Effects of temperature as the selection pressure for resistance to anthracnose crown rot (Glomerella cingulata Spaulding et Schrenk) of young strawberry seedlings

摘要

Strawberry seedlings were inoculated with anthracnose by spraying suspensions of 5 X 105 conidia per millilitre (±1 X 105). Immediately after inoculation, the seedlings were placed in an inoculation chamber at 28deg C and 100% RH for 24 h. In Experiment 1, progenies from 20 hybrid crosses at the young and mature seedling stages were transferred to the greenhouse after inoculation. In Experiment 2, seedlings of Nyoho X Houkouwase were inoculated with spore suspensions as in Experiment 1. The inoculatedseedlings were placed in growth chambers set at 20, 22, 24 and 26deg C for 8 days and then transferred to the greenhouse; control seedlings without inoculation were placed in the greenhouse. In Experiment 1, the mortality rates of progenies from 20 hybridcrosses 15 days after transplanting correlated positively with those of mature seedlings, 37 days after transplanting. This means it should be possible to evaluate the resistance to anthracnose crown rot (Glomerella cingulata) by the longevity at the early stage of seedlings. In Experiment 2, the screening was clearly effective because the susceptible seedlings after the selections at various temperatures became fewer than the control seedlings. The mortality rates for young strawberry seedlings of Nyoho X Houkouwase increased proportionately with the increase in temperature of the growth chamber.