Tuber shape is one of the most important traits for potato breeding. Since poor or irregular shape increases the difficulty of handling and processing, researching the inheritance of potato tuber shape for potato breeding is highly important. To efficiently identify QTL for tuber shape, a diploid potato population (PM7) was generated by self-pollinated M6 (S. chacoense). A QTL TScha6 for tuber shape was identified by the QTL-seq approach at 50.91-59.93 Mb on chromosome 6 in the potato DM reference genome. To confirm TScha6, four SSR and twenty CAPS markers around the QTL were developed and the TScha6 was narrowed down to an interval of ~ 1.85 Mb. The CAPS marker C6-58.27_665 linked to TScha6 was then used to screen 86 potato cultivars and advanced breeding lines. The tuber length/width (LW) ratio was significantly correlated with the presence/absence of C6-58.27_665, and the correlation coefficient was r = 0.55 (p < 0.01). These results showed that C6-58.27_665 could be applied in marker-assisted selection (MAS) for tuber shape breeding in the future. Our research sets the important stage for the future cloning of the tuber shape gene and utilities of the marker in the breeding program.

Potato virus A (PVA) and potato virus Y (PVY) are two members of genus Potyvirus infecting potato crops worldwide. Host resistance offers an economical and effective means for the control or management of these viruses. In this study, 20 potato clones were screened for their resistance against PVA and PVY by mechanical or graft inoculation assay, and were explored for the relationship between extreme resistance genes Ra and Ry by the detection of molecular markers linked to Ry_adg, Ry_sto, and Ry_chc. Six clones, including Barbara, Jizhangshu 8, Longshu 7, Longshu 8, M6, and Solara, were found to be extremely resistant to both PVA and PVY; three clones (AC142, Eshu 3, and Shepody) were deemed to be extremely resistant to PVA but susceptible to PVY. To further reveal the inheritance of the extreme resistance (ER) against PVA, a tetraploid F₁ population of Barbara × F58050 (susceptible to both PVY and PVA) and a tetraploid BC₁ population of BF145 (a PVA-resistant but PVY-susceptible progeny of Barbara × F58050) × F58050 were obtained. Phenotyping of the F₁ and BC₁ populations by graft inoculation with PVA showed segregation ratios of 3:1 and 1:1 (resistant:susceptible), respectively. These results suggest that two independent loci control ER against PVA in Barbara: one confers ER to both PVA and PVY and the other confers ER to PVA only. The deduced genotype of Barbara is RyryryryRararara.

Wild kiwifruit germplasm can broaden breeding pools through complementary fruit-quality and stress-response traits. The Hubei Dabie Mountains contain heterogeneous habitats, but coordinated evaluation of their wild Actinidia resources remains limited. Taxonomy and ploidy were determined for 117 accessions from eight sites spanning 170–1730 m. Nine descriptive fruit traits and detached-leaf responses to bacterial canker and heat were assessed in 41 fruiting accessions. Bacterial canker response was assessed using Pseudomonas syringae pv. actinidiae (Psa), and heat response using maximum photosystem II quantum efficiency (F_v/F_m) after 47 °C treatment. Seven fruit-quality traits were measured in 27 accessions with normally ripened fruit. Three taxa were identified: A. chinensis, A. polygama, and A. chinensis var. deliciosa. Diploid, tetraploid, and hexaploid cytotypes were detected. Shannon–Wiener indices for descriptive traits ranged from 0.26 to 1.64. Twenty-three accessions were classified as highly or moderately resistant to Psa. Heat screening classified 23 accessions as heat tolerant, 16 as moderately heat tolerant, and two as heat sensitive. Fruit-quality coefficients of variation ranged from 12.92% to 120.41%. Fruit-quality ranking followed by Psa screening identified MC-021, MC-026, YS-031, YS-037, and YS-038 as candidate elite germplasm. These accessions are priorities for conservation and further breeding evaluation.