USDA-ARS, Byron, GA, USA.
Noble Research Institute, Ardmore, OK, USA.
BMC Genomics. 2024 Feb 15;25(1):180. doi: 10.1186/s12864-024-10010-0.
Pecan scab is a devastating disease that causes damage to pecan (Carya illinoinensis (Wangenh.) K. Koch) fruit and leaves. The disease is caused by the fungus Venturia effusa (G. Winter) and the main management practice for controlling the disease is by application of fungicides at 2-to-3-week intervals throughout the growing season. Besides disease-related yield loss, application of fungicides can result in considerable cost and increases the likelihood of fungicide resistance developing in the pathogen. Resistant cultivars are available for pecan growers; although, in several cases resistance has been overcome as the pathogen adapts to infect resistant hosts. Despite the importance of host resistance in scab management, there is little information regarding the molecular basis of genetic resistance to pecan scab.The purpose of this study was to elucidate mechanisms of natural pecan scab resistance by analyzing transcripts that are differentially expressed in pecan leaf samples from scab resistant and susceptible trees. The leaf samples were collected from trees in a provenance collection orchard that represents the natural range of pecan in the US and Mexico. Trees in the orchard have been exposed to natural scab infections since planting in 1989, and scab ratings were collected over three seasons. Based on this data, ten susceptible trees and ten resistant trees were selected for analysis. RNA-seq data was collected and analyzed for diseased and non-diseased parts of susceptible trees as well as for resistant trees. A total of 313 genes were found to be differentially expressed when comparing resistant and susceptible trees without disease. For susceptible samples showing scab symptoms, 1,454 genes were identified as differentially expressed compared to non-diseased susceptible samples. Many genes involved in pathogen recognition, defense responses, and signal transduction were up-regulated in diseased samples of susceptible trees, whereas differentially expressed genes in pecan scab resistant samples were generally down-regulated compared to non-diseased susceptible samples.Our results provide the first account of candidate genes involved in resistance/susceptibility to pecan scab under natural conditions in a pecan orchard. This information can be used to aid pecan breeding programs and development of biotechnology-based approaches for generating pecan cultivars with more durable scab resistance.
美洲山核桃干腐病是一种严重影响美洲山核桃（Carya illinoinensis (Wangenh.) K. Koch）果实和叶片的病害。该病害由真菌 Venturia effusa（G. Winter）引起，防治该病的主要管理措施是在生长季节每隔 2-3 周喷施杀菌剂。除了与病害相关的减产外，喷施杀菌剂还会带来相当大的成本，并增加病原菌产生抗药性的可能性。虽然可从种植者处获得抗病品种，但在某些情况下，随着病原菌适应感染抗性宿主，抗性会被克服。尽管宿主抗性在干腐病管理中很重要，但有关其对美洲山核桃干腐病的遗传抗性的分子基础的信息却很少。本研究旨在通过分析来自对干腐病具有抗性和敏感的美洲山核桃叶片样本中的差异表达转录本，阐明其天然抗性的机制。叶片样本取自一个种源收集果园中的树木，该果园代表了美国和墨西哥境内美洲山核桃的天然分布范围。自 1989 年种植以来，果园中的树木一直受到自然干腐病感染，并且在三个季节中都收集了干腐病等级数据。基于这些数据，选择了 10 棵易感树和 10 棵抗性树进行分析。收集和分析了来自易感树的患病和未患病部分以及抗性树的 RNA-seq 数据。在比较无病的抗性和易感树时，共发现 313 个基因存在差异表达。对于表现出干腐病症状的易感样本，与未患病的易感样本相比，有 1454 个基因被鉴定为差异表达。在易感树患病样本中，许多与病原体识别、防御反应和信号转导相关的基因上调，而在抗性样本中，差异表达基因通常下调。我们的研究结果提供了第一个有关在美洲山核桃果园中自然条件下与美洲山核桃干腐病抗性/敏感性相关的候选基因的描述。这些信息可用于辅助美洲山核桃的选育计划，并开发基于生物技术的方法来培育具有更持久干腐病抗性的美洲山核桃品种。
