EFFECT OF SOME HOST AND MICROCLIMATE FACTORS ON INFECTION OF TOMATO STEMS BY BOTRYTIS-CINEREA

The susceptibility of tomato stems to infection by Botrytis cinerea an d the influence of temperature and humidity on disease development wer e investigated with stem pieces and whole plants. Stem rotting resulte d after inoculation of wounded stems with a conidial suspension in wat er or with dry conidia; no symptoms developed following inoculation of unwounded stems. The proportion of inoculated stems developing Botryt is rot increased as the inoculum concentration was increased from 10 t o 10,000 conidia per stem. Stem susceptibility to infection de dined f rom 60 to 8% as wound age increased from 0 to 24 h before inoculation. Wounded stem pieces maintained in a low vapor pressure deficit (VPD) environment (<0.2 kPa) remained susceptible for a longer period than t hose maintained at a high VPD. Infection and stem rotting occurred at temperatures of 5 to 26 degrees C, with disease development most rapid at 15 degrees C. Sporulation was optimal at 15 degrees C and did not occur within 20 days of incubation at 5 or 26 degrees C. Incubation at high humidity following inoculation of fresh wounds (VPD <0.2 kPa) di d not increase infection incidence or tissue rotting, compared with in cubation at a VPD >1.3 kPa; however, incubation at the lower VPD did i ncrease the intensity of sporulation.