2013 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.
A four-year evaluation (2009-2012) for stalk and head rot has been conducted for the backcrossed progenies derived from different ploidy wild perennial Helianthus species. For stalk rot evaluation in 2012, 26 of 62 families of hexaploid H. californicus (crossed with HA 410), nine of 37 progenies derived from five interspecific amphiploids (crossed with HA 410), 12 of 55 families derived from three diploid species (crossed with HA 410), and nine of 94 families derived from two diploid species (crossed with HA 441) had 0% infection in 2012. For head rot, 21 of 95 backcross families derived from two diploid species (crossed with HA 441) and two of 87 families derived from other crosses had 0-1.0 infection, with additional 68 families with 1.1-3.0 infection rating. This high frequency of families with moderate to good resistance in replicated field tests suggests successful gene introgression for head rot and stalk rot resistance. Progeny families susceptible in previous years will be further eliminated. The outstanding families will be prepared for germplasm release, cytogenetic and molecular study, and QTL mapping population preparation. Over 200 advanced backcross progeny families were grown in Fargo in 2012 to provide a continuous seed supply of materials for field evaluation. There was an extensive effort to make new crosses between perennial H. hirsutus, H. salicifolius, H. occidentalis, H. divaricatus, and H. resinosus with HA410 and/or HA451. BC1F1 progeny were successfully obtained using F1 plants as the female or male parent aided by embryo rescue. Over 400 BC1F2 families/rows have been planted in 2013 field for seed increase, and the BC1F3 families will be evaluated for both stalk and head rot resistance in 2014.