Expression of trifoliate leaf character inCitrus limoniaxPoncirus trifoliatahybrids through cryostored pollen

Abstract

SummaryIntergeneric crosses are feasible in citrus, but are seldom accomplished successfully because of lack of flowering synchrony, sterility, polyembryony and biennial bearing. Poncirus trifoliata (L) Raf. was chosen for studying pollen cryobehaviour, as it is widely used as a pollen parent in citrus rootstock improvement programmes. Pollen collected from three Poncirus strains, cryopreserved in liquid nitrogen for 90 and 350 d, remained viable and fertile, producing fruit and setting seed when crossed on emasculated flowers of ‘Rangpur lime’ (Citrus limonia Osbeck). Germinating seedlings expressed the dominant trifoliate leaf character (TLC) from crosses involving two of the three Poncirus pollen strains. This study confirms the fertility of cyropreserved pollen, and facilitates intergeneric transfer and expression of the dominant TLC, segregating the sexual hybrid seedlings from the nucellar seedling population at a very early stage. The possible use of this protocol in citrus breeding, gene conservat...