Frogeye Leaf Spot of Soybean: A Review and Proposed Race Designations for Isolates of Cercospora sojina Hara

Abstract

Frogeye leaf spot (FLS), caused by Cercospora sojina K. Hara, is a common disease of soybean [Glycine max (L.) Merr.] in most soybean‐growing countries of the world. Significant yield losses of soybean (10–60%) have been attributed to FLS under hot and humid growing conditions. The FLS in the southern United States has been kept under control by planting resistant cultivars. Cercospora sojina is a dynamic pathogen with extensive virulence or race diversity. The current number of C. sojina isolates at the University of Georgia collection is 93. Assigning race designations to this large number of isolates has been difficult because of the lack of a well‐defined set of differentials. To facilitate future studies of the genetics of soybean resistance to FLS and the identification and comparison of existing and future races of C. sojina, we have reassessed both the soybean differentials and the C. sojina races. Based on the reactions of 93 isolates of C. sojina on 38 putative soybean differentials, we propose a core set of 12 differentials and 11 races that represent the major diversity among the 93 C. sojina isolates. The definition of these 12 differentials and 11 races should provide the foundation for the identification and comparison of additional soybean resistance genes and new races of C. sojina

The combined effects of temperature and leaf wetness periods on soybean frogeye leaf spot intensity

“…Today, the use of resistant cultivars is the most efficient and cost effective means of controlling frogeye leaf spot, and is the main disease control measure adopted in Brazil (MIAN et al, 2009). This pathogen has not been associated with disease in any other crop or weed host (MIAN et al, 2008).…”

Agressividade de três raças de Cercospora sojina em folhas de soja

“…A doença tem sido esporádica e limitada a algumas regiões produtoras (Reis & Kimati (1973), causando porém, danos, à cultura da soja, que variam de 21 a 60% (Mian et al, 2008). O uso de cultivares resistentes, a partir da incorporação de alelos de resistência em cultivares comerciais susceptíveis, é o meio mais econômi-co e eficiente de controle da doença (Gravina et al, 2004).…”

Genetic diversity ofCercospora sojinarevealed by amplified fragment length polymorphism markers

“…In the United States, estimated soybean yield reductions caused by frogeye leaf spot ranged between 183 868 and 345 148 metric tons from 2006 to 2009 (Koenning & Wrather, 2010). The use of host resistance has been an economical way to manage frogeye leaf spot, but the development of new virulent races that overcome single genes for resistance (Rcs genes) has been a hindrance to developing cultivars with durable resistance to C. sojina (Athow et al, 1962;Ross, 1968;Phillips & Boerma, 1981;Mian et al, 2008). Application of foliar fungicides has been another method of managing frogeye leaf spot; however, C. sojina isolates with resistance to quinone outside inhibitor (QoI) fungicides have been reported recently (Zhang et al, 2012a).…”

“…Mian et al (2008) evaluated 98 C. sojina isolates from different countries on 12 differential soybean lines, and found that the majority of these isolates could be classified within 11 different race groups. Evaluating 50 C. sojina isolates from Ohio on 12 differential soybean lines, Cruz & Dorrance (2009) reported a total of 20 different pathotype groups.…”