Enhanced fusiform rust hazard maps for loblolly pine: Incorporating genotype and climate to predict disease

Abstract

Hazard maps are a critical component in determining the regional disease pressure for fusiform rust disease [caused by the fungal pathogen Cronartium quercuum (Berk.) Miyabe ex Shirai f. sp. fusiforme], which is considered the most important disease of loblolly pine (Pinus taeda L.) in the southeastern United States. Genetically improved fusiform rust resistant stock should be deployed in areas that are estimated to be at a high hazard for the disease, while stocks with lower resistance to the disease, but perhaps other favorable traits, can be deployed in areas with a lower estimated hazard. Current hazard maps are based on the historic presence of the disease but do not consider the effect of host genotype or climate which can influence the presence and distribution of fungal pathogens. Here, we aim to improve current hazard maps for fusiform rust by identifying, modeling, and predicting the relationship between the disease and yearly climate indicators. Different loblolly pine genotypes were tested: one family improved for resistance and non-improved checklots for each location. We found that, for the non-improved genotypes, location, potential evapotranspiration, consecutive cloud cover, diurnal temperature range, and a yearly available water indicator can explain 89.2 % of the deviance for disease occurrence. For the improved family, we found that longitude, yearly water deficit, yearly consecutive frost days, yearly consecutive cloud cover, and yearly diurnal temperature range explain 93.1 % deviance for disease incidence. We produce two rust hazard maps based on each model, illustrating the probability of the incidence of the disease. With this project, we pave the way for a better-informed determination of where and what loblolly pine resistant stock should be deployed to limit the damage and costs associated with the management of fusiform rust disease.