Abstract
Experiments were conducted in Tissue Culture Laboratory, Grill House and Experimental Field of the Department of Crop Botany, BAU, Mymensingh and in Atomic Energy Laboratory of Food and Radio Biology Division, Savar, Dhaka during the period from June 2009 to December 2012 for the genetic improvement of teasle gourd. Twenty seven accessions were collected from different agro-ecological zones of Bangladesh to study different morphological characters with the objective to find out the relatively better one. Out of 27 accessions, 16 accessions were found female and rest of the accessions (11) were male. In respect of male and female plants, leaf, flower, fruit and seed characters were recorded. The highest yield (3.0 kg plant'), fruit weight (68.2 g fruit') and number of fruits (44 plant') were obtained in Acc 3. The highest plant height, number of branches, number of nodes, length of internode, leaf green, leaf length, peduncle length, minimum days to first flowering (50 days), minimum first flowering node (15th) were found in this accession. In case of male plant, Acc5 possessed the larger flower, the highest peduncle length, the minimum number of days to first flowering (52 days) and the minimum first flowering node was 17th. To develop in vitro regeneration protocol, internode, node, leaf, shoot tip and cotyledon explants of Acc 3 were cultured. Cultured temperature was 25±1°C and light intensity of 30-35 μ mol m2s were maintained by air cooler and by florescent tubes. The explants were cultured on MS medium supplemented with various concentrations of BA alone or in combination with NAA for callus and shoot regeneration. Cotyledon was the best explants in this study. They produced the highest percentage of callus induction (98%) and the highest weight (2.1 g) of callus when cultured on MS medium supplemented with 1 mg L of BA. But the lowest percentage of callus induction (15%) and the lowest weight (0.3 g) of callus were produced from leaf explants when cultured in MS medium supplemented with 1.0 mg L BA+ 2.0 mg L1 NAA. Cotyledon explants also produced the highest percentage (95%) of shoot formation, maximum number (17) of shoots callus and maximum length (2.0 cm) of shoot when cultured on MS medium supplemented with 1 mg L BA alone. Leaf explants cultured MS medium supplemented with 1.0 mg L1 BA + 0.5 mg L1 NAA performed the worst. Proximal part of cotyledon produced higher percentage of calli (98%) & higher number of shoots callus', whereas the distal part produced the lower percentage of calli (21%) & lower number of shoots callus'. Shoots were transferred to medium containing different concentrations of IBA and IAA for rooting. IBA at 0.3 mg L1 resulted better root initiation. The highest number of roots (20.0) and longest roots (7.0 cm) were found in shoots from cotyledon explants cultured on 1⁄2 strength of MS medium containing 0.3 mg L' IBA. For acclimatization of in vitro rooted plantlets of about 2-4 cm height (2-3 nodes) were subsequently transferred in earthen pots containing different potting mixtures. Plants grown in potting mixture of soil +cowdung (3:1) had 100% survivability. The highest survival percentage of hardening plantlets was found in the month of May and June (100%) followed April (80%) and March (20%) .The mature calli of teasle gourd cotyledons were subjected to eight different doses of gamma irradiation (1, 3, 5, 7, 9, 11, 13 and 15 gray). The lower dose ( 5 gray) had the highest calli survivability (100%) and induced high frequency multiple shoots (95%). higher number of branches plant (5.0), shortening of internodes, produced medium fruits (67.36 g) having reduced number of seeds fruit' (21.2) with vigorous plant growth (224.4 cm). The higher dose (15 gray) resulted lowest calli survivability (30.2%) and reduced multiple shoots (50.70% ), lower branches plant1 (2.09), produced smaller size of fruit (64.12 g) having reduced number of seeds fruit (17.50). The highest number of pollen/microscopic field was observed in regenerated plant (18.5) compared to normal (10.2) & gamma irradiated plants (9.8). The round shaped pollen was observed in normal flower triangular shaped in regenerated flower, whereas triangular & spindle shaped pollen were found in gamma irradiated flowers. Fruit setting was delayed in gamma irradiated plants (70.20 days) compared to normal (55.16 days) and regenerated (68.73 days) plants. Number of fruits plant from normal, regenerated and gamma irradiated plants were 12.15, 14.18 and 11.20, respectively. Gamma irradiated plants produced medium sized fruit (8.52 cm) which was larger than normal (7.7 cm) but smaller than regenerated one (9.86 cm).The seed number of gamma irradiated fruit was drastically reduced (21.0) compared to normal (33.36) and regenerated fruit (27.20). It was concluded that regenerated fruit was the best due to its large size, weight & reduced number of seeds compared to normal. The 5 gray dose was the best for inducing high frequency of multiple shoots with large sized fruit & reduced number of seeds compared to 15 gray dose and normal.