First Report of Paecilomyces variotii Isolated From Citrus Psyllid (Diaphorina citri), the Vector of Huanglongbing of Citrus, in China

Abstract

HomePlant DiseaseVol. 100, No. 12First Report of Paecilomyces variotii Isolated From Citrus Psyllid (Diaphorina citri), the Vector of Huanglongbing of Citrus, in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Paecilomyces variotii Isolated From Citrus Psyllid (Diaphorina citri), the Vector of Huanglongbing of Citrus, in ChinaX. B. Song, L. H. Zhang, A. T. Peng, B. P. Cheng, and J. F. LingX. B. SongSearch for more papers by this author, L. H. ZhangSearch for more papers by this author, A. T. PengSearch for more papers by this author, B. P. ChengSearch for more papers by this author, and J. F. LingSearch for more papers by this authorAffiliationsAuthors and Affiliations X. B. Song , Agricultural College of South China Agricultural University, Guangdong Province, Key Laboratory of Microbial Signals and Disease Control, Guangzhou 510640, China, and Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Guangzhou 510640, China L. H. Zhang , Agricultural College of South China Agricultural University, Guangdong Province, Key Laboratory of Microbial Signals and Disease Control, Guangzhou 510640, China A. T. Peng B. P. Cheng J. F. Ling , Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Guangzhou 510640, China. Published Online:15 Sep 2016https://doi.org/10.1094/PDIS-04-16-0510-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat The citrus psyllid (Diaphorina citri) is a small insect that feeds on the leaves and stems of citrus trees. It is also the only insect vector of Huanglongbing (HLB), the most devastating disease of the citrus industry in China. Controlling the citrus psyllid population density is an important safeguard measure against HLB, and biocontrol is the most effective method to control citrus psyllid in the future (Meyer et al. 2008). Citrus psyllid adults were collected into sterile centrifuge tubes from a citrus field, which had many diseased citrus trees infected HLB in Guangzhou, China, in 2015. The psyllids were placed directly on a potato dextrose agar (PDA) plate and incubated at 27°C with alternating light and dark for 2 to 3 days. Mycelium was picked into a new PDA culture plate, and the purification was repeated three times. Conidia were then suspended in sterile water for single-spore isolation. An isolate of an entomophagous fungus, GZMS-11, was isolated from citrus psyllid by the above method. GZMS-11 grew well on PDA, showed a round and fluffy colony, turning from white to brown with age. The colony diameter was 5.86 cm after 10 days at 27°C, with alternating light and dark. Brown pigment was produced and diffused into the medium after the colonies were cultured for 3 to 4 days. Conidiophores were erect and most of them were generated on the mycelium individually. Single phialide or multiple phialides were generated from the metulae, and they formed broom-like branches. The phialide size was 2.5 to 3.5 × 15 to 20 μm (avg. 3.0 ± 0.5 × 17.1 ± 1.5, n = 100), slender and acuminate, slightly curved, and the conidia attached with the phialide; the oval conidia size was 5.5 to 7.5 × 2.5 to 3.5 μm (avg. 6.2 ± 0.5 × 3.1 ± 0.5, n = 100). The cultural characteristics of the GZMS-11 was consistent with Paecilomyces variotii. Total DNA of GZMS-11 was extracted and the rDNA ITS region was sequenced by PCR using the universal primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′, forward) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′, reverse). The PCR product showed a sequence identity of 97.0 to 99.0% with sequences of P. variotii strains (AY904061, FJ895878, JN798498, AY753335) reported in GenBank. Based on the biological characteristics and ITS sequence, isolate GZMS-11 was identified as a novel strain of P. variotii. The pathogenicity against citrus psyllid of GZMS-11 was tested by treating citrus psyllid adults with a conidial suspension at the concentration of 1.0 × 108 spores/ml (Gandarilla-Pacheco et al. 2013). The corrected mortality rates were 35.83, 66.71, and 97.16% after 3, 7, and 10 days, respectively. Two days after treatment, mycelium could be observed on the surface of some citrus psyllid through a stereoscopic microscope. After 7 days, spore production structure could be observed visually on the citrus psyllid. These results have indicated that GZMS-11 has strong pathogenicity against citrus psyllid adults, and has the potential for being used for biological control of citrus psyllid in the future.