Comparative study of Pseudomonas solanacearum peanut and tomato isolates

Bacterial wilt in peanut has recently become increasingly important in Thailand, causing severe damages in a certain local cultivar grownh in some areas in the Central Plain. It also was found occasionally, although at a very low incidence, in Chaiyaphum province in the Northeast. These findings indicated the potential of this disease to become outbreak in major growing areas. Therefore, information on the nature of the disease, its etiology and epidemiology are deem necessary. It is widely known that tomato isolates of P. solanacearum can be found in almost any planting areas including those in the Northeast, but wilt in peanut has never been reported or rarely occurs in those areas. This indicates certain differences from the two isolate. In this study, their reactions on common hosts and serological reactions were investigated. When inoculated into Sida tomatoes, the tomato isolate Srichiangmai 11 (TS-11) caused a very severe symptom and subsequently the plants were killed. The peanut isolate Nakhon Sawan (PN-N) (Kindly contributed by the DOA) induced only systemic chlorosis, and the plants survived until fruiting. In contrast, when PN-N was inoculated to Khon Kaen 60-2 and Tainan 9 peanuts, the whole plants withered rapidly and were eventually killed. The TS-11 isolate, however, withered only the inoculated quadrifoliate or caused necrosis along midribs of some leaves and the plants recovered and appeared normal. An antiserum prepared from membrane protein complex (MPC) of TS-11 reacted only to the homologous isolate and other tomato isolates but not PN-N isolate when tested by DAC ELISA. The concentration of primary antiserum was 1:5000 in a conjugate buffer. When undiluted antiserum of TS-11 and other antisera against whole cells of various tomato isolates were used in gel double diffusion test, the antigens from peanut isolate appeared to give two precipitin bands to the antisera against isolates collected from Khon Kaen province (TNS-E and TKKU-B) but only one band was detected if reacted with anti TS-11 and T3204 isolates collected form Nong Kai.