(1) In order to obtain the fundamental aspects on the breeding of disease-resistant tomatoes for processing, the varietal difference was investigated, for resistance to lateblight through inoculation experiments.
Phytophthora infestans (potato race O) was inoculated on the upper and lower leaves (the 4th position leaves from top and the lowest leaves) of tomatoes grown on the same cultivated conditions. Inoculations were given three times in each experiment.
(2) Twenty-one varieties and strains of tomatoes were usea as test plant, such as :
wild strains - West Virginia Accession 700 and 36 ; Italian breeding line for processing - SM_1, SM_2, C_1, SM_3, ASM, LP-3, LP-7 : determinate varieties Roma, Minori, Eary Pack, Ace, ES-24 Campbell 135, varieties for both as edibles and processing-Akafuku No.3, Majesty; edible varieties - Fukuju No-2, Asahi, and F_1 hybrids between commercial varieties and wild strains and its reciprocal cross (SM_2.× W.V.700).
(3) From the results of inoculations, both W.V.700 and W.V.36 showed the strong resistance to Phytophthora infestans, and W.V.700 was 0more resistant than W,V.36.
F_1 hybrids between SM_2. and W.V.700 showed resistance to late-blight fungus and stronger resistance was proved when W.V.700 was used as mother plant.
Among determinate varieties, the resistance decreased as the following order : Campbell＞ES-24＞Minori, but Early Pack, Ace and Roma were remained as susceptible varieties.
Among Italian breeding lines LP-3, LP-7, SM_3, ASM. were resistance but SM_2. and C_1 were susceptible.
Varieties for edibles and both as edibles and plocessing were proved to besusceptible to late-blight.