2011 Annual Report
1a.Objectives (from AD-416)
1) Identify resistant wild Helianthus species populations.
2) Transfer resistance genes into a cultivated background.
3) Study the inheritance of resistance.
1b.Approach (from AD-416)
The head rot evaluation misting facility at Carrington, ND, will be used as the primary site for field Sclerotinia head rot evaluation of wild Helianthus interspecific hybrids and early generation progenies when materials become available. Backcrossed progenies of interspecific hybrids or from amphiploids will be evaluated in replicated field plots as soon as the plants reach 2n=34 chromosomes and have sufficient seeds from either self-pollination or further backcrosses. The field evaluation will be conducted every year as more progeny families are produced.
Five cross combinations between amphiploids, head rot resistant wild sunflower, or stalk rot resistant wild sunflower will be made with HA 441 or HA 410, followed by backcrossing to obtain new resistant lines. For inheritance studies, these new resistant lines will be crossed with susceptible inbred line HA 234, and disease evaluations will be conducted on F1, F2, and F3 progeny families. Due to the quantitative nature of Sclerotinia resistance and low probability of obtaining the resistant recombinant, the number of 2n=34 progeny families for field test will be continuously increased throughout the years of the project. In addition, 2n=36 plants from selfed 2n=35 plants, expected to be disomic additions, will be tested in the field to identify major resistance QTLs associated with specific chromosomes. If major resistance QTLs are found, their transfer into lines HA 410 or HA 441 will be followed and the disomics will be located to specific linkage groups of the sunflower RFLP map.
Eight Sclerotinia-resistant diploid accessions, one hexaploid, and five interspecific amphiploids have been successfully crossed with Sclerotinia-tolerant cultivated lines, backcrossed and selfed to produce progeny families for field evaluation. Replicated field tests of 313 progeny families screened for stalk rot resistance at Carrington, ND in 2009 and 2010 showed good introgression of resistance genes. In addition, 100 new families with seed increased in 2009 were added to the 2010 field evaluation. In 2011, we eliminated the heavily infected families from 2009 and 2010, and further evaluate 223 lightly infected families. The head rot evaluation in 2010 failed due to unexpected midge infestation. The 2010 head rot evaluation was repeated in 2011 with 96 families, with eliminations based on 2009 results. A protocol using genomic in situ hybridization (GISH) to distinguish between chromosomes of perennial Helianthus species and cultivated sunflower has been established providing a new tool for studying gene transfer. A molecular tracking study utilizing SSR markers indicated a higher frequency of gene introgression from diploid perennials than from hexaploid or interspecific amphiploids, suggesting an advantage in using diploid perennials. Molecular tracking using SSR markers suggested a higher frequency of gene introgression when perennial diploids species were used. In 2010, eight accessions from three diploid and one tetraploid perennial species were crossed with HA 410 and HA 451 and are being backcrossed. The new crosses will provide more diverse resistance genes for developing Sclerotinia resistant germplasm.
The ADODR monitors research progress by semiannual meetings with the Cooperator's personnel and by site visits to field plot locations.