 and Mp708 that confer resistance to both fall armyworm and southwestern corn borer. QTL regions on chromosomes 1, 5, 7, and 9 contained resistance to both insects and were present in both resistant lines. These regions correspond with previously identified QTL related to resistance to other lepidopteran insects, suggesting that broad-spectrum resistance to leaf feeding is primarily controlled by only a few genetic regions in this germplasm.     

Genetics of resistance to the pink stem borer (Sesamia nonagrioides) in maize (Zea mays)

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.     

Corn borer (Lepidoptera: Noctuidae and Crambidae) resistance of main races of maize from North America

Resistance to corn borers, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) and Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) in maize, Zea mays L., populations is partial, and more resistant populations are needed. The objective of this research was to compare resistance to corn borers of the main maize races from North America. Twenty open-pollinated maize populations belonging to the races Southern Dent, Corn Belt Dent, and Northern Flint, and three check populations, were evaluated under artificial infestation with S. nonagrioides and O. nubilalis. None of the populations had complete resistance. Northern Flint had the lowest yield under corn borer infestation, whereas Southern Dent had the highest yield but also the largest damage. Corn Belt Dent had a shorter growing cycle and similar yield of infected plants than Southern Dent. The checks had intermediate yield and resistance and were not significantly different from Corn Belt Dent for any trait. The Southern Dent populations Tennessee Red Cob and White Dent (PI221885 and PI311232) could be used as sources of tolerance to corn borers, although they are not expected to provide great gains compared with the levels of tolerance already present in some Corn Belt Dent and European Flint populations and would require adaptation to short growing cycle. The Corn Belt Dent synthetic BS17 had the highest yield and general agronomic performance under corn borer infestation, along with Rustler and Silver King, and the European Flint composite EPS13.     

Free phenols in maize pith and their relationship with resistance to Sesamia nonagrioides (Lepidoptera: Noctuidae) attack

The stem borer Sesamia nonagrioides (Lefèbvre) is the most important insect pest of maize, Zea mays L., in northwestern Spain. Among the metabolites present in maize, phenolic compounds could play an important role in resistance. The objective of this work was to determine whether a relationship between phenols and the amount of resistance exists. Amounts of free phenolic compounds in the pith of 13 inbred maize lines that differ in resistance were measured. The phenolic compounds identified were p-coumaric acid, cafeic acid, ferulic acid, vanillic acid, syringic acid, chorogenic acid, sinapic acid, p-hydroxybenzoic acid, and vanillin. The amount of free p-coumaric acid was correlated with the resistance level. Higher quantities of p-coumaric in the pith could contribute to general resistance to stem borer attack. Jointly with ferulic acid, p-coumaric could provide resistance mechanisms through cell wall fortification and lignification. The other compounds showed no or an unclear relationship with resistance. The vanillic acid showed a decreased tendency after silking, when maize is most attractive for S. nonagrioides, suggesting this acid could act as a chemoattractant for S. nonagrioides larvae or adults. Future studies that focus on these phenolic compounds could be useful in understanding S. nonagrioides resistance.     

Sugarcane borer (Lepidoptera: Crambidae) resistance to transgenic Bacillus thuringiensis maize

Transgenic maize, Zea mays L., expressing the Bacillus thuringiensis (Bt) CrylAb toxin has been planted to extensive areas across the United States and several other countries, but no resistance has been documented in field populations oflepidopteran target pests. This article describes the first report of resistance alleles to commercially available Cry1Ab Bt maize in a Louisiana population of sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae). Two hundred thirteen two-parent isolines of D. saccharalis were screened for Cry1Ab resistance on Bt maize leaf tissue using an F2 screening technique. Larvae representing three isolines survived >15 d on Bt tissue in the F2 generation. The second generation backcross progeny (B1F2) derived from isoline 52 completed larval development on Bt maize in the greenhouse. Segregation and resistance frequency analysis associated with isoline 52 suggested that Bt resistance is probably determined by a nearly completely recessive allele at a single locus. With this assumption, the estimated resistance allele frequency in this population is 0.0023, within a 95% confidence interval of 0.0003-0.0064.     

Molecular changes in the maize composite EPS12 during selection for resistance to pink stem borer

The pink stem borer (Sesamia nonagrioides Lefèvbre) is the most important pest of maize (Zea mays L.) throughout the Mediterranean area. The maize composite EPS12 has been chosen as the base population for a breeding program based on its resistance to pink stem borer, with the main selection criterion being resistance to stem tunneling. Yield was taken as a secondary selection criterion to avoid any unwanted negatively correlated response on this character. The aims of investigation were: (1) to monitor the effects of selection for resistance to pink stem borer on allele frequency at 70 simple sequence repeat (SSR) markers and their impact on the genetic structure of EPS12 and (2) to identify loci at which allelic frequencies changed significantly due to directional selection. Genetic diversity was reduced during the selection process (as expected since random genetic drift as well as selection could reduce genetic variability), but not significantly so. Although the loss of genetic variation was generally consistent with that expected in a model in which random genetic drift acts alone on neutral alleles, the changes observed in the frequency of five alleles were significantly greater than expected. Further, the linear trend of the departure from the random genetic drift model was significant for some allelic versions of two SSR markers, umc1329 and phi076; directional selection was therefore acting on these loci. The significant effect of directional selection on those markers suggests the presence of quantitative trait loci (QTLs) for tunnel length and/or for yield under artificial infestation with Sesamia nonagrioides on the long arm of chromosome 4.     

Effect of environment on resistance to the European corn borer (Lepidoptera: Crambidae) in maize

The European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), is a major pest of maize, Zea mays L., in many temperate parts of the world. Genotype-by-environment interaction effects can make relative performance unpredictable and may hamper selection for resistance to European corn borer. The objective of this study was to determine the effect of environment on genotypic reaction to European corn borer resistance in maize. A set of 12 maize inbred lines was chosen to represent a range of European corn borer responses. Eleven testing environments ranged from Delaware, Ohio, Illinois, Iowa, Nebraska, Missouri, to Mississippi. For length of stalk tunneling, environmental and genotypic main effects (estimated by restricted maximum likelihood) were >20- and 10-fold larger than their interaction effect, respectively. Length of tunneling means for genotypes (across environments) ranged from 10.1 to 35.4 cm. Several putatively resistant genotypes grouped with the susceptible checks, B73 and Mol7. By breaking factors and the interaction into single degree of freedom components, we observed that GEMS-0001 had significant crossover interactions toward less susceptibility in both Mississippi and the Nebraska environments. Environments displaying several crossover interactions indicated that European corn borer screening at these sites would not necessarily apply to other locations, whether due to small differences in experimental conduct and/or environmental effects. The five most resistant genotypes were fairly consistent across environments. Because all environments except Illinois used larvae from the same insectary, and these environments differed in damage intensity and rankings, it is unlikely that insect biotype was a factor contributing to genotype-by-environment effects.     

Inheritance of resistance to ear damage caused by Sesamia nonagrioides (Lepidoptera: Noctuidae) in maize

Sesamia nonagrioides Lefebvre is a major insect pest of maize (Zea mays L.) in northwestern Spain. The inheritance of ear resistance in field corn to this pest has not been studied. This work aims to determine the importance of genetic (additive, dominance, and epistatic effects) and environmental effects in the inheritance of ear resistance to S. nonagrioides. Three field corn inbreds (CM109, EP31, and EP42) were used as parents and two crosses (CM109 x EP31 and CM109 x EP42) were made. These inbreds show different ear resistance levels to S. nonagrioides, with CM109 more resistant than EP31 and EP42. For each cross, parents (P1, P2), F1, F2, and backcrosses to each parent (BC1 and BC2) were evaluated. Correlations among ear damage traits showed that general appearance of the ear should be useful indicator of ear resistance. Ear resistance was dominant to susceptibility and was transmitted from inbreds to their hybrids. The additive-dominance model fit the generation mean analysis for both crosses and the degree of genetic control varied depending on the cross and trait. For both crosses, additive and dominance effects were significant for most ear damage traits. Epistatic gene effects were significant for husk and shank damage, and gene effects for number and length of tunnels were not significant. Because ear resistance involved additive and dominance effects for this set of inbreds, breeding procedures based on both types of gene action should be effective.     

Tolerance of Bt corn (MON 810) to maize stem borer, Chilo partellus (Lepidoptera: Pyralidae)

Transgenic corn (MON 810), expressing the Bacillus thuringiensis (Bt) protein, Cry1Ab, was evaluated under greenhouse conditions for its tolerance to the maize stem borer, Chilo partellus. Bt corn (MON 810) provided effective protection against the stem borer even under a high level of larval infestation in the greenhouse. The observed tolerance is examined and discussed in the light of the susceptibility of C. partellus to the Cry1Ab protein in laboratory bioassays. The implications of the tissue concentrations of Cry1Ab in MON 810, and baseline susceptibility recorded in the current study, for insect-resistance management are discussed.     

Antibiosis of the pith maize to Sesamia nonagrioides (Lepidoptera: Noctuidae)

Thirteen inbred lines of maize (Zea mays L.) with different levels of stem resistance to the stem borer Sesamia nonagrioides Lefevbre were evaluated in the field and the laboratory to determine the antibiotic resistance to this pest. Inbreds CM151, CO125, and EP39 had antibiotic pith as well as stem resistance, so the pith could play a role in stem resistance. Inbreds A509, F473, and PB130 did not have antibiotic pith but had stem resistance; therefore, other mechanisms could confer stem resistance. Finally, the inbred MS1334 had antibiotic pith and did not show stem resistance; thus, other factors could compensate the effect of the pith. Therefore, although pith antibiotic compound seems to play a role in the defense against S. nonagrioides attack, it is not the only possible mechanism of defense.     

Rapid antibody-based field test to distinguish between Helicoverpa armigera (Lepidoptera: Noctuidae) and Helicoverpa punctigera (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) are the two most important insect pests of cotton production in Australia and require application of insecticides to control them. H. armigera has developed resistance to several insecticides but H. punctigera has not. Cost-effective management of insecticide resistance requires that growers be able to determine the proportion of H. armigera eggs or young larvae present on their crop before applying insecticides. This is impossible visually. We generated two monoclonal antibodies that reacted with the insect protein "lipophorin" and were capable of discriminating individuals of the two species at all life-stages. The antibodies were incorporated into a rapid test kit that was tested under field conditions over two growing seasons. Results obtained with the kit agreed closely with those obtained by rearing larvae through to second instar.     

Effect of husk characters on resistance to corn earworm (Lepidoptera: Noctuidae) in high-maysin maize populations

Two maize (Zea mays L.) breeding populations with very high concentrations of maysin, a silk-expressed flavone glycoside, were tested for their ability to resist ear damage by the corn earworm, Helicoverpa zea Boddie, under field conditions. Tests were conducted in 2000 and 2001 at multiple locations in Georgia. The high maysin populations, EPM6 and SIM6, as well as resistant and susceptible checks, were scored for silk-maysin content, H. zea damage, and husk characters. In 2000, there was a negative correlation between husk tightness and earworm damage at three of five locations, while there was no significant correlation between damage and maysin content at any location. In 2001, EPM6 and SIM6 had approximately ten times the maysin content of the low-maysin control genotypes; nevertheless, earworm damage to EPM6 and SIM6 was either greater than or not significantly different from the low-maysin genotypes at all locations. The resistant control genotype, Zapalote Chico, had significantly less earworm damage than EPM6 and SIM6 for both years at all locations. The results of this study highlight the importance of identifying and quantifying husk and ear traits that are essential to H. zea resistance in maize.     

Abundance, dispersion and parasitism of the stem borer Busseola fusca (Lepidoptera: Noctuidae) in maize in the humid forest zone of southern Cameroon

This study was conducted in the humid forest zone of Cameroon, in 2002 and 2003. The main objective was to investigate the effects of intercropping on infestation levels and parasitism of the noctuid maize stem borer Busseola fusca Fuller. Two trials were planted per year, one during the long and one during the short rainy season. Maize monocrops were compared with maize/legume or maize/cassava intercrops in two spatial arrangements: maize on alternate hills or in alternate rows. Spatial analyses showed that the stemborer egg batches were regularly dispersed in the maize monocrop and aggregated in the intercrops, as indicated by b, the index of dispersion of Taylor's power law. Depending on the crop association and planting pattern, intercrops reduced the percentage of plants with stem borer eggs by 47.4-58.4% and egg densities by 41.2-54.5% compared to monocropped maize. Consequently, larval densities were 44.4-61.5% lower in intercrops compared to monocrops. Intercropping maize with non-host plants did not affect larval parasitism. Up to two-fold higher levels of egg parasitism by scelionid Telenomus spp. were recorded in inter- compared to monocrops during the short rainy seasons of 2002 and 2003. No differences were found among the mixed cropping treatments and parasitism was lower during the long compared to the short rainy seasons. It was proposed that differences in levels of parasitism were due to density dependence effects rather than the effect of the presence of non-host plants in the system.     

Phylogeography and population genetics of the maize stalk borer Busseola fusca (Lepidoptera, Noctuidae) in sub-Saharan Africa

The population genetics and phylogeography of African phytophagous insects have received little attention. Some, such as the maize stalk borer Busseola fusca, display significant geographic differences in ecological preferences that may be congruent with patterns of molecular variation. To test this, we collected 307 individuals of this species from maize and cultivated sorghum at 52 localities in West, Central and East Africa during the growing season. For all collected individuals, we sequenced a fragment of the mitochondrial cytochrome b. We tested hypotheses concerning the history and demographic structure of this species. Phylogenetic analyses and nested clade phylogeographic analyses (NCPA) separated the populations into three mitochondrial clades, one from West Africa, and two--Kenya I and Kenya II--from East and Central Africa. The similar nucleotide divergence between clades and nucleotide diversity within clades suggest that they became isolated at about the same time in three different refuges in sub-Saharan Africa and have similar demographic histories. The results of mismatch distribution analyses were consistent with the demographic expansion of these clades. Analysis of molecular variance (amova) indicated a high level of geographic differentiation at different hierarchical levels. NCPA suggested that the observed distribution of haplotypes at several hierarchical levels within the three major clades is best accounted for by restricted gene flow with isolation by distance. The domestication of sorghum and the introduction of maize in Africa had no visible effect on the geographic patterns observed in the B. fusca mitochondrial genome.     

Characterization of eight microsatellite loci in the maize stalk borer Busseola fusca Fuller, 1901 (Lepidoptera: Noctuidae)

The noctuid stem borer Busseola fusca occurs throughout sub‐Saharan Africa, where it is considered as a major pest of corn and sorghum. To understand B. fusca phylogeography, we isolated and characterized eight microsatellite loci in this species. We investigated these loci for polymorphism on a subset sample of individuals from different geographic populations. All loci were polymorphic, showing between four and 10 alleles. Cross‐species amplification of four of these loci was tested on 11 other noctuid species.     

Mass rearing of the pink corn borer, Sesamia cretica Led. (Lepidoptera: Noctuidae) larvae, on semi artificial diets

The effect of two different semi-artificial diets (S.A.D1 and S.A.D2) as well as a natural corn diet on the biology and bionomics of the pink stem borer, Sesamia cretica was studied under laboratory conditions. The insect was successfully mass reared for ten successive generations at the conditions of 27 +/- 2 C degrees and 60-80% R.H. In addition, a photoperiod of 0:24 (L:D) for larvae and 12:12 (L:D) in concern to the other stages, respectively. ALong the ten successive generations, there were no significant differences between the larval periods for both the artificial diets. The S.A.D2 induced the shortest (24.0 days) larval period compared with the natural diet (27.5 days) and S.A.D1 (31.5 days). Rearing larvae on the natural diets revealed a pupal period of 11.0 days, while it was 10.0 days and 8.5 days for the artificial diets (S.A.D1) and in (S.A.D2), in respect. Moth longevity (pre-oviposition, oviposition and post-oviposition periods), to a certain extent, was affected by the larval diets. The maximal moth longevity (13.0 days) was observed for larva reared on corn plants (4, 8 and 1 days). On the other hand, the shortest period (10.5 days) of moth longevity was noticed in SAD2 (1, 9 and 0.5 days). S.A.D1 showed 11.0 days moth longevity (3,7 and 1 days). The longest oviposition period (9.0 days) was recorded in the artificial diet S.A.D2, while it was only 7.0 days in the artificial diet S.A.D1 compared with 8.0 days in case of the natural diet. The number of deposited eggs increased with the progress of the 10 successive generations (G1:G10) from 150 to 265 and from 384 eggs to 564 eggs / female for the S.A.D1 and S.A.D2, in sequence. The highest mean number of deposited eggs per female (564) was for the derived females from larvae fed on the artificial diet in G10 of S.A.D2. The rate of the deposited eggs in S.A.D2 was gradually increased (from 9.70 to 61.14% increase) more than those reared on the natural diet throughout the ten generations. The highest significant percent hatchability (92.69%) has been resulted from the artificial diet SAD2. But, it has been decreased to 85.59% in the artificial diet S.A.D1 in comparison to 65.71% in the natural diet. In addition, the significant shortest total generation period was 44.0 days resulted from the artificial diet S.A.D2, while it was 53.5 and 54.0 days for corn plants and the artificial diet S.A.D1, consequently. In short, results indicated that the S.A.D2 could be considered as a suitable artificial diet for a feasible mass rearing of the pink corn borer, Sesamia cretica led. The S.A.D2 showed the shortest larval, pupal and life span for the generation periods. Moreover, it induced the longest oviposition period and the highest mean number of deposited eggs per female and the highest significant percent of eggs hatchability/fertility. The utilization of this artificial diet (S.A.D2) would supply the researchers with high-quality insects in adequate numbers, at specified times and specific stages of development for the bioassay, toxicological and biological studies.     

Phylogeographic pattern and regional evolutionary history of the maize stalk borer Busseola fusca (Fuller) (Lepidoptera: Noctuidae) in sub-Saharan Africa

Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is one of the major cereal pests in sub-Saharan Africa. Previous phylogeographic investigations on samples collected in Kenya, Cameroon and West-Africa showed the presence of three main clades (W, KI, KII) originated from populations isolated in West and East Africa around one million years ago. Demographic and phylogenetic analyses suggested that this event was followed by local demographic expansion and isolation by distance. These hypotheses were tested by a more comprehensive sampling across B. fusca’s geographic range in Africa. Comparisons of sequences of partial mitochondrial DNA gene (cytochrome b) from 489 individuals of 98 localities in southern, central, eastern and western African countries confirmed the presence of the three main clades. Phylogenetic, F-statistics, demographic parameters and nested clade phylogeographic analyses confirmed that the clades experienced geographic and demographic expansion with isolation by distance after their isolation in three refuge areas. The geographic range of clade KII, already known from East to Central sub-Saharan Africa was extended to Southern Africa. Mismatch distribution analysis and the negative values of Tajima’s D index are consistent with a demographic expansion hypothesis for these three clades. Significant genetic differentiations were revealed at various hierarchical levels by analysis of molecular variance (AMOVA). Hypotheses about the geographic origin of the three main clades are detailed.     

Field resistance in maize cultivars to stem borer Chilo partellus

The Kenyan maize varieties, Hybrid 511, Hybrid 622, Pwani hybrid, Katumani Composite B, and local populations were evaluated along with the varieties of Multiple Insect-Resistant Tropical (MIRT) pool and experimental varieties from The Maize and Wheat Improvement Centre (CIMMYT), Mexico for resistance to the stem borer, Chilo partellus (Swinhoe). The artificial infestation by first-generation C. partellus on maize during the early whorl stage revealed that the leaf feeding damage, the dead heart formation, and the stem damage on the Kenyan hybrids and populations were significantly greater than on the MIRT varieties. The experimental varieties of CIMMYT were also susceptible to C. partellus. When the maize was infested at anthesis, the Kenyan varieties displayed a moderate level of resistance in terms of stem tunnelling and grain damage by C. partellus. The varieties of Multiple Insect Resistance Tropical pool can be effectively used by the breeders to enhance the resistance of agronomically good, but susceptible, varieties of Kenya.     

Southwestern corn borer (Lepidoptera: Crambidae) damage and aflatoxin accumulation in maize

Aflatoxin, a potent carcinogen, is produced by the fungus Aspergillus flavus Link: Fr. Drought, high temperatures, and insect damage contribute to increased levels of aflatoxin contamination in corn, Zea mays L. Plant resistance is widely considered a desirable method of reducing aflatoxin contamination. Germplasm lines with aflatoxin resistance have been developed. This investigation was undertaken to determine whether crosses among these lines exhibited resistance to southwestern corn borer, Diatraea grandiosella Dyar, and to assess the effects of southwestern corn borer feeding on aflatoxin accumulation. Differences in ear damage among southwestern corn borer infested hybrids were significant. Estimates of general combining ability effects indicated that the lines Mp80:04, Mp420, and Mp488 contributed to reduced ear damage, and SC213 and T165 contributed to greater damage when used in hybrids. Mean aflatoxin levels were 254 ng/g for hybrids infested with southwestern corn borer larvae and 164 ng/g for noninfested hybrids in 2000 when environmental conditions were conducive to aflatoxin production. In contrast, the overall mean aflatoxin level for southwestern corn borer infested hybrids was only 5 ng/g in 1999 when environmental conditions did not favor aflatoxin accumulation. Crosses that included lines selected for aflatoxin resistance as parents (Mp80:04 and Mp313E) exhibited lower levels of aflatoxin contamination both with and without southwestern corn borer infestation in 2000. Only the experimental line Mp80:04 contributed significantly to both reduced southwestern corn borer damage and reduced aflatoxin contamination.