Fengnian Wu

The complete mitochondrial genome sequence of Diaphorina citri (Hemiptera: Psyllidae)

Abstract The first complete mitochondrial genome (mitogenome) sequence of Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae) from Guangzhou, China, is presented. The circular mitogenome is 14,996 bp in length with an A + T content of 74.5%, and contains 13 protein-coding genes (PCGs), 22 tRNA genes (tRNAs), two rRNA genes and an AT-rich control region. Synteny was identical to the ancestral insect mitogenomes. All PCGs start with ‘ATN’ codons. Eleven PCGs use the complete termination codons (‘TAA’ or ‘TAG’), while the remaining two (cox2 and nad5) use a single ‘T’ as the stop codon. All tRNAs have the typical cloverleaf structure, except for trnTrp which lacks the variable arm and trnSer (AGN) which lacks the dihydrouridine arm. A phylogenetic tree, including 12 members of Sternorrhyncha, was constructed based on the 13 PCGs sequences. The resulting phylogenetic tree matched the established taxonomic scheme based on morphology.

Draft Genome Sequence of Xylella fastidiosa subsp. fastidiosa Strain Stag's Leap.

ABSTRACT Xylella fastidiosa subsp. fastidiosa causes Pierces disease of grapevine. Presented here is the draft genome sequence of the Stags Leap strain, previously used in pathogenicity/virulence assays to evaluate grapevine germplasm bearing Pierces disease resistance and a phenotypic assessment of knockout mutants to determine gene function.

Feeding behavior of Diaphorina citri and its transmission of ‘Candidatus Liberibacter asiaticus’ to citrus

Huanglongbing (HLB), also known as citrus greening, is currently the most destructive disease of citrus, responsible for huge economic losses in the worlds major citrus production areas. The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), transmits ‘Candidatus Liberibacter asiaticus’ (Clas), the pathogen responsible to cause HLB. Understanding of vector, pathogen, and host plant interactions is important for the management of this vector‐disease complex. We used the direct‐current electrical penetration graph (DC‐EPG) system to evaluate feeding behavior of Clas‐infected D. citri adults, and their potential to transmit the pathogen to healthy citrus, Citrus reticulata Blanco cv. Sunki (Rutaceae), following a 24‐h inoculation access period. Plants were tested for the presence of Clas by qPCR 6 months after inoculation. Findings suggest that inoculation was associated with salivation into the phloem sieve elements (waveform E1). The minimum feeding time for successful transmission by a single adult was 88.8 min, with a minimum E1 duration of 5.1 min. Regression analysis indicated a significant relationship between E1 duration and transmission efficiency. The adults successful in transmitting Clas to healthy citrus were able to penetrate and feed in the phloem much earlier than those which did not transmit. The minimum duration of E1 for a female was shorter than that of a male, but transmission was higher. However, durations of other EPG parameters were not significantly different between male and female. Feeding by single Clas‐infected D. citri adults on 6‐month‐old plants (Sunki) resulted in 23% HLB‐positive plants 6 months after inoculation. Multiple nymphs or adults could transmit the pathogen more efficiently than individual adults in the field, and further enhance the severity of the disease. Effective tactics are warranted to control D. citri and disrupt transmission of Clas.

Draft Genome Sequence of “Candidatus Liberibacter asiaticus” from a Citrus Tree in San Gabriel, California

ABSTRACT The draft genome sequence of “Candidatus Liberibacter asiaticus” strain SGCA5 from an orange citrus tree in San Gabriel, California, is reported here. SGCA5 has a genome size of 1,201,445 bp, a G+C content of 36.4%, 1,152 predicted open reading frames (ORFs), and 42 RNA genes.

Movement of Diaphorina citri (Hemiptera: Liviidae) Adults between Huanglongbing-Infected and Healthy Citrus

Abstract Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is the vector of huanglongbing (HLB or citrus greening disease). Preferences of D. citri adults differed for HLB-infected and healthy citrus under different maturity conditions. The presence or absence of young shoots had a significant influence on the choice by D. citri adults between HLB-infected and healthy citrus hosts. When citrus plants had young shoots, infected plants were more attractive than healthy ones to the adults. Also, D. citri adults fed for a longer time on infected plants with young shoots than on their healthy counterparts. In the absence of young shoots, D. citri adults were at first also more attracted to infected mature leaves, but after 38 h they turned to healthy mature leaves. In a multiple choice experiment, infected young shoots and healthy young shoots were the most attractive, followed by shoots with infected mature-yellow leaves and physiologically mature-yellow leaves, and lastly by healthy or infected mature-green leaves. In an experiment to measure the relative attractiveness of yellow, green, and white boards, yellow color boards attracted more adults than green and white boards, indicating that the adults preferred the yellow color. The results suggest that D. citri adults when first confronted with a choice are more attracted to infected citrus because of the color, but subsequently they move to healthy citrus perhaps because of either the poor nutrition or a feeding barrier in the infected hosts. This behavior appears to facilitate the pathogens spread.

Whole-Genome Sequence of “Candidatus Profftella armatura” from Diaphorina citri in Guangdong, China

ABSTRACT The genome of “Candidatus Profftella armatura” strain YCPA from Diaphorina citri in Guangdong, China, was sequenced. The strain has a chromosome of 457,565 bp, 24.3% G+C content, 364 predicted open reading frames (ORFs), and 38 RNAs, and a plasmid, pYCPA54, of 5,458 bp with 23.9% G+C content and 5 ORFs.