Angular leaf spot of Phaseolus vulgaris is a serious disease caused by Phaeoisariopsis griseola, in which two major gene pools occur, namely Andean and Middle-American. Sequence analysis of the SSU region of nrDNA revealed the genus Phaeoisariopsis to be indistinguishable from other hyphomycete anamorph genera associated with Mycosphaerella, namely Pseudocercospora and Stigmina. A new combination is therefore proposed in the genus Pseudocercospora, a name to be conserved over Phaeoisariopsis and Stigmina. Further comparisons by means of morphology, cultural characteristics, and DNA sequence analysis of the ITS, calmodulin, and actin gene regions delineated two groups within P. griseola, which are recognised as two formae, namely f. griseola and f. mesoamericana.

Phakopsora pachyrhizi has dispersed globally and brought severe economic losses to soybean growers. The fungus has been established in Brazil since 2002 and is found nationwide. To gather information on the temporal and spatial patterns of genetic variation in P. pachyrhizi, we sequenced the nuclear internal transcribed spacer regions (ITS1 and ITS2). Total genomic DNA was extracted using either lyophilized urediniospores or lesions removed from infected leaves sampled from 26 soybean fields in Brazil and one field in South Africa. Cloning prior to sequencing was necessary because direct sequencing of PCR amplicons gave partially unreadable electrophoretograms with peak displacements suggestive of multiple sequences with length polymorphism. Sequences were determined from four clones per field. ITS sequences from African or Asian isolates available from the GenBank were included in the analyses. Independent sequence alignments of the ITS1 and ITS2 datasets identified 27 and 19 ribotypes, respectively. Molecular phylogeographic analyses revealed that ribotypes of widespread distribution in Brazil displayed characteristics of ancestrality and were shared with Africa and Asia, while ribotypes of rare occurrence in Brazil were indigenous. The results suggest P. pachyrhizi found in Brazil as originating from multiple, independent long-distance dispersal events.

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.

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