Abstract
Non-sterilized seeds from 12 cotton (Gossypium barbadense L.) genotypes were examined for qualitative and quantitative estimates of seedborne fungi. The observed fungi were Alternaria alternata, Aspergillus flavus, A. niger, Aspergillus sp. Chaetomium sp. Cladosporium sp. F. oxysporum, Penicillium sp. Rhizopus stolonifer and Stemphylium sp. The quantitative estimates of the fungi showed that R. stolonifer (39.7%), A. niger (33.5%) and Penicillium sp. (23.3%) were the most predominant fungi isolated from the seeds. Other fungi occurred at frequencies ranged from 0.3 to 17.7%. The HPLC analysis of amino acid composition of cottonseed revealed the presence of 17 amino acids but the occurrence of each in the seeds varied with the genotype. Data for frequencies of the isolated fungi (dependent variables) and contents of amino acids (predictors or independent variables) were entered into a computerized stepwise multiple regression analysis. Using the predictors supplied by stepwise regression, eight models were constructed. R-2 values of the models ranged from 57.74 to 99.41%. Thus, it was possible to group the isolated fungi into four distinct categories based on their sensitivity to the amino acids (the size of R-2 value). The first category included the insensitive fungi A. alternata and Chaetomium sp. where no regression models could be constructed. The second category included the moderately sensitive fungi F. oxysporum and R. stolonifer, where R-2 values were 65.72 and 57.74%, respectively. The third category included the sensitive fungi A. flavus, A. niger, Penicillium sp. and Aspergillus sp., where R-2 values were 86.35, 90.84, 90.00 and 82.62%, respectively. The fourth category included the highly sensitive fungi Cladosporium sp. and Stemphylium sp., where R-2 values were 99.41 and 98.76, respectively. The results of the present study suggest that certain amino acids regulate colonization of cottonseed by mycoflora and that control of these fungi may be possible by modifying amino acid content of the seed. (C) 2011 Friends Science Publishers