Effect of some Biotic and Abiotic Applications on Control of Fusarium Wilt of Pepper Plants

Six different pathogenic isolates of Fusarium oxysporum were recovered from diseased pepper plants collected from Dakahlya and Gharbya governorates, in Egypt. The F3 isolate of F. oxysporum recovered from Dakahlya samples was more aggressive hence produced 96.67% wilt severity, that being significantly higher than Tanta isolate F4 producing 71.67% severity. Remarkable variation in wilt producing potentials was found among other isolates denoting different pathogenic capabilities. Chemical substances inducing plant resistance against F. oxysporum were checked for their effect on linear growth of the pathogen. Dipotassium phosphates, potassium sorbate, salicylic acid, ascorbic acid along with chitosan, clove oil, mint oil and cumin oil were evaluated. Trichoderma hamatum and T. harzianum were also considered. A positive relation between a given inducer and inhibition of fungal growth in vitro was concluded. However, clove oil at low concentration (0.25%) inhibited completely the mycelial growth of pathogen, compared to other inducers that decreased the growth in a range between 42.2 and 91.9%, for the low concentrations. In greenhouse trials, a significant reduction in wilt was recorded. Immersed seedlings in the selecting concentration of inducers, bioagents, biocides and Topsin M70 fungicide were compared. The most effective treatments were Bio-Zeid and salicylic acid giving a similar wilt severity (21.67%), followed by ascorbic acid, Bio-Nagi, T. hamatum and T. harzianum that decreased severity in an ascending order from 26.67 to 43.33%. Topsin M70 fungicide gave 16.67% wilt severity, being the best control treatment, compared to 91.67% for cumin oil that could be ignored. Field grown plants of pepper showed significant wilt decrease following application with salicylic acid and Bio-Zeid. Ascorbic acid and Bio-Nagi along with T. hamatum showed promising results. Moreover, application of salicylic acid and Bio-Zeid increased growth parameters. The study suggested that Bio-Zeid and salicylic acid were the most effective treatments for controlling wilt and increasing yield of pepper. Ascorbic acid, Bio-Nagi and T. hamatum were promising in this regard. Further investigations are needed.