Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)Preharvest temperaturesIn the field, moisture and temperature are obviously confounded, since elevatedtemperatures increase poant development rates, evaporation and water utilization. Althoughlaboratory temperature studies have identified A. flavus as a mesophile, it does not exhibit any ofthe properties of an authentic thermophile.Ability of A. flavus to grow on degreening silks and to infect kernels directly without insect activity.These observations have made an important contribution to understanding the breadth ofmetabolic capabilities of A. flavus. However, there appear to be some relatively strict limitations onA. flavus substrate requirements. Broad natural occurrence of aflatoxin in US markets has onlybeen observed in maize, cottonseed, peanuts, grain sorghum, millet, copra, tree nuts and figs.Absence of aflatoxin in freshly harvested soybeans presents an intellectual challege tomycotoxicologists. Since soybean are grown in the southern USA in close proximity to aflatoxincontaminatedmaize, absence of inoculum can not explain the inability of the fungus to establish atoxin-producing presence.Information gathered on preharvest aflatoxin contamination has since been modified byseveral observations:• Characterization of definite association between elevated temperature during kerneldevelopment and increased aflatoxin accumulation;• Elucidation of a mechanism for kernel infection by A. flavus without insect activity and toxincontamination of intact kernels;• Identification of A. flavus resistance factors in inbred lines that reflect variations based onthe inoculation method;• Characterization of a direct correlation between water stress in developing maize andsusceptibility to A. flavus infection and toxin contamination;SummaryScientists gathered under the banner of mycotoxicology have shared unique experiencesduring eh past 15 years. They have participated in the evolution of a new discipline. Creating anew area of inquiry can be controversial and the study of toxic fungal metabolites is no exception.The fundamental dilemma in mycotoxicology is its multidisciplinary nature; the scope and thediversity of professional interests make it difficult to establish a single discipline. The workinherently requires the expertise of microbiologists, plant pathologists, plant physiologists,veterinarians, entomologists, mycologists, agronomists, plant breeders, soil scientists,toxicologists, immunologists, oncologists, biochemists, chemists, public health scientists,epidemiologists, climatologists and nutritionists. In mycotoxicology the dialogue amongpractitioners has often resulted in recognizing common research interests and continuouslylearning new skills.- 136 -