Effect of temperature on gametophytic selection in a Phalaenopsis F1 population

Gametophytic selection has potential to increase the efficiency of breeding for temperature tolerance. Here, we describe orchid seedlings after application of low and high temperatures during gametophytic development. In addition to phenotypic traits, amplified fragment length polymorphism (AFLP) markers were used to determine the genetic variability in seedlings. Two hybrid Phalaenopsis were cross-pollinated and exposed to 30°C day/25°C night for 3 days for a warm pollination or 15°C day/10°C night for 7 days as a cold pollination treatment. The plants were returned to the greenhouse after pollination and green capsules were collected after 150 days. Protocorms obtained from these treatments were evaluated 72 days after initial plating for germination and size on a thermogradient table ranging from 10 to 30°C. Seedlings were then evaluated 1 year after initial plating. The mean number of roots per seedling (4.2) was greater for plantlets that derived from the cold pollination treatment compared to those from warm pollination (3.6). Weight of the seedlings, number of roots and the average root length were significantly affected by the interaction between pollination treatment and germination temperature. The weight, number of leaves, and average root length were significantly affected by the interaction between pollination treatment and incubator/growth chamber. The results indicated that seedlings derived from warm pollination were more vigorous under warm growing conditions and those derived from cold pollination were more vigorous under cold growing conditions. Genetic variation among 16 F₁ seedlings randomly selected from various temperature treatments was analyzed. A dendrogram based on 651 loci resulted in three major groups and one subgroup. The groups and subgroup revealed common selection pressure during the gametophytic stage. The AFLP data support genetic differentiation of Phalaenopsis hybrids pollinated under different temperatures.