ABSTRACT
RESUMEN En Venezuela es prioridad rescatar las papas nativas por representar un gran alimento y un valioso recurso genético. Pero, desafortunadamente estas papas fueron desplazadas por variedades comerciales introducidas y las pocas semillas existentes están degeneradas y reutilizadas en continuos ciclos de siembra, No obstante, estandarizar las condiciones del cultivo aséptico es garantía de "semillas" rehabilitadas con mejor calidad fitosanitaria. Se planteó, entonces investigar el efecto de distintas concentraciones de nitratos y sacarosa en la propagación in vitro de variedades venezolanas ̀̀Cucubaʹ ̀̀Arbolona Negraʹ y ̀̀Rosadaʹ. Segmentos uninodales fueron cultivados e incubados en fotoperíodo de16 horas de luz (76 μmol m-2 s-1) y temperatura 19º C ± 1. Fue implementado el diseño estadístico factorial, estableciendo tres tratamientos partiendo del medio básico Murashige & Skoog (MS), sólido. Hubo un efecto significativo entre los tratamiento, al menos una de las medias es diferente a las otras, para las tres variedades la mayor inducción de crecimiento ocurrió, al modificar MS aumentando sus concentraciones de nitrato de amonio a 1,98 g L-1, nitrato de potasio 2,28 g L-1y bajando sacarosa a 20 g L-1, los vástagos desarrollaron 5,82 cm. de longitud promedio y las raíces 3 cm. Mientras, el MS (tratamiento control), presentó vástagos de 2,94cm. longitud promedio y sin enraizar. Entre las variedades ̀̀Cucuba´ obtuvo el mayor crecimiento. Posteriormente, las vitroplántulas resultantes, tratadas en MS líquido, con sacarosa al 8 % fueron inducidas a producir microtubérculos a los 90 días. Obteniendo así resultados prometedores para la propagación in vitro de las papas nativas.
ABSTRACT The recovery of native potato varieties is a current priority in Venezuela, given their value as a genetic resource of high nutritional quality. Unfortunately, native potato varieties were progressively replaced by exotic commercial, varieties. To date, the limited existing germplasm of native potato varieties is impoverished and of low quality, due to its continual reutilization in crop cycles. Nevertheless, efforts can be made to recover and standardize the production of quality propagules under adequate sanitary conditions. The aim of this study was to assay the effect of varying concentrations of nitrates and saccharose in tissue culture media of three Venezuelan varieties "Cucuba", "Arbolona Negra" and "Rosada". Unimodal segments were planted and incubated using a photoperiod of 16 h light (76 μmol photon m-2 s-1) at 19 ± 1 ºC. The experiment was designed following a standard factor analysis, consisting of three treatments, parting from the basic Murashige & Skoog (MS) medium and data were submitted to an multifactor ANOVA. Our findings indicate significant statistical differences amongst all of the treatments assayed, confirming that all of the varieties reached maximum physiological response under increasing concentrations of nitrates. Such was the case with 1.98 g L-1 ammonium nitrate and 2.28 g L-1 potassium nitrate using a concentration of saccharose 20g L-1. Mean shoot and root lengths under optimal concentrations were 5.82 cm and 3.0 cm, respectively. In contrast, MS basic culture media represented the treatment of least growth induction; yielding un rooted shoots of a mean length of 2.94 cm. Of these three native varieties, "Cucuba" proved to have the highest growth rates. All of the Vitroplantlets were then transferred to liquid MS media, with a saccharose concentration of 8 %, originating microtubers after 90 days. We conclude that these findings may be of use for massive in vitro production of native potato varieties.
ABSTRACT
An efficient micropropagation (direct & indirect) and microtuberization protocol for an endemic and ethanomedicinal plant Ceropegia pusilla is described. The highest number of shoot initiation (3.50 0.34) and higher average shoot number in shoot subculture (15.40 1.65) were recorded on MS medium supplemented with BAP+NAA (2.5+0.5 mg/l). The best performance of callus induction and morphogenesis was found on MS medium supplemented with BAP and NAA from stem. The callus initiation was recorded on MS medium supplemented with BAP+NAA (0.5 + 1.0 mg/l) and the higher percentage of callus forming shoots from callus subculture is determinate to be 90-95 7.93. MS medium supplemented with various concentrations of cytokinins and auxins supported the induction of microtubers, in vitro flowering and roots. The microtubers and root formation occurred on the basal region of the shoots in MS medium containing BAP (1.5mg/l) and NAA (0.5mg/l). The higher average number of root length was (2.8 0.68cm) also observed in the same concentration. The plantlets regenerated in vitro with welldeveloped shoots, microtubers and roots were successfully established in pots containing hardening media and grown in a shade house with 81 3.16% survival rate.
ABSTRACT
Los microtubérculos en algunas especies de plantas constituyen una importante alternativa como material vegetal de plantación. Se definió como objetivo de trabajo evaluar en campo la respuesta morfoagronómica de las plantas obtenidas de los microtubérculos de ñame formados en Sistema de Inmersión Temporal (SIT). Como variantes experimentales se plantaron tres categorías de microtubérculos, clasificados según su masa fresca (I. de 0,5 a 0,9 g; II. de 1,0 a 2,9 g; III. igual o mayor de 3,0 g), plantas in vitro previamente aclimatadas y corona de tubérculo. Se evaluó el efecto de la masa fresca de los microtubérculos sobre su brote, supervivencia y posterior desarrollo de las plantas derivadas de ellos en campo. Con los microtubérculos de ñame, con una masa fresca igual o superior a 3,0 g, se alcanzó el más alto porcentaje de brotación (91,30%) y supervivencia de las plantas (96,50%), así como las mejores respuestas en los caracteres cuantitativos que se evaluaron en campo. Estos resultados confirmaron la importancia de la masa fresca de los microtubérculos para ser empleados como material vegetal de plantación directo en campo.
Microtubers in some plant species represent an important alternative crop-planting material. The presentwork involved field work for evaluating the morphoagronomic response of plants obtained from yam microtubersproduced in a temporary immersion system (TIS). Three categories of microtuber were planted asexperimental variants; they were classified by fresh mass (1 - 0.5 to 0.9 g, 2 - from 1.0 to 2.9 g and 3 - equal to or greater than 3.0 g), previously in vitro-acclimated plants and tuber crowns. The effect of microtuber freshweight on their sprouting, survival and later development of the plants derived from them in the field were evaluated. The highest sprouting (91.30%) and plant survival percentages (96.50%) and the best response in quantitative traits evaluated in the field were obtained with yam microtubers having a fresh mass equal to or greater than 3.0 g. These results confirmed the importance of microtubers fresh weight for using them as plant material in direct planting in the field.