Epidemiological components, damage characterization and control of tropical and temperate rusts at a global climate change scenario

Abstract

There is no doubt that anthropogenic climate change, increasingly evident nowadays, has a major impact on the emergence of crop diseases, particularly on rusts. The 21st century has witnessed pandemics of rust in several hosts, such as soybeans, grapevine, Myrtaceae, among others. Invasive rust pathogens have been responsible for high losses in the crops in which they occur, including in areas where they were absent. Although several studies indicate that climate change will be responsible for increases on rust incidence, few studies have focused on assessing the impact of climate changes on the severity of these diseases. A complex network of molecular interactions control plant stress responses, involving changes in gene expression, which are reflected in histological and physiological changes. Recent studies have revealed that the response of plants to a combination of different stresses is unique and cannot be directly extrapolated from the response of plants to each of the different stresses applied individually. Preliminary results obtained by our research group have shown that abiotic stresses of moderate intensity applied to grapevines may cause a significant increase in the rust severity, caused by Phakopsora euvitis. It has also been observed that raspberry rust causes extensive necrosis in the leaf blade when plants are kept under elevated temperatures. The main hypothesis of this project is that abiotic stresses, mainly moderately elevated temperatures and moderate water deficits, for longer periods than disease latency, cause differential increase in the severity of rusts adapted to the tropical climate and rusts adapted to the temperate climate, being more drastic in these than in those. To test this hypothesis and (i) to increase the understanding of the mechanisms that lead to the synergistic effect between abiotic and biotic stresses (at the histological, physiological and genetic levels); (ii) to quantify the epidemiological consequences of the abiotic stresses in the rusts progress; and (iii) to propose control measures that minimize the severity of these diseases in a future scenario of climate change, we propose a series of experiments that will use Phakopsora euvitis - grapevine and Pucciniastrum americanum - raspberry patossystems as models of temperate rust, and Phakopsora pachyrhizi - soybean and Austropuccinia psidii - guava as models of rusts adapted to the tropics. (AU)