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This study estimates the levels and determinants of farm‐level technical efficiency of shrimp farmers, using the stochastic production frontier function involving a model for technical inefficiency effects. A sample of 90 brackish water shrimp farms were surveyed in the region of Shyamnagar Upazila of the Satkhira District, Bangladesh, to study their economic efficiencies. Data were collected, using a questionnaire survey from September to October 2011. The mean technical efficiency level of the shrimp farmers was estimated at 82%, and thus, farmers operate 18% below the production frontier. The results suggest that the inefficiency effect is significant, and that education, age, non‐farm income and distance of the farm are significant determinants of technical inefficiency. By operating at full technical efficiency levels, shrimp production can increase from the current yield of 225.56 to 265.28 kg/ha. Besides improving technical efficiency, technological progress and extension services (such as dissemination of proper information of the technological practices and further adoption of technological practices) can also contribute to increased shrimp production levels. Finally, quality feed and fingerling at affordable prices need to be ensured to further promote shrimp production.

An experiment was carried out at the Biotechnology Laboratory of Bangladesh Sugarcane Research Institute (BSRI), Ishurdi, Pabna for the development of drought tolerant somaclones. Five sugarcane varieties viz. Isd 20, Isd 35, Isd 36, Isd 37 and Isd 38 were used as plant material. Unexpanded spindle leaf sheaths were used as explants in tissue culture. In the first culture, the MS medium (BM) was supplemented with 2,4-D (3 mgL-1) and coconut water (10 %) for callus induction. The callus was then sub-cultured on fresh BM with BAP (2.0 mgL-1) and Kinetin (1.0 mgL-1) for plantlet initiation (2nd culture). In the third culture, initiated plantlets were sub-cultured again on fresh BM contained NAA (5.0 mgL-1) for root development. In all cultures BM was supplemented with 0.0, 5.0, 7.5 and 10.0% poly ethylene glycol (PEG) and was semi solidified with 0.6% agar to select somaclone variant plantlets of sugarcane in vitro. In the first culture 100% explants initiated callus on medium supplemented with no PEG. Callus induction, proliferation and plantlet regeneration decreased with increased level of PEG. At 7.5% PEG, the callus induction was highest (80%) in varieties Isd 35 and Isd 38. Callus was induced but became reddish black and senescence within 40 days on BM supplemented with 10.0 % PEG. Both shoot and root production decreased with increased PEG level in the medium. At 7.5 % PEG in BM, the highest shoot number was in Isd 38 (5.5 per culture), root number (7.6 per shoot) and root length (1.2 cm) were in the variety Isd 38. The highest shoot length was in Isd 37 and Isd 38 (1.8 cm). Survival percentage of in vitro regenerated plantlets was 100 % during hardening in low cost polythene house and in establishment in the field. Keywords: Somaclone; sugarcane; drought stress; plantlet; in vitro DOI: http://dx.doi.org/10.3329/agric.v9i1-2.9475 The Agriculturists 2011; 9(1&2): 18-28

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