Effects of Cultivar and Boll Age on Aflatoxin in Cottonseed After Inoculation with Aspergillus flavus at Simulated Exit Holes of the Pink Bollworm. P. J. Cotty, Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 19687, New Orleans, LA 70179. . Plant Dis. 73:489-492. Accepted for publication 27 December 1988. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/PD-73-0489.

Seven cultivars of Gossypium hirsutum commonly grown in Arizona, Deltapine (DP) Acala 90 (DP 90), DP 120, DP 77, DP 61, DP 41, DP 20, and McNair 235, became equally contaminated with aflatoxin B₁ when 28- to 32-day-old bolls were wounded to simulate exit holes of the pink bollworm and then inoculated with conidia of Aspergillus flavus. The cultivar Pima S-6 of G. barbadense, however, became more contaminated than the cultivars of G. hirsutum. In subsequent studies, Pima S-6 became more contaminated than DP 90 when bolls were inoculated at 29–36 days of age and less contaminated when bolls were inoculated at 17–21 days. Aflatoxin was predominantly found in seed from wound-inoculated locks. A. flavus did, however, move from inoculated locks to adjacent unwounded locks and contaminate seed produced there with low levels of toxin. Thus, undamaged locks in bolls with exit holes of the pink bollworm may be important sources of contamination in commercial fields. Boll age at inoculation influenced the contamination of both wound-inoculated and adjacent unwounded locks. Wound-inoculated locks of young bolls (13–20 days old at inoculation) became less contaminated than similar locks of bolls 25–32 days old at inoculation. The fungus, however, moved into and contaminated unwounded locks of young bolls more extensively than those of older bolls. Thus, the maturation of the intercarpellary membrane may hinder the interlock spread of A. flavus.

Keyword(s): mycotoxins.