Persistent RNA Viruses of Common Bean (Phaseolus vulgaris): Distribution and Interaction with the Host and Acute Plant Viruses

Abstract

Common bean (Phaseolus vulgaris) is the most important legume for direct human consumption. Common bean originated and was domesticated in the Americas but now is grown worldwide. As in the case of other crops, common bean can be infected with acute and persistent plant viruses. A modified dsRNA extraction method was developed and used in this study. The method was fast, economic, versatile, and required relatively small amounts of desiccated plant tissue. The method was successfully used to extract dsRNAs from plants infected with RNA plant viruses and to investigate the occurrence of two endornaviruses, Phaseolus vulgaris endornavirus 1 (PvEV1) and Phaseolus vulgaris endornavirus 2 (PvEV2), in breeding lines, cultivars, landraces, and wild genotypes of common bean from the two centers of common bean domestication: Mesoamerica and the Andes. The two endornaviruses were detected in many common bean genotypes of Mesoamerican origin but rarely in genotypes of Andean origin. A comparative study of morphological and physiological characteristics between two common bean lines of the cultivar Black Turtle Soup (BTS); one infected with PvEV1 and PvEV2 (BTS+) and the other endornavirus-free (BTS-) was conducted. Morphological differences between the two lines were not observed. However, the study revealed that common bean endornaviruses may promote seed germination, pod length, and carotenoid content. Nevertheless, endornaviruses were associated with lower chlorophyll content. When interactions studies were conducted between PvEV1 and PvEV2 and three acute viruses, synergistic effects were obtained. Quantitative RT-PCR results supported a synergism between PvEV1 and Sunn-hemp mosaic virus. More research should be conducted to determine the type of symbiotic interaction that exists between common bean and endornaviruses.