Windham G L, Williams W P, Davis F M
USDA-ARS, Corn Host Plant Resistance Research Unit, Mississippi State, MS 39762.
Plant Dis. 1999 Jun;83(6):535-540. doi: 10.1094/PDIS.1999.83.6.535.
Field studies were conducted in 1995 to 1997 to determine the effect of the southwestern corn borer (SWCB) on Aspergillus flavus kernel infection and aflatoxin accumulation in maize hybrids. In 1995, when A. flavus conidia were applied to silks in a spray and SWCB neonate larvae in maize cob grits were placed in the leaf axil at the top ear of commercial hybrids, aflatoxin contamination and A. flavus kernel infection were highest in plants treated with both the fungus and the insect. In 1996, using the same inoculation and infestation techniques, aflatoxin levels and kernel infection were much lower than in 1995 and SWCB had no effect on aflatoxin contamination or kernel infection. In another study in 1996, the effect of SWCB on aflatoxin contamination and A. flavus kernel infection in hybrids resistant and susceptible to A. flavus was determined. The inoculation-infestation technique involved applying maize cob grits containing A. flavus conidia and SWCB larvae to silks. When SWCB was combined with A. flavus, aflatoxin levels and kernel infection were dramatically higher than in hybrids inoculated with A. flavus alone, regardless of whether the hybrids were resistant or susceptible to A. flavus. In 1997, the interaction of A. flavus and SWCB was determined on hybrids resistant and susceptible to A. flavus and on a commercial hybrid with and without the Bacillus thuringiensis (Bt) toxin. Maize cob grits were used to inoculate A. flavus and infest SWCB on the silks 7 or 21 days after midsilk (50% of the plants in a row had silks emerged). All four hybrids had the highest levels of Aspergillus spp. kernel infection and aflatoxin contamination when A. flavus and SWCB were applied at 21 days after midsilk. These studies indicate that SWCB can substantially increase aflatoxin levels when combined with A. flavus. However, inoculation and infestation techniques, placement of the fungus and the insect, and timing of inoculation and infestation are all critical in demonstrating a synergistic relationship between A. flavus and SWCB on aflatoxin contamination of maize.
1995年至1997年开展了田间研究，以确定西南玉米螟（SWCB）对玉米杂交种中黄曲霉籽粒感染及黄曲霉毒素积累的影响。1995年，当将黄曲霉分生孢子以喷雾形式施用于花丝，并将装有玉米螟初孵幼虫的玉米芯粗粒放置在商业杂交种顶部果穗的叶腋处时，同时用真菌和昆虫处理的植株中黄曲霉毒素污染和黄曲霉籽粒感染最为严重。1996年，采用相同的接种和侵染技术，黄曲霉毒素水平和籽粒感染率远低于1995年，且西南玉米螟对黄曲霉毒素污染或籽粒感染没有影响。在1996年的另一项研究中，确定了西南玉米螟对黄曲霉抗性和敏感的杂交种中黄曲霉毒素污染及黄曲霉籽粒感染的影响。接种-侵染技术包括将含有黄曲霉分生孢子和玉米螟幼虫的玉米芯粗粒施用于花丝。当西南玉米螟与黄曲霉同时存在时，无论杂交种对黄曲霉是抗性还是敏感，黄曲霉毒素水平和籽粒感染率均显著高于仅接种黄曲霉的杂交种。1997年，在对黄曲霉抗性和敏感的杂交种以及有和没有苏云金芽孢杆菌（Bt）毒素的商业杂交种上，确定了黄曲霉与西南玉米螟的相互作用。在吐丝中期（一行中50%的植株已抽出花丝）后7天或21天，用玉米芯粗粒接种黄曲霉并侵染西南玉米螟于花丝上。当在吐丝中期后21天同时施用黄曲霉和西南玉米螟时，所有四个杂交种的曲霉菌属籽粒感染水平和黄曲霉毒素污染程度最高。这些研究表明，西南玉米螟与黄曲霉共同作用时可大幅提高黄曲霉毒素水平。然而，接种和侵染技术、真菌和昆虫的放置位置以及接种和侵染时间，对于证明黄曲霉与西南玉米螟在玉米黄曲霉毒素污染方面的协同关系均至关重要。
