Seed Storage Behaviour And In-Vitro Recovery Of Cryopreserved Embryo In Pomelo: A Commercially Important Tropical And Subtropical Fruit Crop
Citrus maxima (L.) is a commercially important sub-tropical fruit species throughout the World. Fruit is characterized by a large size, unique taste, and extensively used for diverse uses including religious, cultural and medicinal besides as a table fruit. Genetic diversity of this species are shrinking due to various factors, therefore, management of genetic resources is required using complementary conservation strategies. Besides in situ conservation in the famers backyard, field gene bank conservation has proved to be difficult to adopt embryo conservation in liquid nitrogen for long-term conservation. Seed storage behavior studies were carried out in this commercially important fruit crop and zygotic embryos were successfully cryopreserved. Seeds of this species revealed non-orthodox seed storage behavior with moderate seed longevity and sensitivity to desiccation and freezing. Critical moisture content (13-15%) was observed for successful seed storage and cryopreservation of embryo and embryonic axes of this citrus species. After 42 hour of desiccation, recovery percentage of cryopreserved embryos was decreased by 70%. Freezing of embryonic axes at this moisture content in liquid nitrogen showed a good recovery rate of 80–100% using in vitro method. In vitro recovery after cryopreservation was also carried out using different culture media compositions. MS medium supplemented with 1 mg/L BAP + 1 mg/L NAA growth regulators gave highest shoot initiation (100%) along with maximum number of nodes (3) after 10 days of in vitro culture without any intervening callus. Maximum root formation (90%) along with highest number of roots (3) was obtained with 1/2MS+ 0.1 mg/l BAP+0.5 mg/l NAA+ 2.5 gm phytagel culture medium. Healthy in vitro recovered plantlets were maintained in culture room conditions. Present study successfully demonstrated cryopreservation of embryo and embryonic axes of Pummelo for establishing a cryo - collection with optimal in vitro recovery of Pomelo germplasm for long-term ex situ conservation.
Keywords - Pomelo, desiccation tolerance; intermediate seeds; seed storage behaviour.