EFFECTS OF BIOFERTILIZERS ON MN AND ZN ACQUISITION AND GROWTH OF HIGHER PLANTS: A RHIZOBOX EXPERIMENT

Plant disease resistance and susceptibility are greatly influenced by the availability of micronutrients, particularly manganese (Mn) and zinc (Zn). Take-all disease of wheat, caused by a strong Mn oxidizing fungus (Gaeumannomyces graminis var tritici, Ggt), results in a lack of availability of Mn to plants and increases disease severity in wheat. Three commercial Trichoderma harzianum (Vitalin T-50, BioHealth (R)-WSG, and BioHealth (R)-G) and one Bacillus subtilis (Vitalin SP-11) were investigated individually and in combination (Vitalin T-50 and Vitalin SP-11) for growth promotion and Mn/Zn uptake of take-all infected wheat in a rhizobox experiment under greenhouse conditions. Inoculation with Trichoderma and Bacillus biofertilizers did not increase the shoot dry weight and shoot to root ratio, whilst shoot length was significantly increased with Vitalin T-50 and Biohealth-G treatments in the final harvest. Biofertilizers inoculation that significantly (P < 0.05) enhanced root surface area and root dry weight were Vitalin T-50, BioHelath-G and combination of Vitalin (T-50 + SP-11). The bulk soil pH was not influenced by biofertilizer inoculation, whereas rhizosphere and rhizoplane soil pH were significantly reduced (0.3 - 0.4 pH scale) in Vitalin (T-50 + SP-11) and BioHealth-G treatments and to a lesser extent by Vitalin T-50 inoculation. Manganese uptake in shoots of wheat exhibited no significant differences among the biofertilizer treatments. On the contrary, Zn uptake was significantly higher in Vitalin T-50, Vitalin (T-50 + SP-11), BioHealth-G, and BioHealth-WSG (47, 64, 44, and 45%, respectively) inoculated plants. Therefore, Vitalin T-50 and Biohealth-G showed better performance in improving plant growth and Zn uptake.