Potential male gametophyte competition among <i>camellia sinensis</i> genotypes in isolated biclonal seed orchards

Abstract

Male fertility of crop plants is a function of pollen production and viability. In breeding, it is a requirement that there be similar fertilities among breeding parents within seed orchards. An in-vitro germination method was used in this study to determine variation in pollen viability among eight tea (Camellia sinensis) genotypes, over three flowering seasons in four isolated biclonal seed orchards located at two sites. The effect of environmental conditions on pollen germination was also studied on two popular genotypes, i.e. AHP SC31/37 (an assamica variety) and GW Ejulu-L (a sinensis variety) that were planted in both sites. Significant variation (P < 0.05) in pollen viability among the eight genotypes indicated a potential for male gametophyte competition. There was significant genotype by environment interaction and positive correlation between pollen viability and temperature. Pollen germination was, however, not affected by rainfall and humidity. The variations in pollen viability may contribute to the variable genetic composition of seed produced in the isolated seed orchards of tea.Key Words: In-vitro germination, male fertility, pollen viability RÉSUMÉ La fertilité mâle de plantes culturales est fonction de la production et de la viabilité polliniques. Lors de culture, il est une nécessité que les seuils de fertilité soient similaires parmi les parents des cultures au sein de vergers de semences. Une méthode de germination in vitro était utilisée dans cette étude en vue de déterminer la variation en viabilité de pollen parmi 8 génotypes de thé (Camelia sinensis) de par 3 saisons de floraison dans 4 vergers de semences bi clonaux situés au niveau de 2 sites. Les effets des conditions environnementales sur la germination du pollen étaient également étudiées; sur 2 génotypes populaires c'est-à-dire AHP SC 31/37 (une variété assamica) et GW Ejulu -L (une variété sinensis) qui étaient plantées sur les 2 sites. Des variations significatives (P< 0,05) en viabilité de pollen parmi les 8 génotypes indiquaient un potentiel pour la compétition de gamétophyte mâle. Il y avait une interaction significative genotype par environnement et une corrélation positive entre viabilité de pollen et température. La germination du pollen n'était cependant pas affectée par les pluies ou par l'humidité. Les variations en viabilité de pollen pourraient contribuer à la composition génétique variable de semences produites dans les vergers isolés de semences de thé.Mots Clés: In-vitro, germination, fertilité mâle, viabilité de pollen.

Morpho-physiological and phenological attributes of reproductive biology of tea (Camellia sinensis (L.) O. Kuntze) in Sri Lanka

“…The observations signify variability among the genotypes in the developmental stages at which stigma receptivity and anther dehiscence occurred and also in pollen viability that could result unequal reproductive success in the different genotypes. Muoki et al (2007) and Wachira and Kamunya (2005) have also reported differential success of pollen parents when crossed with known female parents in the Kenyan germplasm. Similar circumstances were experienced by Bezbaruah (1975b), Neog and Singh (2003) and Bezbaruah and Saikia (1977) and the authors stated that the genotypes having variable affinity to the different tea varieties: C. sinensis var.…”

“…Tea is identified as having Group III wet type stigma according to the classification by Helslop-Harrison and Shivanna (1977). Phenological studies of tea flowering and seed setting conducted in the Kenyan and Indian tea germplasm have revealed seasonal variability among the varieties (Bezbaruah 1975a;Neog and Singh 2003;Muoki et al 2007). Pollination biology of tea, specifically in relation to floral visitors and effective pollinator populations has been adequately dealt in a report by Wickramaratne and Vitarana (1985).…”

Comparative study on cross-compatibility between Camellia sinensis var. sinensis (China type) and C. sinensis var. assamica (Assam type) tea

“…Hence, compared to in-vitro germination test the pollen staining tests overestimated the viability of pollen. In-vitro pollen germination is generally believed to provide more reliable estimate of pollen viability (Muoki et al, 2007). Additionally, both viability and in-vitro germinability tests together provided important insight into understanding about the pollen quality.…”

“…Additionally, both viability and in-vitro germinability tests together provided important insight into understanding about the pollen quality. Notably, disparities in pollen quality are evidenced for potential male gametophyte competition and unequal reproductive success among C. sinensis genotypes (Muoki et al, 2007). The paternal traits, that is, phenology of male organ and amount of pollen produced, and pollen grain traits, that is, germination percentage, germination time, pollen tube growth rate, and selective fertilization are the factors that determine the fitness of pollinizers (Muoki et al, 2007).…”

“…Monitoring the pollen grain germination and pollen tube growth in pistils using aniline blue fluorescence microscopy assay subsequently with the fruit and seed set are included in cross-compatibility test in intraspecific hybridization (Heslop-Harrison et al, 1984;Muoki et al, 2007). Although fluorescence microscopy is a practicable approach for examining the pollen tube growth in pistil, this method is relatively time consuming, unfeasible for testing many samples.…”