Influence of 6-Benzyladenine and gelling agent on the reduction of hyperhydricity in Tectona grandis L. Influencia de la 6-Bencilaminopurina y el agente gelificante en la reducción de la hiperhidricidad en Tectona grandis L.

Running title: Controlling hyperhydricity in teak Influencia de la 6-Bencilaminopurina y el agente gelificante en la reduccion de la hiperhidricidad en Tectona grandis L. Abstract: The influence of different factors on shoot proliferation and the occurrence of hyperhydricity in teak ( Tectona grandis L.) have been studied. Four concentrations of BA (2.22, 4.44, 6.66 and 8.88 µM) and a control treatment with 0 BA were examined. Aiming at reducing the costs during commercial propagation by using gelrite in stead of agar, the use of both gelling agent in the proliferation and hyperhydricity was tested. In order to evaluate if hyperhydricity can be reduced by increasing the gelrite concentration in the culture medium, three concentrations (2.0, 2.5 and 3.0 g l -1 ) were tested in combination with 4.44 µM BA. The proliferation and occurrence of hyperhydricity during 21 successive subcultures were evaluated. The highest proliferation was achieved in the treatments with 6.66 or 8.88 µM BA. They yielded 5.22 and 5.56 shoots/explant, respectively. But also, the highest percent of hyperhydric shoots was achieved in this treatment. Gelrite resulted in a higher proliferation, but also an almost two times higher hyperhydricity as compared to agar-solidified media. Satisfactory reduction in hyperhydricity (18%) was achieved with 3.0 g l -1 gelrite. However, the successive subcultures onto proliferation in this treatment favored hyperhydricity compromising shoot quality and its competence to proliferate. In vitro teak plants were ex vitro rooted and then transferred to greenhouse conditions for acclimatization; ten weeks after transfer they were ready for field plantation. Key words: cytokinin; forestry; micropropagation; morpho-physiological disorder; teak Abbreviations: BA- 6-Benzyladenine, MS - Murashige and Skoog basal medium, IBA - Indole-3-butyric acid, ANA -Naphtalene acetic acid Resumen: Se estudio la influencia de diferentes factores en la proliferacion y la ocurrencia de la hiperhidricidad in teca ( Tectona grandis L.). Se probaron cuatro concentraciones de BA (2,22; 4,44; 6,66 and 8,88 µM) y un control sin BA. Con el objetivo de reducir los costos durante la propagacion comercial se experimento sustituir el agar por el gelrite, para lo cual se estudio en efecto de ambos gelificantes en la proliferacion y la hiperhidricidad de los brotes. Se estudiaron, tres concentraciones de gelrite (2,0; 2,5 and 3,0 g l -1 ) combinadas con 4,44 µM BA, con el objetivo de evaluar si la hiperhidricidad podia ser reducida incrementando la concentracion de gelrite. Se evaluo la proliferacion de brotes y la ocurrencia de la hiperhidricidad durante 21 subcultivos. Se logro una alta proliferacion de brotes en los tratamientos con 6,66 y 8,88 µM BA (5,22 y 5,56 brotes), pero el porcentaje de brotes hiperhidricos tambien se incremento. El gelrite resulto en una alta proliferacion de brotes, pero con mayor incidencia de la hiperhidricidad que el medio gelificado con agar. Se obtuvo una reduccion satisfactoria de la hiperhidricidad (18%), cuando la concentracion de gelrite se incremento hasta 3,0 g l -1 . No obstante, la multiplicacion de los brotes en este tratamiento mas alla del 11 no subcultivo favorecio la hiperhidricidad, lo que afecto la calidad de los brotes y su competencia para la proliferacion. Las plantas fueron enraizadas ex vitro , transferidas a condiciones de invernadero para su aclimatizacion y diez semanas despues de la transferencia estaban listas para la plantacion en campo. Palabras clave: citoquinina; forestal; micropropagacion; desorden morfo-fisiologico; teca