Strains of fluorescent pseudomonads increased the growth of tomato plants in nonsolarized soil but not in solarized soil. Vital staining showed that fluorescent pseudomonads colonize the root cortex and, apparently, internally colonize the younger lateral roots of artificially inoculated plants growing in nonsolarized soil. The minor pathogen Penicillium pinophilum caused growth retardation of tomato and cotton plants. It colonized tomato roots in nonsolarized, methyl bromide-fumigated, and solarized soils (to a much lesser extent). Inoculation of tomato roots with fluorescent pseudomonads or transplanting tomato roots to solarized soil suppressed colonization by Penicillium pinophilum and nullified plant-growth retardation. Inoculation of plant roots with plant growth-promoting strains of Pseudomonas putida, P. fluorescens, and P. alcaligenes reduced the incidence of disease caused by Sclerotium rolfsii in bean, Fusarium wilt in cotton and tomato, and reduced colonization of cotton roots by pathogens that cause these diseases. Induced suppressiveness against S. rolfsii in bean and Fusarium oxysporum f. sp. vasinfectum in cotton was observed in solarized soil. We suggest that fluorescent pseudomonads are effective agents in suppressing both major and minor pathogens in soil.

Evolving cotton varieties with built-in resistance to various diseases, is the ultimate option to disease control, Present studies, therefore, were carried-out to compare local varieties with already established multi-adversity resistant (MAR) lines introduced from Texas, USA. Among the varieties studies, two newly evolved indigenous varieties, CRIS-9 and CRIS-6 respectively ranked first and second positions in having MAR property to seedling, boll and root rot diseases as compared with established MAR lines from Texas, USA

Strains of the fungal antagonist Gliocladium virens were separated into two distinct groups on the basis of secondary metabolite production in vitro. Strains of the 'Q' group produced the antibiotics gliovirin and heptelidic acid but not the antibiotic gliotoxin and its companion, dimethylgliotoxin. Strains of the 'Q' group produced gliotoxin and dimethtylgliotoxin but not gliovirin or heptelidic acid. Strains from both groups produced the antibiotic viridin and phytotoxin viridiol. Gliovirin was very inhibitory to Pythium ultimum but had 110 activity against Rhizoctonia solani, and strains that produce it were more effective seed treatment biocontrol agents of disease incited by P. ultimum. Conversely, gliotoxin was more active against R. solani than against P. ultimum, and strains that produced it were more effective seed treatments for controlling disease incited by R. solani. These results indicate that the antibiotic profiles of strains should be considered when screening strains for biocontrol efficacy, and that it may be necessary to treat seeds with a combination of strains in order to broaden the disease control spectrum.