Infection of mungbean seed by Macrophomina phaseolina is more likely to result from localized pod infection than from systemic plant infection

• Published in: Plant pathology Vol. 62; no. 6; pp. 1271 - 1284
• Main Authors: Fuhlbohm, M. J., Ryley, M. J., Aitken, E. A. B.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell 01.12.2013; Wiley Subscription Services, Inc
• Subjects: Biological and medical sciences; charcoal rot; Diquat; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Host plants; infection; Macrophomina phaseolina; mungbean; Paraquat; Pathogens; Phytopathology. Animal pests. Plant and forest protection; seed; Soil moisture; Plant pathology; Plant pathogen; Pod; seed; Systemic; Mung bean; Result; Fungi; Infection; Plant; Rot; mungbean; Macrophomina phaseolina; Fungi Imperfecti; charcoal rot; Localized
• DOI: 10.1111/ppa.12047
• ISSN: 0032-0862

The ubiquitous fungal pathogen Macrophomina phaseolina is best known as causing charcoal rot and premature death when host plants are subject to post‐flowering stress. Overseas reports of M. phaseolina causing a rapid rot during the sprouting of Australian mungbean seed resulted in an investigation of the possible modes of infection of seed. Isolations from serial portions of 10 mungbean plants naturally infected with the pathogen revealed that on most plants there were discrete portions of infected tissue separated by apparently healthy tissue. The results from these studies, together with molecular analysis of isolates collected from infected tissue on two of the plants, suggested that aerial infection of aboveground parts by different isolates is common. Inoculations of roots and aboveground parts of mungbean plants at nine temperature × soil moisture incubation combinations and of detached green pods strongly supported the concept that seed infection results from infection of pods by microsclerotia, rather than from hyphae growing systemically through the plant after root or stem infection. This proposal is reinforced by anecdotal evidence that high levels of seed infection are common when rainfall occurs during pod fill, and by the isolation of M. phaseolina from soil peds collected on pods of mungbean plants in the field. However, other experiments showed that when inoculum was placed within 130 mm of a green developing pod and a herbicide containing paraquat and diquat was sprayed on the inoculated plants, M. phaseolina was capable of some systemic growth from vegetative tissue into the pods and seeds.