PCR-based molecular approaches including RAPD (random amplified polymorphic DNA), ISSR (inter-simple sequence repeat), and SRAP (sequence-related amplified polymorphism) are commonly used to analyze genetic diversity. The aims of this study are to analyze genetic diversity of M. oryzae isolates using PCR-based molecular approaches such as RAPD, ISSR, and SRAP and to develop SCAR marker linked to the pathogenicity of rice blast fungus. Twenty Magnaporthe oryzae isolates were collected mainly from the south of Vietnam and assessed for genetic variation by RAPD, ISSR, and SRAP methods. The comparison of those methods was conducted based on the number of polymorphic bands, percentage of polymorphism, PIC values, and phylogenetic analysis. Then, sequenced characterized amplified region (SCAR) markers were developed based on specific bands linked to fungal pathogenicity of rice blast fungus, M. oryzae. The results indicated that SRAP markers yielded the greatest number of polymorphic bands (174) and occupied 51.7% with polymorphism information content (PIC) value of 0.66. Additionally, the SRAP approach showed stability and high productivity compared with RAPD and ISSR. The SCAR marker developed from the SRAP method identified the presence of the avirulence AVR-pita1 gene involving fungal pathogenicity that can break down blast resistance in rice cultivars. The consistency of SCAR marker obtained in this study showed its efficiency in rapid in-field detection of fungal pathogenicity. SCAR marker developed from SRAP technique provides a useful tool for improving the efficiency of blast disease management in rice fields.

基于 PCR 的分子方法包括 RAPD（随机扩增多态性 DNA）、ISSR（简单序列间重复序列）和 SRAP（序列相关扩增多态性）常用于分析遗传多样性。本研究的目的是使用基于 PCR 的分子方法（如 RAPD、ISSR 和 SRAP）分析米曲霉分离株的遗传多样性，并开发与稻瘟病真菌致病性相关的 SCAR 标记。二十株稻瘟病菌分离株主要从越南南部收集，并通过 RAPD、ISSR 和 SRAP 方法评估遗传变异。这些方法的比较是基于多态性条带的数量、多态性的百分比、PIC 值和系统发育分析进行的。然后，基于与稻瘟病真菌M. oryzae 的真菌致病性相关的特定条带开发了测序特征扩增区域 (SCAR) 标记。结果表明，SRAP标记产生的多态性条带数量最多（174条），占51.7%，多态性信息含量（PIC）值为0.66。此外，与 RAPD 和 ISSR 相比，SRAP 方法显示出稳定性和高生产率。从 SRAP 方法开发的 SCAR 标记确定了无毒力的存在AVR-pita1基因涉及真菌致病性，可以破坏水稻品种的稻瘟病抗性。本研究中获得的 SCAR 标记的一致性表明其在现场快速检测真菌致病性方面的效率。由SRAP技术开发的SCAR标记为提高稻田稻瘟病管理效率提供了有用的工具。