2013 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 been a rapid increase in the spot form of net blotch (SFNB) caused by P. teres f. maculata (Liu and Friesen 2010). However, analysis of isolates collected in 2010 and 2011 from Langdon and Fargo ND determined that NFNB is still prevalent and remains a major threat.
Pyrenophora teres f. teres isolates 15A and 6A, both of which were collected in California, produce different virulence factors and therefore were used to produce a sexual population segregating for virulence on different barley lines. This population was phenotyped on barley lines that have differential reactions to the parents (15A and 6A). The 15A x 6A population was also mapped with AFLP and SSR markers. More recently, we have used a genotyping by sequencing (GBS) approach to identify single nucleotide polymorphism (SNP) markers for use in developing a more saturated map for eventual gene discovery. Currently, we have identified at least eight genomic regions associated with virulence, with five of these regions accounting for at least 20% of the disease phenotype on a given barley line.