Effect of high-temperature on suppression of the lethality exhibited in the intergeneric hybrid between Japanese pear ( Pyrus pyrifolia Nakai) and apple ( Malus× domestica Borkh.)

Abstract

Hybrid lethality is a difficult obstacle that must be overcome in order to produce mature intergeneric hybrids between Japanese pear and apple. High-temperature has been shown to be effective in suppression of hybrid lethality in rice, tobacco and cotton. If a similar response to temperature is observed in the hybrid between Japanese pear and apple, suppression of the lethality should lead to vigorous growth of the hybrid. In this experiment, we observed whether the expression of the lethality was suppressed at high-temperature or not. Clear differences in vegetative growth were observed among the shoots derived from the immature embryo at different temperature conditions. The shoots at 34 °C grew vigorously without exhibiting the lethal symptoms. Similar phenomena was also observed in F 1 seedlings of the cross. More than 80% of the intergeneric seedlings at high-temperature conditions (34/30 °C, day/night and 34 °C) grew without lethal symptoms within 18 days after sowing. Although the high-temperature suppressed the lethal symptoms, the seedlings died within 5 months from the resulting stress. In this study, we clarified that the hybrid lethality between Japanese pear and apple was suppressed at high-temperature in a similar manner to those of hybrids from wide crosses in other plant species. This phenomenon gives the possibility for studying and overcoming lethality.