Assessment of Genetic Diversity of the Rice Dirty Panicle Fungus Curvularia lunata in Thailand

Abstract

Rice dirty panicle disease decreases both the quality and quantity of rice production in Thailand. Curvularia lunata is one of six fungal pathogens involved in the disease and the main causal agent based on disease survey data. The survey and sampling of rice dirty panicle disease were conducted in northern, eastern, central and southern Thailand including 194 fields in 20 provinces. One hundred and twenty two isolates of C. lunata were detected which were divided in to seven groups based on morphological characteristics. Physiological race was screened on 15 differential varieties of rice. Thirty three races from 40 isolates were identified which were divided into six groups by the CANBERRA method and UPGMA clustering using the Numerical Taxonomy System (NTSYS) pc. version 2.20e. The genetic variability of C. lunata was assessed by AFLP markers using nine primer combinations. The 121 polymorphic bands observed were analyzed using Dice’s similarity and UPGMA clustering method in NTSYS program. Eighteen isolates of C. lunata were separated into three groups with a 0.95 cophenetic correlation and a highly supportive bootstrap value. The results indicated that C. lunata causing rice dirty panicle disease in Thailand has a high diversity, which must be taken into consideration in assessing varietal resistance.