Effects of Cultivar and Cropping Type on Growth and Yield of Female and Male Asparagus Plants
Thursday, January 12, 2023
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Posted by: Jane Cerza
Test area and sprouting status of white asparagus in the rootstock forcing culture. Photos courtesy of Satoru Motoki Kawasaki, Japan Asparagus (Asparagus officinalis L.) is a dioecious perennial plant. Male plants have a higher yield than female plants; therefore, all-male cultivars are more commonly produced. In contrast, female plants have a higher spear weight than that of male plants. To increase profitability, selective cultivation of only female plants would increase the yield of asparagus with a thick spear, which has a higher unit price. However, the effects of cultivar and cropping type on the growth and yield of male and female asparagus plants have rarely been examined. A team of scientists in Japan compared the growth and yield of female and male plants of three cultivars grown under various cropping types: a rootstock planting forcing culture (RPFC); a long-term harvest production system (LHPS) in an open field; and a semi-forcing culture. The sex differences in the growth and yield of 1-year-old green asparagus cultivars Early California and UC157 grown in RPFC were investigated to determine which of the cultivars is more suitable for RPFC. Additionally, using a LHPS, this study examined yield differences between the sexes of 2- to 4-year-old asparagus cultivars, specifically green asparagus UC157 and purple asparagus Pacific Purple, in open field and semi-forcing cultures to determine whether the female purple asparagus plants have advantages over the male plants in terms of profitability. UC157 is widely grown in Japan and was used as a control for each cropping type. As a measurement of growth, the rootstock weight was significantly higher for female plants compared with that of male plants with the rootstock planting forcing culture. Regarding yield measurements, the spear weight and yield were not significantly different with the rootstock planting forcing culture. However, with the long-term harvest production system in the open field and semi-forcing cultures, the weight and yield of female plants were equivalent to or significantly higher than those of male plants, regardless of the cultivar, except during some harvest periods. These results indicated that the selective production of female plants may be advantageous in terms of growing heavier spears with a higher unit price in a long-term harvest production system in the open field and semi-forcing cultures in Japan. The sex identification process for plants is time-consuming and can be costly because it involves DNA extraction and polymerase chain reaction analysis. Although the development of simpler sex identification methods is ongoing, the cost of such methods is a factor to be considered when determining the cost-effectiveness of female plant production for each cropping type, cultivar, and region. Dr. Motoki is a professor in the Undergraduate School, School of Agriculture and Director of the Kurokawa Field Science Center. Dr. Motoki designed the test and was involved in the research from start to finish. Akira Kanno was involved in the discrimination of males and females by DNA. Professor Motoki's student, Shumpei Imai, was involved in the early cultivation, and Professor Motoki's students, Kazuki Okada and Takumi Taguchi, were involved in writing the research.
The full study results can be found on the ASHS HortScience electronic journal website at: https://doi.org/10.21273/HORTSCI16786-22. Established in 1903, the American Society for Horticultural Science is recognized around the world as one of the most respected and influential professional societies for horticultural scientists. ASHS is committed to promoting and encouraging national and international interest in scientific research and education in all branches of horticulture. Comprised of thousands of members worldwide, ASHS represents a broad cross-section of the horticultural community — scientists, educators, students, landscape and turf managers, government, extension agents and industry professionals. ASHS members focus on practices and problems in horticulture: breeding, propagation, production and management, harvesting, handling and storage, processing, marketing and use of horticultural plants and products. To learn more, visit ashs.org.
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