Genetic variability of papaya lethal yellowing virus isolates from Ceará and Rio Grande do Norte States, Brazil

Abstract

The papaya (Carica papaya) is a fruit crop of great economic importance throughout the Brazilian northeast, which is responsible for 60% of the national output. Papayas in the states of Ceará and Rio Grande do Norte are affected by lethal yellowing disease, caused by papaya lethal yellowing virus (PLYV). Previous work suggested that PLYV is a putative sobemovirus. To assess the genetic variability of PLYV, foliar samples were collected in October 2008 and October 2009 in commercial fields from Ceará and Rio Grande do Norte states, and total RNA was extracted. Specific primers based on the sequence of a previously characterized PLYV isolate were used for the RT-PCR-based amplification of a 900 bp fragment corresponding to the central region of the viral genome. Fragments from 21 viral isolates were cloned and sequenced. Sequence analyses indicated >97% nucleotide sequence identity among the isolates, 94-100% identity with the previously sequenced PLYV isolate, and a lower but significant identity with sobemoviruses (43-48.5%). These results suggest a low genetic variability among PLYV isolates, and are in agreement with the provisional placement of PLYV in the genus Sobemovirus. Definitive taxonomic conclusions, however, can only be drawn after the determination of the full-length genomic sequence. Key words: Carica papaya, PLYV, sobemovirus. RESUMO Variabilidade genética de isolados do papaya lethal yellowing virus dos estados do Ceará e Rio Grande do Norte, BrasilO mamão (Carica papaya) é uma fruta de grande importância econômica em todo o Nordeste brasileiro, região responsável por 60% da produção nacional. Mamoeiros nos estados do Ceará e Rio Grande do Norte são afetados pela doença denominada amarelo letal do mamoeiro, causada pelo papaya lethal yellowing virus (PLYV). Trabalhos anteriores indicaram que o PLYV é um possível sobemovírus. A fim de estimar a variabilidade genética do PLYV, amostras foliares de mamoeiro foram coletadas em outubro de 2008 e de 2009 em regiões produtoras do Ceará, e Rio Grande do Norte. Oligonucleotídeos específicos baseados na sequência de um isolado de PLYV previamente caracterizado foram utilizados para a amplificação via RT-PCR de um fragmento com 900 pb, correspondente à região central do genoma viral. Fragmentos de 21 isolados virais foram clonados e sequenciados. A análise das sequências de nucleotídeos indicou >97% de identidade entre os isolados, entre 94-100% com o isolado de PLYV previamente sequenciado, e uma identidade baixa, porém significativa, com sobemovírus (43-48,5%). Estes resultados sugerem um baixo grau de variabilidade genética entre isolados de PLYV, e estão de acordo com a classificação provisória do PLYV como membro do gênero Sobemovirus. Conclusões de ordem taxonômica, no entanto, só podem ser tiradas após a determinação da sequência genômica completa.

A Current Overview of the Papaya meleira virus, an Unusual Plant Virus

“…PLDMV emergence in PRSV-resistant papaya transgenic lines was considered as an emerging threat to papaya culture in China [ 4 ]. PYLV is restricted to Brazil and its increasing spread reaching high incidence rates [ 5 ]. PapMV was first reported in 1962 in Florida, USA.…”

Screening of papaya accessions resistant to Papaya lethal yellowing virus and capacity of Tetranychus urticae to transmit the virus

“…Recombinant proteins expressed in prokaryotic systems (generally Escherichia coli) are frequently used in research because they are stable, abundant, and easily purified. Due to the low genetic variability in the CP gene among isolates of PLYV (Daltro et al, 2012), an antiserum against the CP of a specific virus isolate may detect different isolates. Furthermore, the antiserum would constitute an important tool for papaya germplasm screening for genetic resistance to PLYV.…”

Thrips Species (Thysanoptera: Thripidae) in Brazilian Papaya (Brassicales: Caricaceae) Orchards as Potential Virus Vectors

“…The rouging practices, which consist in eliminating plants with initial symptoms of viruses, are required to reduce infected plants and virus dispersion in the field, and yield loss due to viruses may reach up to 100% in Brazil (Ventura et al 2004. Various insect pest species may vector viral diseases, for example, aphids that transmit PRSV-P (Ventura et al 2004;Costa 2005;Martins & Ventura 2007) and chrysomelids and mirids that may be associated with the PLYV disease (genus Sobemovirus) (Martins & Ventura 2007;Daltro et al 2012). The Tospovirus TSWV has been transmitted by at least 10 thrips species (Thysanoptera: Thripidae) (Gonsalves & Trujillo 1986;Bautista et al 1995;Silva et al 1997;Whitfield et al 2005), mainly those of the genera Ceratothripoides, Frankliniella, Scirtothrips, and Thrips (Jones 2005;Whitfield et al 2005).…”