Analysis of genetic diversity of Fusarium tupiense, the main causal agent of mango malformation disease in southern Spain

Authors: CRESPO, M - University Of Malaga; CAZORLA, F - University Of Malaga; DE VICENTE, A - University Of Malaga; ARREBOLA, E - University Of Malaga; TORES, J - University Of Malaga; MAYMON, M - Volcani Center (ARO); FREEMAN, S - Volcani Center (ARO); AOKI, T - National Institute Of Agrobiological Sciences (NIAS); O Donnell, Kerry

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2015
Publication Date: 2/1/2016
Publication URL: http://handle.nal.usda.gov/10113/62941
Citation: Crespo, M., Cazorla, F.M., de Vicente, A., Arrebola, E., Tores, J.A., Maymon, M., Freeman, S., Aoki, T., O'Donnell, K. 2016. Analysis of genetic diversity of Fusarium tupiense, the main causal agent of mango malformation disease in southern Spain. Plant Disease. 100(2):276-286.

Interpretive Summary: The study was conducted to identify fungal pathogens responsible for mango malformation disease (MMD) in southern Spain. MMD is increasingly becoming a constraint to the production of this economically important crop worldwide because infected seedlings have to be destroyed and losses in mature trees can result in an 80% reduction in yield. Because knowledge of pathogen identity and genetic diversity can help inform control measures and the possible source of introduction, pathogen surveys were conducted during 2009 through 2012 of trees exhibiting typical malformation symptoms. Of the 132 Fusarium strains recovered, molecular analyses revealed that 38 of the isolates were F. mangifera, 92 were F. tupiense, and two appeared to represent a novel species closely related to F. phyllophilum. Pathogenicity experiments demonstrated that F. tupiense and the novel Fusarium sp. were capable of inducing typical MMD symptoms on mango. All of the F. tupiense isolates were typed genetically as members of a group that was previously only known from Brazil. Detailed morphological analyses of F. tupiense in pure culture revealed that it could be distinguished from the other MMD pathogens by the production of compact densely-branched spore producing structures in pure culture. The present research should be of interest to plant pathologists, plant breeders, and quarantine officials who are focused, respectively, on developing control measures, breeding cultivars with broad based resistance to the disease, and preventing the introduction and spread of MMD in mango growing regions worldwide.

Technical Abstract: Mango malformation disease (MMD) has become an important global disease affecting this crop. The aim of this study was to identify the main causal agents of MMD in the Axarquía region of southern Spain and determine their genetic diversity. Fusarium mangiferae was previously described in the Axarquía region but it represented only one-third of the fusaria recovered from malformed trees. In the present work, fusaria associated with MMD were analyzed by arbitrary primed polymerase chain reaction (ap-PCR), random amplified polymorphic DNA (RAPD), vegetative compatibility grouping (VCG), a PCR screen for mating type idiomorph, and phylogenetic analyses of multilocus DNA sequence data to identify and characterize the genetic diversity of the MMD pathogens. These analyses confirmed that 92 of the isolates were F. tupiense, which was previously only known from Brazil and Senegal. In addition, two isolates of a putatively novel MMD pathogen were discovered, nested within the African clade of the Fusarium fujikuroi species complex. The F. tupiense isolates all belonged to VCG I, which was first described in Brazil, and the 11 isolates tested showed pathogenicity on mango seedlings. Including the prior discovery of F. mangiferae, three exotic MMD pathogenic species have been found in southern Spain, which suggests multiple independent introductions of MMD pathogens in the Axarquía region.