Potato Minituber Induction In One Step System

Potato (Solanum tuberosum L.) is the fourth most important crop after the three cerealsmaize, rice and wheat in the world. Potato is propagated predominantly by asexual means(tubers and minitubers), which makes it accumulate pathogen, especially virus, in the tubers.That caused the production decreased year by year. In vitro propagation of the potato by serialculture of axillary shoots in separated nodes is now becoming established as an effectivemeans of rapidly multiplying new or existing cultivars in disease-free conditions (Hussey andStacey1984). In potato seed production systems, in vitro derived plantlets are commonly usedfor production of clean seed stock. The plantlets can be planted directly into the field or firstused for production of small minitubers in greenhouses. Large-scale, commercial productionsystems for minitubers typically grow in vitro derived plantlets in organic soil or artificialsubstrates in greenhouse or net house.Many countries lacking isolated and vector-free growing areas that permit the productionof quality potato seed tubers consider microtuber technology a vital component of seed potatoproduction. In other countries, microtubers are one of several propagules favored during earlycertification stages for seed tuber production.Microtubers are particularly convenient for handling, storage and transport of germplasm.Also, unlike in vitro propagated plants, they do not need a hardening period in a greenhouseand may be adapted to some form of large scale mechanized planting. For these reasons,efforts were made to devise an effective practical means of producing microtubers andestablish routine use of this material in the schemes of seed tuber programmes, especially incountries which have no vector-free production areas to produce high quality potato seed tubers.Tuberization of potato in vitro is affected by the culture environment, potato genotypeand medium components. Environmental features implicated in microtuber induction are lightand temperature, medium components implicated in induction include sucrose, nitrogen,growth regulators, and natural products. While a various genetic origin and maturity of potatogenotype response different under different environment and medium components. Otherconcerns within the potato seed tuber industry that prolonged exposure to growth regulatorsduring micropropagation or microtuberization may unnecessarily risk somatic change. In vitrotuberization without growth regulators became introduced by several authors.Utilization of microtubers in elite seed potato production systems has been postulated byseveral authors since the early1980s. Despite their advantage over microplants in storage andexchange, microtubers have not been accepted as propagules of choice by the industry,because of the cumbersome procedures and high input. In conventional micropropagationtechniques, the first step was culture the plantlet in a fresh MS growth medium supplementedwith2-3%(w/w) sucrose, and the second step was the growth medium was replaced withfresh MS growth medium supplemented with8%(w/w) sucrose and also with exogenoushormones, and then incubated in the dark. Approximately eight weeks from plantlet culture tothe microtuber harvested. The conventional micropropagation techniques not only gettinghigher contamination rate in replacing the induction medium, but also need more labor input.The objective of this study was to find a simple and convenient technique without replace themedium to produce microtuber in stationary containers.The result as follows,1. In one step induction, the suitable sugar concentration in the media is60g· L-1. 2. The results showed that short photoperiod is beneficial for the initiation of microtuber,but the microtuber was small. Appropriate extended illumination time is conducive to inducelarger microtuber. Different potato cultivar needs different light intensity to induce microtuber.Alternative temperature (18℃in dark and24℃in light) is optimal for microtuber induction.3. Environment evaluation was needed to screening the optimal condition for microtuberinduction in different potato varieties.4. In cultural stage, light intensity had no effect on microtuber dormancy, extendillumination time increased microtuber dormancy, high temperature shortened microtuberdormancy. In induction stage, microtuber inducted in long darkness had long dormancy.