Effects on photosynthesis and foliar area of lettuce cultivar mechanically inoculated with Lettuce mosaic virus pathotypes and Lettuce mottle virus

Levantamentos realizados no estado de São Paulo indicaram a ocorrência isolada e em infecções mistas do Lettuce mosaic virus (LMV) e do Lettuce mottle virus (LeMoV) em plantas de alface (Lactuca sativa). O presente trabalho teve como objetivo estudar os efeitos da infecção isolada e mista entre o LMV (patótipos II e IV) e o LeMoV, em cultivares de alface suscetível (White Boston) e tolerante (Elisa - gene mol¹) ao LMV patótipo II. As plantas foram inoculadas via extrato vegetal tamponado com isolados de LMV-II, LMV-IV e LeMoV separadamente e em diferentes combinações, com intervalo de 24 h ou simultaneamente com os dois vírus. As plantas infetadas foram analisadas utilizando-se hospedeiras diferenciais para o LMV e o LeMoV, e no caso do LMV pelo teste sorológico de PTA-ELISA. Nas avaliações de peso fresco e seco, área foliar e teor de clorofila, observou-se que a cultivar White Boston foi a mais afetada por ambos os vírus. As infecções mistas e isoladas na cultivar Elisa causaram efeitos semelhantes, provavelmente devido a presença do gene mo1¹ de tolerância ao LMV-II. O isolado LMV-IV foi considerado o mais agressivo nestas cultivares quando comparado ao LMV-II e o LeMoV.A survey of virus isolates causing mosaic in lettuce (Lactuca sativa) in the state of São Paulo, Brazil, indicated the occurrence of Lettuce mosaic virus (LMV) and Lettuce mottle virus (LeMoV) alone or in mixed infections. The objective of this work was to study the effects of single and mixed infections between LMV (pathotypes II and IV) and LeMoV in susceptible (White Boston) and tolerant (Elisa, mo1¹ gene) lettuce cultivars. Plants were sap-inoculated with LMV-II, LMV-IV and LeMoV, in single infections and in different combinations, with either a 24 h interval between the two viruses or simultaneously. Plants were tested for the presence of LMV and LeMoV using differential hosts and, in the case of LMV, the serological test (PTA-ELISA) was used. In the evaluations of fresh and dry weight, leaf area and chlorophyll content, the White Boston cultivar was observed to be the most affected by both viruses. This cultivar's response to single and mixed infections was similar, probably due to the presence of the mo1¹ gene which confers tolerance to LMV-II. When compared to LMV-IV and LeMoV, LMV-IV was the most aggressive isolate