Seedlings dampling-off of mahogany, cassia and koelreutaria plants and some aspects to its control

Nigrospora phaerica, Fusarium oxysporum and Thanatephor-us cucumeris were isolated from damped-off seedlings of mahogany [Khaya senegalensis]. Nigrospora sphaerica, F. oxysporum, Sclerolium rolfsii and S.bataticola were isolated from infected seedlings of cassia [Cassia fistula] and Koelreutaria opiculata. Nigrospora sphaerica was the most destructive to seedlings of cassia and Koelreutaria, whereas T. cucumeris was the most pathogenic organism that induced mahogany seedling damping-off [80%]. Gibberellic acid [GA3], kinetin and cycocel [CCC] decreased the percentage of damped-dff seedlings of all tested plants than the control treatment. Increasing the concentration of CCC to 40 ppm level decreased infection down to 6-28%. The mixture of the tested fungi was able to initiate seedling infection [ranged between 8 and 64%] in four different soil types [namely, loamy soil, sand calcareous soil, sand calcareous + activated cotton seed hulls and sand calcareous + nonactivated cotton seed hulls; 1:1 w/w]. However, maximal seedling infection occurred in the loamy soil, and the least percentage of infected seedlings occurred in the sand calcareous soil, specially when seeds were previously treated with 40 ppm kinetin. Reducing sugars and amino nitrogen contents were increased either as a result of fungal infection or due to growth regulator treatment. The higher contents of both reducing sugars and amino nitrogen was found in seedlings treated with GA3. Whereas, CCC at 40 ppm increased the total phenol [s] content in both healthy and infected seedlings

Bacterial leaf blight of cowpea in Egypt: 1 Causal organism and factors affecting its growth

Naturally infected plants showed leaf blight and stem canker symptoms. Leaf inoculated plants exhibited irregular reddish brown blotches followed by leaf wilting, while stem or pod inoculated ones develop either cankers or brownish water-soaked spots, respectively, at the sites of inoculation. Diagnostic tests suggested the pathogen to be Xanthomonas campestris p.v. vignicola. Varietal response test showed that isolate varied as regards the severity of symptoms they initiated in a given variety of bean or cowpea. Host range studies revealed that the pathogen is able to initiate a hypersensitive reaction in tobacco, tomato, squash, braod bean and common apricot. Trials on antibacterial compounds revealed that Terramycin, Penicillin, Chloramphenicol, Streptomycin and Erythromycin as well as Marfazin and formaldehyde had the most pronounced inhibitory effect on growth of the bacterial isolates tested