Environmental and cultural factors affecting the production of myoga (Zingiber mioga Roscoe) in Australia

Myoga (Zingiber mioga Roscoe) is a new vegetable crop in Australia, cultivated for its edible flower buds. Originating from Japan, the crop was introduced into Australia with the expectation that it could be produced over the summer months, with flower buds then exported to Japan, where they retail at a high out-of-season price. fudustry has identified a number of challenges to the successful commercialisation of this crop in Australia. The majority of these relate to cultural aspects ofmyoga production and manipulation of the growing environment to control crop performance, in particular, extension of harvest season. A lack of knowledge of the effect of environmental factors on the production of myoga flower buds has hampered initial efforts to successfully cultivate this crop in the Australia. Photoperiod was identified as a potentially important environmental factor affecting the production of myoga flower buds. A series of trials conducted within controlled environment cabinets determined that myoga had dual photoperiod requirements for successful flower bud production, with flower bud initiation having a quantitative short day requirement while flower bud development had a qualitative long day requirement. Differences in the critical daylength required for successful flower bud development in cultivar S and I myoga plants was identified as the reason why cultivar I plants senesced prematurely when field cultivated in Southern Australia. The critical daylength for flower bud development in cultivar S plants was determined to be approximately 13 hours, while cultivar I plants required a daylength closer to 14 hours. Low night temperatures were observed to interact with photoperiod, resulting in successful flower bud development in daylength conditions that at higher night temperatures would have been too short. From the results of these trials, photoperiod was deemed to be a crucial determinant of the location of future production sites and the timing of production seasons. Environmental factors affecting general plant growth and development were also deemed important areas of research, in particular the tolerance of myoga plants to strong light conditions. There have been reports of variations in the shade requirement of myoga plants grown in different climatic regions. This led to the hypothesis that these plants were susceptible to cold induced photoinhibition of photosynthesis. This was confirmed during a number of trials which used chlorophyll fluorescence techniques to investigate the function of photosynthetic systems within myoga plants when placed into stressful conditions. Exposure ofmyoga to light intensities greater than 750 µmol m-2 s-1 resulted in the engagement of photoprotective mechanisms to prevent photodamage occurring. Sensitivity to low temperatures meant that these plants became photoinhibited at far lower light intensities and the engagement of photoprotective mechanisms was sustained, when plants were exposed to low temperatures in conjunction with light. The acclimation of these plants to low temperature and the successful engagement of photoprotective systems within the photosystem indicate that myoga can cope with strong light intensities over a shortterm period. However exposure to strong light intensities at warm temperatures or moderate light intensities at low temperatures, for an extended period of time, is likely to result in permanent photodamage occurring. Additional cultural factors affecting commercial production of myoga flower buds were identified during the first two years of cultivation. At Albion Park, NSW it was determined that myoga plantings remaining in the ground for longer than one year did not require artificial chilling, and with correct management of vegetation could produce higher flower bud yields than first year plants. Production trials conducted in Rockhampton, QLD investigated the effect of daylength and temperature on flower bud production, and confirmed that myoga was well suited to cultivation in a subtropical environment provided due consideration was given to photoperiod and the potential need for artificial chilling. Recommendations based on the above research findings have already been adopted into commercial production protocols and as such many of the challenges to myoga production in Australia have now been successfully resolved.