Evaluation of annual ryegrass genotypes for forage yield and blast resistance

Abstract

The annual ryegrass (Lolium multiflorum Lam.) is a key winter forage, but its productivity is limited by diseases, especially blast, caused by Magnaporthe oryzae (syn. Pyricularia oryzae). This study aimed to evaluate the productive performance and reaction to blast of commercial cultivars and advanced lines of annual ryegrass in two edaphoclimatic environments in Santa Catarina, Brazil: Lages (Cfb climate) and Agronomica (Cfa climate). The experiment utilized a randomized block design with eight genotypes and four replicates. Variables analyzed included dry matter yield and blast severity. A bifactorial analysis of variance (genotype x local) and Spearman correlation were performed. The results revealed a significant genotype x environment (GxA) interaction for both dry matter yield and blast severity, indicating a dependence on local conditions. Blast pressure was drastically higher in Agronomica, which is climatically more favorable to the disease. Annual ryegrass genotypes Altovale and Taio were superior, combining high and stable productivity with low disease severity in both locations. Conversely, the cultivar Ponteio showed high yield only in Lages, suffering a severe reduction and higher susceptibility in Agronomica. Ceronte was the most susceptible genotype, reaching 86.25% severity in Agronomica. The Spearman correlation confirmed a negative and significant impact of blast on forage productivity, with a stronger correlation in Agronomica ({rho} = -0.689) than in Lages ({rho} = -0.497). These findings underscore that the GxA interaction is primarily driven by the differential resistance response to blast. Altovale and Taio are the most recommended options. It is concluded that the selection of ryegrass genotypes must be conducted in the target environment, considering blast as a primary selection factor to ensure the stability and sustainability of forage production in southern Brazil.