Identification and distribution of fungal pathogens associated with seedling blight of rice in the southern United States

Abstract

Surveys were conducted in the five southern rice‐producing states of Arkansas, Louisiana, Mississippi, Missouri and Texas in the United States during the 2018 and 2019 cropping seasons to determine the distribution and pathogenicity of fungal pathogens associated with seedling blight in rice. A total of 349 pathogenic fungal isolates were collected and identified as belonging to four genera: Rhizoctonia solani, Fusarium spp., Sclerotium rolfsii and Marasmius graminum based on morphological characteristics, molecular analysis and Koch's postulates. R. solani (252 out of 349 pathogenic isolates) was the most prevalent fungus isolated from diseased samples. Of the 252 pathogenic R. solani isolates, 245 were further classified as anastomosis group 11 (AG‐11) and 7 as AG‐4. Isolates of R. solani AG‐4 and M. graminum were the most aggressive, with the highest stand loss (63% to 100%) and median disease rating (DR; 5.0), followed by isolates of R. solani AG‐11 (stand loss = 4% to 100% and DR = 0.6 to 5.0), Fusarium spp. (stand loss = 26% to 48% and DR = 2.0 to 5.0) and S. rolfsii (stand loss = 33% to 48% and DR = 2.0 to 3.0) in causing seedling blight in rice. R. solani (62% to 83% of total pathogenic isolates) and Fusarium spp. (10% to 24% of total pathogenic isolates) were predominant in all the five states surveyed. S. rolfsii and M. graminum were present only in Louisiana and Texas. The results of this first systematic survey of rice seedling diseases in the southern United States will help develop effective fungicide seed treatment strategies for control of stand loss caused by seedling blight, one of the major factors limiting rice production.

Multiple Biosynthetic Gene Pathways are Revealed in Whole-Genome Sequence of Endophytic Biocontrol Strain Pantoea stewartii subsp. indologenes ST25

“…Rice seeds were ground in PBS using a sterile mortar and pestle. Strain ST25 was demonstrated to be non-pathogenic to rice, with antifungal activities against Rhizoctonia solani AG11 and R. solani AG4, two causative agents of seedling blight in rice, in our previous study ( 4 ).…”

De novo genome sequence of endophytic biocontrol strain Bacillus sp. ST24 isolated from rice seed

“…Approximately 20 g of seeds was ground in phosphate-buffered saline (PBS) buffer using a sterile mortar and pestle and plated on tryptic soy agar (TSA). Strain ST24 exhibited strong antagonistic activities against Rhizoctonia solani AG11 and R. solani AG4, the causative agents of rice seedling blight ( 5 ), in our in vitro dual-culture plate assays ( 6 ).…”

Streptomyces as a promising biological control agents for plant pathogens

“…U. virens thrives in 25–30°C and >90% relative humidity ( Abade et al, 2021 ). Early seedling blight ( Sclerotium oryzae , Sclerotium rolfsii ) is a major developing disease in nursery beds during the cold season (winter months) ( Gaire et al, 2023 ). Seedlings in the nursery bed begin withering.…”