Submitted to: Thai Journal of Agricultural Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/12/2002
Publication Date: 1/20/2004
Citation: Thammakijjawat, P., Thaveechai, N., Kositratana, W., Chumwongse, J., Frederick, R.D., Schaad, N.W. 2004. Genetic variability of Ralstonia solanacearum strains from pepper (Capsicum annuum) in Thailand and their genetic relationship to strains from other hosts. Thai Journal of Agricultural Science. 35:397-408. Interpretive Summary: Bacterial wilt caused by Ralstonia solanacearum (RS) is responsible for severe losses in pepper crops in Thailand. To determine the genetic diversity among pepper strains of RS from Thailand, 21 strains from Thailand, five from Malaysia, and two from Taiwan along with 69 strains from other hosts in Thailand were investigated using restriction fragment length polymorphism (RFLP) assays. Results showed that the RS strains from Thailand were very different (30% related) from the Malaysia and Taiwan strains. The Thailand pepper strains typed together with strains from tomato, potato, tobacco, peanut, marigold and sesame. RS strains from ginger and pathumma clustered together, while the strains from potato formed a unique group. These results show that the pepper strains of RS from Thailand are genetically uniform and distinct from pepper strains from Malaysia and Taiwan.
Technical Abstract: Genetic variability of the bacterial wilt pathogen, Ralstonia solanacearum (RS), in Thailand was assesed using the amplified fragment length polymorphism (AFLP) technique. DNA was extracted from 97 RS strains, digested with EcoRI and Tru9I (MseI), ligated to adapter sequences, and selective PCR amplification was conducted with three different pairs of primers (Eco+0/Mse+C, Eco+0/Mse+G and Eco+A/ Mse+C). Twenty-one pepper strains from Thailand, five from Malaysia and two from Taiwan had 19 common bands and 118 polymorphic bands. Cluster analysis by unweighted pair-group method using an arithmetic average (UPGMA) with Dice's coefficient separated Thai strains from Malaysian and Taiwanese strains at 30 percent similarity. Results showed that the pepper Thai strains typed with strains from tomato, potato, tobacco, ginger, sesame, peanut, marigold and pathumma (Curcuma alismatifolia) and separated into three groups, which correlated to biovar properties. Group I, consisted of biovar 3 and divided into two subgroups, Ia strains from pepper, tomato, potato, tobacco, peanut, marigold, and Ib sesame strains. Group II contained biovar 4 strains from ginger and pathumma, whereas Group III included strains of biovar 2 from potato which have less than 10 percent similarity to Group I (biovar 3) and Group II (biovar 4) strains.