The distribution and multiplication of Ralstonia solanacearum in tomato plants of 11 resistant cultivars derived from different genetic sources and susceptible cultivar Ponderosa were examined. Bacterial multiplication in stems of resistant tomato plants was suppressed owing to the limitation of pathogen movement from the protoxylem or the primary xylem to other xylem tissues. The limitation was most conspicuous in Hawaii 7996. Grafting experiments indicated that the percentage of wilting of Ponderosa scions was less on Hawaii 7996 rootstocks than that on the most resistant rootstock (LS-89) used in Japan. Hawaii 7996 could be an alternative genetic source for breeding for resistance to bacterial wilt.

No abstract

A highly potent attractant of zoospores of Aphanomyces cochlioides, a causal fungus of the root rot disease of spinach (Spinaeia oleracea), was isolated from spinach roots, and its structure was determined by spectroscopic evidence and chemical synthesis as cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone, 1). A chromosorb particle prepared by soaking in solution of 1 showed a potent attracting activity toward the zoospores using concentrations of 1 above 10 -9 or 10 -10 M.

Global warming is predicted to increase air temperatures. With the aim of ensuring future stable production of strawberry under high autumn air temperatures, we examined the effect of a crown-cooling treatment on flower bud differentiation, flowering characteristics and fruit yield in a June-bearing strawberry (Fragaria ananassa Duch. cv. Fukuoka S6). We forced strawberries under high air temperature conditions (controlled day/night temperatures of 30/27°C) to simulate future global warming. For approximately 40 d after transplanting in August, strawberry crowns were cooled using a crowncooling tube filled with water controlled to temperatures of 10, 15, 20 and 25°C. The crown-cooling treatments of 10, 15 and 20°C significantly (P 0.05) promoted flower bud differentiation in the first inflorescence compared with controls. This earlier differentiation resulted in quicker anthesis, and led to an increase in marketable fruit yield in December. However, continuous cooling treatments of 10 and 15°C after flower bud differentiation negatively affected anthesis and fruit yield. These data suggest that crown-cooling treatment for an appropriate period may be able to stabilize strawberry production under high air temperatures.