Identification of tolerance to Huanglongbing and canker diseases in polyploid ponkan (Citrus reticulata)

作者：Lei Gong, Guibing Yang, Jing Xu, Songliang Jiang, Nan Cai, Chenxing Hao, Ziniu Deng, Yunlin Cao, Xianfeng Ma · 发表于：Horticultural Plant Journal · 年份：2026 · DOI：10.1016/j.hpj.2026.05.004 · 研究领域：Phytoplasmas and Hemiptera pathogens、Plant Virus Research Studies、Plant Pathogenic Bacteria Studies

Ponkan ( Citrus reticulata Blanco), renowned for its sensory quality and ease of peeling, is a widely cultivated mandarin in China. However, like most commercial citrus cultivars, it is susceptible to citrus canker and Huanglongbing (HLB). Polyploid breeding may be a useful way to identify resistant or tolerant varieties. In this study, we obtained 1 060 seeds from six pollination combinations using ‘Xinnv’ ponkan and its bud mutation ‘Zaomi’ as parents. Among these, 876 seeds were classified as normal and 184 as small. Twenty-four tetraploids and one chimera were identified from progeny populations by flow cytometry. The polyploid frequency varied among combinations, with the highest rate (7.89%) observed in small seeds from open-pollinated ‘Zaomi’, compared to 1.55% to 4.76% in other groups. Morphological and microscopic analyses revealed that tetraploid progeny displayed increased leaf thickness, epidermal cells, and stomatal apparatus, whereas stomatal density was reduced compared with diploid lines. In vitro and in vivo evaluations for citrus canker tolerance demonstrated that lines #007, #315, and #369 exhibited reduced lesion area, lesion density, and Xanthomonas citri subsp. Citri content at 7 days post-inoculation relative to the diploid control ‘Zaomi’. Regarding HLB evaluation, tetraploid line #331 exhibited a lower titer of Candidatus Liberibacter asiaticus than the diploid control and maintained superior growth at 6 months post-inoculation, evidenced by a 96.3% i...