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Abstract
The nematicidal activity of the wild type and three mutants namely (24, 10, 32 ) of the chitinolytic bacteria, Bacillus thuringiensis using U.V. irradiation was evaluated against eggmasses, eggs and juveniles of the root - knot nematode, Meloidogyne incognita, as safer and environment friendly control alternate chemical nematicides under both laboratory and greenhouse conditions.
Results, generally indicated that all tested treatments of mutants had reduced activity aganist M. incognita compared to untreated control .The mutant no. 24 is more effective on the nematode stages ( eggmasses, eggs and juveniles) followed by mutant no.10, then mutant no. 32 as compared to the wild type which achieved the lowest mortality %. In case using eggmasses percentage inhibition of juveniles ranged from (39 to 100 % ), ( 37.1 to 100 % ) (43.9 to 100 % ), ( 37.9 to 100 %) and percentage inhibition of eggs ranged from ( 87 to 100 % ), (85.9 to 100 %), (88.7 to 100 % ), ( 85.9 to 100 % ) in using mutant 24, 10, 32 and the wild type ; respectively and in case using eggs stages the effect ranged from (90.8 to 96.6 % ), (79.8 to 89.9 %), ( 70.2 to 79.5 %), (46.3 to 68.8 %) ; respectively compared to 2.3% in untreated control after after 96 hr. while with using juveniles stages these values ranged from (64.2 to 86.6 %), (55.2 to 57.7 %), (51.2 to 54.5 %), (35.5 to 49.7 %); respectively compared to 7% in untreated treatedment after the same time. In eggmassses as source of incolum. infecting sunflower, % reduction in galls ranged from (79.2 to 97%) and from (90.2 to 98.4 %) in eggmasses. In case of using eggs as a source of incolum, % reduction in number of juveniles ranged from (80 to 89.6 %) and reduction in galls ranged from (68 to 96.3 %), and ranged form (86.8 to 96 %) for eggmasses. In case using juveniles a source of incolum percentage reduction in number of galls standard concentration ranged from (72.5 to 88.9 %) and % reduction in number of eggmasses ranged from (88.9 to 97.8 %). There were positive relation- ship between the percentage of mortality and the chitinase production from mutants. Also, the results indicated that the greenhouse results confirmed the laboratory tests. Moreover, the same trend extended to eggmasses, eggs and juveniles numbers, different plant growth parameters of the nematized sunflower plants were significantly increased with using the tested mutants and the wild type of B.t.. Also generally, the best plant growth improvement was found at using the mutant no.24 followed by no.10 then no.32 as compared to the wild type which gave the lowest plant growth, promotion.