An attempt to induce polyploidy in genotypes of ber (Zizhyphus mauritiana Lamk)

Abstract

Organised efforts to induce various levels of ploidy have been made in crop plants and to use them in developing superior varieties. Transfer of powdery mildew resistance from diploid genotypes of Zizhyphus to tetraploid cultivars required doubling of chromosomes in resistant genotypes in order to overcome the possible post-fertilization barriers. It was in this context that an attempt has been made to induce polyploidy in some of the resistant diploid genotypes of Zizhyphus that were confirmed cytologically [1]. Colchicine treatment was initially given to young emerging shoots of (two, four and six months age) bud grafted plants of the four genotypes at six different concentrations. However, there was hardly any response probably due to woody nature of the plant. Therefore apical meristems of seedlings of each of the four genotypes (Darakhi-1, Darakhi-2, Guli and Villaiti) were treated with 0.10, 0.20, 0.40, 0.50, 0.75 and 1.00 per cent colchicine solution for 6h in polyhouse for ten days continuously. Treated portions were washed immediately by distilled water after the period of treatment to make them free from colchicine. Similarly apical buds of the young shoots emerging from the pruned plants of nine months age were treated with higher concentrations (0.75 and 1.00 per cent) of colchicine solution for 12h for ten days continuously. A cotton swab was placed on the apical buds and maintained wet by putting colchicine solution on it by using a dropper. After treatment the buds were washed with distilled water.