关键词: Esteya vermicola, 内寄生真菌, 松材线虫, 侵染力, 产孢

Abstract: [Objective] As one of the most serious worldwide conifer diseases, pine wilt disease caused by pinewood nematode (PWN), Bursaphelenchus xylophilus, has brought irreparable damages to the forest ecosystems and industries with great economic and environmental losses. Esteya vermicola is the first recorded endoparasitic fungus of PWN, has exhibited high infectivity and potential as a biocontrol agent of pine wilt disease. Through the comparison among different E. vermicola isolates in their morphological characteristics, sporulation and infectivity against PWN, the excellent isolate can be screened out and to be developed as the biocontrol agent of pine wilt disease. This work will provide useful knowledge and information for the biocontrol of devastating pine wilt disease in the future.[Method]Four E. vermicola isolates (ATCC 74485 and CNU 120806 from Asia, CBS 115803 and CBS 100821 from Europe) were compared systemically in terms of the growth, sporulation and infectivity against PWN with three most commonly used nature culture media for the nematophagous fungi (potato dextrose agar, corn meal agar and 2% water agar, served as an example of carbon nutrition-rich, -weak and -poor culture media, respectively). In addition, the influences of carbon sources on the growth, sporulation and infectivity of four isolates also were simply analyzed.[Result] Four E.vermicola isolates showed obvious variation on different culture media in terms of the colonial feature, growth speed, sporulation and infectivity, although they shared the basic morphological characteristics and nematode infection process. The nutrition of culture medium showed different influences on the growth, sporulation and infectivity of different isolates, had a markedly positive correlation with the growth and sporulation of E.vermicola, but a negative correlation with the proportion of lunate infective conidia and the infectivity against PWN. Among the four isolates, the growth speed and total conidia number of ATCC 74485 were the highest (P<0.01), but the number and proportion of its lunate conidia were the lowest (P<0.01), and hence had the lowest (P<0.05) infectivity against PWN in which it was the same as CNU 120806. On the contrary, although CBS 115803 showed slightly slower growth speed, it produced the biggest amount and the highest proportion of lunate infective conidia, and accordingly exhibited the highest (P<0.01) infectivity by killing all of the tested PWNs within three days. In addition, the isolates from the same continent (Asia or Europe) shared similar characteristics in the colony morphology, growth, sporulation and infectivity, suggesting that the geographical location has an influence on E.vermicola characteristics to some extent.[Conclusion] Although E.vermicola CBS 115803 showed slower growth speed, it produced the biggest amount of infective conidia and exhibited the significantly higher (P<0.01) infectivity against PWN than the other three isolates did. Therefore, CBS 115803 can be selected and developed into the biocontrol agent against pine wilt disease in the future.

Key words: Esteya vermicola, endoparasitic fungus, pinewood nematode, infectivity, sporulation