A Fusarium sp. different from Fusarium oxysporum and F. mangiferae is associated with mango malformation in Michoacán, Mexico

Abstract

Verticillium wilt caused by the fungus Verticillium dahliae is found world-wide and attacks a wide range of plants. In the summer of 2001, a wilt disease of Amygdalus communis (sweet almond) cultivated in the Xinjiang municipality in China was first observed. The characteristic symptoms of typical wilt included wilt of leaves and twigs, and brownish discoloration of vascular tissues. Ultimately, the branches and entire trees wilted and died. To identify the causal agent, both traditional and PCRbased methods were attempted.In 2004 and 2005, a Verticillium sp. was isolated from the xylem of diseased branches on potato dextrose agar (PDA). The fungus produced dark colonies on PDA, produced rotiform conidiophores with 2 -4 layers, one-celled colourless olivary conidia, and small black microsclerotia. It was identified as V. dahliae based on morphological characteristics according to the description of Smith (1965). Ribosomal DNA (regions ITS1, 5·8S rDNA and ITS2) was amplified and sequenced (GenBank Accession No. EU109532). Sequence analysis revealed that the fungus isolated from A. communis is identical to a Greek strain of V. dahlia (GenBank Accession No.AF104926).Each of six seedlings of A. communis , approx. about 20 cm high in sterile soil, was inoculated by injecting 20 μ L single-conidial suspension containing 1 × 10 6 conidia mL -1 into the base of the stem. The inoculated seedlings were incubated at 25 ° C. Water-soaked lesions appeared on the leaves of all of the inoculated seedlings after 4 days and then dark brown lesions appeared around the injected sites and spread rapidly upwards. The inoculated seedlings wilted and died after 7 days. The pathogen was reisolated from the inoculated stems. Control seedlings, inoculated with an equal volume of sterile water, remained healthy.The fungus was previously recorded in Xinjiang municipality and other provinces in China infecting many Rosaceae and Malvaceae plants (Tai, 1979), but this is the first report of V. dahliae associated with wilt of A. communis in China. ReferencesSmith HC, 1965. The morphology of Verticillium albo-atrum , V. dahliae , and V. tricorpus .

New Insights into Mango Malformation Disease Epidemiology Lead to a New Integrated Management Strategy for Subtropical Environments

“…How ever, descriptions of the MMD agents in the Western Hemisphere have only been made in Florida, Brazil (36), and Mexico (55,65). Additional work is needed to determine whether F. mangiferae occurs elsewhere in the West.…”

“…nov., was described from Mexico (55). With multilocus sequenc ing, F. mexicanum was shown to differ significantly from other MMD taxa in the G. fujikuroi species complex (55,65) (Fig. 4).…”

“…Zheng and Ploetz (78) developed a pair, I-3F/R, that amplify a 608-bp fragment for F. mangiferae, and have been used for diag nostic purposes (75). Another pair, 61-2F/R, developed to diagnose F. verticillioides (published as F. moniliforme in 46), failed to am plify F. mangiferae DNA, but when amplification protocols were modified, the pair amplified a 445-bp fragment for strains of F. sterilihyphosum and F. mexicanum (65,78). Additional primer pairs have been developed for F. mangiferae (50).…”

The role of eriophyoids in fungal pathogen epidemiology, mere association or true interaction?

“…Aceria mangiferae, the mango bud mite, was hypothesized as the causal agent of mango malformation for over 40 years mainly due to high numbers of mites observed in malformed trees, and also because other members of the Eriophyoidea are known to cause proliferation, ''witches broom'' and gall symptoms of inflorescences in other plants (Westphal and Manson 1996). Despite the fact that the fungal theory was well established following Koch's postulates with several fungi, certain members of the genus Fusarium have been shown to cause the disease (Summanwar et al 1966;Varma et al 1974;Chakrabarti and Ghosal 1989;Manicom 1989;Ploetz and Gregory 1993;Freeman et al 1999;Noriega-Cantú et al 1999;Britz et al 2002;Ploetz 2003;Marasas et al 2006;Kvas et al 2008;Lima et al 2009;Rodríguez-Alvarado et al 2008), It is also clear now that A. mangiferae is not the causal agent of mango malformation, however, various studies suggest that the mite interacts with the fungal pathogen resulting in increased severity of disease (Prasad et al 1972;Sternlicht and Goldenberg 1976;Gamliel-Atinsky et al 2009a). …”

Coconut malformation: An emerging disease caused by Fusarium proliferatum in southern Iran

“…Floral malformation is economically important since affected inflorescences usually do not bear fruit (Steenkamp et al, ). In several countries such as Mexico (Rodríguez‐Alvarado, Fernández‐Pavía, Ploetz, & Valenzuela‐Vázquez, ), Brazil (Lima et al, ; Lima, Pfenning, Costa, Campos, & Leslie, ) and South Africa (Britz et al, ; Steenkamp et al, ), malformation disease has left a serious impact on mango orchards and threatened mango production industry.…”