Evaluation of some wild weeds and yeasts isolates to control root-knot nematodes on tomato.

In this study, eight different wild weeds [Atriplex lindleyi Moq. subsp. inflata (F. Muell) P.G., Chenopodium album, Hyoscyamus muticus, Mesembryanthemum nodiflorum, Pluchea dioscoridis, Senecio squalidus, Zygophyllum qatarense and Amaranthus ascendens] and four yeast isolates [Pichia guilliermondii ATCC 9058, Saccharromyces servicaea, Candida albicans ATCC 10231 and Saccharromyces sp.] were evaluated against root-knot nematodes (RKNs) under laboratory and greenhouse conditions. The ability of weeds and yeasts to inhibit egg-hatching and kill second-stage juveniles (J2s) was tested at different exposure periods (24-48-72-120-168 hrs) under laboratory conditions. Weeds and yeasts were evaluated against RKNs on tomato plants under greenhouse conditions as soil amendments. Weeds in different forms (powder - fresh and aqueous extracts) were added with different concentrations (1, 2 and 4% of soil weight), while yeasts at different application time (one week prior, one week post and at the same time of seedlings transplanting) were also added with the same concentration. Results revealed that under laboratory conditions, the weed A. lindleyi (Moq.) subsp. inflata (F. Muell) P.G. and the yeast P. guilliermondii ATCC 9058 was the most effective in egg-hatching inhibition and J2s mortality. Under greenhouse conditions, all treatments significantly affected nematode parameters (galls, egg masses, females and J2s/250g soil, gall index, nematode final population and reproduction factor) and promoted growth parameters (shoot and root fresh weights, shoot and root lengths as well as plant dry weight) over the control. Activities of two enzymes (peroxidase and polyphenol oxidase) were increased by all treatments compared to the control. The most effective concentration of both weeds and yeast isolates was (4%), followed by (2%), while (1%) was the least effective. The most effective application form of weeds was (powder), followed by (fresh), while (aqueous extract) was the least effective. The most effective application time of yeasts relative to seedlings transplanting was one week prior, followed by at the same time while one week post was the least effective. Atriplex lindleyi (Moq.) subsp. inflata (F. Muell) P.G. and P. guilliermondii ATCC 9058 showed the highest efficiency in reducing nematode parameters and increasing growth parameters. Combining P. guilliermondii ATCC 9058 with the powder form of A. lindleyi (Moq.) subsp. inflata (F. Muell) P.G. one week prior seedlings transplanting at 4% of soil weight for both treatments achieved a close percentage in reducing nematode parameters to Nemaphos which recorded 100% reduction, but the combination proved to be more effective than separately and enhanced plant growth parameters much greater than Nemaphos. The most effective treatments can be used as biocontrol agents against Meloidogyne spp. even separately or combined, which is considered promising results.