Bacteria controlling cucumber foot and root rot and promoting growthof cucumber and tomato in salinated soils

Abstract: Seventeen percent of cucumber plants grown in a Uzbek greenhouse were diseased.The major cucumber and tomato pathogens of Uzbek agricultural soils were identified as strainsof Fusarium solani. Fifty two beneficial bacteria from collections of our institutes were screenedfor their ability to promote growth and/or to control diseases caused by F. solani on cucumberand tomato plants. The five best strains were used in large scale greenhouse trials. Four out offive strains significantly controlled cucumber foot and root rot, reducing the percentage ofdiseased plants from 54% in the negative control to between 10 and 29% in bacterized plants. Allfive strains increased the dry weight, by 29 up to 62%. In two consecutive years all five strainssignificantly increased the plant height (by 4 to 15%) as well as the fruit yield (by 12 to 32%).Tests of plant-beneficial traits suggest that auxin production, antibiosis and competition fornutrients and niches are mechanisms involved in the observed plant growth stimulation andbiocontrol. The results with tomato were similar. We conclude that many beneficial bacteriaisolated from plants grown on non-salinated soil are perfectly able to promote plant growth andcontrol plant diseases in salinated soil. In other words, salination caused by a possible futureclimate change does not seem to be a threat for the application of presently used plant-beneficialbacteria. In addition, our results show that the dogma that beneficial strains should be isolatedfrom the plant and climate on/in which they should be applied is not valid: all our strains wereisolated from plants other than cucumber and came from cold or moderate climates.