IMPACT OF ENVIRONMENTAL VARIABLES ON SPORE DISPERSAL TREND OF FUSARIUM MANGIFERAE CAUSING MANGO MALFORMATION DISEASE IN PAKISTAN

Abstract

Malformation is one of the most destructive mango diseases. Although trees are not killed, the vegetative phase of the disease impedes canopy development during vegetative phase of the host plant and floral phase dramatically reduces fruit yield with overwintering inoculums during dormant phase of the host plant. Environmental conditions and trend of spore liberation of its pathogenic fungus “Fusarium mangiferae” were recorded during flowering phase (Feb-April, 2014), fruit development phase (May-July, 2014), vegetative phase (Aug-Oct, 2014), and dormant phase (Nov-Jan, 2014-15), of the mango plants. Through installation of spore traps of various distance levels containing Nash-Synder media in petri plates. During these phases, different environmental variables including temperature (T), relative humidity (R.H) and wind speed (W.S) were observed. Maximum number of colonies were observed through the spores trapped from the centre of the experimental block (0m) while minimum numbers of colonies were developed from the spores trapped at 150 m distance. Amongst different phenological phases of mango, fruit development remained very much contaminated with spores of the fungus while minimum spore liberation was noted during flowering phase of mango indicating very rare infection during this phase. This study also reflected that maximum number of airborne macro conidia of F. mangiferae were recorded when R.H was below 55%. Low R.H appeared to be a major factor associated with the diurnal conidial dispersal of airborne pathogen. Hence primary infection of F. mangiferae starts from vegetative and floral buds differentiation and control strategy including spray of systemic fungicides should start at this stage of development.