Identification of Blooming Type, Blooming Process, and Pollen Germination Rate of Jujube (Ziziphus jujuba Mill) in New Mexico

Jujube (Ziziphus jujuba Mill) cultivars were imported into the US about 100 years ago. Jujube is recognized as functional food because it has high value on both nutritional and medicinal perspectives. Even though the acreage is limited, jujubes are widely distributed in the US, and they grow and produce well especially in the Southwest. But, few cultivars are commercially available. To recommend more cultivars for growers and consumers for different uses, the NMSU Sustainable Agriculture Science Center collected and imported a total of over 50 cultivars. One of our objectives is to identify the blooming type, pollen germination and self-fertility for each cultivar which would be useful for cultivar recommendation and future breeding purposes. In this study, 55 jujube cultivars were examined for their blooming type and forty-one cultivars were studied for pollen germination. According to the sepal slitting time, jujube cultivars can be classified as morning blooming type or afternoon blooming type. Twenty-four of them belonged to morning type with sepal slitting between 5-8:00 am. The other thirty-one belong to afternoon blooming type with sepal slitting between 1-3:00 pm. Sepal slitting time varied by cultivar and was affected by weather conditions, but blooming type for each cultivar in general was consistent across the season. For the morning blooming type cultivars, pollen releasing reached a peak between 10:00 am to 2:00 pm, while the afternoon blooming type cultivars released pollen after 3:00 pm and continued to 8-10:00 am the next day. Hourly pictures of jujube flowers for three cultivars were taken under dissecting scope from 6:00 am to 5:00 pm. Each flower experienced sepal slitting, sepal flatting, petal flatting, anther petal separation, anther flatting and stigma browning stage within 1-2 d. For pollen germination study, 9-12 flowers from each cultivar were collected and directly inoculated into media, which consisted of 15% sucrose, 1% agar, and 0.01% boric acid. Cultivars can be classified as high, medium or low in pollen germination rate. ‘September Late’, ‘Shuimen’ and ‘Fitzgerald’ had high pollen germination rate, while Sherwood was low in germination rate. The low pollen germination rate cultivars are not suitable as pollinizers and require pollination cultivars in production. One cultivar had extremely low pollen number which would be useful for breeding purposes.¹This project is supported by a USDA Agricultural Marketing Service Specialty Crop Block Grant through the New Mexico Department of Agriculture.