Sucrose phosphate synthase (SPS) is a rate-limiting enzyme that works in conjunction with sucrose-6-phosphate phosphatase (SPP) for sucrose synthesis, and it plays an essential role in energy provisioning during growth and development in plants as well as improving fruit quality.  However, studies on the systematic analysis and evolutionary pattern of the SPS gene family in apple are still lacking.  In the present study, a total of seven MdSPS and four MdSPP genes were identified from the Malus domestica genome GDDH13 v1.1.  The gene structures and their promoter cis-elements, protein conserved motifs, subcellular localizations, physiological functions and biochemical properties were analyzed.  A chromosomal location and gene-duplication analysis demonstrated that whole-genome duplication (WGD) and segmental duplication played vital roles in MdSPS gene family expansion.  The Ka/Ks ratio of pairwise MdSPS genes indicated that the members of this family have undergone strong purifying selection during domestication.  Furthermore, three SPS gene subfamilies were classified based on phylogenetic relationships, and old gene duplications and significantly divergent evolutionary rates were observed among the SPS gene subfamilies.  In addition, a major gene related to sucrose accumulation (MdSPSA2.3) was identified according to the highly consistent trends in the changes of its expression in four apple varieties (‘Golden Delicious’, ‘Fuji’, ‘Qinguan’ and ‘Honeycrisp’) and the correlation between gene expression and soluble sugar content during fruit development.  Furthermore, the virus-induced silencing of MdSPSA2.3 confirmed its function in sucrose accumulation in apple fruit.  The present study lays a theoretical foundation for better clarifying the biological functions of the MdSPS genes during apple fruit development.

DNA methylation plays an important role in plant growth and development, and in regulating the activity of transposable elements (TEs).  Research on DNA methylation-related (DMR) genes has been reported in Arabidopsis, but little research on DMR genes has been reported in Brassica rapa and Brassica oleracea, the genomes of which exhibit significant differences in TE content.  In this study, we identified 78 and 77 DMR genes in Brassica rapa and Brassica oleracea, respectively.  Detailed analysis revealed that the numbers of DMR genes in different DMR pathways varied in B. rapa and B. oleracea.  The evolutionary selection pressure of DMR genes in B. rapa and B. oleracea was compared, and the DMR genes showed differential evolution between these two species.  The nucleotide diversity (π) and selective sweep (Tajima’s D) revealed footprints of selection in the B. rapa and B. oleracea populations.  Transcriptome analysis showed that most DMR genes exhibited similar expression characteristics in B. rapa and B. oleracea.  This study dissects the evolutionary differences and genetic variations of the DMR genes in B. rapa and B. oleracea, and will provide valuable resources for future research on the divergent evolution of DNA methylation between B. rapa and B. oleracea.

The potato cyst nematodes (PCN) Globodera rostochiensis (Wollenweber) Skarbilovich, 1959 is considered the most damaging nematode pest of potato worldwide that causes significant yield losses, and this nematode is recognized and listed as a quarantine nematode in many countries (EPPO 2017).  China is currently the largest producer of potato in the world, while the total production is also the highest (Guan and Cai 2019).  The survey for cyst nematodes on potato were conducted in Yunnan and Sichuan provinces of China during 2018–2020, numerous cysts were observed on potato roots in Huize County and Ludian County of Yunnan Province, Zhaojue County and Yuexi County of Sichuan Province.  Cysts and second-stage juveniles (J2s) were isolated from each soil sample using the Cobb decanting and sieving method.  The morphology of cysts and J2s and molecular analysis established the identity of this species as golden cyst nematode Globodera rostochiensis (Subbotin et al. 2010).  For morphological analysis, the cysts were characterized by smoothly rounded with a small projecting neck, brown and golden color, terminal cone was absent and circumfenestrate.  The key morphometrics of cysts (n=25) were: length excluding neck 705±24 (689–747) μm, width 698±28 (678–759) μm, number of cuticular ridges between anus and vulval fenestra 17.3±1.7 (14–19); fenestral diameter 13.6±1.1 (12.25–15.45) μm; distance from anus to the edge of fenestra 63.7±11.3 (48.23–79.14) μm; Granek’s ratio 4.7±0.7 (3.92–5.75).  The key morphometrics of J2s (n=25): body length 453.9±16.6 (440–496) μm, stylet length 21.9±1.0 (20.3–24.3) μm, tail length 51.1±3.2 (45.5–55.5) μm, and hyaline region length 24.4±2.5 (21.7–29.9) μm.  Morphology of the cysts and J2 were consistent with those of G. rostochiensis (Subbotin et al. 2010; EPPO 2017).  Moreover, the identification result was confirmed by PCR using universal primers TW81 (5´-GTTTCCGTAGGTGAACCTGC-3´) and AB28 (5´-ATATGCTTAAGTTCAGCGGGT-3´) for ITS region and D2A (5´-TTTTTTGGGCATCCTGAGGTTTAT-3´) D3B (5´-AGCACCTAAACTTAAAACATAATGAAAATG-3´) for rDNA-28S region, respectively.  The ITS rDNA sequences (GenBank accessions MZ042365, MZ042366, MZ042369, and MZ042370) exhibited 99.83% identity match to G. rostochiensis sequences available in the GenBank (GQ294513).  Sequence from the 28S region (GenBank accessions MZ057595, MZ057596, MZ057599, and MZ057600) was 99.33% similar to those of G. rostochiensis isolate from MF773722.  The species was also confirmed with species-specific primers ITS5 (5´-GGAAGTAAAAGTCGTAACAAGG-3´) and PITSr3 (5´-AGCGCAGACATGCCGCAA-3´) (Bulman and Marshall 1997), a single 434-bp fragment was obtained from Huize, Ludian, Zhaojue and Yuexi populations.  The pathog enicity testing of Huize, Ludian, Zhaojue and Yuexi, three weeks-old potato plants (cv. Qinshu 9)

were inoculated with 2 000 eggs, and cultured in an incubator at 23°C/20°C with a 16 h/8 h light/dark photoperiod.  After three months inoculation, 36±7.2 cysts and females were extracted from the infested potato roots, no females and cysts were observed on control plants.  

This is the first report of potato golden cyst nematode G. rostochiensis in China.  

To dissect the genetic control of the sensory and textural quality traits of Chinese white noodles, a population of recombinant inbred lines (RILs), derived from the cross of waxy wheat Nuomai 1 (NM1) and Gaocheng 8901 (Gc8901), was used.  The RILs were tested in three different environments to determine the role of environmental effects on quantitative trait loci (QTL) analysis.  A total of 45 QTLs with additive effects for 17 noodle sensory and textural properties under three environments were mapped on 15 chromosomes.  These QTLs showed 4.23–42.68% of the phenotypic variance explained (PVE).  Nineteen major QTLs were distributed on chromosomes 1B, 1D, 2A, 3B, 3D, 4A, and 6A, explaining more than 10% of the phenotypic variance (PV).  Clusters were detected on chromosomes 2B (3 QTLs), 3B (11 QTLs) and 4A (5 QTLs).  The cluster detected on chromosome 4A was close to the Wx-B1 marker.  Five co-located QTLs with additive effects were identified on chromosomes 2B, 3D, 4A, 6A, and 7B.  The two major QTLs, Qadh.sdau-3B.1 and Qspr.sdau-3B.1, in cluster wPt666008–wPt5870 on chromosome 3B were detected in three different environments, which perhaps can be directly applied to improve the textural properties of noodles.  These findings could offer evidence for the selection or development of new wheat varieties with noodle quality using molecular marker-assisted selection (MAS).

The Chinese wheat line Yu 356-9 exhibits a high level of resistance to leaf rust. In order to decipher the genetic base of resistance in Yu 356-9, gene postulation, inheritance analyses, and chromosome linkage mapping were carried out. Gene postulation completed using 15 leaf rust pathotypes and 36 isogenic lines indicated that Yu 356-9 was resistant to all pathotypes tested. F1 and F2 plants from the cross Yu 356-9 (resistant)/Zhengzhou 5389 (susceptible) were tested with leaf rust pathotype “FHNQ” in the greenhouse. Results indicated a 3:1 segregation ratio, indicative of the presence of a single dominant leaf rust resistance gene in Yu 356-9 which was temporarily designated as LrYu. Bulk segregant analysis and molecular marker assays were used to map LrYu. Five simple sequence repeat (SSR) markers on chromosome 2BS were found closely linked to LrYu. Among these markers, Xwmc770 is the most closely linked, with a genetic distance of 5.7 cM.

A segregating population with 410 F2 individuals from the cross MERCIA (Rht-B1a) × Dwarf 123 was made to identify a new major dwarfing gene carrying by novel wheat germplasm Dwarf 123. Combination of bulk segerant analysis method was used. A total of 145 SSR markers were tested for polymorphisms among parental lines and DNA bulks of F2 population. Out of 145 primer pairs only three markers revealed corresponding polymorphism among parental lines and F2 DNA bulks. The marker Barc20 was close to the dwarfing gene with a genetic distance of 1.8 cM, and markers Gwm513 and Gwm495 were linked to the gene with genetic distance of 6.7 and 13 cM, respectively. Linkage analysis mapped the dwarfing gene to the long arm of chromosome 4B with the order of Barc20-dwarfing gene-Gwm513-Gwm495. The Comparision between the new gene and the known Rht-B1 alleles showed that dwarfing gene Rht-Ai123 was different from the others. The identification of the new dwarfing gene and its linked markers will greatly facilitate its utilization in wheat high yield breeding for reducing plant height.