No abstract

Plum, belonging to the genus Prunus of Rosaceae family, is one the most important fruit crops in the world, with a high economic value and an extensive genetic diversity. China is now the largest plum producer, with an annual production of 6,801,187 t in 2018, accounting for 53.9% of the world's total (FAOSTAT, http://www.fao.org/faostat/en/ #data). Chinese plum (Prunus salicina Lindl., 2n = 2x = 16), also known as Japanese plum, is widely grown for fresh market consumption and the processing industry. During the past decades, Chinese plum cultivars introduced from the United States and Japan, including 'Black Amber', 'Formosa', 'Angeleno', 'Fortune', 'Friar', and 'Akihime', have been widely cultivated in China for their productivity and storability (Liu et al., 2019). With the substantially improved living standards, consumers' demand for better eating quality increases gradually, which brought Chinese native or improved plum cultivars into sight, such as 'Zaohongxiang', 'Qingcuili', 'Yuhuangli', 'Zuili', 'Naili', and 'Sanhuali', being known for their excellent flavor and unique aroma (Huang et al., 2019; Liu et al., 2019). In this context, the breeding objectives of our group are to select plum cultivars that possess not only high productivity and fruit storability, but also high eating quality to meet the needs of both the consumer and the market. Here, we introduced a newly selected high-quality Chinese plum cultivar Zhongli

Background: ‘M9’ is a widely used apple dwarfing rootstock due to the outstanding effects on both precocity and vigorous control. Two quantitative trait loci (QTLs), Dw1 and Dw2 , for the dwarfing effect were previously mapped on ‘M9’, but the genetic variations that underpin the dwarfing ability have not been elucidated to date. Result: By using ‘Red Fuji’ trees grafted on 1123 hybrids from ‘ M alus baccata ’ × ‘M9’, the intervals of Dw1 and Dw2 were narrowed down. MdLBD3 and MdARF6 were predicted as candidate genes from Dw1 , while MdG3OX3 was a candidate gene from Dw2 . An 11 bp deletion at -339 bp upstream of the transcription start site (TSS) of MdLBD3 generated a new cis-element binding site with MdWRKY2 and caused increased expression of MdLBD3 . Coincidently, a ten bp deletion at -278 bp upstream of the TSS of MdG3OX3 created an additional binding site of MdABI5 , leading to higher expression of MdG3OX3 . At -954 bp of the MdARF6 promoter, a 14 bp insertion destroyed the binding ability by MdABI5 and reduced MdARF6 expression. The genotype effects of these insertion and deletions as diagnostic markers on dwarfing traits (tree height, trunk diameter, and canopy width) were estimated in 108 F1 hybrids. The genomic predicted genetic values (GEGV) were calculated by adding up the genotype effects of the three markers and the population mean phenotype. The GEGV of the dwarfing traits exhibited high correlation coefficients of 0.93, 0.94, and 0.93 in terms of tree height, trunk diameter, and canopy width for the observed phenotype values, respectively. The predictability of GEGV was validated in 64 Malus accessions. Conclusion : The development of the three functional markers, Ld/Li, Ad/Ai, and Gd/Gi, ensures the accurate genomic assisted prediction of dwarfing ability in apple rootstock breeding. The data also suggested that ABA, auxin, GA, and zeatin signals may be involved in the regulation of apple rootstock dwarfing mechanism.

Peach (Prunus persica L. Batsch) is one of the most important fruit crops in China (Wang et al. 2011). Yangshan Town of Jiangsu Province is one of the four major peach producing areas in China, with a growing area of 2,000 ha (Tian et al. 2018). During June 2020, a postharvest disease presenting with brown necrosis and rot occurred on peaches in Yangshan Town. The estimated damage was more than 10% of the total harvest. The symptoms included soft rot, and the lesion appeared sunken, accompanied with sour odor and white mycelia. Twelve peaches with representative symptom were sampled for pathogen isolation. Pieces (about 5 mm × 5 mm) from the lesion edge of symptomatic fruits were dissected and surface disinfected (3% NaClO for 10 s and 75% ethanol for 30 s), then rinsed three times with distilled water, dried on sterile filter paper and transferred to Potato Dextrose Agar (PDA) media plates supplemented with 150 ng/mL streptomycin sulfate. The plates were incubated at 28 ℃ for 3 days. Forty-eight isolations were obtained from the plates and isolates were single-spored. All isolates presented white, flat, milky yeast-like colonies with radial mycelia. Hyphae under microscope were septate, branched, disarticulating into arthroconidia measuring 3.39 to 9.27 × 2.05 to 7.71 μm. The morphological characteristics are consistent with Geotrichum candidum (De Hoog et al. 1986). Internal transcribed spacer (ITS) and 18s nuclear ribosomal small subunit (SSU) of the 48 isolates were amplified and sequenced using the primers ITS5/ITS4, and NS1/NS4 for molecular identification (Schoch et al. 2012). The resulted sequences showed no difference among all the isolates. Alignment by blastn showed the sequence of ITS and SSU were 100% (accession number. GQ376093) and 99.7% identical (accession number. KY977411.1) to Geotrichum candidum, respectively. The sequences of ITS (accession number MW493646) and SSU (accession number MW493648) were submitted to the GenBank. Commercial ripe peaches with the size of about 15 cm × 15 cm × 10 cm was used for pathogenicity test. Peaches were surface disinfected with 75% ethanol, then a wound with 4 mm in diameter and 5 mm in depth was made on the surface of each fruit. Ten peaches were inoculated with 10 μL (1×105 spores /mL) of the isolate suspension. Another ten peaches were inoculated with 10 μL sterile water as the control. Peaches were incubated individually at 28 ℃and a relative humidity of about 85%. After three days, large scale of pits and necrosis appeared on every peach inoculated, and the symptoms were consistent with the diseased peaches in Yangshan Town, while no symptoms non-inoculated on the control peaches were observed. The pathogen was re-isolated from the diseased fruit and was identified again by sequencing of ITS and SSU. All the tests were conducted three times. Considering the evidence, we identified the pathogen as G. candidum. This pathogen has been reported to cause sour rot was reported in kiwifruit, strawberry, melon and other fruits (Alonzo et al. 2020; Cheng et al. 2020; Halfeld-Vieira et al. 2020). To our knowledge, this is the first report of G. candidum causing sour rot of peach in China, which may cause a great loss to peach industry of China.