Characterization of host plant resistance to zebra chip disease from species-derived potato genotypes and the identification of new sources of zebra chip resistance

‘Candidatus Liberibacter solanacearum’ (Lso), an uncultivable phloem-limited phytopathogenic bacteria, is known to be associated with Zebra Chip disease (ZC), which represents a major threat to potato production in the US and elsewhere. This pathogen is transmitted by the phloem-feeding potato psyllid, Bactericera cockerelli Sulc (Hem. Triozidae). Currently, there are no reports of resistance to ZC in cultivated potatoes. This greenhouse study was conducted to evaluate Lso transmission success and the susceptibility of 11 potato breeding clones, representing diverge genetic background, to ZC, in relation to a susceptible commercial cultivar, Russet Burbank. Individual plants were exposed to two Lso-positive potato psyllids for 48 hours. The percentage of successful Lso transmission varied across the evaluated genotypes ranging between 7 and 57%. Freshly-cut and fried tubers showed significant variation in ZC symptom severity among the breeding clones, with several genotypes expressing relative tolerance when compared to Russet Burbank. None of the evaluated clones showed statistically lower Lso titers than Russet Burbank with the exception of one genotype in the second year of the study. However, the presence of a non-significant relationship between average symptom severity and Lso titer indicated variations in phenotypic responses (i.e. tolerance) to Lso existed among evaluated breeding lines. Breeding clones A07781-3LB, A07781-4LB and A07781-10LB had relatively lower Lso titer (low susceptibility) and tuber symptom expression (high tolerance) among the tested genotypes. As these three clones represent full siblings, the observed effects could be indicative of the presence of a genetic basis for resistance/tolerance to ZC. Findings provide a better understanding of resistance/tolerance to ZC, and contribute to continued efforts in breeding for resistance to this disease.'Candidatus Liberibacter solanacearum'（Lso）是一类无法体外培养、仅定殖于植物韧皮部的植物病原细菌，已知其与斑马纹病（Zebra Chip disease，ZC）相关，该病害对美国及全球其他地区的马铃薯生产构成重大威胁。该病原菌由取食韧皮部的马铃薯木虱——Bactericera cockerelli Sulc（半翅目：Triozidae科）传播。目前，栽培马铃薯中尚未见对斑马纹病具有抗性的相关报道。本温室试验旨在以易感商业品种‘赤褐色伯班克（Russet Burbank）’为对照，评估11份具有不同遗传背景的马铃薯育种无性系对Lso的传毒成功率及斑马纹病感病性。每株供试植株均接种2头携带Lso的马铃薯木虱，接种时长为48小时。供试基因型间的Lso成功传毒率存在显著差异，范围为7%至57%。鲜切块茎与油炸块茎的斑马纹病症状严重度在各育种无性系间均存在显著差异，相较于赤褐色伯班克，多个基因型表现出相对耐性。除试验第二年的1个基因型外，其余供试无性系的Lso菌量均未显著低于赤褐色伯班克。然而，平均症状严重度与Lso菌量之间未呈现显著相关性，这表明供试育种株系间对Lso的表型响应（即耐性）存在差异。在供试基因型中，无性系A07781-3LB、A07781-4LB与A07781-10LB的Lso菌量相对较低（感病性弱），且块茎症状表现程度较轻（耐性较强）。由于这三个无性系为全同胞株系，本研究观察到的效应提示，马铃薯对斑马纹病的抗性/耐性可能存在遗传基础。本研究结果增进了学界对斑马纹病抗性/耐性机制的认知，可为该病害的抗病育种工作提供理论依据与实践支撑。