Bowman Kim D, McCollum Greg, Seymour Danelle K
U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Ft. Pierce, FL, United States.
Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA, United States.
Front Plant Sci. 2023 Feb 8;14:1061663. doi: 10.3389/fpls.2023.1061663. eCollection 2023.
Although the citrus scion cultivar primarily determines the characteristics of the fruit, the rootstock cultivar of the graft combination has a major role in determining the horticultural performance of the tree. The disease huanglongbing (HLB) is particularly devastating to citrus, and the rootstock has been demonstrated to modulate tree tolerance. However, no existing rootstock is entirely suitable in the HLB-endemic environment, and citrus rootstocks are particularly challenging to breed because of a long life cycle and several biological characteristics that interfere with breeding and commercial use. This study with Valencia sweet orange scion documents the multi-season performance of 50 new hybrid rootstocks and commercial standards in one trial that forms the first wave of a new breeding strategy, with the aim of identifying superior rootstocks for commercial use now, and mapping important traits to be used in selection for the next generation of outstanding rootstocks. A large assortment of traits were quantified for all trees in the study, including traits associated with tree size, health, cropping, and fruit quality. Among the quantitative traits compared between rootstock clones, all except one were observed to have significant rootstock influence. Multiple progeny from eight different parental combinations were included in the trial study, and significant differences between parental combinations of the rootstocks were observed for 27 of the 32 traits compared. Pedigree information was integrated with quantitative trait measurements to dissect the genetic components of rootstock-mediated tree performance. Results suggest there is a significant genetic component underlying rootstock-mediated tolerance to HLB and other critical traits, and that integration of pedigree-based genetic information with quantitative phenotypic data from trials should enable marker-based breeding approaches for the rapid selection of next-generation rootstocks with superior combinations of traits that are needed for commercial success. The current generation of new rootstocks included in this trial is a step toward this goal. Based on results from this trial, the new hybrids US-1649, US-1688, US-1709, and US-2338 were considered the four most promising new rootstocks. Release of these rootstocks for commercial use is being considered, pending the evaluation of continuing performance in this trial and the results from other trials.
虽然柑橘接穗品种主要决定果实的特征，但嫁接组合中的砧木品种在决定树体的园艺性能方面起着主要作用。黄龙病（HLB）对柑橘具有特别大的破坏性，并且已证明砧木能调节树体的耐受性。然而，在黄龙病流行的环境中，现有的砧木没有一种是完全合适的，而且由于柑橘砧木生命周期长以及一些影响育种和商业应用的生物学特性，柑橘砧木的育种尤其具有挑战性。本研究以伏令夏橙接穗记录了50种新杂交砧木和商业标准砧木在一项试验中的多季表现，该试验构成了新育种策略的第一波，目的是现在就鉴定出适合商业用途的优良砧木，并定位用于下一代杰出砧木选择的重要性状。对研究中的所有树木的大量性状进行了量化，包括与树体大小、健康状况、产量和果实品质相关的性状。在比较砧木无性系之间的数量性状时，除一个性状外，其他所有性状均观察到有显著的砧木影响。试验研究包括来自八个不同亲本组合的多个后代，在所比较的32个性状中，有27个性状在砧木的亲本组合之间观察到显著差异。系谱信息与数量性状测量相结合，以剖析砧木介导的树体性能的遗传成分。结果表明，砧木介导的对黄龙病的耐受性和其他关键性状存在显著的遗传成分，并且将基于系谱的遗传信息与试验中的数量表型数据相结合，应该能够实现基于标记的育种方法，以便快速选择具有商业成功所需优良性状组合的下一代砧木。本次试验中包含的新一代新砧木是朝着这个目标迈出的一步。根据该试验的结果，新杂交种US - 1649、US - 1688、US - 1709和US - 2338被认为是最有前景的四种新砧木。在评估本试验中的持续表现以及其他试验的结果之前，正在考虑将这些砧木投放商业使用。
