Effect of Coexistence of Bacterial and Fungal Isolates with Cotton’s “Aleppo 118” Variety in Improving Cotton Growth and Enhancing Cotton’s Resistance to the Whitefly Bemisia tabaci (Genn.) by Using Different Inoculation Methods

Abstract

In this study, four methods of inoculation were used to assess coexistence of microorganisms with cotton plant: seeds coating (chemical shaved / unshaved), aerial spraying, irrigation and their effects on germination, endophytic symbiosis, growth parameters, density of whitefly’s population density. For this purpose a number of bacterial and fungal isolates were tested (3 isolates of Trichoderma harzianum (Twood, T.L.C, T950), 2 isolates of Beauveria bassiana (GHA, K), 2 isolates of Bacillus subtilis (B.s, B.bacteria), one isolate of Lecanicillium lecanii (B), and one isolate of Aspergillus sp. (Asp)). Propagation of these isolates were conducted. Fungal isolates were propagated on burgol (cracked wheat), whereas bacterial isolates were propagated in Petri dishes contained NA medium, then suspension concentration was adjusted to 1x108 cell/ml for bacterial isolates and 1x106 conidia/ml for fungal isolates. Seeds of each treatment were planted in pots with 3 replicates per treatment, in addition to a control treatment. The results obtained showed that there was no significant difference between control and each of other treatments in germination rate, whereas highest coexistent rates were recorded for GHA, K, B, Asp isolates in all plant parts. Also, there were significant differences in roots length, foliage height, dry and fresh weight between Twood, B.bacteria, GHA, T950,Asp, B.S. treatments and control treatment. Inoculation with the isolates T.L.C, K, GHA, T950, Asp, B.bacteria produced low densities of whitefly’s nymphs per leaf. Finally, shaved and unshaved seeds coating and soil irrigation methods produced low densities of whitefly’s nymphs compared with the spraying treatment and all inoculation methods used had significant differences with control treatment. Microorganisms used improved cotton growth and decreased whitefly population density. This approach can be used as a component in integrated pest management programs for cotton. Keywords: Beneficial microorganisms, growth parameters, resistance, cotton, whitefly