MANGO MALFORMATION IN FLORIDA: DISTRIBUTION OF FUSARIUM SUBGLUTINANS IN AFFECTED TREES, AND RELATIONSHIPS AMONG STRAINS WITHIN AND AMONG DIFFERENT ORCHARDS

RANDY C. PLOETZ, N. GREGORY
Mango (Mangifera indica L.) malformation was first reported in Florida in 1972. Although the disease is not an important problem in the state, its incidence and severity have increased during the last several years. We recently investigated the biology and epidemiology of the disease in southern Florida (Dade County). In a series of studies, Fusarium subglutinans (Wollenweb. & Reinking) Nelson, Toussoun & Marasas comb. nov. (basionym: F. moniliforme Sheldon var. subglutinans Wollenweb. & Reinking) was always recovered from malformed panicles. In one study, it was the predominant fungus isolated from malformed 'Keitt' panicles in three different orchards; an average of 85.4% of the pedicel and peduncle tissues from malformed panicles yielded the fungus. In another study on 'Keitt', the fungus was recovered from 65.7% of the tissues from malformed shoots (primarily panicles) but from only 10% of the tissues from nonmalformed shoots; in all cases in which F. subglutinans was recovered from nonmalformed panicles, they were either in physical contact with or were on the same branch as malformed panicles. Fusarium subglutinans was recovered infrequently from branch tissue. Only 2.2% of the tissues from branches that supported malformed floral and vegetative shoots yielded the fungus and it was not recovered from branches that supported nonmalformed shoots.

Two strains of F. subglutinans from malformed 'Keitt' and 'Tommy Atkins' panicles caused vegetative and floral malformation on five of twelve 'Van Dyke' trees 4 mo after inoculation. Results from this experiment, and another in which symptoms did not develop, suggested that both wounding and timing of inoculation may be critical factors when artificially reproducing this disease.

The two strains used in inoculation studies and 53 other strains of the fungus recovered from the three 'Keitt' orchards above were in the same vegetative compatibility group (VCG); they apparently comprise a major, clonally related population of the pathogen. Compatibility was not apparent between nine remaining strains that were tested and the VCG above. These strains fell into five additional VCGs and may represent genetic variation within what may be a relatively homogeneous population of F. subglutinans on mango in Dade County.

PLOETZ, RANDY C. and GREGORY, N. (1993). MANGO MALFORMATION IN FLORIDA: DISTRIBUTION OF FUSARIUM SUBGLUTINANS IN AFFECTED TREES, AND RELATIONSHIPS AMONG STRAINS WITHIN AND AMONG DIFFERENT ORCHARDS. Acta Hortic. 341, 388-394
DOI: 10.17660/ActaHortic.1993.341.43
https://doi.org/10.17660/ActaHortic.1993.341.43

Acta Horticulturae