Variation in virulence and resistance in the bean-bean rust pathosystem in Ecuador

Abstract

Twenty two Uromyces appendiculatus isolates were tested on 20 differential and 25 Ecuadorian Phaseolus vulgaris cultivars in the seedling stage. Based on the infection types 20 races could be discerned. The Ecuadorian cultivars differed greatly in their reaction to the isolates, from resistant to only one isolate ('Red Small Garden') to resistant to all isolates ('G2333'). The isolates showed a wide range of virulence to the Ecuadorian cultivars, from virulent to only two cultivars (isolate 13) to virulent to 21 cultivars (isolates 5 and 23).Seven cultivars with a basically susceptible infection type appeared to differ greatly in quantitative resistance when tested in three consecutive crop cycles. The disease severities in percentage leaf area affected averaged over the three cycles ranged between 83.9% for 'Red Small Garden' and 13.1% for 'INIAP-414'.Race-specific resistance does not seem an advisable breeding strategy, but the quantitative resistance offers a good alternative.

Common Bean Rust: Pathology and Control

“…The most susceptible differential was 'Brown Beauty' with Ur-4. (Ochoa et al 2007). 'PI 181996' and 'PI 260418' were the most resistant of the 2002 differential set to 65 isolates from the Dominican Republic (Jochua et al 2008).…”

“…'PI 260418' has been reported to have between one and three rust resistance genes (Pastor-Corrales 2005). CIAT accession 'G 2333', a Mexican landrace possessing three resistance genes for anthracnose (Young et al 1998), was reported resistant to all rust isolates tested in Ecuador (Ochoa et al 2007), and resistance to all Brazilian rust races tested was found in 'Ouro Negro' Faleiro et al 2001). The latter also contains the Co-10 gene for anthracnose resistance (Alzate-Marin et al 2001a;Ragagnin et al 2003).…”

“…APR in beans is fully expressed above the third trifoliolate stage and was reported to be controlled by a different gene from that controlling specific resistance on the primary leaves (Bokosi et al 1994a,b;Jung et al 1998). Accessions reported to show APR in the field and/or to multiple isolates include 'Pompadour Checa 83-30', 'Alubia 33-1' (and other 'Alubia' selections), 'Jose Beta', 'Diacol Calima', 'Kabanima', and'Jamaica Red' (Mmbaga andSteadman 1990, 1992a;Zaiter et al 1990b), 'Nasaka' (a Malawian landrace selection) (Bokosi et al 1994b(Bokosi et al , 1997b, 'PC 50' (Sandlin and Steadman 1994), 'BAT 93', 'BAT 308' and 'EMP 81' (Beebe and PastorCorrales1991) as well as 'INIAP-414' (Ochoa et al 2007). The CIAT line 'CAL 143' (registered in Malawi as 'Napilira') is rust tolerant in the field in South Africa and exhibits APR (in the form of reduced pustule size) to at least one race in the greenhouse (M. M. Liebenberg, unpubl.).…”

Partial Resistance in the Linum-Melampsora Host-Pathogen System: Does Partial Resistance Make the Red Queen Run Slower?

“…Second, Burdon (1994) showed clear evidence of single‐locus determination of partial resistance in one interpopulation cross in the same system. As noted above, the occurrence of partial resistance types has also been recorded in other wild plants (e.g., Glycine spp.– Phakopsora pachyrhizi , Burdon 1987; Senecio vulgaris–Erysiphe fischeri , Bevan et al 1993) and in gene‐for‐gene systems of crop plants (e.g., Phaseolus spp.– Uromyces sp., Ochoa et al 2007) including the closely related cultivated flax–rust system ( L. usitatissimum – M. lini ) (Flor 1955). Third, we simulated random variation in disease expression and this did not result in distinct clusters of intermediate phenotypes, as observed in the data from the experimental inoculations.…”