2012 Annual Report
1a.Objectives (from AD-416):
The objective of this proposal is to characterize the NDB112 barley population for resistance to the spot form of net blotch (SFNB) on barley. The HN population has been developed over the last several years and has been mapped with several hundred markers for use in characterizing disease resistance, including spot form net blotch resistance.
1b.Approach (from AD-416):
The Hector × NDB112 (HN) population was developed for the characterization of NFNB, SFNB, and spot blotch of barley. NDB112 contains the spot blotch resistance that is currently being used in most Midwestern 6-row barley varieties. NDB112 also harbors resistance to NFNB, but is susceptible to SFNB. Hector however harbors resistance to SFNB, therefore this population can be used for the identification and characterization of each of these diseases. Previously, a molecular map for HN population was developed. The current map contains a combination more than 300 single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers spread across all 7 barley chromosomes. Given the segregation of SFNB resistance and the level of molecular marker coverage, this population can be effectively used for evaluating SFNB resistance coming from Hector barley.
Phenotypic analysis - Individual lines will be planted and inoculated with conidia of P. teres f. maculata at the two- to three-leaf stage. Following inoculation, plants will be placed in 100% relative humidity in the light at 21°C for 24 h, and then placed in a controlled growth chamber under a 12-h photoperiod at 21°C. Disease reactions will be evaluated seven days post-inoculation. Disease evaluations will be done using a 1-5 scale where reaction type 1 is resistant and reaction type 5 is susceptible. The HN populations will be evaluated for reaction to multiple P. teres f. maculata isolates collected from various regions of North America and the world to thoroughly evaluate the resistance present. P. teres f. maculata isolates to be used will include several collected in North Dakota, as well as Australia, New Zealand, and Europe. The evaluation of isolates from diverse geographical locations will provide understanding of the potential durability of the resistance identified in the HN population.
Net blotch of barley has long been a problem for North Dakota barley producers and until recently the net form of net blotch (NFNB) caused by P. teres f. teres has been the predominant form of the disease. Recently there has also been a rapid increase in the spot form of net blotch (SFNB) caused by P. teres f. maculata (Liu and Friesen 2010), however isolates collected in 2010 and 2011 from Langdon and Fargo, ND determined that the NFNB is still prevalent and remains a major threat.
Evaluation of the virulence effectors corresponding to the already identified barley susceptibility genes on chromosome 6H varieties Rika and Kombar has been initiated. A pathogen population segregating for virulence on Rika and Kombar has been mapped using 35 SSR markers and 212 AFLP markers. This map consists of 192 total markers assembled into 24 linkage groups of 3 or more markers each. QTL analysis using disease reaction data collected on several barley lines including Rika, Kombar, TR306, Hazera, CI11558, CIho497, PI356715, and PI 399482. Four linkage groups/markers showed significant QTLs that were associated with different barley lines. QTL1 was identified in barley lines Rika, CI11458, TR306, and PI399483 and explained as much as 26% of the disease variation. QTL1 was the only significant locus identified on these lines. Two QTLs (QTL1 and QTL2) were identified when inoculating barley lines Rika and Kombar, accounting for 22-23% and 18-21% respectively. One additional Barley line, PI356715, showed a different QTL that alone accounted for 47% of the disease variation indicating a single major virulence in the pathogen that is likely specific to a single susceptibility in that host line.