Low diversity and fast evolution in the population of Puccinia triticina causing durum wheat leaf rust in France from 1999 to 2009, as revealed by an adapted differential set

摘要

No internationally agreed differential set is available for characterization of virulences in populations of Puccinia triticinacausing wheat leaf rust on durum wheat. In a first step, 73 potentially differential host genotypes were tested with 96 durumleaf rust isolates collected in France. A differential set, adapted to the local epidemiological context and useful for comparisonwith international studies was selected, including French commercial cultivars, Thatcher lines with Lr genes, and internationalcultivars. In the second step, a sample of 310 isolates collected in France from 1999 to 2009 was characterized onthis set. Diversity was very low, as only five pathotypes were distinguished. Genotyping of a subset of 76 isolates accordingto 20 SSR markers confirmed this low diversity, with 73 isolates belonging to a single dominant genotype. Population wasstrongly shaped by cultivars, and the findings explain the successive breakdown of resistance sources deployed in Frenchdurum wheat cultivars. The gene Lr14a, suggested to be an efficient source of resistance in several European and Americancountries, was overcome by pathotypes frequent in France since 2000. Postulation of resistance genes in the commercial cultivarsled to a proposed simplified version of the differential set. This study, providing new information about leaf rust resistancegenes present in the French durum wheat germplasm, highlights the need to diversify sources of resistance toP. triticina in this germplasm. The results are also discussed in terms of relatedness and intercontinental migration of P. triticinaon durum wheat.