Abstract
Sheath blight, caused by the fungal pathogen Rhizoctonia solani AG-1 IA is one of the most important rice diseases worldwide. The objetives of this study was to determine the predominant reproductive system and the genetic structure of 18 rice-infecting populations of R. solani sampled from China, Japan and the Philippines, the most important rice production countries in Asia. Knowledge about the population genetic structure of the pathogen in Asia is useful in identifying sources of infection and formulating sustainable management strategies for rice sheath blight. From a total of 717 isolates, 423 unique multilocus genotypes were detected based on nine microsatellite loci. The three country populations of R. solani AG-1 IA exhibited a mixed reproductive system, which included both sexual and asexual components. A moderate degree of clonality indicated that the asexual sclerotia represent important source of inoculum. Population subdivision varied within and among countries, fitting the isolation by distance model. While no subdivision was found among populations within Japan or within the Philippines, subdivision was detected among populations within China. Historic migration indicated high influx of immigrants from Japan into Northern, Central and Eastern China populations. Southern China contributed a high number of immigrants to the populations from the Philippines.
Highlights
The basidiomycetous fungus Rhizoctonia solani Kühn [sexual stage: Thanatephorus cucumeris (Frank) Donk] anastomosis group 1 index of association (IA) (AG-1 IA) is an extremely important soilborne pathogen causing the rice sheath blight disease, which has a worldwide distribution (Lee & Rush, 1983; Singh, Sunder, & Kumar, 2016)
The main objectives of this study were: (i) to determine the main reproductive system shaping the structure of R. solani AG-1 IA populations from Japan and the Philippines and compare with the structure described for the Chinese populations of the pathogen (Bernardes de Assis et al, 2009); (ii) to determine the current levels of gene flow and differentiation among regional populations of the pathogen; and (iii) to determine the main historical migration path associated with the current genetic struture of regional and country populations of R. solani AG-1 IA
A total of 423 different miltilocus genotypes were identified among the 717 isolates analysed from the 18 regional rice-infecting populations of R. solani AG-1 IA sampled from China, Japan and the Philippines (Table 1)
Summary
The basidiomycetous fungus Rhizoctonia solani Kühn [sexual stage: Thanatephorus cucumeris (Frank) Donk] anastomosis group 1 IA (AG-1 IA) is an extremely important soilborne pathogen causing the rice sheath blight disease, which has a worldwide distribution (Lee & Rush, 1983; Singh, Sunder, & Kumar, 2016). Sheath blight ranks as the second most important rice disease in China, Japan and in Southeast Asia countries. Yield losses due to the rice sheath blight has been estimated as 24 – 38 thousands tons per year in Japan but can reach 6 million tons of rice grains per year in China. In the Philippines, rice sheath blight can cause 5 – 80% reduction in rice grain yield and the yield losses per hectare ranges from 0.27 – 1.29 tons in the dry season to 0.23 – 1.37 tons in the wet season (Ou, 1985; Ren, Gao, & He, 2001). Disease management practices with fungicides increases the production costs, are not fully effective and may select for resistance in the pathogen’s populations, besides causing environmental impact (Gnanamanickam, 2009; Singh et al, 2016)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
