Charlton Nikki D, Yi Mihwa, Bock Clive H, Zhang Minling, Young Carolyn A
Noble Research Institute , LLC, Ardmore, Oklahoma 73401.
Southeastern Fruit and Tree Nut Research Laboratory, Agricultural Research Service, United States Department of Agriculture , Byron, Georgia 31008.
Mycologia. 2020 Jul-Aug;112(4):711-721. doi: 10.1080/00275514.2020.1759998. Epub 2020 May 29.
Pecan scab, caused by , is the most prevalent disease of pecan in the southeastern United States. Recent characterization of the mating type () distribution of revealed that the idiomorphs are in equilibrium at various spatial scales, indicative of regular sexual recombination. However, the occurrence of the sexual stage of has never been observed, and the pathogen was previously considered to rely entirely on asexual reproduction. We were able to generate the sexual stage by pairing isolates of opposite mating types on oatmeal culture media. Cultures were incubated at 24 C for 2 mo to allow hyphae from isolates of each mating type to interact. Culture plates were then incubated at 4 C for 4 mo, after which immature pseudothecia were observed. Following exposure to a 12-h photoperiod for 2 wk at 24 C, asci and ascospores readily developed. Pseudothecium and ascospore production was optimal when incubated for 4 mo at 4 C. We utilized progeny from a cross of an albino isolate and wild-type (melanized) isolates to determine that recombination had occurred. Multilocus genotyping using 32 microsatellite markers confirmed that progeny were the result of recombination, which was further supported by segregation of mating types and culture pigmentation. Albino progeny were all confirmed to contain the same mutation in the polyketide synthase () melanin biosynthesis gene as the albino parent. The results of this study demonstrate the heterothallic nature of . The impact of determining the source of the overwintering ascostroma will aid in management decisions to reduce the primary inoculum in the disease cycle.
山核桃疮痂病由[病原菌名称缺失]引起，是美国东南部山核桃最普遍的病害。最近对[病原菌名称缺失]交配型（[相关类型缺失]）分布的特征分析表明，两种异型在不同空间尺度上处于平衡状态，这表明存在规律的有性重组。然而，从未观察到[病原菌名称缺失]有性阶段的发生，且该病原菌以前被认为完全依赖无性繁殖。我们通过在燕麦培养基上配对相反交配型的分离株成功诱导出了有性阶段。将培养物在24℃下培养2个月，以使每种交配型分离株的菌丝相互作用。然后将培养皿在4℃下培养4个月，之后观察到未成熟的假囊壳。在24℃下给予12小时光周期处理2周后，子囊和子囊孢子迅速发育。当在4℃下培养4个月时，假囊壳和子囊孢子的产生最为理想。我们利用白化分离株与野生型（黑化）分离株杂交的后代来确定是否发生了重组。使用32个微卫星标记进行的多位点基因分型证实后代是重组的结果，交配型的分离和培养物色素沉着进一步支持了这一点。所有白化后代均被证实与白化亲本在聚酮合酶（[基因名称缺失]）黑色素生物合成基因中含有相同的突变。本研究结果证明了[病原菌名称缺失]的异宗配合特性。确定越冬子囊座来源的影响将有助于做出管理决策，以减少病害循环中的初始接种体。
