Flower color inheritance of Rhynchostylis gigantea (Lindl.) Ridl.

Abstract

Rhynchostylis gigantea has been subjected to a conventional breeding program in order to determine genetic inheritance of flower color. Generally, there are three varieties with four different flower patterns, i.e., white, white with red−pink spots, white with red blotches and red. The pure red is called R. gigantea var. rubrum Sagarik whereas the pure white is called R. gigantea var. harrisonianum HolH., and the white with red−pink spots or blotches is called R. gigantea. Recently, another color, orange−peach, has been developed. The objectives of this study were to determine genetic inheritance and conduct chemical component analysis of flower color in R. gigantea. Chemical analysis of all colors was conducted to identify major color components of the flowers using liquid chromatography−mass spectrometry (LC−MS). Three major components, cyanidin, peonidin and delphinidin were found in the red, white with red blotches and white with red−pink spots forms, whereas pelargonidin was found only in the orange−peach flowers. Anthocyanins were not found in the white color flower. Hybridization was carried out in order to determine color inheritance in these four−color forms: white, white with red blotches, white with red−pink spots and red. Twenty crosses of intraspecific hybridization of R. gigantea were made for F1−progeny production and progeny segregation in which color inheritance was analyzed. A Mendelian genetic analysis was designed to identify the major genes controlling these traits and to evaluate allelic and linkage relationships. In this study, three major genes have been proposed to govern color inheritance in R. gigantea. The C gene is responsible for the cyanidin accumulation which gives red−pink coloration, and the P gene for the expression of peonidin accumulation which gives red coloration, while the D gene for the delphinidin accumulation which gives purple coloration of flowers, and it might promote solid−red color accumulation. The CCPPDD and ccppdd genotypes gives solid− red and pure white flower forms respectively, while C−P−D− and C−P−dd gives white with red−pink spots or blotches flower forms, whereas the orange−peach color might be derived from other species or hybrids, but not through hybridization within R. gigantea varieties.