Breeding for rust resistance increases dry bean productivity in South Africa

Abstract

Infection of dry beans (Phaseolus vulgaris L.) by rust, caused by Uromyces appendiculatus Pers.:Pers. (Unger), results in regular yield and quality losses in South Africa. The growing of resistant varieties is generally considered the most cost effective control measure. To meet this objective, rust resistance has been an important selection criterion since the dry bean breeding programme of the Agriculture Research Council (ARC) was initiated at Potchefstroom in the 1970's. The breakdown of resistance in earlier varieties indicated that pathogenic variation occurred in U. appendiculatus in South Africa and that a more coordinated resistance breeding programme, including race surveys, was needed. This article describes the approach that was followed at the ARC and reviews progress made with germplasm improvement by means of backcrossing. Rust resistance has been transferred from 16 donor lines, including the genes Ur-3+, Ur-5, Ur-11 and uncharacterized genes, to adapted germplasm. Results from field testing of rust infected and rust-free lines showed that resistance was considerably improved without yield loss. Incorporating the Ur-3+ gene in Teebus increased yield ca. 2.5 fold. To protect the durability of the resistance sources used, emphasis has been placed on concurrent research to combine several genes in a single well-adapted background. Attention is also being paid to race-non-specific resistance.

Common Bean Rust: Pathology and Control

“…It is therefore probable that the sexual stage is common in temperate climates. However, some races-for example, those occurring in areas with warmer climates such as California, Florida, and northeastern South Africa-appear to have lost the ability to form teliospores (Harter et al 1935;Zaumeyer and Thomas 1957;Linde et al 1990;Liebenberg 2003). Davison and Vaughan (1963b) obtained minimal germination of urediniospores stored at 3 to 4 C for 446 days and speculated that urediniospores could overwinter on bean debris and staking poles in Oregon, considering that, in the spring, early rust pustules were found on bean plants closest to stakes.…”

“…In some cases, necrotic lesions may contain sporulating pustules (Fromme and Wingard 1921;Harter and Zaumeyer 1941). These pustules are generally small (Fromme and Wingard 1921;Stavely 1984b;Stavely et al 1989b) but can reach 0.8 mm or more (Liebenberg 2003).…”

“…Co-evolution between pathogen and host for the two major P. vulgaris gene pools (Middle American and Andes) has been demonstrated for Pseudocercospora griseola (previously Phaeoisariopsis griseola) (causal agent of ALS) and Colletotrichum lindemuthianum (causal agent of anthracnose) (Pastor-Corrales 1996;Chacó n et al 1997) and also for the rust pathogen (Steadman 1995;Sandlin et al 1999;Liebenberg 2003;Pastor-Corrales and Aime 2004). In a study using rust isolates from the Americas and a differential set consisting of 30 common bean landraces of known origin, distinct specificity of Andean isolates for large-seeded (Andean) landraces was found, whereas the Middle American isolates exhibited no marked specificity and were more broadly virulent.…”

“…In Africa, presumably due to the predominance of largeseeded beans, the most effective sources of disease resistance and, in particular, rust resistance are of Middle American origin (Liebenberg and Vermeulen 1984;Anon. 1988;Liebenberg 1994b;Liebenberg 2003;Jochua et al 2004). …”

Distribution and severity of bacterial brown spot on dry beans in South Africa: An update

“…18,19 Yield losses of up to 55% associated with BBS have previously been reported in South Africa. 17 This loss remains a concern, mainly in commercial farming, because the crop has been reported as an important field crop on account of its nutritional composition 20 and it is a staple food in the eastern parts of the country. Commercial annual dry bean production averages 65 000 tonnes on approximately 50 000 hectares.…”