Morphological and molecular characterization of Phytophthora species associated with root and crown rot of pomegranate in Iran

The purpose of this research was to identify the pathogens causing root and crown rot in major pomegranate-growing areas of Iran. Infected tissue samples were collected from trees with symptoms from 49 pomegranate orchards in four provinces of Iran: Fars, Markazi, Isfahan, and Kohgiluyeh va Boyer-Ahmad. In total, 23 Phytophthora spp. isolates were obtained, which were identified as P. cryptogea species complex (12 isolates) and P. cinnamomi (11 isolates) based on morphological characters. Molecular confirmation of identification was performed by inference of phylogeny of ITS-rDNA regions, β-tubulin gene, and the mitochondrial gene cytochrome c oxidase subunit 1. The results of our phylogenetic analysis confirmed the morphological identification of P. cinnamomi isolates and placed them in Clade 7c of Phytophthora. In addition, the P. cryptogea species complex isolates, despite morphological similarities, were in fact four distinct species including P. cryptogea sensu stricto (two isolates), P. pseudocryptogea (one isolate), P. sp. kelmania (one isolate), and P. erythroseptica (six isolates). This is the first report of pomegranate root and crown rot caused by P. cinnamomi and P. cryptogea species complex.     

中国近海铜藻ITS与coxI序列相似性分析

本研究分别对2016和2017年中国近海10个铜藻(Sargassum horneri)漂浮地理种群以及 3个定生种群的51个采集样本进行了ITS和coxI序列分析及相似性比对。结果显示,51个样本的coxI序列完全一致,ITS序列存在2个变异位点,按基因型的异同可分为4个类型,其中大连龙王塘、烟台大钦岛和南隍城岛的漂浮铜藻基因型相同,青岛金沙滩漂浮型、烟台大钦岛和大连獐子岛的定生铜藻基因型相同,威海俚岛和温州洞头的漂浮铜藻基因型相同,青岛雕塑园、王哥庄、大珠山、威海乳山的漂浮型和枸杞岛定生铜藻基因型相同,而同一种群内部即便是不同年份的个体间基因型并没有差异。基于ITS序列构建的系统树显示,来自中国的所有铜藻样本聚为一支,与来自韩国的铜藻样本有一定的遗传距离。以上结果说明,我国近海漂浮和定生铜藻的不同地理株间ITS和coxI的遗传变异水平较低,漂浮铜藻可能具有不同的来源,为进一步探明中国近海海域铜藻的分子遗传背景提供依据。