Until now, only Lasiodiplodia theobromae has been reported in association with gummosis and dieback of cashew plants and other tropical fruit plants in northeastern Brazil. This study aims to identify and characterize species of Lasiodiplodia associated with gummosis and dieback on tropical fruit plants grown in Cear a, Para ıba, Pernambuco, Piau ı and Rio Grande do Norte States in northeastern Brazil with a description of two new species: Lasiodiplodia caatinguensis sp. nov. and Lasiodiplodia pontae sp. nov. Fungal identification was accomplished using a combination of morphophysiological and pathogenic characteristics, together with phylogenetic analyses based on partial translation elongation factor 1-a sequence (TEF1-a), internal transcribed spacer (ITS) and b-tubulin (b-tub). Six species of Lasiodiplodia were identified as being associated with several tropical fruit species: Lasiodiplodia brasiliense (Manilkara zapota, Mangifera indica and Spondias purpurea), L. caatinguensis sp. nov. (Anacardium occidentale, Citrus sinensis, S. purpurea and S. lutea), L. euphorbicola (Annona muricata and Cocos nucifera), L. pontae sp. nov. (A. occidentale and S. purpurea), L. pseudotheobromae (A. occidentale, S. purpurea and Tamarindus indica) and L. theobromae (A. occidentale, S. purpurea and Talisia esculenta). This is the first study to use molecular data of Lasiodiplodia taken from the stems and branches of Annona spp., A. occidentale, M. zapota, T. indica, T. esculenta and Spondias spp. After L. caatinguensis sp. nov., the species L. pseudotheobromae and L. theobromae were the second most frequent species. All identified species were able to cause necrotic lesions at different levels of severity when inoculated on mango fruits and young plants of Annona spp., cashew and Spondias spp.
The incidence–severity relationship for cashew gummosis, caused by Lasiodiplodia theobromae, was studied to determine the feasibility of using disease incidence to estimate indirectly disease severity in order to establish the potential damage caused by this disease in semiarid north‐eastern Brazil. Epidemics were monitored in two cashew orchards, from 1995 to 1998 in an experimental field composed of 28 dwarf clones, and from 2000 to 2002 in a commercial orchard of a single clone. The two sites were located 10 km from each other. Logarithmic transformation achieved the best linear adjustment of incidence and severity data as determined by coefficients of determination for place, age and pooled data. A very high correlation between incidence and severity was found in both fields, with different disease pressures, different cashew genotypes, different ages and at several epidemic stages. Thus, the easily assessed gummosis incidence could be used to estimate gummosis severity levels.
In recent years, a viral disease on melon plants has become a serious problem in Brazil. Symptoms were principally yellowing and mottling on older leaves. Long filamentous virus particles, resembling those of carlaviruses, were seen in symptomatic leaves. In this study, the 3' terminal region of the virus genome isolated from an infected plant, including the last two ORFs, was cloned and sequenced. The sequence comprised a polyadenilated tail and two ORFs, one exhibiting similarity to potexvirus and carlavirus coat protein gene and the second to a carlavirus protein with potential nucleic acid-binding property. The sequence analysis, the genome organization and the particle morphology indicated that the virus could be classified as a novel whitefly-transmitted flexivirus. The name Melon yellowing-associated virus (MYaV) is tentatively suggested for this virus.
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