Novel Sources of Wheat Head Blast Resistance in Modern Breeding Lines and Wheat Wild Relatives

• Published in: Plant disease Vol. 104; no. 1; p. 35
• Main Authors: Cruppe, Giovana, Cruz, Christian D, Peterson, Gary, Pedley, Kerry, Asif, Mohammad, Fritz, Allan, Calderon, Lidia, Lemes da Silva, Cristiano, Todd, Tim, Kuhnem, Paulo, Singh, Pawan K, Singh, Ravi P, Braun, Hans-Joachim, Barma, Naresh C D, Valent, Barbara
• Format: Journal Article
• Language: English
• Published: United States 01-01-2020
• Subjects: Asia; Bolivia; Brazil; Breeding; Disease Resistance - genetics; Plant Diseases - microbiology; Triticum - genetics; Triticum - microbiology; Brazil; Bolivia; Asia; genetic resistance; 2NVS translocation; Magnaporthe oryzae triticum; wheat head blast
• ISSN: 0191-2917
• DOI: 10.1094/pdis-05-19-0985-re

Wheat head blast (WHB), caused by the fungus
pathotype
, is a devastating disease affecting South America and South Asia. Despite 30 years of intensive effort, the 2N
S translocation from
contains the only useful source of resistance to WHB effective against
isolates. The objective of this study was to identify non-2N
S sources of resistance to WHB among elite cultivars, breeding lines, landraces, and wild-relative accessions. Over 780 accessions were evaluated under field and greenhouse conditions in Bolivia, greenhouse conditions in Brazil, and at two biosafety level-3 laboratories in the United States. The
isolates B-71 (2012), 008 (2015), and 16MoT001 (2016) were used for controlled experiments, while isolate 008 was used for field experiments. Resistant and susceptible checks were included in all experiments. Under field conditions, susceptible spreaders were inoculated at the tillering stage to guarantee sufficient inoculum. Disease incidence and severity were evaluated as the average rating for each 1-m-row plot. Under controlled conditions, heads were inoculated after full emergence and individually rated for percentage of diseased spikelets. The diagnostic marker Ventriup-LN2 was used to test for the presence of the 2N
S translocation. Four non-2N
S spring wheat International Maize and Wheat Improvement Center breeding lines (CM22, CM49, CM52, and CM61) and four wheat wild-relatives (
TA10142, TA1624, TA1667, and TA10140) were identified as resistant (<5% of severity) or moderately resistant (5 to <25% severity) to WHB. Experiments conducted at the seedling stage showed little correlation with disease severity at the head stage.
isolate 16MoT001 was significantly more aggressive against 2N
S-based varieties. The low frequency of WHB resistance and the increase in aggressiveness of newer
isolates highlight the threat that the disease poses to wheat production worldwide and the urgent need to identify and characterize new resistance genes that can be used in breeding for durably resistant varieties.