Nakarin Suwannarach

Molecular and morphological evidence support four new species in the genus Muscodor from northern Thailand

The genus Muscodor comprises fungal endophytes which produce mixtures of volatile compounds (VOCs) with antimicrobial activities. In the present study, four novel species, Muscodor musae, M. oryzae, M. suthepensis and M. equiseti were isolated from Musa acuminata, Oryza rufipogon, Cinnamomum bejolghota and Equisetum debile, respectively; these are medicinal plants of northern Thailand. The new Muscodor species are distinguished based on morphological and physiological characteristics and on molecular analysis of ITS-rDNA. Volatile compound analysis showed that 2-methylpropanoic acid was the main VOCs produced by M. musae, M. suthepensis and M. equiseti. The mixed volatiles from each fungus showed in vitro antimicrobial activity. Muscodor suthepensis had the highest antifungal activity.

Evaluation of Muscodor suthepensis strain CMU‐Cib462 as a postharvest biofumigant for tangerine fruit rot caused by Penicillium digitatum

BACKGROUND This study investigated both the in vitro and in vivo biofumigant ability of the endophytic fungus Muscodor suthepensis CMU-Cib462 to control Penicillium digitatum, the main cause of tangerine fruit rot. RESULTS Volatile compounds from M. suthepensis inhibited mycelial growth of the pathogen. The most abundant compound was 2-methylpropanoic acid, followed by 3-methylbutan-1-ol. They showed median effective doses (ED50) on P. digitatum growth of 74.91 ± 0.73 and 250.29 ± 0.29 µL L(-1) airspace respectively. Rye grain was found to be a suitable solid medium for M. suthepensis inoculum production. The results indicated that mycofumigation with a 30 g rye grain culture of M. suthepensis for 12 h controlled tangerine fruit rot. The percentage weight loss and soluble solids concentration of fumigated tangerines were similar to those of non-infected and non-fumigated fruits. CONCLUSION Muscodor suthepensis has potential as a biofumigant for controlling postharvest disease of tangerine fruit.

First report of leaf spot disease on oil palm caused by Pestalotiopsis theae in Thailand

A leaf spot on oil palm, caused by Pestalotiopsis theae, was found in a plantation of Elaeis guineensis for the first time in the world in Chiang Mai Province, Thailand. The fungus was isolated from lesions on leaves, and its pathogenicity was confirmed. Pathogenicity tests showed that P. theae could infect E. guineensis, which developed the same symptoms after inoculation as those observed naturally in the field. The fungus was identified based on morphological characteristics and confirmed using comparisons of DNA sequences of internal transcribed spacer (ITS)1, ITS2 and 5.8S rDNA. This report is the first on oil palm leaf spot disease caused by P. theae.

Basidiome formation of an edible wild, putatively ectomycorrhizal fungus, Phlebopus portentosus without host plant

Phlebopus portentosus is a popular wild edible ectomycorrhizal fungus in northern Thailand. In general ectomycorrhizal fungi produce basidiomes when associated with a host plant. In this paper mycelium growth and basidiome production of P. portentosus were examined in pure culture both in vitro and in pot-culture experiments. Five mycelial strains of P. portentosus were isolated from basidiomes and used in the experiments. The mycelia grew fastest on sorghum grains supplemented with fungal-host solution. The mycelia produced sclerotia-like structures after 3 wk incubation in darkness at 30 C. All strains of P. portentosus had the ability to form primordia. The primordia were formed under lowered temperature, high humidity and a 12 h photo-period. They developed to mature basidiomes after 8–12 d in in vitro. In the pot-culture primordia were found after 28–35 d incubation in the greenhouse and mature basidiomes released basidiospores within 6–8 d. Basidiospores were germinated on fungal-host medium and formed mycelial colonies. This fungus showed an ability to produce basidiomes even 2 y after the original isolation from tissues. This research provides valuable information concerning the techniques and protocols for the large scale commercial production of P. portentosus basidiomes in the absence of a host plant.

Evaluation of Muscodor cinnamomi as an egg biofumigant for the reduction of microorganisms on eggshell surfaces and its effect on egg quality

The presence of microorganisms on the eggshell surface is a factor of consideration in determining egg quality. These microorganisms can contribute to egg spoilage and can infect the egg. In this study, 18 morphotypes of microorganisms were isolated from eggshells. Morphological, biochemical, physiological and molecular analyses were used to identify these morphotypes into 7 species; Bacillus drentensis, Staphylococcus arlettae, Stap. cohnii, Stap. kloosii, Stap. saprophyticus, Stap. sciuri and Stap. xylosus. The potential of Muscodor cinnamomi to reduce the presence of microorganisms on eggshells by biological fumigation was investigated. The result showed that 16 strains of the tested microorganisms were inactivated after the exposure of the fungal volatile organic compounds. The most abundant compound was 2-methylpropanoic acid, followed by 3-methylbutan-1-ol. Our results indicated that a 24-h period of fumigation of 100g rye grain culture of M. cinnamomi was the minimum dose that could significantly reduce the number of microorganisms on the eggshell surface. Fumigated eggs from both box and cabinet fumigation trials showed significantly lower microbial numbers on the eggshell than non-fumigated eggs during the storage period of 14days. It was found that the values of the yolk index, albumen index and the Haugh unit of the eggs decreased during this storage time. However, those values of the fumigated eggs from both fumigation trials were found to be significantly higher than the non-fumigated eggs after the 24-h fumigation period and following storage for 5, 7 and 14days. However, the values of the albumen index were not found to have significantly increased over 5days of the box trial. This study is the first to report on mycofumigation activity for the purposes of reducing the presence of microorganisms on the surface of eggshells.

A new whitish truffle, Tuber thailandicum from northern Thailand and its ectomycorrhizal association

A new species of whitish truffle, Tuber thailandicum, is described based on collections from northern Thailand. This species is characterized by whitish ascomata with dark brown gleba and subglobose spores with an alveolate reticulum. Tuber thailandicum is similar to T. castilloi, but differs in the thicker peridium and wider spores in one-spored asci. Molecular analysis of the internal transcribed spacer region and large subunit of ribosomal DNA also supports that T. thailandicum is clearly different from previously described whitish truffle species. It grows in mycorrhizal association with Betula alnoides, and the morphology and anatomy of mycorrhizae are described. Moreover, the identification of mycorrhizal status was confirmed by molecular methods.

First report of sour rot on tomato caused by Galactomyces reessii in Thailand

In May 2014, sour rot, an important postharvest disease of tomato, was found on tomato fruit (Solanum lycopersicum var. Roma) in Chiang Mai Province, Thailand. The causal yeast was isolated from lesions and identified as Galactomyces reessii based on morphological, biochemical and physiological characteristics and confirmed using comparisons of DNA sequences of D1/D2 domains of the large subunit ribosomal DNA. The isolated yeast caused rot symptoms on inoculated tomato fruits similar to natural symptoms in the field. This is the first report of tomato sour rot caused by G. reessii.

First report of Phoma leaf spot disease on cherry palm caused by Phoma herbarum in Thailand

Abstract A leaf spot disease caused by Phoma herbarum was observed in a plantation of cherry palm (Pseudophoenix sargentii) in Chiang Mai Province, Thailand. The fungus was isolated from lesions on leaves and pathogenicity tests showed that Ph. herbarum could infect P. sargentii, producing the same symptoms after inoculation as those observed naturally in the field. The fungus was identified based on morphological characteristics and confirmed using comparisons of DNA sequences of internal transcribed spacer (ITS)1, 2 and 5.8S rDNA. This is the first report of this disease on cherry palm.

Biosynthetic pathway and optimal conditions for the production of indole-3-acetic acid by an endophytic fungus, Colletotrichum fructicola CMU-A109

Endophytic fungi are known to produce indole-3-acetic acid (IAA), which can stimulate plant growth. Twenty-seven isolates of endophytic fungi were isolated from Coffea arabica in northern Thailand. Only one isolate (CMU-A109) produced IAA in vitro. This isolate was identified as Colletotrichum fructicola based on morphological characteristics and molecular phylogenetic analysis of a combined five loci (internal transcribed spacer of ribosomal DNA, actin, β-tubulin 2, chitin synthase and glyceraldehyde-3-phosphate dehydrogenase genes). Identification of a fungal IAA production obtained from indole 3-acetamide (IAM) and tryptophan 2-monooxygenase activity is suggestive of IAM routed IAA biosynthesis. The highest IAA yield (1205.58±151.89 μg/mL) was obtained after 26 days of cultivation in liquid medium supplemented with 8 mg/mL L-tryptophan at 30°C. Moreover, the crude fungal IAA could stimulate coleoptile elongation of maize, rice and rye. This is the first report of IAA production by C. fructicola and its ability to produce IAA was highest when compared with previous reports on IAA produced by fungi.

Leaf spot on cattleya orchid caused by Neoscytalidium orchidacearum in Thailand

Abstract Leaf spots caused by plant pathogenic fungi are among the main diseases affecting orchid plants worldwide. A leaf spot disease was widespread in a nursery of cattleya orchid (Cattleya lueddemanniana var. lueddemanniana) in Lampang Province, Thailand in 2016. A fungus was isolated from leaf lesions and identified as Neoscytalidium orchidacearum based on morphological characteristics and the identification was confirmed using a molecular phylogenetic analysis of the combined internal transcribed spacer and large subunit regions of ribosomal DNA sequences. The isolated fungus caused spot symptoms on inoculated orchid leaves similar to symptoms observed in the field. This is the first report of orchid leaf spot disease caused by N. orchidacearum.