Morphology Phylogeny Pucciniales Vitaceae a b s t r a c t Three distinct groups were revealed among the grapevine leaf rust fungi from Japan, Taiwan, Thailand, Malaysia, Indonesia, East Timor and Australia in phylograms generated from sequence analyses of the internal transcribed spacer 2 and the large-subunit rRNA gene (D1/D2 region). A group of Thai, Malaysian-Indonesian and East Timorese-Australian fungi was distinct from two other groups of grapevine leaf rust fungi, Phakopsora meliosmaemyrianthae and P. montana, distributed in temperate East Asia. Although complete life cycle and native host plants are unknown for the Southeast Asian and Australasian fungus, it is likely to be a biologically distinct species.

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Leaf blight disease of water hyacinth was observed and collected from different geographical areas of Thailand. The disease is caused by a fungal pathogen that was identified as Myrothecium roridum by using its morphological characteristics. The most effective fungal strains were evaluated for pathogenicity on water hyacinth under greenhouse and natural conditions. Myrothecium roridum isolate, Kamphaeng Sean Campus (KKFC) 448, was found to be the most virulent. Different fungal formulations were evaluated for their level of control of water hyacinth. The results showed that spore suspensions with 10% palm oil or 1% Tween 20 caused a higher level of disease severity, compared to spores applied in water alone. The host range of KKFC 448 was evaluated by using 77 plant species that belong to 40 plant families. The fungus did not cause disease on 74 economically important plants but did produce disease signs on water hyacinth and two other aquatic weeds, duckweed and water lettuce. Leaf blight occurs on water hyacinth leaves after being treated with crude extracts of M. roridum and it was indicated that secondary metabolites were released from the fungal mycelia. Myrothecium roridum that was grown on boiled paddy rice produced β-1,4-exoglucanase, β-1,4-endoglucanase, β-glucosidase, xylanase and pectinase more than M roridum that was grown on potato dextrose agar. The results indicated that M. roridum is a pathogen of water hyacinth and the fungus is capable of producing different enzymatic activities on potato dextrose agar and boiled paddy rice, which might be important for infection.

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Paramyrothecium eichhorniae sp. nov. was observed and collected from Chiang Mai and Phetchaburi Provinces, Thailand. This new species is introduced based on morphological and molecular evidence. This fungus is characterized by its production of sporodochium conidiomata with a white setose fringe surrounding an olivaceous green to dark green slimy mass of conidia, penicillately branched conidiophores, and aseptate and cylindrical to ellipsoid conidia. Phylogenetic analyses of combined LSU rDNA, ITS rDNA, tef1 , rpb2 , tub2 and cmdA sequence data using maximum parsimony, maximum likelihood and Bayesian approaches placed the fungus in a strongly supported clade with other Paramyrothecium species in Stachybotryaceae (Hypocreales, Sordariomycetes). The descriptions of the species are accompanied by illustrations of morphological features, and a discussion of the related taxa is presented.

Dirty panicle disease is one of the most important diseases that can cause yield losses in rice production. Despite the severity of the disease, the molecular basis of resistance to the pathogen is poorly understood. Using QTL-seq with an F2 population, we identified three genomic regions on chromosomes 1, 9, and 10, namely qDP1, qDP9, and qDP10. These regions are significantly associated with resistance to dirty panicle disease caused by two fungal pathogens, Bioplaris oryzae and Cirvularia lunata. qDP1 was significantly associated only with resistance to B. oryzae, whereas qDP9 and qDP10 were significantly associated with both B. oryzae and C. lunata. We also developed KASP markers for each QTL detected and validated them in the F2 population. The markers were able to explain phenotypic variation in a range of 5.87–15.20%. Twelve potential candidate genes with annotated functions as resistance-related genes were proposed. These candidate genes include those encoding RLK, MATE, WAK, NBS-LRR, subtilisin-like protease, and ankyrin repeat proteins. The results of this study provide insights into the genetic mechanism of dirty panicles in rice and will be useful for future breeding programs for dirty panicle resistance. This is the first report of QTLs associated with resistance to dirty panicle disease in rice.

Pythium sp. was isolated from the roots, crowns and rhizosphere soil of Catharanthus roseus (L.) G. Don. (common name; vinca) showing symptoms of root and crown rot disease in plantation areas in Chiang Mai Thailand. The pathogen was studied by morphological and molecular analysis based on internal transcribed spacer (ITS) sequence. The Pythium isolate was confirmed as Pythuim deliense. The pathogenicity of the isolate was tested by inoculating with an agar disc containing mycelium of the fungus on detached C. roseus leaves compared with an agar disc alone as the control. It was found that P. deliense infected the vinca leaves causing a brown rot. Moreover, P. delicense infected and caused rot symptoms on plant crowns 5 d after inoculation with a mycelial suspension. This is the first report of P. deliense as pathogenic to C. roseus in Thailand.

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