Techniques for using sprouts for potato production in the tropics
A series of experiments were conducted in Vietnam to develop a system whereby detached sprouts from physiologically old green sprouted seed tubers could be used to grow potatoes. Three node segments from the mid or basal portion of the detached sprout produced the greatest percentage of shoots and roots. Growth was best in a medium of equal parts of sub-soil, pig manure and brick kiln ash. Sprout cuttings produced plantlets ready for transplanting in 14–20 days with mean daily temperatures of 22 to 24°C. When transplanted in mid-November, yields from sprout cuttings in field experiments were 10 to 18 t/ha which were 33% lower than from healthy seed tubers but more than the national average yield using degenerated seed tubers. Tubers produced by plants grown from sprout stored well and gave good yields when replanted the following year.
Potato production using tissue culture in Vietnam: The status after four years
Farmers in Dalat, Vietnam, (1500 m asl) have established a unique method of using in vitro plants as a source for planting material (1). The rapid adoption of this approach was attributed to several factors. Farmers had been using degenerated seed of cultivars susceptible to Phytophthora infestans, resulting in low yields and decreasing area under cultivation. Three new high yielding cultivars were introduced as clones: CFK 69.1, B71-240.2 and Atzimba and were named as V4, V8 and VI2, respectively after having shown good P. infestans resistance and given high yields. No seed tubers were available for these new cultivars. This communicat ion reports the evolution of the demand for and use of cutting technology in the spread of these new cultivars f rom late 1980 to late 1984.
Growth in Netted Gem potatoes as influenced by transplanting and by greensprouting
The basis of difference in field growth and yield in Netted Gem potato plants grown from greenhouse transplants, from seed which was greensprouted for two weeks prior to planting and from seed which was retained in storage until planting was studied by measuring changes in plant dry weight and leaf area throughout the season. Cut seed, approximately 70g in size, which were either two or four-cut from 142g or 283g mother tubers respectively, were used in the comparisons. Transplants were started in 7.6 cm peat pots in the greenhouse and were transplanted to the field when 10 cm high. The greensprouted seed was cut from mother tubers which had been sprouted under fluorescent light at 15–18°C for two weeks producing strong sprouts 5 mm long. Transplants, greensprouted seed and seed from mother tubers held in 3°C storage were all planted in the field May 30, 1974, coinciding with commercial plantings of Netted Gem in the province. Backup field experiments, comparing similarly treated greensprouted and storage seed and transplants, were conducted in 1974 and 1975 but were not subjected to growth analysis. All plantings were grown on a Riverbank sandy loam soil. The 1974 growing season in New Brunswick was excellent while that for 1975 was dry and required extensive irrigation.The use of transplants established a substantial advantage in terms of early emergence and yields were consistently and significantly greater than those of greensprouted-seed and unsprouted-seed plants. The transplant yield advantage was attributed to the fact that tuberization was advanced substantially compared with the latter two types. Higher relative growth rates were associated with later emergence so that the rate for plants growing from unsprouted seed was greater than that for plants growing from greensprouted plants which, in turn, was superior to that of transplants. This pattern was maintained through the season. Consequently, small advantages in time of emergence, such as that obtained with greensprouted-seed plants, were not accompanied by significant yield differences. Canopy size decreased as emergence was delayed and canopy size differences were determined largely by the amount of branching. As canopy size decreased and emergence was delayed, the net assimilation rate was found to increase.ResumenLos factores que contribuyen a establecer las diferancias de crecimiento y rendimiento de las plantas de papa (var. Netted Gem) provenientes de trasplantes, de las provenientes de semilla verdeada dos semanas previas a la siembra, y de aquellas provenientes de semilla mantenida en almacén hasta el momento de la siembra fueron estudiados midiendo los cambios en materia seca y en el área foliar a través de su desarrollo. Para realizar las comparaciones de utilizó semilla partida, de aproximadamente 70 gr. que se obtuvo cortando tubéculos madrés de 142 ó 283 en dos o cuatro partes, respectivamente. Los trasplantes fueron sembrados primero en invernadero, en macetas de 7.6 cm., usando musgo como sustrato, siendo trasplantados al campo una vez alcanzados los 10 cm. de altura. Las semillas partidas se obtuvieron de tubérculos madres que fueron brotados bajo luz fluorescente a una temperatura de 15 a 18°C durante dos semanas, produciendo brotes fuertes de 5 mm. de longitud. Los trasplantes, la semilla con brotes verdes y la semilla sin brotes (mantenida en almacén a 3°C) fueron sembrados en el campo el 30 de Mayo de 1974, fecha que coincidió con la siembra comercial de Netted Gem en la provincia. En 1974 y 1975 se llevó a cabo experimentos de campo comparando tratamientos similares, pero en esa oportunidad no se realizó el análisis de crecimiento. Todas las siembras se realizaron en un suelo franco arenoso. El período de cultivo de 1974 en New Brunswick rue excelente, pero el de 1975 fue seco, requiriéndose una irrigatión intensiva.El uso de trasplantes signícó una gran ventaja en términos de emergencia temprana, siendo los rendimientos consistente y significativamente mayores a los rendimientos de semillas con brotes verdes y semillas sin brote. La ventaja del trasplante fue atribuída a la tuberización temprana. El indice mayor de crecimiento relativo se asoció con la emergencia tardía, de manera que el índice de la semilla sin brote fue mayor que el de la semilla verdeada, y éste a su vez, fue mayor que el índice de los trasplantes. Esta diferencia se mantuvo a través de todo el ciclo de desarrollo. Consecuentemente, las pequeñas ventajas observadas durante el periodo de emergencia, tales como las obtenidas con semillas con brotes verdes, no fueron acompañadas de diferencias significativas en rendimiento. El area foliar disminuyó a medida que se retardaba la emergencia y la diferencia fue mayormente determinada por el volumen de ramificación. A medida que el area foliar disminuyó y la emergencia se retardaba, la asimilación neta también aumentó.