Genetic diversity studies of Papaya meleira virus

Abstract

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 ...

Seed transmission of Papaya meleira virus in papaya (Carica papaya) cv. Maradol

“…Furthermore, this finding may explain how this virus came to Mexico even though no PMeV has been detected in any other country in Central or South America. This conclusion is consistent with the hypothesis of Daltro et al (2014), who suggested, due to its recent detection in Mexico, that PMeV could be transmitted through seeds. In this work, the reduced percentage germination observed in the seeds from PMeV-positive fruits was associated with the presence of the virus in the seeds, as all other factors that could have influenced this process were held constant for each group.…”

“…This conclusion is consistent with the hypothesis of Daltro et al . (), who suggested, due to its recent detection in Mexico, that PMeV could be transmitted through seeds.…”

Early diagnosis of a Mexican variant of Papaya meleira virus (PMeV-Mx) by RT-PCR

“…Analysis of variation in 6 PMeV isolates from different states in Brazil showed that 2 isolates, PMeV-2 and PMeV-23, exhibited 22 and 26% nucleotide divergence within the 669-bp sequence (Daltro et al, 2010). Recently, a larger study showed that 31 PMeV isolates diverged by up to 12% in the same region (Daltro et al, 2014). These results provide a strong correlation for PMeV as the causal agent of the Mexican disease, and also provide molecular evidence to support the first report of PMeV in Mexico (Perez-Brito et al, 2012).…”

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

“…PMeV has not been sequenced nor classified by the International Committee on the Taxonomy of Viruses (ICTV). A comparative analysis of a ~560 bp fragment amplified from the PMeV replicase gene from the major Brazilian papaya-producing states isolates indicated that PMeV possesses a similarity with the mycoviruses of the family Totiviridae [ 12 , 13 ]. However, a conclusive taxonomic classification will only be possible when the full genome is sequenced.…”

“…Sticky disease spreads rapidly, and currently it occurs mostly in Northeast Brazil [ 12 ]. Outside Brazil, Mexico is the only other country where the disease was reported [ 11 ]; at this time, the virus continues its dissemination and it has been detected in all producer states and its incidence in papaya orchards has been increasing.…”