• 식물병연구
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• 제30권1호
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• pp.78-81
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• 2024

This study aims to isolate and identify the fungal pathogen responsible for gummosis disease affecting Thanh Tra pomelo in Vietnam. Through molecular identification utilizing primer pairs ITS5 and ITS4, the analysis pinpointed Lasiodiplodia theobromae as the specific fungal pathogen. Notably, the fungal colonies exhibited vigorous growth on potato dextrose agar. Initially, these colonies appeared whitish-grey, transforming into a black-grey hue within 5-7 days at a temperature of 30℃. According to previous reports, Phytophthora spp. was the most common pathogenic genus causing gummosis on Thanh Tra pomelo in Vietnam. To our knowledge, this is the first report on L. theobromae causing gummosis on Thanh Tra pomelo in Vietnam.

• Mycobiology
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• 제43권1호
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• pp.63-70
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• 2015

Phytophthora diseases have become a major impediment in the citrus production in Thailand. In this study, an isolate of Phytophthora denominated as PHY02 was proven to be causal pathogen of root rot of Pomelo (Citrus maxima) in Thailand. The isolate PHY02 was morphologically characterized and identified as Phytophthora palmivora based on molecular analysis of an internal transcribed spacer rDNA sequence. This work also presents in vitro evaluations of the capacities of Chaetomium spp. to control the P. palmivora PHY02. As antagonists, Chaetomium globosum CG05, Chaetomium cupreum CC3003, Chaetomium lucknowense CL01 inhibited 50~61% mycelial growth, degraded mycelia and reduced 92~99% sporangial production of P. palmivora PHY02 in bi-culture test after 30 days. Fungal metabolites from Chaetomium spp. were tested against PHY02. Results showed that, methanol extract of C. globosum CG05 expressed strongest inhibitory effects on mycelial growth and sporangium formation of P. palmivora PHY02 with effective dose ED50 values of $26.5{\mu}g/mL$ and $2.3{\mu}g/mL$, respectively. It is interesting that C. lucknowense is reported for the first time as an effective antagonist against a species of Phytophthora.

• Mycobiology
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• 제43권3호
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• pp.288-296
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• 2015

Thailand is one of the largest citrus producers in Southeast Asia. Pathogenic infection by Phytophthora, however, has become one of major impediments to production. This study identified a pathogenic oomycete isolated from rotted roots of pomelo (Citrus maxima) in Thailand as Phytophthora nicotianae by the internal transcribed spacer ribosomal DNA sequence analysis. Then, we examined the in vitro and in vivo effects of Chaetomium globosum, Chaetomium lucknowense, Chaetomium cupreum and their crude extracts as biological control agents in controlling this P. nicotianae strain. Represent as antagonists in biculture test, the tested Chaetomium species inhibited mycelial growth by 50~56% and parasitized the hyphae, resulting in degradation of P. nicotianae mycelia after 30 days. The crude extracts of these Chaetomium species exhibited antifungal activities against mycelial growth of P. nicotianae, with effective doses of $2.6{\sim}101.4{\mu}g/mL$. Under greenhouse conditions, application of spores and methanol extracts of these Chaetomium species to pomelo seedlings inoculated with P. nicotianae reduced root rot by 66~71% and increased plant weight by 72~85% compared to that in the control. The method of application of antagonistic spores to control the disease was simple and economical, and it may thus be applicable for large-scale, highly effective biological control of this pathogen.

• 한국환경농학회지
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• 제27권3호
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• pp.253-259
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• 2008

과수의 생육기간동안 양분흡수는 과원토양의 환경에 영향을 받는다. 수확기에 신고 배에 Ca 결핍장해과로 보이는 과실의 발생 원인을 조사하기 위하여 과실에 생리장해가 발생한 4개 지역(울산,경주,평택,안성)의 과원 토양의 화학성 및 잎과 과실의 무기성분 함량을 조사하였다. 과실에 생리장해가 발생한 과원 토양의 치환성 Ca 함량은 정상관원에 비해 낮은 반면, 치환성K와 Mg 함량 및 T-N 함량은 높았다(P=0.05). 생리장해 과실의 과육과 과피의 Ca 함량은 건전한 과실에 비해 낮았으며, 과육과 과피의 Mg/Ca 비율은 건전 과실보다 높았다(P=0.05). 잎에 N/Ca 및 K/Ca 비율은 생리장해가 발생한 나무가 건전한 나무의 잎 보다 높았다. 따라서 신고 배의 생리장해는 Ca 함량의 부족에 의해 발생하는 유부과로 판단되며, 이는 토양에 치환성 K와 Mg 이온 및 T-N가 Ca 이온의 흡수에 장해요인으로 작용한 것으로 생각된다.