Detection and identification of the phytoplasma associated with pear decline in Taiwan

Abstract

Pear decline (PD) is an important phytoplasmal disease that occurs mainly in Europe and North America. In 1994, pear trees exhibiting symptoms typical of PD disease were observed in orchards of central Taiwan. The sequence of 16S rDNA and 16S-23S rDNA intergenic spacer region (ISR) of the causative agent of pear decline in Taiwan (PDTW) were amplified with polymerase chain reaction (PCR) using a DNA template prepared from the diseased leaves. Sequence analysis of 16S rDNA revealed that the PDTW agent was closely related to the phytoplasmas of the apple proliferation group that cause diseases in stone fruits, pear and apple. Consistent with the result of 16S rDNA sequence analysis, sequence analysis of the 16S-23S rDNA ISR and putative restriction site analyses of 16S rDNA and 16S-23S rDNA ISR sequences provided further support for the view that the PDTW phytoplasma causing pear decline in Taiwan may represent a new subgroup of the apple proliferation group. According to the rDNA sequence of PDTW phytoplasma, two specific PCR primer pairs, APf2/L1n and fPD1/rPDS1, were designed in this study for the detection of the etiological agent in pear trees and insect vectors. Based on the sequence analyses of the PCRamplified fragments, two species of pear psyllas, Cacopsylla qianli and Cacopsylla chinensis, were found to carry PDTW phytoplasma.

Multilocus sequence analysis reveals the genetic diversity of European fruit tree phytoplasmas and supports the existence of inter-species recombination

“…AP affects European and Turkish apple orchards (Seemüller, 1990;Sertkaya et al, 2008) and the highest economical impact occurs in Germany and northern Italy. PD has been reported in Europe, North America and the Middle East (Battle et al, 1999;Blomquist & Kirkpatrick, 2002b;Choueiri et al, 2007;Davies et al, 1992;Lorenz et al, 1995;Malinowski et al, 1996;Sharbatkhari et al, 2008) and also in Taiwan (Liu et al, 2007). ESFY is present in the Euro-Mediterranean basin (Marcone et al, 2010) and kills 5 % of the apricot trees per year in southern France (Jarausch et al, 2001) due to a severe form of apricot chlorotic leafroll.…”

CHAPTER 14: Apple Proliferation Phytoplasma

“…P. mali' is phylogenetically closely related to the other AP group members. In interspecific comparisons of the API PD, AP/PDTW, AP/ESFY, and AP/PYLR agents, differences in l6S rDNA sequences were 1.0-1.1, 1.1-1.3, 1.3-1.5, ·and 1.4-1.6%, respectively (Liu et al, 2007;Seemüller and Schneider, 2004). These differences are below the recommended threshold of 2.5% for assigning species rank to phytoplasmas (IRPeM, 2004).…”

“…P. pyri' (the PD agent), 'Ca. P. prunorum' (the ESFY agent), the peach yellow 1eaf roll (PYLR) agent, and the new1y identified PD (PDTW) agent from Taiwan (Lee et al, 2000;Liu et al, 2007;Seemüller and Schneider, 2004). Sequence a1ignment revealed that the 16S rDNA sequences of four AP phytop1asma strains from Germany, Ita1y, and Spain are identica1 or nearly identical, with simi1arity values of 99.9-100% (Seemüller and Schneider, 2004).…”

Analysis of the Genetic Population Structure of Cacopsylla chinensis (Hemiptera: Psyllidae) with Mitochondrial DNA Markers in Saga and Yamaguchi prefectures, Japan

“…Moreover, their leaves remained small and pale the following spring, and few or no shoots developed (Chen et al 2001). The symptoms of diseased pear trees in Taiwan were apparently associated with phytoplasma that was transmitted by Cacopsylla chinensis (Liu et al 2007(Liu et al , 2011.…”