Witches'-Broom Disease of Lime Affects Seed Germination and Seedling Growth But Is Not Seed Transmissible

Abstract

Faghihi, M. M., Bagheri, A. N., Bahrami, H. R., Hasanzadeh, H., Rezazadeh, R., Siampour, M., Samavi, S., Salehi, M., and Izadpanah, K. 2011. Witches'-broom disease of lime affects seed germination and seedling growth but is not seed transmissible. Plant Dis. 95:419-422.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'-broomaffected 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.Witches'-broom disease of lime (WBDL), caused by 'Candidatus Phytoplasma aurantifolia' was found first in a small area in southern Iran in 1997 (17). Since then, WBDL has spread to many areas, devastating Mexican lime plantations in major lime-growing provinces of Hormozgan, Sistan-Baluchistan, and Kerman (16). In the field, the phytoplasma is naturally spread by the vector leafhopper Hishimonus phycitis (18). The pathogen has been experimentally transmitted to several species of citrus by graft inoculation, and to periwinkle and a number of solanaceous plants such as tomato, eggplant, and tobacco by dodder or graft inoculation (19)(20)(21). Several studies have focused on the detection of WBDL phytoplasma in various parts of the lime seed. were the first to suggest the possibility of seed transmission of WBDL phytoplasma. Later, Khan (9) used the polymerase chain reaction (PCR) assay to study seed transmission of WBDL phytoplasma in 6-month-old seedlings. Based on this repo...

Complete Chloroplast Genome Sequence of Omani Lime (Citrus aurantiifolia) and Comparative Analysis within the Rosids

“…Omani lime is sensitive to several biotic agents, the most serious of which is ‘ Candidatus Phytoplasma aurantifolia’, the cause of witches’ broom disease of lime (WBDL). Recent studies on WBDL focused on effect of genetic diversity of Omani limes on the disease [13] , transcriptome and proteomic analysis of lime response to infection by phytoplasma [14] – [16] and effect of phytoplasma on seed germination, growth and metabolite content in lime [17] , [18] .…”

An analysis of Sorghum halepense’s behavior in presence of tropane alkaloids from Datura stramonium extracts

“…Allelopathy is a plant’s effect on another plant [11] manifested as chemical compounds released and diffused in the environment [12,13]. Most allelochemicals are found in plants in an inactive state; they are defene substances against pests [14].…”

Pest categorisation of Witches' broom disease of lime (Citrus aurantifolia) phytoplasma

“…There is no confirmed evidence that the phytoplasma is seed transmitted, but seed from infected plants was shown to have lower germination rates than that from uninfected plants (Faghihi et al., ).…”