2004 Volume 16 Issue 4 Pages 173-182
To identify the effects of seasonal temperature on geranium flowering throughout year-round cultivation in a greenhouse, the flowering characteristics of 4 wild species, 2 varieties and 13 hybrid derivatives were investigated at 4 times : May, August, and November in 2002, and February in 2003. Based on these results, the possible usage of high-temperature stress tolerance in hybrids was discussed.
The daily mean temperatures were 20∼23°C in May, 28∼31°C in August, 12∼13°C in November, and 9∼11°C in February in the greenhouse. It was 26∼32°C from the first 10 days of July to the middle 10 days of September, the most severe high-temperature term for geraniums.
The flowering characteristics varied among seasons, and the general trend was that the appearance was the worst in August. Seasonal change in peduncle number was different among the strains. In August, peduncle length and floret number per peduncle decreased obviously. From the variation pattern, it was found that the high temperature in summer greatly affected the flowering characteristics for a long period. Correlations between the parents and their hybrids were positive in all flowering characteristics. For breeding high-temperature stress-tolerant hybrids, the selection of high-temperature stress-tolerant strains for parents may be efficient. Strains 9, 10, 11, and 13, which are descendants of P. frutetorum, P. salmoneum, and P. inquinans, respectively, showed hybrid vigor throughout the year-round cultivation. Strain 10, especially, showed higher hybrid vigor for all traits in August, making it useful for year-round cultivation in the greenhouse.
