Transcriptome analysis of peach (Prunus persica L. Batsch) during the late stage of fruit ripening.

Fruit ripening is a complex developmental process, the details of which remain largely unknown in fleshy fruits. In this paper, the fruit flesh of two peach varieties, "Zhongyou9" (a nectarine; Prunus persica L. Batsch) and its mutant "Hongyu", was analyzed by RNA-seq technology during two stages of ripening at 20-day intervals. One hundred and eighty significant upregulated and two hundred and thirty-five downregulated genes were identified in the experiment. Many of these genes were related to plant hormones, chlorophyll breakdown, accumulation of aroma and flavor volatiles, and stress. To the best of our knowledge, this is the first transcriptome analysis of peach ripening, and our data will be useful for further studies of the molecular basis of fruit ripening.

Identification of Pseudomonas syringae pv. actinidiae strains causing bacterial canker of kiwifruit in the Anhui Province of China, and determination of their streptomycin sensitivities.

Bacterial canker, caused by Pseudomonas syringae pv. actinidiae, is one of the most severe diseases of kiwifruit. It has become an international pandemic and threatens the sustainable development of kiwifruit production in all main kiwi-growing regions worldwide. Streptomycin has been the major bactericide for the control of kiwifruit canker, especially in Anhui Province, one of the main kiwifruit production regions in China. However, until now, no studies on the baseline sensitivity to streptomycin of field isolates of P. syringae pv. actinidiae from China have been available. During 2012-2013, a total of 102 single-colony P. syringae pv. actinidiae strains were isolated: 36, 12, 13, 26, and 15 strains from Yuexi, Jinzhai, Huoshan, Qianshan, and Taihu counties, respectively. All strains were confirmed by production of a 280-bp fragment using the specific primers PsaF1/R2 upon polymerase chain reaction amplification, followed by an assay for confirmation of pathogenicity to fulfill Koch's postulates. In this study, the streptomycin sensitivity of the 102 isolated strains was determined. The half-maximal effective concentration values for inhibition of growth by streptomycin were 0.03-0.42 µg/mL (average 0.12 ± 0.06 µg/mL). The baseline sensitivity curve was unimodal, representing range-of-variation factors of 14.0. No resistant subpopulation was identified among the strains used in the study. Thus, these sensitivity data could be used as a baseline for monitoring the shift in sensitivity of P. syringae pv. actinidiae populations to streptomycin in Anhui Province. Continuous resistance monitoring should be carried out, as streptomycin is an at-risk bactericide agent.