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Hormonal profiling of the Fusarium mangiferae infected mango buds in relation to mango malformation

Usha, Kalidindi, Singh, Bhupinder, Kamil, Deeba
Scientia horticulturae 2019 v.254 pp. 148-154
Fusarium fujikuroi, Fusarium mangiferae, abnormal development, auxins, branches, buds, conidia, fruit yield, in vitro studies, internodes, mango malformation disease, mangoes, meristems, panicles, phylogeny, rice, seedlings
Mango malformation is a serious threat to mango cultivation in various countries and causes 30–80% of fruit yield losses annually. It is now well established that Fusarium mangiferae induces the symptoms of mango malformation disease. Fusarium mangiferae is phylogenetically closely related to Fusarium fujikuroi. However, visible symptoms of floral malformation caused by F. mangiferae and bakanae disease of rice caused by F. fujikuroi are distinctly opposite. In bakanae disease, infected seedlings exhibit abnormal elongation, whereas in mango malformation, length of the primary axis and secondary branches of the panicle are reduced, which is characterized by appreciably reduced internodes that give them a witches’ broom-like appearance. These morphological differences may be attributed to a differentially altered hormonal balance by the respective pathogenic organism. Artificial inoculation of meristems with F. mangifera under phytotron conditions produced malformed inflorescence. In our in vitro studies, the number of macro and micro conidia of F. mangiferae increased with increase in the concentration of GA3 suggesting that GA is needed for causing infection. The current study investigated the endogenous hormone levels in healthy and malformed tissues at different bud development stages. Our results demonstrate that significantly low GA and high auxin levels in mango buds infected with F. mangiferae lead to development of malformed panicles.