CALCIUM NUTRITION AFFECTS RESISTANCE OF TOMATO SEEDLINGS TO BACTERIALWILT

The relationship between Ca nutrition and bacterial wilt development w as studied on three tomato (Lycopersicon esculetum Mill.) cultivar see dlings with various degrees of resistance to the disease. Seedlings we re transplanted into nutrient solutions with Ca at 0.4, 4.4, or 20.4 m M. One week after initiating the Ca treatment,tomato seedlings were in oculated by wounding the stem with scissors dipped in a suspension of the pathogen (Pseudomonas solanacearum E.F. Smith). Disease developmen t was rapid in 'Ponderosa' (a susceptible cultivar) at all Ca concentr ations. Increased Ca concentration in the nutrient solution reduced di sease severity in 'Zuiei' (a moderately resistant cultivar). Resistanc e was negated at the low Ca concentration in 'Hawaii 7998' (a highly r esistant cultivar). Pathogen populations in stems decreased with incre ased Ca concentrations and degrees of resistance.