Papaya meleira virus (PMeV) is the causal agent of papaya sticky disease, which is characterized by a spontaneous exudation of fluid and aqueous latex from the papaya fruit and leaves. The latex oxidizes after atmospheric exposure, resulting in a sticky feature on the fruit from which the name of the disease originates. PMeV is an isometric virus particle with a double-stranded RNA (dsRNA) genome of approximately 12 Kb. Unusual for a plant virus, PMeV particles are localized on and linked to the polymers present in the latex. The ability of the PMeV to inhabit such a hostile environment demonstrates an intriguing interaction of the virus with the papaya. A hypersensitivity response is triggered against PMeV infection, and there is a reduction in the proteolytic activity of papaya latex during sticky disease. In papaya leaf tissues, stress responsive proteins, mostly calreticulin and proteasome-related proteins, are up regulated and proteins related to metabolism are down-regulated. Additionally, PMeV modifies the transcription of several miRNAs involved in the modulation of genes related to the ubiquitin-proteasome system. Until now, no PMeV resistant papaya genotype has been identified and roguing is the only viral control strategy available. However, a single inoculation of papaya plants with PMeV dsRNA delayed the progress of viral infection.

Papaya meleira virus (PMeV), the causal agent of papaya sticky disease, was first reported in Brazil and more recently in Mexico. Yield losses in papaya (Carica papaya) orchards related to this virus can be considerable over relatively short time spans. To date, very little is known regarding the transmission mechanisms of PMeV, which has made it difficult to effectively control the virus and to prevent dissemination. A few published reports have claimed that PMeV is not seed‐transmissible. However, in this study, evidence is presented for seed transmission of PMeV in papaya cultivar Maradol. Three seed materials (whole dry seed, seed coat and embryo–endosperm) from Maradol were analysed using reverse transcription‐polymerase chain reaction. A seed transmission rate of c. 81% was observed, suggesting that this mechanism is an important route of virus dissemination. For the first time, this study shows that PMeV is seedborne and can be transmitted to the next generation through contaminated papaya seeds.

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