The Fruit Setting, Quality and Tolerance to Stem Canker (Neoscytalidium dimidiatum) in ‘Mei’ Pitaya.

• Main Authors: Cheng-Yao Wang, 王政耀
• Other Authors: 林慧玲
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/2rah5c

碩士 === 國立中興大學 === 園藝學系所 === 107 === Pitaya is a new and rapidly progressing fruit crop in Taiwan. It is popular among growers, due to its easy cultivation and wide adaptability. However, as the cultivated area increases, the associated disease problems also gradually emerge. Among them, stem canker disease (Neoscytalidium dimidiatum) is the most serious, which causes rotten stem, and lumpy brown spots in fruit skin, and significantly reduces the quality of pitaya fruit. To control this disease, in addition to the application of chemical agents, screening of disease-resistant lines is also an effective strategy. ‘Mei’ is a red pitaya cultivar and its stem has short thorn characteristics and does not stab farmers in corp management. However, it is generally believed that its fruits have inferior quality and light flavor. This study first investigated the fruit setting, quality and disease tolerance to stem canker in ‘Mei’ Pitaya, and then evaluated whether this pitaya cultivar has the potential to become a commercial cultivar. The characteristics of fruit setting, self-pollination, open-pollination and hand-pollination experiments were conducted. Our results showed that all different pollination methods might result in fruit setting, and there were no difference in fruit size, weight, total soluble solid (TSS) and titratable acidity (TA) among different pollination methods, suggesting that ‘Mei’ pitaya is self-compatibility. In terms of fruit quality, the average mature fruit weight in ‘Mei’ was 623 g, TSS was 20.6° Brix (center of flesh), and TA was 0.25% with a slightly grassy aroma in flesh. For the disease tolerance test, the spore suspension (106 spore/mL) was inoculated on the mature fruit and the stem. Our results showed that 11 days after inoculation, the disease tolerance of ‘Da hong’ is the worst with the disease severity index reaches 5 (80-100% rotted area). ‘Mei’, ‘Fu gui hong’ and ‘Vietnamese white’are more tolerant to disease with the fruit disease severity index between 2-4 (20-80% rotted area). In the stem portion, the lesion diameter of ‘Mei’ and ‘Yi lan’ at 19 days after inoculation were 0.13cm and 0.61cm. Results from this study indicated that the mature stem of ‘Mei’ has high disease resistance. Taken together, ‘Mei’ pitaya has the potential of becoming a commercial cultivar based on its fruit setting, quality and stem canker disease tolerance.