Effects of extracts of plants and chemical reagents on Papaya lethal yellowing virus and distribution in papaya.

O mamoeiro (Carica papaya) à uma importante fruteira tropical e sua produÃÃo està aumentando no Nordeste Brasileiro. O Papaya lethal yellowing virus (PLYV) à encontrado infetando o mamoeiro somente no Nordeste brasileiro, aonde vem constituindo sÃrio problema para os produtores. O PLYV à bastante estÃvel e pode ser transmitido por inoculaÃÃo mecÃnica, solo, Ãgua de irrigaÃÃo, mÃos e instrumentos de corte contaminados. A presente atividade de pesquisa teve por objetivo avaliar os efeitos de produtos quÃmicos e de extratos de plantas de uso medicinal sobre a infectividade do PLYV; acompanhar a distribuiÃÃo do vÃrus em plantas inoculadas e avaliar sua interaÃÃo com o Papaya ringspot virus (PRSV). Extratos de plantas infetadas com PLYV foram misturados com igual volume de um dos seguintes produtos quÃmicos: Ãlcool, n-butanol, sabÃo lÃquido comercial, Triton X-100, sÃdio dodecilsulfato (SDS), hipoclorito de sÃdio e carbonato de sÃdio e com extratos de 23 espÃcies vegetais de uso medicinal. As misturas foram incubadas por 30 min em condiÃÃes de laboratÃrio e mecanicamente inoculadas em plantas de mamoeiro. Amostras iguais de tecidos de plantas inoculadas com PLYV foram avaliadas por ELISA indireto para determinar o tempo necessÃrio para sua infecÃÃo sistÃmica. De acordo com os resultados, somente SDS, hipoclorito de sÃdio e carbonato de sÃdio inativaram o vÃrus, mas o SDS ocasionou danos nas plantas e o carbonato ocasionou pequenas pontuaÃÃes esbranquiÃadas. De outra parte, nenhum dos extratos de plantas inativou completamente o PLYV, mas o extrato de Schinus terebinthifolius retardou os sintomas do vÃrus. Tais resultados demonstram a importÃncia do uso de soluÃÃes de hipoclorito de sÃdio para a inativaÃÃo do PLYV na superfÃcie de ferramentas agrÃcolas. Estudos da movimentaÃÃo do vÃrus em plantas inoculadas indicaram que a presenÃa do PLYV pode ser detectada por sorologia nas folhas inoculadas trÃs a quatro dias apÃs a inoculaÃÃo, seis dias no caule, 10 dias nas raÃzes, 15 dias nas folhas mais jovens e a planta inteira foi infetada sistemicamente somente apÃs 25 a 30 dias. Estudos de gama de hospedeiros confirmaram que o PLYV nÃo infeta espÃcies das famÃlias: Amaranthaceae, Brassicaceae, Fabaceae, Pedaliaceae e Solanaceae, nem ocasiona lesÃes locais nas indicadoras Chenopodium amaranticolor; C. murale e C. quinoa. Os estudos sobre a interaÃÃo entre PLYV e PRSV demonstraram a existÃncia de sinergismo entre os dois vÃrus em mamoeiro. A tÃcnica de imunoprecipitaÃÃo de RT-PCR (IP-RT-PCR) demonstrou ser um mÃtodo prÃtico e especÃfico para amplificaÃÃo do RNA do vÃrus, reduzindo problemas de contaminaÃÃo com o RNA de plantas.Papaya (Carica papaya) is an important tropical fruit crop and its production is increasing every year in Northeastern Brazil. Papaya lethal yellowing virus (PLYV) is found infecting papaya only in Northeastern Brazil where it has become a serious problem for the papaya producers. PLYV is very stable and it can be readily transmitted by human actions including contaminated hands, agricultural tools, soil and irrigation water. The present study had the objective to evaluate the effects of chemical products and the extracts from 23 medicinal plants on the infectivity of PLYV in greenhouse experiments; to determine the distribution and movement of PLYV in mechanically inoculated plants and evaluate its interaction with Papaya ringspot virus (PRSV). Extracts from PLYV infected plants were mixed with equal amount of either one of the following chemical products: alcohol, n-butanol, commercial liquid soap, Triton X-100, sodium dodecilsulfate (SDS), sodium hypochlorite and sodium carbonate, and with equal amount of extracts from 23 medicinal plant species. The mixtures were incubated for 30 min at room temperature and mechanically inoculated in healthy papaya. Equal amounts of tissue from each part of papaya plants inoculated with PLYV were serologically evaluated to demonstrate how long the virus takes to infect systemically inoculated plants. According to the results only SDS, sodium hypochlorite and sodium carbonate inactivated the virus, but SDS caused damage in the plants and carbonate caused small whitish points on the treated leaves. On the other hand, neither one of the used medicinal plant extracts inactivated completely the PLYV infectivity, but extracts from Schinus terebinthifolius inhibited the symptoms induced by the virus. Those results demonstrated the importance of sodium hypochlorite to inactivate PLYV in contaminated agriculture tools. The presence of PLYV in inoculated plants was serologically detected three to four days after inoculation in the inoculated leaves, only after six days in the stem, ten days in the roots, 15 days in the younger leaves and the plants were systemically infected only 25 to 30 days after inoculation. Host range studies confirmed that PLYV does not infect plant species from the families: Amaranthaceae, Brassicaceae, Fabaceae, Pedaliaceae and Solanaceae, neither cause local lesions in Chenopodium amaranticolor; C. murale and C. quinoa. Interaction studies indicated a synergistic effect between PLYV and PRSV in papaya. The technique of RT-PCR immunoprecipitation (IP-RT-PCR) has proven to be practical and specific for amplification of PLYV RNA, reducing problems of contamination with plant RNAs