ANTAGONISTIC POTENTIAL OF FLUORESCENT Pseudomonas AND ITS IMPACT ON GROWTH OF TOMATO CHALLENGED WITH PHTOPATHOGENS

This study focused on the antagonistic potential of fluorescent Pseudomonas in vitro, and its inoculation effect on growth performance of Lycopersicon esculentum in Fusarium oxysporum and Rhizoctonia solani infested soil. Biochemical characteristics of fluorescent Pseudomonas showed that all ten isolates were positive to catalase, amylase, gelatinase and siderophore production. While three isolates (Pf5, Pf6 and Pf9) were oxidase positive, nine isolates (Pf1, Pf2, Pf3, Pf4, Pf6, Pf7, Pf8, Pf9, and Pf10) were tolerant to 6.5% NaCl. Isolates Pf5 and Pf6 were resistant to all the test antibiotics; in contrast, the remaining eight isolates responded differently to different antibiotics. Isolates Pf5 and Pf6 were antagonistic against 14 bacterial species, and two pathogenic fungi (F. oxysporum and R. solani). Inoculation with fulorescent Pseudomonas Pf5 induced a significant increase in root and shoot length, and dry weight. Treatment of plants with either F. oxysporum or R. solani drastically reduced the root and shoot length and dry weight of the plant. However, in the presence of fluorescent Pseudomonas the adverse effect of the pathogens on growth of L. esculentum was alleviated.Cette \ue9tude a port\ue9 sur le potentiel antagonistique du Pseudomonas fluorescent, in vitro et les effets de son inoculation sur la performance en croissance du Lycopersicon esculentum dans le sol infest\ue9 par le Fusarium oxysporum et le Rhizoctonia solani . Les caract\ue9ristiques biochemiques du Pseudomonas fluorescent ont montr\ue9 que tous les dix isolats \ue9taient positives eu \ue9gard \ue0 la production de catalase, amylase, g\ue9latinase et sid\ue9rophore. Alors que trois isolats (Pf5, Pf6 and Pf9) \ue9taient oxidase positifs, neuf isolats (Pf1, Pf2, Pf3, Pf4, Pf6, Pf7, Pf8, Pf9, et Pf10) \ue9taient tolerant au 6.5% NaCl. Les isolats Pf5 et Pf6 \ue9taient r\ue9sistants \ue0 tous les test antibiotiques; au contraire, les huit isolats restants ont r\ue9pondu diff\ue9remment aux diff\ue9rents antibiotiques. Les isolats Pf5 et Pf6 \ue9taient antagonistiques contre 14 esp\ue8ces de bact\ue9ries, et deux champignons pathogeniques (F. oxysporum et R. solani). L\u2019inoculation avec Pseudomonas fulorescent Pf5 a induit une augmentation significative des raciness et de la longueur des tiges, ainsi que du poids sec. Le traitement de plants avec du F. oxysporum ou du R. solani ont radicalement r\ue9duit la longueur des raciness et tiges ainsi que le poids sec du plant. Cependant, en pr\ue9sence du Pseudomonas fluorescent, l\u2019effet adverse du pathog\ue8ne sur la croissance du L. esculentum \ue9tait allevi\ue9

General and applied plant physioloGy -2010

Summary. Gramineous plants establish strong symbiosis with arbuscular mycorrhizal fungi that can improve the uptake of P from soil. They also associate with some diazotrophic bacteria and get biologically fixed nitrogen. Sorghum bicolor is a sugar-rich multipurpose fodder crop well suited to dry farming. In the present study, S. bicolor plants were grown in a green house and the impact of inoculation with Herbaspirillum seropedicae and Glomus fasciculatum on growth, N and P nutrition of the plant was studied. A single inoculation with either H. seropedicae or G. fasciculatum supported plant growth promotion effect resulting in enhanced root length (5-7%), shoot length (18-22%), root biomass (40-58%), shoot biomass (46%), total N content (21-49%), and total P content (46-167%) compared to the control. The dual inoculation with H. seropediae and G. fasciculatum resulted in enhanced root length (15%), shoot length (40%), root biomass (105%), shoot biomass (91%), total N content (108%), and total P content (138%) compared to the control. Within the single inoculated plants, N accumulation was higher by 23% after H. seropedicae inoculation compared with G. fasciculatum inoculation. In contrast, P accumulation in plants was higher by 82% after G. fasciculatum inoculation compared with H. seropedicae inoculation. There was little difference in hyphal (92-95%) and vesicular (82-83%) infection between G. fasciculatum inoculated plants and G. fasciculatum + H. seropedicae inoculated plants indicating no interference of bacteria on mycorrhizal colonization in roots of S. bicolor