Exploitation of potential target tissues to develop polyploids in citrus

One of the rich sources of germplasm development to improve citrus crop is the ploidy management through in vivo and in vitro techniques. In vitro and in vivo applications of colchicine change the chromosome number by interfering with chromosomal segregation at anaphase, restricting cell wall formation and yielding polyploid cells. Further, endosperm culture under aseptic conditions also allows regeneration of plants with variable genetic make up. We report here the development of polyploids through in vitro culturing of endosperm and application of colchicine. Somatic embryos were developed from 'Kinnow' mandarin (Citrus reticulata L.) and 'Succari' sweet orange (Citrus sinensis L. Osbeck) on basal medium modified with higher concentrations of BA and NAA (10mgL ^-1 and 2mgL ^-1, respectively) from calli induced on Murashige and Tucker (MT) medium supplemented with BA, 2,4-D, KIN, ME and CH. Recovery of polyploids from endosperm culture was significantly low (32%) compared to colchicine induced ploids (53.67%). Bud sprouting percentage and shoot length was found inversely proportional while leaf size was directly proportional to colchicine application. The stomatal studies of the regenerated plants revealed them as polyploids. These strategies are promising techniques for production of citrus polyploids, however; further genetic characterization of the ploids is suggested for future breeding and biotechnology applications. Abbreviations: BA 6-benzaylaminopurine, CH Casein hydrolysate, KIN Kinetin, ME Malt Extract; NAA 1-naphthaleneacetic acid, 2,4-D 2,4-Dichlorophenoxyacetic acid.