Growth and Yield of Potato Plants Grown from Microtubers in Fields

American Journal of Potato Research,  Nov/Dec 2003  by Kawakami, Jackson,  Iwama, Kazuto,  Hasegawa, Toshihiro,  Jitsuyama, Yutaka

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ABSTRACT

Despite many reports of the in vitro production of microtubers, little is known about plant growth and yield from microtubers planted in the field. This study clarified differences in growth and yields between potato plants grown in the field from microtubers and from conventional seed tubers. The experiments were performed at Hokkaido University, Japan, over four years. Conventional seed tubers of about 50 g and microtubers of two sizes (0.5-1.0 g and 1.0-3.0 g) of the late-maturity cultivar Norin 1 were planted, and plant growth and tuber yields were analyzed. The microtuber plants had a lower initial increase in root and leaf area index than conventional seed tuber plants, but had the same leaf area index after about 40 days from emergence. The first tuber formation in microtuber plants was about 7 days later than in conventional seed tuber plants, while tuber bulking occurred about 14 days later in microtuber plants. Consequently, the onset of tuber weight increase was later in microtuber plants, but the rate of increase thereafter was similar between conventional seed tuber and microtuber plants. At harvest the tuber fresh weight of microtuber plants was 82% that of conventional tuber plants, suggesting a potential for using microtubers for field planting.

RESUMEN

A pesar de los muchos reportes sobre produccion de microtuberculos in vitro, se conoce muy poco acerca del desarrollo y rendimiento de las plantas provenientes de microtuberculos en el campo. Este estudio pone en claro las diferencias en desarrollo y produccion en el campo de plantas provenientes de microtuberculos con las provenientes de tuberculo semilla convencional. Los experimentos se realizaron en la Universidad de Hokkaido, Japon durante cuatro anos. Se sembraron tubercules de semilla convencional de unos 50 g y microtuberculos de dos tamanos (0.5 a 1.0 g y 1.0 a 3.0 g) del cultivar de maduracion tardia Norin 1, y se analizo tanto el desarrollo de las plantas como el rendimiento de los tubercules. Las plantas provenientes de microtuberculos mostraron un incremento inicial del indice en area de raices y hojas menor que las plantas provenientes de tubercule semilla convencional, pero 40 dias despues de la emergencia, el indice de area foliar fue la misma. Las plantas de tubercule semilla convencional y las plantas de microtuberculos mostraron muy poca diferencia en cuanto al numero de dias en que se produjo el inicio de la formacion de tubercules, pero el aumento en el volumen del tubercule se produjo 10 dias despues, en las plantas provenientes de microtuberculos. El incremento en tubercules y peso seco total desde el comienzo de la formacion de tubercules hasta el maximo crecimiento de los vastagos fue mayor en las plantas originadas de tubercule semilla convencional que en las plantas provenientes de microtuberculos. Al momento de la cosecha, el peso fresco de tuberculos de plantas provenientes de microtuberculos fue 82% de aquel proveniente de plantas de tubercules convencionales, lo cual sugiere que los microtuberculos tienen potencial para su uso en el campo.

Accepted for publication 23 August 2003.

ADDITIONAL KEY WORDS: minitubers, seed tuber, Solanum tuberosum L.

INTRODUCTION

Potato plants are generally propagated by tubers and have a low multiplication rate. Seed tubers must be grown in areas where virus transmission is minimal to prevent the spread of pathogens to the following generation by seed tubers. In countries without a cold winter to interrupt the pathogen life cycle, the production of seed potato is difficult because of the high disease pressure throughout the year. As a result, these countries (mainly tropical and subtropical) import much of their seed tubers from regions with better climatic conditions for potato seed production (van der Zaag 1990). Because pathogen-tested seed tubers are generally expensive, accounting for up to 50% of the total production cost in tropical and subtropical countries (van der Zaag and Horton 1983), potato farmers are often forced to use locally grown seed despite severe yield losses. In such cases, the use of potato microtubers (MT), small potato tubers weighing less than 5 g fresh weight and produced in vitro can be a potential alternative to conventional imported seed because they are typically pathogen-tested and can be produced in any region.

Studies on MT can be divided in two areas: in vitro production and ex vitro growth and yield. Although much study is still needed, laboratory procedures to produce potato MT in vitro have been well documented (Wang and Hu 1982; Uyen and van der Zaag 1985), favoring commercial production of MT. In contrast, little information is available on ex vitro growth and yields of potato plants grown from MT. Goodwin and Brown (1980), Wattimena et al. (1983), and Leclerc and Donnelly (1990) compared the growth and yield of transplanted MT plants with those of plants from conventional seed tubers (CT). Transplant cultivation, however, is not practical because of increased labor and cost. Haverkort et al. (1991) and Ranalli et al. (1994) harvested tubers from field-planted MT plants and reported that they yielded 50% less than CT plants, mainly because of reduced ground cover from MT plants. As both of these studies harvested MT plants just at maturity or over long intervals (i.e., 22-57 days), however, seasonal courses of growth and development and their effects on final yields of MT plants remain unclear.