EFFECT OF ERWINIA-CAROTOVORA SUBSP ATROSEPTICA ALONE AND WITH ALTERNARIA-SOLANI OR VERTICILLIUM-DAHLIAE ON DISEASE DEVELOPMENT AND YIELD OFPOTATOES IN ISRAEL

Tubers of 17 cultivars were inoculated with Erwinia carotovora subsp. atroseptica (ECA) and planted in 1986 and 1987 in the Negev in randomi sed plots in three blocks where either Verticillium dahliae or Alterna ria solani were present or where both were absent. ECA reduced the yie ld in the control block and exacerbated the yield losses in the diseas e blocks, but the intensity of symptom expression did not always accor d with the extent of yield loss. ECA had a greater effect on plants in fected with A. solani than on those with V. dahliae. It was possible t o categorise the cultivars as resistant, intermediate or susceptible w ith respect to ECA and early blight, but resistance to V. dahliae coul d not be differentiated from foliage maturity.