Vietnam is very rich in indigenous citrus cultivars, most of local widely cultivated citrus cultivars are seedy. For breeding of triploid seedless citrus varieties, it is necessary to induce autotetralploid plants derived from diploid ones.
The elite clones selected from 5 different citrus cultivars have been used for polyploidization experiments. There are Two orange Cultivars: Van du and Song Con( Citrus sinensis), King mandarin: Cam Sanh ( C. nobilis), mandarin cultivar: Quyt Chum (Citrus reticulata) and pummelos cultivar Buoi Phu trach. The method of colchicine in vivo treatment on the axillary buds of two-year old plants has been used for inducing tetraploids. Different colchicine concentrations (0; 0.05; 0.1; 0.2; 0.3; 0.4 and 0.5 percentages) with different treatment times( 0h; 24h; 48h and 72h) have been applied. The percentage of surviving and shooting axillary buds is strongely depended on the colchicine concentration, treatment time and also genotype. The low concentration (0.05%) has showed any or very litlte effect on shooting of treated buds even the treating duration is extended up-to 48 and 72 h. The higher colchicine concentrations, starting from 0.2%, have showed toxic effects at all the treated times. The most effective treatment has been observed at colchicine concentration 0.1% with treating time 24h. Ploidy level variation of the plants derived from treated buds have been verified by Flow Cytometry. Total of 19 plants were polyploidized ( tetraploids),from which 16 plants are chimeras,only 3 plants are homogenous tetraploids. The homogenous autotetraploids have been obtained from 3 local cultivars Van du,Cam Sanh and pummelos cultivar Buoi Phu trach. The colchicine treatment at concentration of 0.1% and treating time 24h is most effective for tetraploid plant induction.
Ha Thi Thuy, Tran Ngoc Thanh, Do Nang Vinh
Vu Van Vu