Allelic Differences at Two Loci Govern Different Mechanisms of Intraflower Self-Pollination in Self-Pollinating Strains of Periwinkle

Abstract

Periwinkle [Catharanthus roseus (L.) G. Don], an ornamental and medicinal plant, is a self-compatible, insect-pollinated plant species in which intraflower self-pollination does not occur because of spatial separation of the stigma and anthers. Recently three self-pollinating strains-MJ, VI, and OR-were identified. Self-pollination in these strains was found to be brought about by continuous increase in gynoecium length from anthesis to self-pollination, in contrast to non-self-pollinating strains, in which the stigma remained below the base of the anthers from anthesis to flower drop. Self-pollination in these strains was found to be controlled by duplicate, recessive genes. Self-pollination in strains MJ and VI was brought about by an increase in gynoecium length resulting from an increase in the length of the ovary, while in the strain OR, the increase in gynoecium length was because of an increase in the length of the style from anthesis to self-pollination. The three strains were intercrossed to determine the relationship between genes governing self-pollination in these strains. The F(1) plants and all plants of the F(2) generation of the cross MJ x VI exhibited self-pollination that was brought about by an increase in the length of the ovary, indicating that the same genes were involved in these two strains. The F(1) plants of crosses OR x MJ and OR x VI, exhibited self-pollination that was brought about by an increase in the length of the ovary, indicating that self-pollination brought about by an increase in the length of the ovary was dominant over self-pollination brought about by an increase in the length of the style. In the F(2) and backcross [(OR x MJ) x OR and (OR x VI) x OR] generations, both self-pollinating and non-self-pollinating plants were observed. The ratio of plants with self-pollination brought about by an increase in the length of the ovary, non-self-pollinating plants, and plants with self-pollination brought about by an increase in the length of the style in the F(2) and backcross generations fit 9:6:1 and 1:2:1 ratios, respectively. All plants of the backcrosses [(OR x MJ) x MJ and (OR x VI) x VI] exhibited self-pollination brought about by an increase in the length of the ovary. The results thus supported the earlier finding that self-pollination in the studied strains was controlled by duplicate, recessive genes and suggested that three alleles at two loci determine the occurrence or nonoccurrence of intraflower self-pollination in periwinkle.

Cytological study on chromosome behaviour and new report on nature of mode of pollination ofSwertia chirayita, a high value endangered medicinal plant of North Eastern Himalayan region

“…More over the reason is also there for taking the lengths because, behind the self pollinating mechanism of any plant, there is a relation of the morphology of androceium and gynoceium (KUlKarNI et al 2005). In this plant, the length of whole filament with anther sacs almost coincides with the total length of the style and stigma.…”

Genetic diversity in Nepalese population of Swertia chirayita (Roxb. Ex Fleming) H. Karst based on inter-simple sequence repeats (ISSR) markers

“…The pollinators such as bees and insects are responsible for cross pollination as they collect nectar from nectar glands (Khoshoo and Tandon, 1963). The morphological reason behind the self-pollination can be the structure pattern of androecium and gynoecium (Kulkarni et al, 2005). In S. chirayita, the distance between the anther sac and stigma is less which creates the condition for self-pollination (Proctor et al, 1996).…”

Morphology and Inheritance of Double Floweredness in Catharanthus roseus

“…Hence, automatic intraflower self-pollination does not occur because of spatial separation of the stigma and anthers. Three alleles at two loci were shown to determine the occurrence of automatic intraflower self-pollination in periwinkle through either ovary or style elongation (Kulkarni et al, 2005).…”

“…Periwinkle is a self-compatible plant species. However, the receptive portion is mainly on the base of the stigmatic head and thus automatic intraflower self-pollination does not normally occur (Kulkarni et al, 2005;Sreevalli et al, 2000). Nectar-seeking pollinators with probosces such as butterflies and hawkmoths are required for effective pollination by pressing pollen from dehisced anthers to the basal stigma (Miyajima, 2004).…”

“…Nectar-seeking pollinators with probosces such as butterflies and hawkmoths are required for effective pollination by pressing pollen from dehisced anthers to the basal stigma (Miyajima, 2004). Automatic intraflower self-pollination, however, occurred in cultivars/strains with the continued growth of the gynoecium beyond the base of the anthers, i.e., the overlap between stigma and anthers (Kulkarni et al, 2001(Kulkarni et al, , 2005Miyajima, 2004).…”