Early Appearance of Aflatoxin in Developing Corn Kernels After Inoculation withAspergillus flavus

regimes were defined in thermal units Thompson, D. L., Payne, G. A., Lillehoj, E. B., and Zuber, M. S. 1983. Early appearance of (Table 1), which were calculated as f[(day aflatoxin in developing corn kernels after inoculation with Aspergillus flavus. Plant Disease temp. X 9 hr) + (night temp. X 67:1321-1322. 15 hr)]/241 -10 C. For each replicate, half of the plants were moved morning Developing kernels of corn (Zea mays L.) of the cultivar Gaspe X W103 were inoculated with and evening between the two rooms to Aspergillusfilavus Link ex Fr., grown in four postinoculation regimes, harvested at weekly intervals achieve the four temperature regimes. from 2 to 37 days after inoculation, and assayed for aflatoxin B 1. Aflatoxin B 1 levels averaged 238 One room was set to a day/ night ppb 2 days after inoculation and 2,482 ppb for all other dates. Aflatoxin levels were near maximum 9 days after inoculation and accumulations were minimal after that time. There was no evidence of temperature of 26/ 22 C and the other at a temperature effect in the range of 13.5-21.5 C thermal units per day. 34/30 C with day/ night times of 9/15 hr and uninterrupted night to give a short day length effect. Aflatoxin contamination of preharvest MATERIALS AND METHODS Ears were harvested in the shuck, dried corn (Zea mays L.) continues to be a This study was conducted in controlled- for 1 wk at 60 C, bulked, and shelled for serious problem in the southeastern environment rooms at the Southeastern each cultivar-replicate treatment. Kernels United States (13). Infection of develop- Plant Environment Laboratories, Raleigh, were ground, blended, and assayed for ing kernels by Aspergillus.flavus Link ex NC. Lighting and other environmental aflatoxin by the Official First Action Fr. and subsequent production of aspects of the rooms have been de- Method of AOAC, Sections 26.049aflatoxin is influenced by many factors. scribed (3). 26.051, and 26.075 (1). Quantities of Temperature is one factor that appears to Plants of the corn cultivar Gaspe X aflatoxin B 1 were determined on influence aflatoxin production in grain. W103 were grown singly in 20.3-cm activated thin-layerchromatographic The warmer temperatures of the plastic pots (4,000 ml) in a substrate of (TLC) plates coated with 0.5 mm of Southeast have been implicated as a one-third gravel and two-thirds Peat-lite. Absorbosil- 1. Plates were developed with major reason for higher levels of Before inoculation, plants were grown at water:acetone:chloroform ( 1.5:12:88, aflatoxin in the Southeast than in the the day/night temperature regime of v/v/v) in unequilibrated tanks and Midwest (13). In support of this 26/22 C with an interrupted night to fluorescent zones were measured densitohypothesis, Thompson et al (12) found a provide long day length. Plants were metrically (2). Aflatoxin B, was congeneral trend toward increased toxin with irrigated twice each day with a modified firmed in representative positive samples increased temperature over a range of half-strength Hoagland's solution (3). A by formation of water adduct (I). 9.5-17.5 thermal units per day and treatment unit consisted of five plants. Aflatoxin B 1 values were transformed suggested that temperatures higher than Each of two replicates was grown at a to logarithms for analyses of variance those used may give higher toxin levels, different time.