Previous studies have shown that abscisic acid (ABA) and ethylene are involved in pulp maturation and peel coloration in the nonclimacteric citrus fruits. There are also signs indicating that other plant hormones may play some roles in citrus fruit ripening. In this study, we compared profiles of genome-wide gene expression and changes in hormones and peel pigments between fruits of Shatangju mandarin (Citrus reticulata Blanco, designated WT) and its natural mutant, Yuenongwanju (designated MT). The MT fruit matures ~2 months later than the WT fruit. Significant differences in fruit diameter, total soluble solids, titratable acid content, chlorophylls and carotenoids were detected between the fruits of the two genotypes at the sampled time points. Genome-wide transcriptome profiling showed that many genes involved in auxin and ABA metabolism and/or signaling pathways were differentially expressed between the MT and the WT fruits. Importantly, the expression of CrYUCCA8 was significantly lower and the expression of CrNCED5 was significantly higher in WT than in MT fruits at 230 and 250 DPA, respectively. In addition, the indole-3-acetic acid (IAA) level in the MT fruit was significantly higher than that in the WT counterpart, whereas a significantly lower level of ABA was detected in the mutant. Treatment of the WT fruit with exogenous IAA significantly delayed fruit maturation. Our results provide experimental evidence supporting the notion that auxin is a negative regulator of fruit maturation in citrus.

A new pomelo cultivar Zhengtian 1043 was found from the bud mutation of Shatianyou (Cit-rus grandis Osbeck), which has been widely planted in southern China. This bud sport was discovered from a citrus grove in 2010. The bud of the mutant was selected and then grafted on Suanyou root-stocks. The cultivar was registered in 2019 after DUS testing. This cultivar has an upright tree shape and a medium branching ability, and shows self-incompatibility or weak self-compatibility. It is neces-sary to plant 10%Suanyou or Miyou (Citrus grandis Osbeck) of the total trees in an orchard to provide enough pollens for pollination. The leaf is oval with a dark-green color. The leaf size and shape of the mutant were almost the same as those of Shatianyou. Flower of the new cultivar is raceme, white and long obovate. Each flower has 26-34 anthers, with light yellow sacs and yellow pollens. There are erect and long styles, and stamens are sloping toward the style. The length of stamen is higher than the pistil when the flowers are in full bloom. The stigma is oblate. The appearance index of fruits is different be-tween both cultivars. The fruits are larger than the parent, pear-shaped with a smooth and yellow color peel, and weighing about 1380 g. The length of fruit neck is shorter than that of Shatianyou. It is easier to peel than the parent. There are 78 seeds on average per fruit and the eatable proportion is 46%. The pulp color of different fruits varies from light-red to red, and the texture is little bit hard. The total solu-ble solid, total sugar and titratable acid contents are 10.7%, 5.6%and 0.69%, respectively, and the ascor-bic acid content is 44 mg · 100 mL-1. The SSR molecular markers were selected to discriminate the dif-ference between new cultivar and the parent. The results showed that two cultivars were different at ge-netic level. The bud-breaking time, flowering and fruit ripening period of new cultivar are basically thesame as those of Shatianyou. The spring shoots started to grow in early February, the flower bloomed in early to late February, and the fruit ripened in early November in Guangzhou city of Guangdong prov-ince. The suitable growing areas for Zhengtian 1043 are also the same as for Shatianyou.

华丰甜橘(Citruts reticulata Blanco'Huafengtianju')是从贡柑、椪柑、甜橙和沙糖橘混种果园中收集的沙糖橘果实种子,后经实生选种获得的新品种.该品种树势强健,枝条萌芽率和成枝力均强于对照沙糖橘,易成花坐果.果实为扁球形,果个比对照大,平均单果质量70.4g,约是对照的1.4倍;果皮厚度约为2.0 mm,易剥皮,完熟果实的果面为橙黄色、平滑、有光泽.果瓣易分离,果肉橙色,化渣,无籽,风味清甜有芳香味,可溶性固形物含量(w,后同)为10.4％～11.0％,总糖含量为7.9％～8.1％,可滴定酸含量为0.25％～0.29％,维生素C含量(ρ)为 14.3～15.7mg·100mL-1.果实成熟期为12月中旬到翌年1月上旬,与对照基本相同.盛果期的产量可达53 100kg·hm-2,比对照增产约15％.SSR分子标记遗传鉴定结果显示,华丰甜橘与对照沙糖橘在基因组水平上存在明显差异,是一个遗传稳定的柑橘新品种.

“华丰甜桔”是从贡柑、椪柑、甜橙和沙糖桔混种果园中收集的沙糖桔果实种子，经实生选种获得的新品种。2019年12月获得农业农村部植物新品种权证书，品种权号CNA20170893.7。该品种果实扁球形，部分果肩向一侧歪，平均单果重约为70.4 g。果实纵径约为4.5 cm，横径约为5.6 cm，果形指数0.8。果顶和果蒂处均稍凹陷，梗洼浅，成熟时状态基本一致；

粤橘1号是从沙糖橘芽变中选育的柑橘新品种.该品种树势健壮,枝梢萌发力较强,成花能力强,易坐果.果实比沙糖橘大,扁球形,果皮厚2.5 mm,易剥皮,果面橙红色,平滑有光泽,平均单果质量约86g,少籽.果肉风味浓甜,有香味,化渣性好,可溶性固形物质量分数13.1％～14.2％,可滴定酸质量分数0.24％～0.39％,总糖质量分数10.3％～11.57％,维生素C质量浓度17.3～32.4mg·100mL-1.在广东广州、清远和河源12月中旬至翌年年1月上旬成熟,与普通沙糖橘一致.粤橘 1号适合我国沙糖橘产区栽培,盛果期产量可达51 700kg·hm-2,比沙糖橘增产约12％.采用SSR分子标记对粤橘1号的遗传鉴定表明,粤橘1号与普通沙糖橘在DNA水平上存在差异,具备成为新品种的遗传基础,是一个稳定变异.

The endophytic bacterial and fungal profiles were comparatively studied between Citrus Huanglongbing (HLB) infected and uninfected healthy leaves of a mandarin cultivar, Shatangju (Citrus reticulata Blanco), by using the next generation sequencing technology. A total of 53 endophytic bacterial orders in12 phyla and 24 endophytic fungal orders in 2 phyla were detected in healthy, asymptomatic and symptomatic leaf midribs. It was found that the predominant endophytic bacteria belonged to Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes and the predominant endophytic fungi belonged to Ascomycota and Basidiomycota. Operational taxonomic unit (OTU) analysis showed that OTU_2 and OTU_6 were the core endophytic fungal OTUs, and OTU_10, OTU_4 and OTU_141 were the core endophytic bacterial OTUs. The richness and diversity of the endophytic microbes were affected by infection of the HLB bacterium, Candidatus Liberibacter asiaticus (CLas). The most significant change was the reduction in endophytic fungal OTUs following CLas infection. Eleven endophytic fungal OTUs and 24 endophytic bacterial OTUs were found to be associated with tree healthy status in citrus. Some of the healthy and HLB disease specific OTUs were discussed, with emphasis on their possible roles in HLB pathogenesis.

为选育无核金桔(柑)优良品种,以优质、有核的实生金桔群体接穗为试材,采用60Co-γ射线5 000～8 000 R照射,单芽嫁接,繁育诱变群体,栽种结果后初选出无核突变单株(V1代),再单芽嫁接分离繁殖,复选出无核突变性状稳定的优良株系(V2代),繁育种苗(V3代)在广东省中北部金桔区进行品种比较试验和中间试验.结果表明:该株系一年开3次花,果熟期11月下旬至翌年3月下旬;果实长球形,单果质量13～18 g,无核;全果打浆测定可溶性固形物含量为21.7％、总酸0.166％,固酸比达130.7;果皮与果肉鲜食风味浓甜、芳香、无苦辣味.本研究认为,“无核金桔优株”的果实品质优良,适宜在广东省中北部等金桔生产区种植.

Two closely related pathogens of Phytophthora are responsible for stem gummosis and root rot diseases in Citrus worldwide. In this study, a neglected local mandarin called duanggan (Citrus reticulata) was identified to be strongly resistant to one of the pathogens, P. nicotianae. No visible symptom was seen on all leaf explants within one week or on 50% of in vivo inoculated stems within one month after inoculation with the pathogen. Drenching of the soil with zoosporangial and zoospore suspensions did not cause any reduction in tree growth and leaf chlorophyll content of pot-grown Guanggan seedlings. Quantitative real-time PCR analysis suggested that its resistance to P. nicotianae may be associated with high basal and induced expression of some defense-related genes, particularly the PR3 gene. In conclusion, C. reticulata var. Guanggan is a promising material that can be exploited to improve Phytophthora resistance in Citrus.

The structure of citrus cultivars and its problems in Guangdong Province were analyzed, and the countermeasures for improvement of citrus varieties and the principles and potential effective measures for restructuring of citrus varieties were discussed.

Allele-specific PCR(AS-PCR)and high resolution melting analysis(HRMA)are two widely used SNP genotyping methods but no research has been done to compare them in terms of genotyping efficiency. In this study,16 pummelo cultivars and 8 pummelo hybrids were genotyped using AS-PCR and HRMA respectively on two different sets of 7 SNP loci. It was shown that both methods generated the same genotyping results in which 24 accessions were assigned into 22 genotypes. It was noteworthy that Hassaku and Red Hassaku were identical at all SNP loci,indicating both accessions shouldhave originated asexually from the same mother cultivar,as was the same case for the two Japanese summer orange cultivars ,Beni Amanatsu and Kawano Natsudaidai. Interestingly,the early-and middle-season‘Zhenlong’pummelo cultivars possessed different genotypes,indicating clearly that they unlikely had the same origin as bud mutations as was thought before,and further analysis of HRMA results showed there is no direct hereditary relationship between them. Our results showed that both AS-PCR and HRMA were suitable methods for the identification of pummelo-related accessions. AS-PCR is a reliable and low-cost SNP genotyping method and easily accessible to ordinary laboratories though the method was found to be sensitive to changes in PCR conditions. HRMA is proven to be a reliable,quick,simple and high throughput SNP genotyping method;However,it uses special equipment and expensive reagents.

柑橘新品种‘粤农晚橘’是从‘砂糖橘’芽变枝条中选育而成.生长健壮,果实扁球形,单果质量39.9 g,果皮橙黄或橙色,果肉细嫩,多汁,甜酸可口,风味浓,果汁含可溶性固形物16.0％～16.89％,总酸0.606％ ～ 0.89％,总糖12.2％～ 13.92％,维生素C 163 mg.L“,果实可食率70％,无核,品质优良.成熟期比‘砂糖橘’晚2.5～3个月.适宜在广东省‘砂糖橘’适栽区种植.

Mingliutianju(Citrus reticuiata Blanco cv.Mingliutianju,MT),a new cultivar selected from Chuntianju(Citrus reticuiata Blanco cv.Chuntianju,CT)through bud mutation,has been extensively cultivated in South China.Their fruits have excellent quality,and can be harvested during the last ten days of February and the middle ten days of March.In present paper,we systematically compared differences of morphological characters between CT and MT through years of efforts on both field experiments and laboratory analysis.Our results showed that CT and MT were similar to each other in phonological period and habits of bearing fruits and growth.Compared with CT,MT showed more attractive agricultural characteristics.These include more vigorous growth,higher and more stable yield,an increase of 37% in average fruit weight,more obvious stria and thicker fruit peels,and most importantly,much less preharvest cracking rates.MT and CT showed no significant difference in fruit texture,soluble solids content,total sugar and vitamin C,and dietary fiber in pulp.Total acid content,crude fiber in pulp and peels were significantly higher in MT than those in CT.

The total proteins in peels and leaves of Citrus reticuiata Blanco ' Chuntianju ' were extracted by four methods,such as Tris-HCl,Thi/Urea,trichloroacetic acid/pacetone precipitation(TCA) and phenol(Phe) extraction methods,respectively,and their effects were compared by protein production,one-way SDS-PAGE and two-dimensional electrophoresis(2-DE).The results showed that TCA method was the best for both leaves and peels of C.reticuiata ' Chuntianju'.The 2-DE map of proteins extracted by TCA method had high resolution,the protein spots were clear and uniform without stripes,and the number of protein spots were large.It suggested that the TCA method could not only remove the interfering substances in peels and leaves of C.reticuiata 'Chuntianju',but also get more stable protein spots.

The paper studied the performances of Eureka lemon introduction in Guangzhou and Heyuan of Guangdong province.The primitive main characters of eureka lemon was maintained in above places: tree middle vigorous,spreading,spines less and short.Young twigs and buds purple-tinged.Flower large,everflowering.Fruit ellipsoid,apex mammiform,base obtuse to rounded,striped with radial grooves and ridges.The fruit is mature and light yellow in early september by bagging,the fruit quality was excellent and had a good storage quality.

“金葵蜜桔”是由广东省佛冈县“沙糖桔”园中的变异优株选育而成。生长健壮，果实紧实，扁球形，其果实比“沙糖桔”早熟15～20天．可溶性固形物含量（15．50％～16．19％）比“沙糖桔”（14．20％）高，

Ruanzhidalimei is a new clonal cultivar selcted from Qinzhumei group in Longjue village,Gaopu town, Puning, Guangdong Province. It has been approved by Provincial Agriculture Crop CultivarsAssessment Committee in July, 2009. The cultivar is vigorous in tree potential with an open shape. Thebranch, soft and drooping, is in a high density. The cultivar bears early and yields highly and stablely.The fruits mature in late April. The fruit is nearly round in shape and uniform in size. The average fruitweight is 24.5 to 26.49 g. the fruit skin is yellowish green with a slightly purplish red in sunside. The fruitpulp is slightly yellow and tight in texture. The flav or is sour with little bitterness and astringency. Thecontent of total soluble solids is 8.0% to 8.59%, titratable acid 49.6 to 55 g.L-1, and total sugar 8.9 to 11.2 g.L-1. Edible rate accounts for 90.6%. It is good for processing dried plum, crisp plum, salted plum,and confecting plum. The cultivar is suitable for the coastal mountain areas in the east of Guangdong Province.

In order to study the genetic diversity of Prunus mume germplasm in Guangdong on molecular level,57 Prunus mume germplasm were analysed by using AFLP technique.Eight AFLP primer combinations(MseⅠand EcoRⅠ) were screened out from 64 pairs of primers.The clear fingerprint maps were obtained from the 57 germplasm.The results suggested that the eight pairs of primers could be used to distinguish all the materials tested.A total of 33117 fragments were generated from the eight pairs of AFLP primers,9 624 of which were polymorphic.The level of mean polymorphism was 29.06%.The genetic similarity indexes of 57 Prunus mume germplasm ranged from 0.56 to 0.90,and the ratio of polymorphic varied from 0.172 0 to 0.423 9.The results of genetic diversity analysis among 57 Prunus mume germplasm indicated that the diversity was more abundant on morphological level than on molecular level.The 57 Prunus mume germplasm were clustered into 8 groups by UPGMA dendrogram at genetic similarity coefficient value of 0.75.

To study the effects of topography on quality of Longmen Nianju(Citrus reticuiata Blanco) fruits stored on the tree,experiment was made in three consecutive years.The results showed that the orchard's topography have a certain impact on the appearance and endoplasmic of fresh fruit on the tree.Vc content,soluble solids content,reducing sugar,sucrose and total sugar content of fruit on plain orchard were more than those on slope orchard.The maximum of those in slope orchard appeared in mid-February in the same time or later than in the plains.Thereafter,the contents of these quality parameters decreased at different speeds,but the topography did not significantly affect them.Before the appearance of maximum,the Pn of leaves in sloping fields were higher than that the plains,but those in the plains increased gradually with the decline of fruit quality parameters.The fruits of slope orchard were available to storage on the tree because they matured later than those in the plain orchard.

＇Jinkui Miju＇tangerine is a chance mutation selected from Shatangju tangerine,in Fogang County,Guangdong Province.It grows vigously.The fruit is globose.The average fruit weight is 39.7 g.The peel is thin,orange-red.The pulp is crisp and tender.TSS 15.50%-16.19%,total acid 0.46%-0.89%,total sugar 11.60%-14.87%,vitamin C 0.379-0.465 mg.mL-1.It matures about 15 days earlier than Shatangju.It is suitable to be planted in Shangtangju cultivation area,Guangdong Province.

1 选育经过 1984 年,在普宁市高埔镇龙堀村的青竹梅群体中,发现1株树姿较开张,枝梢较软垂,果实大,果实向阳面呈浅紫红色,肉厚核小,产量高的优良单株,列为初选单株.自初选以来,逐年对其进行高接和繁殖,其后代同样表现出母树的优良性状.