In vitro induction of polyploids of watermelon (Citrullus lanatus Thunb.)

In the present studies four explants E1 (transversely) cut epicotyl), E2 (transversely cut hypocotyl), E3 (cut cotyledons) and E4, (embryonic end of 5 days Seedlings) were Cultured On different concentrations of colchicine (0, 0.01%, o.5% and o.1%) on MS medium + 1 uM Benzyladenine for 4 and 7 days. The data were recorded for percent of explant producing callus, days to initiate callus, percent of explants producing, shoots, number of shoots per explant, percent of explant producing roots and number of roots per explant. In case of test experiment the highest percent of (90.25% and 91.06%) explants producing callus was observed on the explant E2 (transversely cut hypocotyl) cultured on MS medium with 1uM and 5uM Benzyladenine (BA), respectively. The highest (9.55) number of shoots were produced on the explant E3 (cotyledons) cultured on MS medium supplement with 1uM BA. Further studies were carried out on MS medium + 1uM BA with various levels of colchicine (0, 0.01%, 0.05% and 0.1%). Callus took least (4.06) days to initiate on the explant E2 (transversely cut hypocotyl cultured for 4 days while among the colchicine added media M1 (0.01% colchicine) proved to take least (12.75) days. The greatest (85.25) percent of explants producing callus, among colchicine containing media, was exhibited by the explant E2 (transversely cut hypocotyl) cultured on M1 (0.01% colchicine) for 4 days duration. The maximum (50.25) percent of explants producing shoots among colchicine added media was on the explant E2 (cotyledons) cultured on media with 0.01 % colchicine (M1) for the duration D1. The explant E4 regenerated maximum (8.55) shoots and the explant E3 (cotyledons) induced 7.20 shoots on the media supplemented with 0.01% colchicine (M1) which was maximum among colchicine added media. The highest (100) percent of explant producing roots was observed on the explant E3 (embryonic end) cultural on all the media for the both duration of treatments. The concentration of colchicine and duration of treatment did not effected the rooting ability of embryonic ends (E4). The greatest (4.15) number of roots per explant among colchicine added media were recorded on the explant E4 (embronic end) cultured for 4 days on media containing 0.01 % colchicine (M1). There must be some research in future on these explants to turn the non embryogenic callus into embryogenic ones. Here we recommend to use cotyledons and embryonic ends of 5 days old seedling cultured in vitro for shoot regeneration. The maximum tetraploids were produced, on the explants E3 (cotyledons) and E4 (embryonic end) cultured for 4 days duration on 0.01% colchicine containing media (M1). The same explants when cultured on similarly medium for 7 days produced mixploids. So 0.01 % colchicine treatment for 4 days proved to be the best. The other parameters also showed the best results on this concentration of colchicine in the media. The present studies prove that by using spectrophotometric measurements the polyploids can be easily identified from diploids. It is concluded that this technique is reliable and efficient to identify polyploids from in vitro regenerated plants.