First Report of Pythium sylvaticum Causing Corn Root Rot in Northeastern China

Area of Science:

• Plant Pathology
• Mycology
• Agricultural Science

Background:

• Corn is a vital global crop, with increasing importance in China.
• Recent years have seen frequent poor corn seedling stands in northeastern China, leading to significant economic losses.
• Observed symptoms include stunted growth, necrotic roots, and plant collapse.

Purpose of the Study:

• To identify the causal agent of poor corn seedling stands in Heilongjiang province, China.
• To confirm the pathogenicity of the isolated organism on corn.
• To provide foundational data for disease management strategies.

Main Methods:

• Soil samples were collected from affected fields in Heilongjiang province.
• Corn seedlings were grown in collected soil, and pathogens were isolated from symptomatic roots using selective media (PARP+B).
• Morphological characterization and molecular analyses (COⅡ and ITS gene sequencing) were used for pathogen identification.
• Pathogenicity was confirmed through controlled greenhouse experiments, fulfilling Koch's postulates.

Main Results:

• A fungal isolate, designated COPS, was identified as Phytophthora sylvaticum based on morphological and molecular data.
• Sequence analysis showed high identity (97.93% for COⅡ, 99.89% for ITS) with known P. sylvaticum isolates.
• Pathogenicity tests successfully reproduced field symptoms in corn seedlings, and the pathogen was re-isolated from diseased plants.

Conclusions:

• This study reports the first occurrence of Phytophthora sylvaticum causing disease in corn in China.
• The identified pathogen poses a significant risk to corn production in the region.
• Accurate identification of P. sylvaticum is essential for developing effective control measures.