Cochineal Scale (<em>Porphyrophora ningxiana</em>) Enhances <em>Fusarium</em> Wilt and Root Rot of Chinese Licorice Plant (<em>Glycyrrhiza uralensis</em>)

Research Article

Austin Biol. 2016; 1(4): 1016.

Cochineal Scale (Porphyrophora ningxiana) Enhances Fusarium Wilt and Root Rot of Chinese Licorice Plant (Glycyrrhiza uralensis)

Shang W¹, Fan S², Short D³, Cao X¹, Zhang H4, Kasson MT³, Chen Y5 and Hu X¹*

¹Department of Plant Pathology, Northwest A&F University, China

²Department of Biochemistry and Molecular Biology, Northwest A&F University, China

³Department of Plant and Soil Sciences, West Virginia University, USA

4Department of Entomology, Northwest A&F University, China

5Beijing University of Agriculture, China

*Corresponding author: Xiaoping Hu, State Key Laboratory of Crop Stress Biology for Arid Areas, Department of Plant Pathology, College of Plant Protection, Northwest A&F University, Yangling 712100, China

Received: November 03, 2016; Accepted: November 29, 2016; Published: December 01, 2016


Chinese licorice, the dried root of Glycyrrhiza uralensis, is used in traditional Chinese medicine. However, root rot of G. uralensis has gradually become a serious problem in licorice production in China. A 2012 survey of 22 commercial licorice fields revealed a root rot incidence of 36.5% infected plants. Infected plants were wilted with chlorotic foliage and discolored vasculature, and were significantly associated with a scale insect (Porphyrophora ningxiana) that parasitized plant roots (r = 0.9790, P < 0.001).Two previously characterized fungal isolates (FLR and G013) collected from infected licorice plant roots were used to inoculate licorice plant roots, which resulted in symptoms similar to those observed in field plants. Roots of licorice plant inoculated with FLR showed vascular discoloration, whereas those inoculated withG013 resulted in cortical root rot. Using phylogenetic analyses of the ribosomal Intergenic Spacer (IGS), ribosomal DNA and Internal Transcribed Spacers (ITS), translation elongation factor 1-alpha (EF1-a), and RNA polymerase II large subunit (RPB2), isolate FLR was identified as a novel sequence type within the Fusariumoxysporum Species Complex (FOSC), while isolate G013 was identified as a member of F. Solani Species Complex (FSSC) 11. Pathogenicity experiments revealed that isolate FLR can infect and cause disease in melon, soybean and potato; isolate G013 can infect and cause disease in pea, broad bean, soybean and potato. Additional experiments revealed that the incidence of root rot of licorice plants was significantly enhanced when cochineal scales presented in the soil.

Keywords: Glycyrrhiza uralensis; Fusarium oxysporum; Fusariumsolani; Fusarium wilt; Root rot; Porphyrophora ningxiana


Glycyrrhiza uralensis Fisch, a leguminous perennial herb, is native to the Middle East and Central Asia including China, Afghanistan, Pakistan, Azerbaijan, Uzbekistan, Turkmenistan, Syria, and Turkey. Licorice, the dried root of G. uralensis, is used in two primary forms: root and extract. Records of licorice plant cultivation date back to the third century [1]. Licorice is a Chinese traditional medicine used for the treatment of various ailments including ulcers, sore throats, arthritis, and allergies [2-4]. It has also been a popular herbal medicine in Europe for centuries [2,5-12]. In addition, licorice is used as a food additive, a raw material in cosmetics and a flavoring agent for tobacco [13-15].

Licorice plant mainly grows in arid desert steppes and was historically harvested from wild resources, mainly limited to northwest and northeast areas of China, before domestic cultivation was established in the 1990s. Licorice plant cultivation has increased dramatically in recent years to fill shortages of wild licorice supplies. For example, licorice was produced on an estimated 125,408 hain 2011 [16]. Since 2002, there have been serious outbreaks of root rot and wilton cultivated G. uralensis plants in Ningxia, China, which severely reduced the yield and quality of licorice. Up to 30% mortality of cultivated licorice plants have occurred in fields and the disease complex is considered to be the most significant threat to commercial production of licorice in this area [17].

Previously, we reported the occurrence of two pathogens associated with Fusarium wilt of licorice plant [17], which were putatively identified as members of the F. oxysporum Species Complex (FOSC) and F. solani Species Complex (FSSC) based on sequence identity of the translation elongation factor 1-alpha (EF-1a) locus [18]. Subsequently, it was observed that 0the death of licorice plant was also associated with Porphyrophora ningxiana Yang (Hemiptera: Margarodidae), a subterranean scale insect commonly referred to as ‘ground pearls’ on account of the nymph stage being enclosed in a pearl-like cyst on the roots of plants. The ‘Cochineal Scale’ (CS), is a sessile plant parasite with one generation each year and four developmental stages: egg, 1st nymph, 2nd nymph (pearl scale), and adult (Figure 1). The CS mainly overwinters as eggs in egg oocysts. In soil, the nymphs can locate and attach to roots to extract sap, and produce the characteristic pearl-like cysts before the growing season commences. In August, adults emerge, mate, and then lay eggs in eggoocystsin soil between 2-6 cm underground [19].