In Vitro regneration of three local potato (Solanum tuberosum L.) varieties of Bangladesh
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The present study was conducted to develop an efficient and reliable protocol for in vitro regeneration of potato varieties. Experiments were conducted with a view to standardize in vitro regeneration of three local potato varieties, viz. Zaubilati, Shadaguti and Challisha. Newly sprouted potato varieties were collected and surfaces sterilized with 0.1% (w/v) HgC12 for 1 minute and were cultured on PROP medium for sprout regeneration. Explants, such as, shoot apex, nodal segment, internode and leaf were collected from these in vitro grown shoots and the effect of hormonal treatments viz. cytokinins (BAP and Kn) with or without auxins (GA3, IAA and IBA) were observed for in vitro direct shoot regeneration and root induction. For shoot apex explant, the minimum days required for shoot initiation, the highest shoot length, number of leaves per plantlet, and fresh weight of shoot per plantlet were recorded at Shadaguti variety in PROP medium supplemented with 1.5 mg/I BAP. In case of Kn, no single concentration was found best for all regeneration parameters, but the regeneration frequency of potato varieties in PROP with 0.5 mg/l Kn showed better than BAP treatments. For nodal segment explant, PROP medium supplemented with 1.0 mg/I BAP and 0.5 mg/I Kn found the best concentrations for all regeneration parameters of Shadaguti and Zaubilati varieties but without BAP and Kn supplements Challisha showed better response. For internode explant, Shadaguti variety respond better than other varieties, when cultured in PROP medium supplemented with 1.0 mg/I BAP along with GA3 (0.2 mg/I) and IAA (0.5 mg/I), while Kn along with GA3 (0.2 mg/1) and IAA (0.5 mg/I) produced only direct root. For leaf explants, all the regeneration parameters of Shadaguti variety showed better response with PROP medium supplemented with 0.5 - 1.0 mg/I BAP along with GA; (0.2 mg/I) and IAA (0.5 mg/I). On the other hand, Kn along with GA3 (0.2 mg/1) and IAA (0.5 mg/1) showed only direct root regeneration. Depending on the above four explants, shoot apex of potato showed better performance than nodal segment explant and the appropriate concentration was 1.5 mg/I BAP and Shadaguti variety showed the best genotype for in vitro shoot regeneration. Similar to shoot apex, internode of potato showed better than leaf explant and PROP medium supplemented with 1.0 mg/I BAP + 0.2 mg/l GA3 + 0.5 mg/I IAA was the best combination while the best genotype was Shadaguti variety for direct in vitro shoot regeneration . For root induction , among the four different treatments, '/2 PROP medium supplemented with 0.5 mg/I IBA performed the best. Rooted plantlets were established after proper hardening and acclimatization in poly bags containing garden soil, sand and decomposed cow dung at the ratio of 1:1:1. After transplantation 50% plantlets survived in the natural environment.