Rhizosphere Pseudomonas sp. strains reduce occurrence of pre- and post-emergence damping-off in chile and tomato in Cent
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ORIGINAL PAPER
Rhizosphere Pseudomonas sp. strains reduce occurrence of pre- and post-emergence damping-off in chile and tomato in Central Himalayan region Alok Sharma Æ Victor Wray Æ Bhavdish N. Johri
Received: 12 October 2006 / Revised: 25 October 2006 / Accepted: 14 November 2006 / Published online: 8 December 2006 Springer-Verlag 2006
Abstract Based on in vitro screening for PGP and anti-mycelial activity against three zoosporic pathogenic oomycetes, Pythium aphanidermatum 123, P. aphanidermatum 4746, and Phytophthora nicotianae 4747, seven bacterial isolates were selected for field trials on tomato and chile to test for plant growth promotion under natural and artificial disease-infested field sites in both winter and wet seasons. The effectiveness of isolates in the field trials correlated with the in vitro antagonism screening data. Pseudomonas sp. FQP PB-3, FQA PB-3 and GRP3 showed substantial beneficial effects on plant growth promotion and lowered considerably the incidence of pre- and postemergence damping-off in both the crops under various disease scenarios. For example, seed bacterization with these bacterial strains reduced pre-emergencedamping off by ca. 60–70% in the two natural sites, with and without histories of fungicide use in the winter season, and to a lesser extent, ca. 20–40%, in the warmer wet (high humidity; 85–92%) season. The
A. Sharma B. N. Johri Department of Microbiology, CBS&H, GB Pant University of Agriculture and Technology, Pantnagar 263145, India A. Sharma (&) V. Wray Department of Structure Biology, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany e-mail: [email protected]; [email protected] Present Address: B. N. Johri Department of Biotechnology, Barkatullah University, Bhopal 462026, India
suppression efficacy for post-emergence damping-off was less compared to pre-emergence damping-off although still significant (P > 0.05). Our data unambiguously show that screening of a large number of bacterial pool identifies promising isolates that show beneficial effects on all stages of plant growth in natural oomycete-infested regimes.
Introduction Over the last few years the agricultural policy in India has undergone a major change to meet the increased demand of food in the global competitive scenario through diversification and emphasis on sustainable production systems. The latter is a consequence of problems associated with non-judicious use of fertilizers and pesticides as well as the low buying power of the marginal farmer. Intervention of biotechnologies in development strategies is therefore of prime significance. Biological control, using microorganisms to suppress plant diseases, offers a powerful and necessary alternative to the application of synthetic chemicals. With the growing importance of such control systems in plant disease management, the study of the mechanisms involved is paramount (Martin 2003; Moenne-Loccoz and Defago 2004). Consequently, it is imperative to establish the molecular basi
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