Spatial Patterns of Aflatoxin Levels in Relation to Ear-Feeding Insect Damage in Pre-Harvest Corn

Key impediments to increased corn yield and quality in the southeastern US coastal plain region are damage by ear-feeding insects and aflatoxin contamination caused by infection of Aspergillus flavus. Key ear-feeding insects are corn earworm, Helicoverpa zea, fall armyworm, Spodoptera frugiperda, maize weevil, Sitophilus zeamais, and brown stink bug, Euschistus servus. In 2006 and 2007, aflatoxin contamination and insect damage were sampled before harvest in three 0.4-hectare corn fields using a grid sampling method. The feeding damage by each of ear/kernel-feeding insects (i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs), and maize weevil population were assessed at each grid point with five ears. The spatial distribution pattern of aflatoxin contamination was also assessed using the corn samples collected at each sampling point. Aflatoxin level was correlated to the number of maize weevils and stink bug-discolored kernels, but not closely correlated to either husk coverage or corn earworm damage. Contour maps of the maize weevil populations, stink bug-damaged kernels, and aflatoxin levels exhibited an aggregated distribution pattern with a strong edge effect on all three parameters. The separation of silk- and cob-feeding insects from kernel-feeding insects, as well as chewing (i.e., the corn earworm and maize weevil) and piercing-sucking insects (i.e., the stink bugs) and their damage in relation to aflatoxin accumulation is economically important. Both theoretic and applied ramifications of this study were discussed by proposing a hypothesis on the underlying mechanisms of the aggregated distribution patterns and strong edge effect of insect damage and aflatoxin contamination, and by discussing possible management tactics for aflatoxin reduction by proper management of kernel-feeding insects. Future directions on basic and applied research related to aflatoxin contamination are also discussed

Registration of the Maize Population Zapalote Chico 2451F

Zapalote Chico 2451F (ZC-2451F) (Reg. no. GP-370, PI 618810), a maize (Zea mays L.) germplasm population was released in April 2001 by the Florida Agricultural Experiment Station and the USDA-ARS Crop Genetics and Breeding Research Unit. This population was released as a source of improved resistance to silk and ear feeding by larvae of the corn silk fly [Euxesta stigmatias Loew. (Diptera: Otitidae)], the fall armyworm [Spodoptera frugiperda (J.E. Smith)], and the corn earworm [Heliocoverpa zea (Boddie) (Lepidoptera: Noctuidae)]. Zapalote Chico 2451F is distinct from Shrunken Zapalote Chico (ZC-sh2) (PI 612343), and the Zapalote Chico land race collected in the state of Oaxaca, Mexico, in the late 1940s, and first acceded to the National Seed Storage Laboratory as PI 217413 (Scully et al., 2000; Anderson, 1959; Straub and Fairchild, 1970). PI 217413 was one of the earliest Zapalote Chico populations identified as a source of natural compounds with insecticidal properties (Wais et al., 1979;Wilson and Wiseman, 1988). Resistance in Zapalote Chico 2451F is also due to elevated levels of the flavone glycoside maysin that is found in fresh silk (Ellinger et al., 1980; Snook et al., development of new germplasms or parental lines. 1993, 1995). Maysin is synthesized in the flavonoid pathway W.L. Rooney and known to specifically confer antibiosis-based resistance to silk feeding (Byrne et al., 1996)

Cytochrome P450-derived eicosanoids: the neglected pathway in cancer

Endogenously produced lipid autacoids are locally acting small molecule mediators that play a central role in the regulation of inflammation and tissue homeostasis. A well-studied group of autacoids are the products of arachidonic acid metabolism, among which the prostaglandins and leukotrienes are the best known. They are generated by two pathways controlled by the enzyme systems cyclooxygenase and lipoxygenase, respectively. However, arachidonic acid is also substrate for a third enzymatic pathway, the cytochrome P450 (CYP) system. This third eicosanoid pathway consists of two main branches: ω-hydroxylases convert arachidonic acid to hydroxyeicosatetraenoic acids (HETEs) and epoxygenases convert it to epoxyeicosatrienoic acids (EETs). This third CYP pathway was originally studied in conjunction with inflammatory and cardiovascular disease. Arachidonic acid and its metabolites have recently stimulated great interest in cancer biology; but, unlike prostaglandins and leukotrienes the link between cytochome P450 metabolites and cancer has received little attention. In this review, the emerging role in cancer of cytochrome P450 metabolites, notably 20-HETE and EETs, are discussed

The Present and Future Role of Insect-Resistant Genetically Modified Maize in IPM

Commercial, genetically-modified (GM) maize was first planted in the United States (USA, 1996) and Canada (1997) but now is grown in 13 countries on a total of over 35 million hectares (\u3e24% of area worldwide). The first GM maize plants produced a Cry protein derived from the soil bacteriumBacillus thuringiensis (Bt), which made them resistant to European corn borer and other lepidopteran maize pests. New GM maize hybrids not only have resistance to lepidopteran pests but some have resistance to coleopteran pests and tolerance to specific herbicides. Growers are attracted to the Btmaize hybrids for their convenience and because of yield protection, reduced need for chemical insecticides, and improved grain quality. Yet, most growers worldwide still rely on traditional integrated pest management (IPM) methods to control maize pests. They must weigh the appeal of buying insect protection “in the bag” against questions regarding economics, environmental safety, and insect resistance management (IRM). Traditional management of maize insects and the opportunities and challenges presented by GM maize are considered as they relate to current and future insect-resistant products. Four countries, two that currently have commercialize Bt maize (USA and Spain) and two that do not (China and Kenya), are highlighted. As with other insect management tactics (e.g., insecticide use or tillage), GM maize should not be considered inherently compatible or incompatible with IPM. Rather, the effect of GM insect-resistance on maize IPM likely depends on how the technology is developed and used

Registration of the Maize Population Zapalote Chico 2451F

Zapalote Chico 2451F (ZC-2451F) (Reg. no. GP-370, PI 618810), a maize (Zea mays L.) germplasm population was released in April 2001 by the Florida Agricultural Experiment Station and the USDA-ARS Crop Genetics and Breeding Research Unit. This population was released as a source of improved resistance to silk and ear feeding by larvae of the corn silk fly [Euxesta stigmatias Loew. (Diptera: Otitidae)], the fall armyworm [Spodoptera frugiperda (J.E. Smith)], and the corn earworm [Heliocoverpa zea (Boddie) (Lepidoptera: Noctuidae)]. Zapalote Chico 2451F is distinct from Shrunken Zapalote Chico (ZC-sh2) (PI 612343), and the Zapalote Chico land race collected in the state of Oaxaca, Mexico, in the late 1940s, and first acceded to the National Seed Storage Laboratory as PI 217413 (Scully et al., 2000; Anderson, 1959; Straub and Fairchild, 1970). PI 217413 was one of the earliest Zapalote Chico populations identified as a source of natural compounds with insecticidal properties (Wais et al., 1979;Wilson and Wiseman, 1988). Resistance in Zapalote Chico 2451F is also due to elevated levels of the flavone glycoside maysin that is found in fresh silk (Ellinger et al., 1980; Snook et al., development of new germplasms or parental lines. 1993, 1995). Maysin is synthesized in the flavonoid pathway W.L. Rooney and known to specifically confer antibiosis-based resistance to silk feeding (Byrne et al., 1996)