Faghihi M M, Bagheri A N, Bahrami H R, Hasanzadeh H, Rezazadeh R, Siampour M, Samavi S, Salehi M, Izadpanah K
Hormozgan Agriculture and Natural Resources Research Center, Iran.
Department of Plant Protection, College of Agriculture, Shiraz University, Shiraz, Iran.
Plant Dis. 2011 Apr;95(4):419-422. doi: 10.1094/PDIS-06-10-0400.
Witches'-broom disease of lime (WBDL), caused by 'Candidatus Phytoplasma aurantifolia', has devastated many Mexican lime orchards and is currently a threat to lime production in neighboring provinces of southern Iran. Several reports have suggested transmission and spread of WBDL phytoplasma through the seed of infected plants. In the present study, claims of seed transmission of this phytoplasma were examined. Fruit were collected from infected trees in the infested areas of Minab (Hormozgan Province) and from symptomless trees in noninfested areas. Lime seed from symptomless and witches'-broom-affected trees were sown in separate beds in an insect-proof screenhouse and the resulting seedlings were examined for phytoplasmal infection. Leaf, stem, and root samples were collected from both groups of seedlings every 3 months for 2 years and tested for WBDL phytoplasma using direct and nested polymerase chain reaction (PCR). Repeated PCR tests on the seedlings did not reveal the presence of phytoplasmal DNA. Likewise, symptoms of the disease were not observed on these seedlings after 2 years. PCR assays detected the phytoplasma in coats of some seed from infected trees; however, no excised embryos were positive for the phytoplasma. All positive PCR results were confirmed by restriction fragment length polymorphism assay. One-year-old seedlings derived from seed of noninfected plants appeared more vigorous in terms of height, number of leaves, and fresh weight of shoot compared with those from infected trees. The germination percentage, mean daily germination, peak value, and germination value were significantly higher for seed of fruit from noninfected trees and seed from fruit on asymptomatic branches of infected trees than those from fruit on symptomatic branches of infected trees.
酸橙丛枝病（WBDL）由‘Ca. Phytoplasma aurantifolia’引起，已使许多墨西哥酸橙果园遭受重创，目前对伊朗南部邻近省份的酸橙生产构成威胁。几份报告表明，WBDL植原体可通过受感染植物的种子传播扩散。在本研究中，对这种植原体通过种子传播的说法进行了检验。从米纳卜（霍尔木兹甘省）疫区的受感染树木以及非疫区的无症状树木上采集果实。将无症状树木和患丛枝病树木的酸橙种子分别播种在防虫网室内的苗床中，对长出的幼苗进行植原体感染检测。在两年时间里，每隔3个月从两组幼苗上采集叶片、茎和根样本，使用直接和巢式聚合酶链反应（PCR）检测WBDL植原体。对幼苗进行的多次PCR检测未发现植原体DNA的存在。同样，两年后在这些幼苗上未观察到该病症状。PCR检测在一些受感染树木的种子表皮中检测到了植原体；然而，没有切除的胚呈植原体阳性。所有阳性PCR结果均通过限制性片段长度多态性分析得到证实。与来自受感染树木种子的一岁幼苗相比，来自未感染植物种子的一岁幼苗在高度、叶片数量和地上部分鲜重方面显得更有活力。未感染树木果实的种子以及受感染树木无症状枝条上果实的种子，其发芽率、日均发芽数、峰值和发芽值均显著高于受感染树木有症状枝条上果实的种子。
