ARS | Publication request: Relationship between aflatoxoin contamination and physiological responses of corn plants under drought and heat stress

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2012
Publication Date: November 20, 2012
Citation: Kebede, H.A., Abbas, H.K., Fisher, D.K., Bellaloui, N. 2012. Relationship between aflatoxoin contamination and physiological responses of corn plants under drought and heat stress. Toxins. 4:1385-1403.

Interpretive Summary: Drought and heat stress are frequent occurrences in the southern United States during the flowering and kernel development stages of the corn plant, and these weather conditions have been associated with increased aflatoxin contamination produced by the fungus Aspergillus flavus. Aflatoxins are potent carcinogens which pose serious health hazards to humans and domestic animals, and accordingly have economic impact on the grain industry. The objective of this study was to evaluate the relationship between aflatoxin contamination and physiological measurements in corn plants grown under drought and heat stress using five commercial corn hybrids, P31G70, P33F37, P32B34, P31B13 and DKC63-42 and two inbred corn germplasm lines, PI 639055 and PI 489361. The results suggested that drought and heat stress effects were more severe on corn inbreds PI 639055 and PI 489361 and corn hybrid DKC63-42. P31G70 was the most stress tolerant among all the genotypes. The aflatoxin resistant inbred PI 639055 had the lowest aflatoxin contamination followed by hybrid P31G70, whereas hybrid DKC63-42 and inbred PI 489361 had the highest contamination. The results suggested that there was a relationship between the physiological measurements and the level of aflatoxin contamination in the corn plants. Understanding these and other physiological responses of corn plants to stress can help explain differences among corn genotypes in aflatoxin contamination, enabling better control of aflatoxin using altered production practice or through development of more resistant corn hybrids.

Technical Abstract: In the southern United States, corn production frequently encounters a period of drought and heat stress during flowering and kernel development, and these weather conditions have been associated with increased aflatoxin production by the fungus Aspergillus flavus. The objective of this study was to evaluate the relationship between aflatoxin contamination and physiological measurements in corn plants grown under drought and heat stress conditions. The study was conducted in Stoneville, MS, in 2009 and 2010 under irrigated and non-irrigated conditions. Five commercial hybrids, P31G70, P33F37, P32B34, P31B13 and DKC63-42 and two inbred germplasm lines, aflatoxin resistant (PI 639055) and drought stress tolerant (PI 489361), were evaluated. The plants were inoculated with Aspergillus flavus (K-54) at mid-silk stage, and aflatoxin contamination was determined on the kernels at harvest. To determine the extent of moisture deficit and heat stress imposed on the plants, measurements were made on air and soil temperatures and soil moisture status using an automated monitoring system. To examine the response of the corn plants to these stresses, leaf water potential, canopy temperature, photosynthetic pigments, cell membrane thermostability, maximum quantum efficiency of Photosystem II, and seed composition were determined. The results suggested that PI 639055, PI 489361 and hybrid DKC63-42 were under severe stress in the non-irrigated plots, particularly in 2010. P31G70 was the most stress tolerant among all the genotypes. The aflatoxin resistant germplasm, PI 639055, had the lowest aflatoxin contamination (20 ppb) followed by P31G70 (37 ppb), whereas DKC63-42 and PI 489361 had the highest contamination, 202 ppb and 186 ppb, respectively. These results suggested that the physiological responses of the corn genotypes were associated with the level of aflatoxin accumulation, except for PI 639055. Possible reasons for these differences are discussed. These and other physiological responses of corn plants to stress can help explain differences among corn genotypes in aflatoxin contamination.