New virulent race of Phialophora gregata f. sp. adzukicola associated with continuous cultivation of adzuki bean cultivar Acc259

Abstract

Adzuki bean cultivar Acc259,

Screening of cultivated and wild adzuki bean for resistance to race 3 of Cadophora gregata f. sp. adzukicola, cause of brown stem rot

“…Thus, a considerable number of cultivars and lines in the group B resistant to race 1 also seemed to be resistant to race 3. This result may be reflected by the fact that the frequencies of races 1 and 3 were much lower than that of race 2 in the BSR pathogen population of the experiment field of TAES where a large number of genotypes resistant to race 1 had been cultivated for more than 20 years (Kondo et al 2005). A putative pleiotropic resistance gene Pga1 in Syumari that is resistant to races 1 and 3 of BSR and AFW on a locus located in the third linkage group also has been predicted (Han et al 2005;Takeda et al 2007).…”

“…Meanwhile, cultivar Akamame and wild adzuki bean Acc2515 were eventually determined to be completely resistant to all pathogens including BSR race 3, although resistance to AFW in Akamame and to all three races of BSR in Acc2515 have been reported (Kondo and Kodama 1989;Kondo et al 2005). Both cultivars Hatsune-shozu and Akeno-wase in group A, which were originally derived from Akamame, were previously developed BSR-tolerant cultivars (Adachi et al 1988;Shimada et al 1992), but we categorized them as susceptible in the present test because obvious foliar or stem symptoms were observed in artificial inoculation tests with races 1 and 3 of BSR.…”

“…The following isolates of C. gregata were used and deposited in NIAS Genebank (National Institute of Agribiological Science, Tsukuba, Japan): T96-1 (race 1, accession MAFF 241056), T96-5 (race 2, MAFF 241057), and T650 (race 3, MAFF 241055) (Kondo et al 1998(Kondo et al , 2005. Inocula for C. gregata were produced in liquid V8 juice medium (200 ml V8 juice containing 2 g CaCO 3 was centrifuged at 1,4009g for 15 min and the supernatant was diluted to 1 L with distilled water) at 25°C on a reciprocal shaker (TB-128, Takasaki Scientific Instrument, Kawaguchi, Japan) at 120 oscillations/min.…”

“…Although race 2 of BSR, that is virulent to these two cultivars, was discovered in 1995 (Kondo et al 1998, several cultivated and wild adzuki bean accessions resistant to both races 1 and 2 of BSR were selected as potential sources of BSR resistance for breeding programs ). However, Acc259, one of the accessions used as a gene donor for a pyramid-type resistance in new lines, was completely susceptible to a new race (race 3) (Kondo et al 2005). Thus, resistance to race 3 also needed to be considered in breeding for multiple resistances in adzuki bean.…”

“…We hypothesized that a considerable number of cultivars and lines of adzuki bean should be resistant to race 3; these were identified easily because Syumari and Kita-no-otome have been determined to be resistant to both races 1 and 3 (Kondo et al 2005), a pleiotropic resistance gene against both races, and predicted in both cultivars by specific DNA markers. The same markers for the resistance gene were indeed identified in several other cultivars (Takeda et al 2006).…”