Acta Agronomica Hungarica, 55(2), pp. 243–249 (2007) DOI: 10.1556/AAgr.55.2007.2.12 0238–0161/$ 20.00©2007 Akadémiai Kiadó, Budapest IMPORTANCE OF PLANT GROWTH-PROMOTING RHIZOBACTERIA IN ENHANCING THE SEED GERMINATION AND GROWTH OF WATERMELON ATTACKED BY FUNGAL PATHOGENS S. LOKESH 1* , B. G. BHARATH 1 , V. B. RAGHAVENDRA 1 and M. GOVINDAPPA 2 1 DEPARTMENT OF STUDIES IN APPLIED BOTANY, SEED PATHOLOGY AND BIOTECHNOLOGY, UNIVERSITY OF MYSORE, MANASAGANGOTHRI, MYSORE, INDIA; 2 DEPARTMENT OF PLANT PATHOLOGY, INSTITUTE OF AGRICULTURE AND NATURAL SCIENCES, UNIVERSITY OF NEBRASKA, LINCOLN, NE, USA Received: 20 July, 2006; accepted: 2 April, 2007 In the present study, seven isolates of plant growth-promoting rhizobacteria were used for seed treatment to suppress seedling diseases caused by fungi. Their effect on the seed germination and seedling vigour of watermelon was also studied. Among them INR-7 was able to inhibit a broad range of fungal species, GBO3 and IPC-11 were found to be effective against Fusarium spp. and Didymella bryoniae, while isolates SE-34 and T-4 were effective against Myrothecium species and also reduced the development of symptoms on the seedlings. Isolates GBO3, IPC-11 and INR-7 increased seed germination and seedling vigour to the greatest extent. Key words: watermelon, fungal disease, PGPR, fungal inhibition, promotion of seed germination and growth Introduction Watermelon is an important crop, commonly grown for its fruits especially during summer. Seed-borne fungal pathogens play a major role in seedling diseases and cause considerable losses in the yield of the crop in the field. Many chemical fungicides are used to control these diseases. The control of plant diseases using antagonistic bacteria is now considered as a promising alternative method that could reduce the use of hazardous chemical fungicides or bactericides. Bio-pesticides are up to 50% cheaper than synthetic pesticides. They are ecofriendly in nature, have a high cost-benefit ratio and do not pose the risk of the pathogen developing resistance. They are easy to apply and are compatible with bio-fertilizers. Many root-colonizing bacteria are known to promote plant growth by producing gibberellins, cytokinin and indole acetic acid (Dubeikovsky et al., 1993) and are hence called Plant Growth-Promoting Rhizobacteria (PGPR) (Kloepper and Schroth, 1978). Several PGPR strains have