Papaya (Carica papaya) is a fruit crop of great economic and social importance for Brazil and other papaya-producing countries. Brazil is the second largest producer in the world. The papaya sticky disease, caused by Papaya meleira virus (PMeV), has caused great losses in the major Brazilian papaya-producing states. In order to estimate the genetic diversity of PMeV, latex samples were collected from papaya plants in the states of Bahia, Espírito Santo, Pernambuco, Ceará and Rio Grande do Norte, and total RNA was extracted. Specific primer for the replicase region allowed the amplification, by RT-PCR, of a fragment of approximately 560 bp from 31 isolates. The sequence analysis indicated a level of conservation greater than 88% among isolates. Furthermore, comparative analyzes indicated that PMeV has similarity with mycoviruses of the family Totiviridae. This phylogenetic relationship was reinforced by the presence of conserved motifs within in the RdRp regions from mycoviruses. Key words: Carica papaya, Totiviridae, sticky disease, variability, viruses.Papaya (Carica papaya L.), is a fruit crop that originated and was domesticated in southern Mexico, and now is globally distributed and cultivated in many countries around the world. According to data from the Food and Agriculture Organization (FAO), the global production of papaya in 2010 was about 8 million tons, representing 10% of all tropical fruits produced worldwide (faostat.fao. org). The world's leading producers are India (42%) and Brazil (23.4%). Papaya production in Brazil was about 1,87 million tons on 35,000 hectares, with a value estimated at US$ 650 million (IBGE, 2011). The major papaya producing states are Bahia (928,000 tons), followed by Espírito Santo (560,000 tons), Ceará (112,000 tons) and Rio Grande do Norte (69,000 tons).The main factors that threaten papaya production are insect pests and diseases, especially those caused by viruses. The papaya sticky disease, caused by Papaya meleira virus (PMeV) was reported in the 1980's affecting papaya plants in the south of Bahia and north of Espírito Santo (Nakagawa et al., 1987;Rodrigues et al., 1989). Soon afterwards, the disease was detected in the states of Pernambuco, Ceara and Rio Grande do Norte (Barbosa et al., 1998a,b). Outside Brazil, Mexico is the only other country where the disease has been reported (Perez-Brito et al., 2012).The disease's typical symptoms are: excessive exudation of watery latex on the fruit surface, which oxidizes and gives the fruit a stained and sticky aspect; fruit malformation, uneven ripening and changes in the organolepctic properties, rendering it unmarketable.The PMeV genome composition and size are uncommon among plant viruses. PMeV has a double strand RNA (dsRNA) genome, approximately 12 Kb in length, packed into an isometric particle with ca. 50 nm diam (Kitajima et al., 1993; Maciel-Zambolin et al., 2003). The virus can be transmitted by latex injection into the stem apex, and previous work suggests that the virus could be transmitted by Bemisia ...

Papaya sticky disease ('meleira') was first observed in Brazil at the beginning of the 1980s. The disease is characterized by intense latex exudation from the fruit surface that becomes dark as it oxidizes, which makes it difficult to sell. The causal agent, which has been called papaya meleira virus (PMeV), has been identified as an isometric virus particle, approximately 50 nm in diameter, with a double-stranded RNA genome. Here, we report the first complete sequence and organization of the 8.7-kb viral dsRNA genome. Two ORFs coding for a putative coat protein and RNA-dependent RNA polymerase (RdRp) were predicted. In silico analysis revealed that the translated ORF2 contains the conserved domains characteristic of an RdRp protein (pfam02123:RdRP 4), which is a family that includes RdRps from members of the genera Luteovirus, Totivirus and Rotavirus. Evolutionary analysis with amino acid sequences with the RdRps from members of the family Totiviridae and some dsRNA viruses showed that PMeV RdRp did not root itself in any genus.

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.