Comparative transcriptome analysis reveals the mechanism involving ethylene and cell wall modification related genes in Diospyros kaki fruit firmness during ripening.

Rapid loss of firmness is a major handicap for persimmon (Diospyros kaki Thunb.) transportation and retail. The present study employed a comparative transcriptomic approach to elucidate the mechanism involving ethylene and cell wall modification related genes in fruit firmness control of two cultivars during post harvest ripening. In contrast to the short shelf life cultivar (Mopan), the long shelf life cultivar (Yoho) kept high firmness during ripening. Extensive loss of firmness in Mopan drove an intense transcriptional activity. Globally, Mopan and Yoho shared very few common differentially expressed structural genes and regulators. Yoho strongly repressed the expression of ACC synthase and several classes of cell wall degradation genes at the onset of ripening and only induced them during late ripening period. Various ERF, WRKY, MYB, bHLH transcription factors were found highly active during fruit ripening. Overall, this study generates novel gene resources as important tools for extending persimmon shelf life.

The Potential of Gaseous Chlorine Dioxide for the Control of Citrus Postharvest Stem-End Rot Caused by Lasiodiplodia theobromae.

The focus of this study was to develop technologies using chlorine dioxide (ClO2) gas to control postharvest stem-end rot of citrus caused by Lasiodiplodia theobromae. Mycelial growth of L. theobromae on potato dextrose agar (PDA) plugs was completely inhibited by a 24-h ClO2 exposure provided by 0.5 g of solid ClO2 generating granular mixture in a 7.7-liter sealed container. In vivo experiments were conducted on artificially inoculated Tango and naturally infected U.S. Early Pride mandarins. When ClO2 treatments were initiated 0 to 6 h after inoculation, decay development was significantly reduced as compared with the control, and higher ClO2 doses were more effective. A ClO2 treatment (using 3 g of generating mixture per 7.7-liter sealed container) administered 0 h after inoculation resulted in 17.6% Diplodia stem-end rot incidence compared with 95.6% in the control, whereas the same treatment administered 24 h after inoculation was much less effective, resulting in 63.0% incidence compared with 85.4% in the control. Diplodia stem-end rot incidence of naturally infected fruit after using 6 or 9 g of generating mixture per 24-liter sealed box was 23.8 or 25.7%, respectively, compared with 47.9% for control fruit. The ClO2 treatments had no negative effects on fruit quality characteristics including weight loss, firmness, puncture resistance, titratable acids (TAs), total soluble solids (TSSs), and rind color. Albedo pH at wounds was significantly reduced from 6.0 to 4.8 by the ClO2 treatments, whereas undamaged albedo remained at 5.8. In addition, no visible physiologic defects, such as peel browning and bleaching, were observed on ClO2-treated fruit. These results indicate that ClO2 gas has the potential to be developed as a component of an integrated citrus postharvest decay control system to minimize fruit losses.