Evaluation of triticale accessions for resistance to wheat bacterial leaf streak caused by Xanthomonas translucens pv. undulosa

The bacterium Xanthomonas translucens pv. undulosa (Xtu) causes bacterial leaf streak (BLS) on wheat and other small grains. Several triticale accessions were reported to possess high levels of resistance to wheat Xtu strains. In this study, a worldwide collection of triticale accessions as well as the major North Dakota hard red spring and durum wheat cultivars were evaluated for reaction to two local Xtu strains. All wheat cultivars showed a susceptible reaction but a wide range of reactions was observed among triticale accessions. Out of the 502 accessions tested, 45 and 10 accessions were resistant to the two virulent strains BLS‐LB10 and BLS‐P3, respectively, with five accessions, PI 428736, PI 428854, PI 428913, PI 542545 and PI 587229, being highly resistant to both strains. Statistical analysis showed significant difference among the accessions, strains, and the accession by strain interaction (P < 0.001). Bacterial population growth in resistant triticale was significantly slower than that in susceptible triticale. Molecular cytogenetic characterization in four representative triticale accessions confirmed the hexaploid level of the species and the presence of 12 or 14 rye chromosomes. The triticale accessions identified are valuable materials for developing wheat germplasm with high levels of BLS resistance.