| Late blight of Tomato mainly depends on the temperature 18～22°C and the humidity 100%.To complex climate in China, climate rapidly changes in the middle and lower reaches of Changjiang River especially, which was favorable to happening of late blight of tomato. Jiangsu Province is lie in the middle and lower reaches of Changjiang River, which is one of the main tomato growth regions. Owing to geography intersection, climate transition, growth multiplicity, pathogen complexly distributed in according to climate and growth fashion. Disease occurs more and more, and it brings on worse influence to output of tomato. It is necessary that researches carry on late blight of tomato. It was no report that researches on genetic analysis of tomato resistance to late blight and protective enzyme activities on tomato inoculated with Phytophthora infestans were carried. There were a few reports on isolating of pathogen and variety of resistance, but variety of resistance varied the races in the different zones. Therefore, the races was isolated and identified in the Jiangsu Province and part of neighbor zone where lied in the middle and lower reaches of Changjiang River. In order to definitude buildup and distributing of the races in the zone, varieties of tomato were inoculated with preponderant race in order to screening of resistance resource of tomato to late blight. The researches on genetic analysis of tomato resistance to late blight and changes in protective enzyme activities on tomato inoculated with Phytophthora infestans were carried, in order to provide reference for gene marker and breeding resistance cultivar on late blight on tomato. It made progress in the four fields as follows:1. Identification of physiological races of Phytophthora infestans on tomato in Jiangsu province and part neighbor zoneThirty-five isolates were obtained from 72 tomato late blight specimens collected from Jiangsu Province and part of neighbor zone. The result indicated that the isolates were assessed with five differential tomato cultivar from The World Vegetable Center, T0, T1, T1.2, T1.2.3, T1.3.4. Race T1.2 was widely distributed and predominant one with a frequency of 45.7%. Followed by T1 occurred with frequency of 25.8%, The races T1.2.3, T1.3.4, T0 were narrowly distributed with frequencies of 17.1%,5.7% and 5.7% respectively.2. Screening of resistance resource of Late Blight on tomatoMethods of the artificial spraying inoculation were used by dominant race T1.2 in the seedlings of 54 tomato varieties or lines. The result indicated that high resistance cultivar ratio is 14.8%, which were from wild tomato species or wild tomato accessions.7.4% is the interim resistance cultivar ratio. High susceptible cultivar ratio is 77.8%, which they were dominant cultivated tomato in Jiangsu Province. It is necessary that and introducing resistance sources and breeding resistance cultivars were used in tomato production in Jiangsu Province.3. Study on physiological reaction of Phytophthora infestans on tomatoThe changes of PAL,POD,SOD,CAT,APX activities tomato were studied by infecting with Phytophthora infestans and analysis the physiological basis of tomato breeding for resistant to late blight. The results showed that the activities of PAL,POD,SOD,CAT in resistant cultivar and susceptible cultivar were significantly stronger than of the control (CK) after infection;Besides CAT, increase in activity of three enzymes in resistant cultivar varied faster and higher than those in susceptible cultivar,the activities of CAT in resistant cultivar was lower than those in susceptible cultivar and the control;the activities of APX in susceptible cultivar were higher than that of the control (CK),with the peak value increased by 20.83%,but the activities of APX in resistant cultivar was inferior to the control (CK),with the peak value increased by 41.18%.Analysis of variance to the changes of PAL,POD,SOD,CAT,APX activities after inoculated by Phytophthora infestans to tomato.The result showed that the difference of activity of peroxidase existed between resistant cultivars and susceptible cultivar at the level of 0.01 and 0.05. Difference and great difference existed between resistant cultivars and the control. There was no difference or a little difference between susceptible cultivar and the control. Therefore, it must confer the level of resistance of tomato to late blight by great difference of activity of peroxidase after inoculating with Phytophthora infestans to tomato cultivars.4. Genetic analysis of resistance Late Blight on tomatoGenetic analysis showed that Tomato resistance to Late Blight was incomplete recession. Average degree of dominance was fewer than one. Effect of back-cross was very obviously, effect of reciprocal cross is obvious too. Resistance was dominated by cytoplasm gene, and effect of cytoplasm and nucleolus were existed together. Through analysis of F1 and F2 generation, at least there were more than two pairs of genes to control the resistance. To some evident, the resistance to Late Blight was a quantitative character. Narrow heritability is comparatively high, and this showed in the inheritance of Tomato resistance to Late Blight, there was a comparatively big additive variance and comparatively small non-additive variance. This indicated heritability of Tomato resistance to Late Blight was very strong.Analysis of variance and analysis of combing ability were carried out in complete diallel-cross generation of four parents. The result showed both general coming ability (GCA) and special coming ability (SCA) were very obvious, but general coming ability was much bigger than special coming ability, and the ratio (GCA/SCA) was 37.4987. This showed the additive effect was major. Through genetic analysis of variance and covariance, the resistance conformed to the additive-dominance model, and both additive effect and dominance were major, but interaction between non-allelomorph was not obvious.
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