Resistance to powdery mildew in selections from Tunisian landraces of barley

Abstract

Two!hundred and thirty!two accessions of barley landraces collected from Tunisia were screened for resistance to powdery mildew[ A number of race!speci_c genes were detected using the detached leaf technique[ Among the 121 accessions tested\ 058 were susceptible to powdery mildew\ 19 were resistant and 32 showed di}erential reactions to the three isolates of powdery mildew used[ An attempt was made to deter! mine the number of genes\ the types of gene\ the types of gene action and the gene loci in 19 resistant accessions[ Three types of cross were made] "0# the accessions were crossed to the susceptible variety {Pallas|\ "1# the accessions were crossed with {Pallas| isolines\ and "2# accessions with identical powdery mildew reaction patterns were intercrossed[ Three isolates of Erysiphe`raminis f[ sp[ hordei were used] Bzm!0\ KM 07Ð64\ R02C[ A number of di}erent resistance genes were detected among the 19 resistant accessions[ Surprisingly\ segregation indicating single genes only were detected with the isolates used[ Some of these genes could be associated with loci already known[ In 08 cases a domi! nant and in one a recessive mode of inheritance was detected[ The recessive gene was not located at the mlo locus[ This investigation represents the _rst systematic study of race!speci_c genes for powdery mildew resistance in Tunisian landraces[ The newly identi_ed sources of resistance may be used in many strategies of breeding for disease resistance[

Selections from barley landrace collected in Libya as new sources of effective resistance to powdery mildew (Blumeria graminis f.sp. hordei)

“…Since 1930, when isolates of powdery mildew with different virulence genes were identified by Mains and Dietz (1930), specific isolates (usually 1 3 isolates) were used for screening collections of barley for genes for resistance (Jørgensen 1994, Czembor andJohnston 1999). However for a total number of about 280 000 of barley accessions (most of them landraces) which is estimated to exist world-wide in ex situ germplasm collections (Knüpffer and Hintum 1995) only less than 2 percent attempts have been made to identify powdery mildew resistance genes using differential lines and isolates (Czembor 1996(Czembor , 2001).…”

“…Identification of powdery mildew resistance genes based on tests performed on seedlings using isolates with different virulence spectra is effective and sufficient for breeders and pathologist needs (Brückner 1964, Dreiseitl 1999, Dreiseitl and Jørgensen 2000. However, confirmation of putative resistance genes or alleles can only be established through the evaluation of progeny from crosses among appropriate genotypes (Jørgensen 1994, Czembor and Johnston 1999. Vavilov (1926) proposed that the region of Mediterranean Sea is major center of crop origin.…”

Resistance to powdery mildew in one Spanish barley landrace hardly resembles other previously identified wild barley resistances

“…This broad RS is not surprising in view of the landrace-derived origin of this line. Landraces have been used extensively within the primary gene pool of barley to mine both genes and alleles associated with disease resistance (Jørgensen and Jensen 1997;Czembor 1999;2001). Indeed, several powdery mildew resistance genes used commercially are derived from barley landraces (Fischbeck and Jahoor 1991).…”

Assessment of powdery mildew (Blumeria graminis f. sp. hordei) resistance genes in Turkish barley varieties

“…By contrast, the genes Mlg, Mlak, Mla7, and Mla(Ab) have also been detected in North American cultivars (Dreiseitl and Steffenson 2000). Likewise, the genes Mlg, Mlk, Mla7, MI(CP), and Mla1 were previously detected in a population of 108 Baltic spring barley cultivars and breeding lines (Tueryapina et al 1996), the genes Mla1, Mla7, and Mlk were detected in Tunisian landraces (Czembor and Johnston 1999), and the genes Mlg and Mla7 were detected in a population of 20 cultivars from Greece (Czembor and Bladenopoulos 2001). Based on these previous reports and on the present study, the most commonly found R-genes for powdery mildew in barley appear to be Mlg, which has been introduced into many European cultivars a long time ago, and Mla7, which has also been introduced into common barley varieties over the years.…”

“…As a first step towards the effective use of powdery mildew R-genes in breeding programs, it is essential to test for the presence of those genes in registered cultivars and for the virulence of the pathogen through periodical surveys (Czembor and Bladenopoulos 2001;Czembor 1998, 2000a;Czembor and Gacek 1990;Czembor and Johnston 1999). In practice, such surveys are conducted based on the gene-for-gene hypothesis, i.e.…”