Meiotic chromosome analysis in tropical orchid genus Sobralia

Abstract

Tropical orchid genus Sobralia comprises terrestrial plants with elongated, cane-like stems and large symmetrical, yet ephemeral flowers. This genus is distributed throughout Central and South America and may hold horticultural potential. Nonetheless, little is known about the reproductive viability of species that comprise this genus. In this project male meiocytes have been examined by light microscopy to determine chromosome numbers, frequency of chromosome segregation defects and the frequency of normal tetrads at the end of meiosis II. The species sampled belong to an ex situ collection managed by the Lankester Botanical Garden of the University of Costa Rica. The species were: S. amparoae, S. artropubescens, S. boucheri, S. bradeorum, S. carazoi, S. crispissima, S. danjanzenii, S. fenzliana, S. geminata, S. helleri and S. rosea. Our results indicate that meiocytes from these species have a variable diploid (2n) chromosome number of 24, 30 and 32, that segregation defects are rare and that tetrad formation rates exceed 80%, suggesting efficient meiotic progression and high pollen viability. Taken together our results suggest that at least in Costa Rica the populations sampled are reproductively healthy and amenable to horticultural breeding.