Biological Control of Fusarium Wilt of Chickepa through Seed Treatment with the Commercial Formulation of Thricoderma harzianum and/or Pseudomonas fluorescens

The effect of treating seed of chickpea (Cicer arietinum L.) cv. BG 256 with commercial formulations (2 g kg-1 seed) of Trichoderma harzianum and Pseudomonas fluorescens, singly and jointly, to control wilt caused by Fusarium oxysporum f. sp. ciceri was examined in chickpea plants growing in microplots under field conditions. On untreated control plants, the wilt fungus caused the characteristic symptoms of wilt and significantly (P=0.05) decreased dry weight and the yield of chickpea by 20 and 18% respectively (significant at P=0.05). On chickpea without wilt, treatment with P. fluorescens improved the yield by 36% and T. harzianum+P. fluorescens by 25%. Both biofungicides suppressed wilt severity (P=0.05), the most effective being T. harzianum+P. fluorescens (66%). Carbendazim reduced wilt severity by 51%. On chickpea inoculated with the wilt, yield increased by 39% with P. fluorescens, by 33% with T. harzianum+P. fluorescens, by 44% with T. harzianum, and by 20% with carbendazim as compared with the inoculated control. The soil population of the wilt fungus (cfu g-1 soil) in untreated plots increased during the first two months (P=0.05), but in the biofungicide/fungicide treated plots it gradually and significantly (P=0.05) decreased during the four months of the crop season. The greatest decrease in the soil population of the wilt fungus occurred with T. harzianum or T. harzianum+P. fluorescens, followed by P. fluorescens and carbendazim. The rhizosphere population of the bioagents increased significantly in those plots where wilt populations decreased. The greatest increase in the population of the bioagents was recorded for T. harzianum (108–120%), followed by P. fluorescens (65–119%) in the combined treatment, compared with the pre-plant control (December). When the bioagents were applied alone, the population of T. harzianum increased by 71–96% and that of P. fluorescens was by 46–103%