F1 hybrid true potato seed progenies with multiple sources of specific resistance to Pseudomonas solanacearum and adaptation were evaluated under tropical greenhouse conditions for resistance to a race 1 isolate of P. solanacearum . Results indicated that genes for adaptation are involved in conferring resistance to bacterial wilt . The effect of a particular resistant parent clone on the resistance level of its progeny depended on the resistance, adaptation or the combination of both characteristics of its mate . A heat tolerant parent gave a higher frequency of resistant offspring in combination with an ascertained source of resistance . Combining ability was an apparent feature of resistance to bacterial wilt and resistance was highest in the majority of the crosses that had a wide genetic background for both resistance and adaptation . The possible genetic nature of the resistance to bacterial wilt is discussed.

Host-pathogen-environment interaction in the potato -P. solanacearum pathogenic system was investigated by testing eight true potato seed progenies and four clones for resistance to three potato isolates of P . solanacearum under two temperature regimes . Highly significant interactions of all types : progeny x isolate, isolate x temperature, progeny x temperature, and progeny x isolate x temperature were observed . Changes in pathogenicity of isolates with temperature were the major source of the total variation . Host-pathogen interaction effect was small as compared to the main (progeny, isolate) effects . Aspects of strain specificity and host-pathogen interaction are discussed .

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