Improving the micropropagation efficiency of hybrid Dendrobium orchids with chitosan

The appropriate chitosan types and concentrations for enhancing the in vitro micropropagation of Dendrobium ‘Eiskul’ were studied using 70, 80 and 90% N-deacetylated polymeric (P-70, P-80 and P-90) and oligomeric (O-70, O-80 and O-90) forms of crab (Portunus pelagicus) chitosan. For the initial protocorm-like body (PLB) multiplication, the application of 10 mg/L of P-70 or 20 mg/L of P-90 was optimal, although 10 mg/L of P-80 and O-70 were also effective, and attained maximal PLB replication rates without increasing the detectable levels of somaclonal variation. However, during PLB-shoot induction, 10 or 20 mg/L of O-80 was the most appropriate chitosan and also induced further PLB formation. For plantlet regeneration, the addition of 10 mg/L of O-80 or P-80 gave the best quantity and quality, respectively, of plantlets. Finally, 20 mg/L of P-70 chitosan as a supplement during exflasking enhanced both the survival rate and the growth of the plantlets at one month after exflasking. Together, these data reveal a potentially beneficial and applicable protocol for commercial orchid micropropagation.     

Beyond the farm-turn-out: on-farm development dynamics in the Kamphaengsaen irrigation project, Thailand

Many large-scale state-run irrigation projects in the world have been constructed with limited investment in on-farm infrastructure. In most cases, it was expected that local farmers would themselves make improvements on their farms. In general, insufficient attention is paid to water control which has a negative impact on productivity. Farmers' strategies to offset poor access to water are very varied and depend on site-specific factors such as topography, the existence of other potential water sources, market opportunities or capital availability. This article presents a case study in the Central Plain of Thailand and describes the patterns of land development which occurred since the construction of the Irrigation Project 25 years ago. It shows how land and water use evolved as both a mover and a response to on-farm development and who initiated new investments, such as ditch and tube-well digging, regulators in drains, which have allowed secondary water sources to be tapped, the development of conjunctive use, increased reliability in water supply and crop diversification. The importance of individual farm pumps is shown. Poor land levelling is conducive to high costs and reduced water use. Prospects for land consolidation are assessed.