Evaluation of Coffee (Coffea arabica L. var. Catuaí) Tolerance to Leaf Rust (Hemileia vastatrix) Using Inoculation of Leaf Discs Under Controlled Conditions

Coffee leaf rust (CLR), caused by the obligate biotrophic fungus Hemileia vastatrix, is considered one of the most devastating diseases of Arabica coffee. The use of leaf rust resistant or tolerant coffee varieties is a critical component for effective management of this disease at the farm level. Conventional breeding of Arabica coffee for leaf rust resistance requires many years of breeding and field-testing. Induced mutagenesis is an effective tool to increase genetic variability and generate new alleles with potential benefit for addressing abiotic and biotic stresses such as leaf rust in Arabica coffee. Efficient screening methods are required to evaluate coffee germplasm or mutant populations for resistance to H. vastatrix. Here, we present a screening method that uses inoculation of leaf discs in a controlled environment. The method was evaluated using M1V1 and M2 plants derived from chemically mutagenized Arabica coffee cell suspensions. In this method, the first rust symptoms appear on the leaf discs approximately 29 days after inoculation while the disease severity and incidence can be scored about 47 days after inoculation. Our results show that the methodology is simple, efficient and suitable to rapidly screen large mutant populations in a small area.