Abstract：
Hazelnut is among the most important nut crops in Chile, currently covering 46,000 ha. In 2023, the country exported 30,000-ton. In recent years the incidence of plants with internal discoloration, cankers and dieback has been increasing. In some cases, the trees died and had to be removed and, after a year, purple resupinate fruiting bodies were observed growing from the stumps. To determine the etiology of the symptoms and signs, wood samples (n=318) were collected since 2020, from 38 symptomatic orchards from Maule to La Araucanía Regions, primarily from the cvs. Tonda di Giffoni and Lewis. Wood sections 0.5 cm diameter were cut from the symptomatic tissues, disinfected using a sodium hypochlorite (10%) solution, and plated on a quarter-strength acidified potato dextrose agar (aPDA1/4). The plates were incubated and purified on PDA. Subsequently, isolates were identified by morphological and molecular means. Almost half of the isolates (47%) were preliminarily identified as basidiomycetes, based on mycelial features such as the presence of clamp connections, with 45% of them exhibiting abundant whitish cottony fast-growth mycelia, resembling Chondrostereum purpureum (Grinbergs et al., 2020). DNA was extracted and the 500-bp fragment, located between 5S and 18S ribosomal regions, was amplified using APN1 specific primers (Becker et al. 1999), identifying the isolates as C. purpureum. In addition, 5.8S gene of RGM1 (35°13\'40.9\"S 71°25\'14.1\"W), RGM2 (36°31\'27.95\"S 71°46\'58.31\"W), RGM3 (37°10\'54.8\"S 72°03\'39.6\"W), RGM4 (35°19\'25.2\"S 71°19\'54.7\"W) and RGM5 (36°35\'30.8\"S 72°05\'18.8\"W) isolates, representing different locations within the hazelnut growing area, was amplified using ITS1/ITS4 primers (White et al., 1990). The PCR product was sequenced, and the analysis showed 100% homology among isolates (Genebank codes: PP839283, PP839284, PP839285, PP839286 and PP839287, respectively). To determine the pathogenicity of the isolates, 30-cm healthy cuttings cv. Lewis were inoculated with mycelial plugs, while control shoots were inoculated with sterile agar plugs. Cuttings were vertically arranged in pots with 3-cm water and incubated for 60-d at 22°C. In addition, fresh cuts of 3-y potted plants cv. Lewis were inoculated with mycelial plugs and incubated for 137-d in a shadehouse. After incubation, bark was removed from inoculated cuttings and the length of necrotic lesions was measured. Although discoloration was reproduced by all the isolates in both pathogenicity tests, RGM1 isolate was the most aggressive, causing the complete discoloration of the cuttings and the death of the inoculated plants. To our knowledge this is the first report of C. purpureum causing wood disease in hazelnut. These findings are significant because the disease may not only reduce orchard longevity but also decrease fruit yield and quality, as observed in other fruit crops (Grinbergs et al., 2021).
摘要：
榛子是智利最重要的坚果作物之一，目前覆盖46,000公顷。2023年，该国出口3万吨。最近几年来植物发生了内部变色，溃疡和死亡人数一直在增加。在某些情况下,树木死亡，不得不被移除，一年后,观察到从树桩上生长出紫色的子实体。为了确定症状和体征的病因，自2020年以来，从Maule到LaAraucanía地区的38个有症状的果园中收集了木材样本（n=318），主要来自cvs。TondadiGiffoni和Lewis.从有症状的组织上切下直径0.5厘米的木材切片，用次氯酸钠（10%）溶液消毒，并铺在四分之一强度的酸化马铃薯葡萄糖琼脂(aPDA1/4)上。培养板并在PDA上纯化。随后，分离物通过形态学和分子鉴定。几乎一半的分离株（47％）被初步鉴定为担子菌，基于菌丝体特征，如夹钳连接的存在，其中45%表现出丰富的白色棉质快速生长菌丝体，类似于紫癜性软骨(Grinbergs等人。,2020）。提取DNA和500-bp的片段,位于5S和18S核糖体区之间，使用APN1特异性引物扩增(Becker等人。1999),鉴定分离株为紫癜。此外,RGM1的5.8S基因(35°13\'40.9\"S71°25\'14.1\"W),RGM2(36°31\'27.95\"S71°46\'58.31\"W),RGM3(37°10\'54.8\"S72°03\'39.6\"W),RGM4(35°19\'25.2\"S71°19\'54.7\"W)和RGM5(36°35\'30.8\"S72°05\'18.8\"W)分离,代表榛子种植区域内的不同位置，使用ITS1/ITS4引物扩增(White等人。,1990).对PCR产物进行测序,分析显示分离株之间具有100％的同源性（基因库代码分别为：PP839283，PP839284，PP839285，PP839286和PP839287）。为了确定分离株的致病性，30厘米健康的插条简历。刘易斯接种菌丝体栓，而对照芽接种无菌琼脂栓。将插条垂直排列在具有3厘米水的盆中，并在22°C下孵育60天。此外,3-y盆栽植物的新鲜切块。用菌丝体塞接种刘易斯，并在阴凉处孵育137天。孵化后,从接种的插条中去除树皮，并测量坏死病变的长度。尽管在两种致病性测试中，所有分离株都复制了变色，RGM1分离株最具攻击性，导致插条完全变色和接种植物死亡。据我们所知，这是在榛子中引起木材病的紫菜的第一份报告。这些发现具有重要意义，因为这种疾病不仅会降低果园的寿命，还会降低果实的产量和质量。正如在其他水果作物中观察到的那样(Grinbergs等人。,2021)。
