Amer M A
Department of Agricultural Botany, Faculty of Agriculture (Saba-Basha), Alexandria University, P.O. Box 21531- Bolkley, Alexandria, Egypt.
Commun Agric Appl Biol Sci. 2005;70(3):281-93.
Preharvest of corn and its contamination with aflatoxin is a serious problem. Some environmental and cultural factors responsible for infection and subsequent aflatoxin production were investigated in this study. Stage of growth and location of kernels on corn ears were found to be one of the important factors in the process of kernel infection with A. flavus & A. parasiticus. The results showed positive correlation between the stage of growth and kernel infection. Treatment of corn with aflatoxin reduced germination, protein and total nitrogen contents. Total and reducing soluble sugar was increase in corn kernels as response to infection. Sucrose and protein content were reduced in case of both pathogens. Shoot system length, seeding fresh weigh and seedling dry weigh was also affected. Both pathogens induced reduction of starch content. Healthy corn seedlings treated with aflatoxin solution were badly affected. Their leaves became yellow then, turned brown with further incubation. Moreover, their total chlorophyll and protein contents showed pronounced decrease. On the other hand, total phenolic compounds were increased. Histopathological studies indicated that A. flavus & A. parasiticus could colonize corn silks and invade developing kernels. Germination of A. flavus spores was occurred and hyphae spread rapidly across the silk, producing extensive growth and lateral branching. Conidiophores and conidia had formed in and on the corn silk. Temperature and relative humidity greatly influenced the growth of A. flavus & A. parasiticus and aflatoxin production.
玉米收获前及其被黄曲霉毒素污染是一个严重问题。本研究调查了一些导致感染及随后黄曲霉毒素产生的环境和栽培因素。发现玉米生长阶段和玉米粒在玉米穗上的位置是玉米粒被黄曲霉和寄生曲霉感染过程中的重要因素之一。结果表明生长阶段与玉米粒感染之间呈正相关。用黄曲霉毒素处理玉米会降低发芽率、蛋白质和总氮含量。作为对感染的响应，玉米粒中的总可溶性糖和还原糖增加。两种病原菌都会使蔗糖和蛋白质含量降低。地上部系统长度、幼苗鲜重和幼苗干重也受到影响。两种病原菌都会导致淀粉含量降低。用黄曲霉毒素溶液处理的健康玉米幼苗受到严重影响。它们的叶子先是变黄，进一步培养后变成褐色。此外，它们的总叶绿素和蛋白质含量显著下降。另一方面，总酚类化合物增加。组织病理学研究表明，黄曲霉和寄生曲霉可在玉米花丝上定殖并侵入发育中的籽粒。黄曲霉孢子发生萌发，菌丝迅速在花丝上蔓延，产生大量生长和侧枝。分生孢子梗和分生孢子在玉米花丝内和花丝上形成。温度和相对湿度极大地影响黄曲霉和寄生曲霉的生长以及黄曲霉毒素的产生。
