Effect of Phosphate Solubilising Bacteria on Tomato Growth and Biological Control of Pythium sp., the Causal Agent of Tomato Root Rot Disease under Pot Grown Conditions
Donald Tchouomo Dondjou *
Department of Chemistry-Biology, Laboratory of Applied Chemistry and Biosciences, the Faculty of Sciences, the University of Bertoua, P.O. Box 416 Bertoua, Cameroon.
Claude Simo
Department of Plant Biology, Laboratory of Plant Biology and Physiology, Faculty of Science, the University of Douala, P.O. Box 24157 Douala, Cameroon.
Gylaine Vanissa Tchuisseu Tchakounté
Department of Plant Biology, Laboratory of Plant Biology and Physiology, Faculty of Science, the University of Douala, P.O. Box 24157 Douala, Cameroon.
Hélène Laure Mafokoua
Department of Plant Biology, Laboratory of Plant Biology and Physiology, Faculty of Science, the University of Douala, P.O. Box 24157 Douala, Cameroon.
Victor Désiré Taffouo
Department of Plant Biology, Laboratory of Plant Biology and Physiology, Faculty of Science, the University of Douala, P.O. Box 24157 Douala, Cameroon.
Henri Fankem
Department of Plant Biology, Laboratory of Plant Biology and Physiology, Faculty of Science, the University of Douala, P.O. Box 24157 Douala, Cameroon.
*Author to whom correspondence should be addressed.
Abstract
Poorly soluble phosphates may become more available to plants through the activity of phosphate-solubilising bacteria, potentially improving growth where P is limiting. Four strains, identified as Bacillus sp., Paenibacillus sp., Curtobacterium sp. and Burkholderia sp., were examined for their ability to release phosphorus from rock phosphates of different origins and to affect tomato growth with or without Pythium sp., the organism associated with root rot. Initially, the strains were tested in solid and liquid NBRIP media containing Algerian, Senegalese, Malian, Moroccan or Mexican rock phosphate. Solubilisation indices on agar ranged from 1.92 to 3.21, with the highest overall value recorded for Bacillus sp. Algerian and Senegalese phosphate gave the greatest indices (3.55 and 3.48, respectively). In liquid culture, soluble P varied from 95.56 mg/L with Burkholderia sp. to 335.54 mg/L with Curtobacterium sp. Release of soluble P was highest from Senegalese phosphate, followed by the Malian, Algerian, Mexican and Moroccan sources. A greenhouse pot study then assessed tomato growth in Senegalese rock-phosphate-amended soil after bacterial inoculation, either with or without Pythium sp. Effects on plant height, stem diameter and dry biomass differed between strains. For certain growth measures, Bacillus sp., Curtobacterium sp. and Burkholderia sp. performed better than the negative control. These results suggest a possible contribution of selected strains to phosphate solubilisation and tomato growth, although validation under field conditions remains necessary.
Keywords: Tomato, Bacillus sp., Paenibacillus sp., Curtobacterium sp., Burkholderia sp., root rot disease, Pythium sp.