Impact of Aflatoxin Produced by Aspergillus flavus on the Biochemical Profile of Seeds of Oryza sativa. Linn

Abstract

Aflatoxins are a group of secondary metabolites produced by certain toxigenic strains of Aspergillus flavus on various food and feed commodities. These group of mycotoxins are highly oxygenated heterocyclic compounds. Aflatoxins occupy the most important position among mycotoxins in view of their potent carcinogenic nature and high frequency of occurrence under natural conditions. Rice (Oryza sativa L.) is consumed by millions of people all over the world in different forms. Thus, any form of contamination may prove to be deleterious to health. Aspergillus flavus and A. parasiticus were reported to contaminate cereal grains with their toxic secondary metabolites, the Aflatoxins. Seventeen varieties of paddy seeds were infested with a highly toxigenic strain of Aspergillus flavus under laboratory conditions. None of the varieties was totally resistant to aflatoxin production but they facilitated aflatoxin production at varying levels. Four rice varieties viz. Turanta IET-7991, Vaidehi, Dhanlaxmi and Mansuri produced aflatoxin B1 in very low amount i. e. 51.35, 65.52, 62.53 and 67.25µg/Kg and may be considered as highly resistant varieties. Shakuntala IET-11183, Gautam IET-13439, Birsa Dhan-202, Sita, Kanak, Jaishree, Pusa 2-21 produced aglatoxin B1 in the range of 115.45 to 173µg/Kg after infestation with Aspergillus flavus and therefore, may be regarded as moderately resistant varieties. Pusa-33, Basmati-370, Katarni, Sugandha, BR-9 and Kamini produced relatively high aflatoxin B1 after A. flavus infestation in the range of 218.25 to 370µg/Kg and may be considered as susceptible varieties. The kernel of different paddy varieties contained different concentration of amylase (in the range of 121mg/g to 168mg/g) after infestation with A. flavus. Obviously amylopectin content of total starch of different kernel varieties showed negative correlation with amylose content. In contrast to amylose content, the amylopectine level was found to be the highest, 571.8mg/g and 570.3mg/g in respectively in BR-9 and Kamini variety and the lowest (438.4 mg/g) in the Gautam IET-13439 variety. Significant reduction in protein content was observed during fungal infestation, the maximum being in Turanta IET-7991 (17.39%) and Vaidehi-625 (17.74%). After infestation with A. flavus all the paddy varieties showed an increase in total sugar content. Analysis of protein contents in the kernels shows that higher levels of protein in kernels somewhat inhibit the production of aflatoxin B1. Thus, the varieties containing higher amount of proteins were found to resist the production of aflatoxinB1 production. Significant reduction in protein content was observed in those varieties that facilitated higher amount of aflatoxin B1. Correlation coefficient (r) was calculated to be -0.59, which shows moderate negative correlation between the amount of protein and levels of aflatoxin production. Analysis of sugar contents shows that higher levels of both reducing and non-reducing sugar have an inhibitory effect on the production of aflatoxin B1 produ...