Abstract :
A study was carried out to isolation and diagnosis of damping –off pathogen of eggplant seedlings (Solanum melongena) in Hamza AL-Garby nurseries, Babylon Province, also detect the biocontrol potential by Trichoderma harzianum for this disease and a relationship between eggplant cultivar and biocontrol and induced the resistance by T. harzianum ,also, detect the percentage of entirely colonized roots of eggplant cultivars by T. harzianum. The results of isolation and pathogenicity showed that pathogen of damping –off of eggplant was Fusarium verticillioides (Saccardo) Nirenberg (previously F. moniliforme Sensu) that isolated from infected stems of eggplant seedlings .The results of biological control showed that biological agent T.harzianum was highly reduced percentages of disease to 7.5 and 5.9% in Abdasud and Mosully eggplant cultivars respectively compared with control treatment(37.75and 20% respectively), but it increased percentages of disease in Black Beuty cultivar to 20% compared with control treatment that was 6.25% . Therefore there are difference between eggplant cultivars in response to efficacy of T.harzianum . Abdasud cultivar was significantly more susceptible than other cultivars with percentages of disease was 37.75% , its followed by mosully cultivar . Bioassay of induced resistance as increase of peroxidase activity showed that T.harzianum and F. verticillioides were significantly increased of peroxidase activity in all cultivars tissues of eggplant compared with control except the treatment of peroxidase activity in Black Beuty tissues which was infested by F. verticillioides. The higher increase of peroxidase activity after infection with pathogen was in seedling of eggplant cv. Abdasud then Mosully .Also, there are difference in percentage of entirely colonized roots of eggplant cultivars by T. harzianum, therefore higher percentage of entirely colonized roots was in eggplant cv. Abdasud compared with other cultivars. Therefore, I think that there are positive correlation among biocontrol , induced resistance and percentage of entirely colonized roots by T. harzianum ,also there are negative correlation between biocontrol and susceptibility of cultivars to infection such as observed in Abdasud cultivars .
