Identification of resistance to rust (Uromyces appendiculatus) and powdery mildew (Erysiphe diffusa) in Portuguese common bean germplasm

Abstract

Portugal has a diverse common bean germplasm, which is still grown in farmers' fields. In this work, we searched for resistance to rust (Uromyces appendiculatus) and powdery mildew (Erysiphe diffusa) in a representative collection of the Portuguese common bean germplasm. Despite many accessions depicting intermediate levels of resistance when compared to the susceptible check, 24 and 13 accessions showed low levels of infection, in spite of a compatible interaction (disease severity (DS) values lower than 5% and infection type (IT) of 4), to rust and powdery mildew, respectively, indicative of partial resistance. Moreover, a resistant reaction was observed in 11 accessions when inoculated with powdery mildew (IT = 0-1) and in additional 11 accessions (one in common) when inoculated with rust (IT = 0-2). The levels of resistance found in this report anticipate great potential of the Portuguese national germplasm, recently reported as genetically closer to the Andean common bean gene pool, for disease resistance breeding of this important crop.

Achievements and Challenges in Legume Breeding for Pest and Disease Resistance

“…In many instances, histology has not been performed, but the reported quantitative resistance, based on reduced infection frequency, prolonged latent period and reduced uredia/colony size not associated with macroscopically visible host cell necrosis (Statler and McVey, 1987;Sillero et al, 2000;2012;Rubiales et al, 2011;Trabanco et al, 2012;Leitão et al, 2013) is likely due to this pre-haustorial resistance, which is known to play a major role in the so-called partial resistance, and may be more durable than resistance controlled by R genes (Niks and Rubiales, 2002).…”

Establishing the Bases for Introducing the Unexplored Portuguese Common Bean Germplasm into the Breeding World

“…In Portugal, a great diversity of bean landraces has been cultivated for generations and is still maintained in small fields for farmers' personal consumption and to sell in local markets (Vaz Patto et al, 2007 ; Leitão et al, 2013 ). Nevertheless, yield instability, especially due to diseases, pests and drought susceptibility make bean less attractive for extensive farming, particularly under Mediterranean conditions in which heat waves and periods of drought are becoming more frequent.…”

Warm Season Grain Legume Landraces From the South of Europe for Germplasm Conservation and Genetic Improvement

“…Based on morphological and reproductive traits, considerable diversity has been described among common bean landraces from the North of Portugal ( Rodiño et al, 2001 ) and from Madeira Island ( Freitas et al, 2010 ). In particular, different sources of resistance and partial resistance to rust and powdery mildew have been identified in a dedicated germplasm collection screening ( Leitão et al, 2013 ), anticipating a high potential for disease resistance breeding in the Portuguese germplasm. The genetic variation of the Portuguese common bean accessions was also characterized using RAPD and SSR molecular markers ( Martins et al, 2006 ; Leitão et al, 2017 ) not detecting clear relation between the geographic distribution and the genetic distance.…”