Compatibility and horticultural performance of Pera sweet orange clones grafted to Swingle citrumelo rootstock

ABSTRACT Despite its interesting agricultural traits, Swingle citrumelo (Citrus paradisi Macfad. ‘Duncan’ × Poncirus trifoliata L. Raf.) rootstock exhibits severe incompatibility when grafted with Pera sweet orange [Citrus sinensis (L.) Osb.] scions, and this fact limits its use for propagation purposes. Nonetheless, the existence of certain Pera sweet orange clones that are compatible with Swingle citrumelo represents a substantial gain for the entire citrus industry. This study investigated the compatibility between seven Pera sweet orange clones and Swingle citrumelo rootstock, regarding the presence of a necrotic line at the graft union junction, the difference in diameter between rootstock and scion, the influence of clonal cleaning by micrografting, and the horticultural performance of the selected combinations. No trees died because of grafting incompatibility, even after twenty years (trial I), except for clone CV1, or after six years and nine months (trial II) from planting. The rootstock/scion trunk diameter ratio was not related to the presence of a necrotic line in the graft-union region. Additionally, these variables did not influence fruit yield and quality, and they were not affected by clonal cleaning or pre-immunisation of the old Pera sweet orange clones.

摘要
尽管斯温格枳柚（Swingle citrumelo，亲本为柚‘邓肯’[Citrus paradisi Macfad. ‘Duncan’] × 枳[Poncirus trifoliata L. Raf.]）具备优异的农艺性状，但其作为砧木与佩拉甜橙（Pera sweet orange，学名Citrus sinensis (L.) Osb.）接穗嫁接时，会表现出严重的嫁接不亲和性，这一缺陷制约了其在柑橘育苗生产中的推广应用。不过，部分与斯温格枳柚亲和的佩拉甜橙无性系的发现，对整个柑橘产业而言是一项重要进展。
本研究围绕7个佩拉甜橙无性系与斯温格枳柚砧木的嫁接亲和性展开系统探究，考察指标包括：嫁接口坏死线的发生情况、砧木与接穗的茎粗差异、微嫁接（micrografting）脱毒处理对亲和性的影响，以及优选嫁接组合的园艺性状表现。
本研究设置两个定位试验：试验I的观测周期长达20年，试验II的种植后观测周期为6年9个月；结果显示，除CV1无性系外，其余供试植株均未因嫁接不亲和性出现死亡。
砧木与接穗的茎粗比与嫁接口坏死线的发生并无显著关联。此外，上述指标对果实产量与品质均无显著影响，且不受老佩拉甜橙无性系脱毒处理或预免疫（pre-immunisation）处理的影响。