PATHOGENIC POTENTIALITY OF FUNGI ASSOCIATED WITH THE SEEDS OF DIFFERENT COTTON (GOSSYPIUM HIRSUTUM L.) VARIETIES IN BANGLADESH

Abstract

A total of 24 species of fungi, namely Aspergillus flavus Link, A. fumigatus
Fresenius, A. niger (Type 1 and Type 2) Van Tiegh, A. ochraceus K. Wilhelm, A.
nidulans Eidam, Aspergillus sp.1, Aspergillus sp.2, Aspergillus sp.3, Curvularia lunata
(Wakker) Boedijn, Colletotrichum gloeosporioides Penz & Sacc, C. gossypii Southw.,
Chaetomium globosum Kunze., Fusarium nivale (Fr.) Sorauer, F. moniliforme J. Shelden,
F. oxysporum Schlechtendal, F. fujikuroi Nirenberg, Mucor sp. P. Micheli ex L.,
Penicillium sp.1 and sp.2 Link, Rhizoctonia solani Khun., Rhizopus stolonifer (Ehrenb.)
Vuill., Rhizomucor sp. Lucet & Costantin, Syncephalastrum racemosum Cohn and
Trichoderma viride Pers. were found to be associated with the seeds of 14 varieties (CB
1- CB 14) of cotton. Out of these 24 fungal species, nine were found to be pathogenic
to cotton. They were Aspergillus flavus, A. niger (Type 1), Aspergillus sp. 1,
Colletotrichum gloeosporioides, Curvularia lunata, Fusarium nivale, F. moniliforme, Mucor
sp. and Rhizoctonia solani. These pathogenic fungi had remarkable effect on seed
germination, vigor index, root-shoot length and mortality of cotton seedlings. The
germination percentage of control seeds was 88 but because of the presence of
pathogenic fungi the rate showed considerable reduction in all the varieties and it
varied from 20 to 82%. Among the nine fungal isolates Rhizoctonia solani showed
maximum reduction in seed germination. Aspergillus flavus, Colletotrichum gloeosporioides
and Fusarium moniliforme also caused near about 50% reduction in seed
germination. Mortality percentage of control seedling were also less (6) whereas, in
inoculated seeds it was higher and varied from 7 - 23%. Root- shoot ratio of control
seedlings was high but less in inoculated seedlings. The vigor index of control plant
was high (1548.8) but less in inoculated plants. The lowest vigor index was noticed
for Rhizoctonia solani (202.0) and highest for Aspergillus sp. 1(1213.6). Results indicated
that Curvularia lunata and Rhizoctonia solani showed a greater impact in reduction of
cotton seed germination and vigor index.