Development of an elite tomato aspermy virus-free medicinal chrysanthemum crop and evaluation of its performance in the field

Chrysanthemum morifolium cv. ‘Huaihuang’ (HH) is a medicinal cultivar that is widely cropped for its dried flowers used in Traditional Chinese Medicine (TCM). To date, tomato aspermy virus (TAV)-infected disease has led to a severe decrease in flower production. Herein, we report a combinatory protocol to produce TAV-free HH plants for flower production. Stem segments were collected from field-grown TAV-infected plants (YD5), and surface-sterilized for micropropagation. Adventitious shoots were induced and then rooted to obtain plantlets, from which shoot apexes (SAs) were used to test KT concentrations. SA culture (SAC) and SAC combination with heat treatment (HT) were conducted to remove TAV. RT-PCR was completed to specifically amplify TAV to identify virus-free plants. The results showed that the KT concentration was optimized to be 0.03 mg/L for both micropropagation and less vitrification. SAC-HT of 38 °C/30 °C for six weeks could get 80 % TAV-free plants, from which a strain YD5J6 was selected for continuous 3-generations’ field practice. The results showed that YD5J6’s heights, crown sizes, flower capita and production, and flower yields per acre were significantly increased. The contents of chlorophyll and carotenoids and the activities of NR and GS were dramatically increased in YD5J6 leaves. Crude enzyme assays revealed that the activities of PAL, C4H, and 4CL extracts from YD5J6 flowers were enhanced. Chlorogenic acid, luteoloside, and 3, 5-dicaffeoylquinic acid contents were augmented in YD5J6 flowers. Taken together, TAV-free elite YD5J6 was developed for the high production of flowers for TCM.