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Abstract. Pramunadipta S, Widiastuti A, Wibowo A, Suga H, Priyatmojo A. 2020. Short Communication: Sarocladium oryzae associated with sheath rot disease of rice in Indonesia. Biodiversitas 21: 1243-1249. One of the obstacles in increasing rice production is the presence of sheath rot pathogen infection, which causes changes in color on the rice sheath to brown or reddish-brown, sometimes does not produce rice grain. The major fungal pathogens that cause sheath rot disease are Sarocladium oryzae and Fusarium spp. The loss of rice yields reaches 85%. The disease found in six provinces, some of which are the largest rice-producing centers in Indonesia. A total of twenty-four Sarocladium sp. were isolated from leaf sheath symptom on potato dextrose agar and water agar medium. Sheath rot pathogen identification based on molecular method was performed using internal transcribed spacer (ITS) rDNA gene sequencing. Necrosis occurs after artificial inoculation in Ciherang rice variety was observed and showed that all isolates were pathogenic. Morphological characterization of the isolates identified them as Sarocladium sp. Molecular identification showed that six representatives isolates belonging to S. oryzae. These findings are important information about the fungal pathogen that causes sheath rot disease in Indonesia, and in studies for formulating control measures of the pathogen in the future to prevent the disease epidemic on rice. This is the first report about the existence of sheath rot disease, morphological characterization and molecular identification of S. oryzae in various rice fields in Indonesia.

Fusarium incarnatum-equiseti species complex (FIESC) contain over 40 members. The primer pair Smibo1FM/Semi1RM on the RPB2 partial gene has been reported to be able to identify Fusarium semitectum. The F. fujikuroi species complex (FFSC) contains more than 50 members. The F. verticillioides as a member of this complex can be identified by using VER1/VER2 primer pair on the CaM partial gene. In this research, the Smibo1FM/Semi1RM can amplify F. sulawesiense, F. hainanense, F. bubalinum, and F. tanahbumbuense, members of FIESC at 424 bp. The VER1/VER2 can amplify F. verticillioides, F. andiyazi, and F. pseudocircinatum, members of FFSC at 578 bp. Polymerase chain reaction-restriction fragment length polymorphism by using the combination of three restriction enzymes EcoRV, MspI, and HpyAV can differentiate each species of FIESC used. The two restriction enzymes HpaII and NspI can distinguish each species of FFSC used. The proper identification process is required for pathogen control in the field in order to reduce crop yield loss.

Rice becomes the main commodity cultivated in Asia. Sheath rot disease becomes one of the challenges in increasing rice production. Sarocladium oryzae is known to be one of the major pathogens in causing sheath rot disease. This pathogen has been reported in several rice production countries, such as Brazil, India, Taiwan, Philippines, Thailand, including Indonesia, and causing yield loss of up to 85%. The study of genetic diversity is important to investigate the rapid shift in genetic structures. A total of six S. oryzae strains showed diverse in molecular using repetitive-PCR (rep-PCR). The isolate SO8 and SO13 isolate SO2 and SO11 and isolate SO3, and SO5 has the relatively same the band patterns in BOX, ERIC, and REP sets of primers. The results of the UPGMA analysis show that S. oryzae in the various primers can be divided into three different group consistency. This result indicates that the rep-PCR method can genetically distinguish S. oryzae. The use of the three main sets, BOX, ERIC, and REP, suggested differentiating the other fungal species.

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