การระบุชนิดของเชื้อราสกุล Annulohypoxylon และ Hypoxylon ในพื้นที่ภาคใต้ของประเทศไทย และการนำไปใช้ควบคุมโรคใบจุดในต้นกล้าปาล์มน้ำมัน

Abstract

Annulohypoxylon and Hypoxylon are fungal species currently belonging to the family Hypoxylaceae that separated from family Xylariaceae (Phylum Ascomycota). These fungal genera are the decomposers that play an important role in the ecosystem. They can produce many beneficial secondary metabolites and enzymes. In Southern Thailand, the study of these fungal genera are limited because they are high diversity and difficult to identify by morphological characteristics. Thus, in this study one hundred forty-six samples of Annulohypoxylon and Hypoxylon were collected from the nature trail, planted forest and rubber plantation in Southern Thailand except for three border provinces (Pattani, Yala and Narathiwat). All collected samples were identified based on morphological and molecular characterization. They were classified into 15 species (4 species of genus Annulohypoxylon and 11 species of genus Hypoxylon) namely A moriforme, A nitens, A. stygium, A. thailandicum, H. duranii, H. fendleri, H. griseobrunneum, H. haematostroma, H. hypomiltum, H. jaklitschii, H. lenormandii, H. macrocarpum, H. monticulosum, H. pilgerianum and H. sublenormandii. Besides, twelve species were undescribed. Forty-five culturable isolates were grown on PDA and tested for their antagonistic properties by dual culture technique. The results showed three efficacy groups of the fungi; the first group presented the percentage inhibition of Curvularia oryzae over 70% i.e. A moriforme (SKW12), A. nitens (PNGPW04) and A. stygium (PTW09). The second group, mycelium grew rapidly and covered colony of C. oryzae i.e. A nitens (SKW11) and Hypoxylon species C (STW04). The final group presented the colony abnormalities of C. oryzae l.e. H. lenormandii (CHPWO3), H. polyporoideum (SKWPMO2), H. sublenormandii (SKW30) and H. fendelri (PJB04). After that, three groups of fungi were screened for the production of chitinase, celtulase, and volatile compound for inhibition the mycelial growth of C. oryzae It was found that A. moriforme (SKW12), A. nitens (PNGPW04) and A. stygium (PTW09) could produce chitinase to degrade fungal cell wall and produced volatile organic compound to inhibit mycelial growth of C. oryzae. The culture filtrates of 3 selected isolates were tested for the inhibition ability against C. oryzae. The result showed that all culture filtrates were not inhibited the hyphal growth of C. oryzae in laboratory condition. Therefore, the mycelial suspension of A. nitens (PNGPW04) and A stygium (PTW09) were tested for disease control on oil palm leaf by detached leaf technique. Fifteen percentage (W/v) of mycelial suspension of A. nitens (PNGPW04) showed a lower level of disease incidence (0.66) and not significantly different from the other high concentrations while the mycelial suspension of A. stygium (PTW09) covered oil palm leaf that may effected to photosynthesis. Therefore, the used of mycelial suspension to control leaf spot on oll palm seedlings was investigated The mycellal suspension of A nitens (PNGPW04) was low eficency to control leaf spot disease when compared with mancozeh.