A chromosome-level genome assembly for Chinese plum‘Wushancuili'reveals the molecular basis of its fruit color and susceptibility to rain-cracking

Chinese plum(Prunus salicina Lindl.)originates from China and makes a large contribution to the global production of plums.The P.salicina‘Wushancuili'has a green coloration and high fruit quality and is economically important in eliminating poverty and protecting ecology in the Yangtze River Three Gorges Reservoir.However,rain-induced cracking(rain-cracking,literally skin cracking caused by rain)is a limitation to‘Wushancuili'fruit production and causes severe losses.This study reported a high-quality‘Wushancuili'genome assembly consisting of a 302.17-Mb sequence with eight pseudo-chromosomes and a contig N50 of 23.59 Mb through the combination of Illumina sequencing,Pacific Biosciences HiFiⅢsequencing,and high-throughput chromosome conformation capture technology.A total of 25109 protein-coding genes are predicted and 54.17%of the genome is composed of repetitive sequences.‘Wushancuili'underwent a remarkable orthoselection during evolution.Gene identification revealed that loss-of-function in four core MYB10 genes results in the anthocyanin deficiency and absence of red color,revealing the green coloration due to the residual high chlorophyll in fruit skin.Besides,the occurrence of cracking is assumed to be closely associated with cell wall modification and frequently rain-induced pathogen enrichment through transcriptomic analysis.The loss of MYB10 genes might render fruit more susceptible to pathogen-mediated cracking by weakening the epidermal strength and reactive oxygen species(ROS)scavenging.Our findings provided fundamental knowledge regarding fruit coloration and rain-cracking and will facilitate genetic improvement and cultivation management in Chinese plums.

Key Points of Breeding and Cultivation Techniques of Wushan Crisp Plum,a New Cultivar of Green Crisp Plum

Wushan crisp plum is a new cultivar of green crisp plum with dignified fruit shape,crisp and tender flesh,pit separability and sweet taste.It is bred from natural bud mutant of Jiang'an Dabaili,a local green crisp plum cultivar by Wushan County Fruit Industry Development Center,Southwest University and Chongqing Agricultural Technology Extension Station.Wushan crisp plum has won the gold award in the National High-quality Plum and Apricot Appraise and Elect and the tile of"the king of fruit"in the"Three-Gorge Cup"High-quality Crisp Plum Appraise and Elect.In the southwestern region of China,the planting area of Wushan crisp plum has been extended to 33000 ha.The cultivar has strong robust and fast growth.In the area along the Yangtze River in the Three Gorges Reservoir area of Chongqing,it ripens from early to middle July.The fruit is ovoid and of medium size,with average longitudinal diameter of 3.3 cm,average horizontal diameter of 4.0 cm,average single fruit mass of 37.2 g,carpopodium length of 1.5 cm,and carpopodium diameter of 0.1 cm.The top of the fruit is slightly concave.The peel is green to green-yellow in background color and medium in thickness,with obvious fruit dots and thick white fruit wax.The flesh is light yellow,compact,short in fiber length,juicy,crisp,tender,pure and sweet,with soluble solids content of 12%-15%,titratable acid content of 0.43%-0.72%and vitamin C content of 6.12-8.99 mg/100 g.The pit is small,separable,and oblate.The percentage of edible flesh is up to 94.80%-96.88%.There is no obvious pre-harvest cracking and intra-fruit pectin.The cultivar is mid-ripening and high in yield.In the firm ripe stage,the flesh is crunchy;and after entering the soft ripe stage,the flesh becomes powdery,and the hardness decreases.At room temperature,the fruit is not resistant to storage and transportation.Wushan crisp plum is tolerant to the climate with high temperature,high humidity and less sunshine,with good adaptability.It is suitable for promoting in the upper reaches of Yangtze River within 180-1000 m elevation.

Production Forecast of Citrus in China and Production and Marketing Situation of Citrus in Chongqing in 2016 Production Season

According to the statistics of the Ministry of Agriculture,the planting area of citrus would increase steadily,and the yield would decline slightly,2. 556 7 million ha and 36. 168 million t,respectively. Compared with 2015,the planting area would increase by 1. 97% and the yield would increase by 1. 17%. According to the production scheduling of Chongqing Agricultural Commission,the citrus production in Chongqing in 2016 would continue to maintain a steady and rapid growth,the estimated area and yield were 0. 206 7 million ha and 2. 8 million t,increasing by 4. 27% and 4. 48% compared with 2015 respectively. By the end of November 2016,most of mature citrus products in Chongqing would show different degree of rise in purchasing price,while the purchasing price of red orange and some processed raw material fruits would show different amplitude of decline. On the whole,the production and marketing situation of Chongqing citrus would become better.