ARS | Publication request: Determination of fire blight resistance and construction of a molecular genetic map in a bi-parental Malus sieversii population

Submitted to: Fire Blight International Workshop
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 2010
Publication Date: August 16, 2010
Citation: Lalli, D., Norelli, J.L., Malnoy, M., Pindo, M., Fazio, G., Forsline, P.L., Aldwinckle, H.S., Gardiner, S.E., Chagne, D., Wisniewski, M.E. 2010. Determination of fire blight resistance and construction of a molecular genetic map in a bi-parental Malus sieversii population [abstract]. Fire Blight International Workshop. p. 117.

Technical Abstract: Malus sieversii (Ms) is believed to be the main progenitor of the domestic apple. Ms PI613981 is elite scion material collected at a xerophytic site in Kazakhstan from a tree free of disease and insect damage. The F1 family GMAL4593 [‘Royal Gala’ (RG) X PI631981] is segregating for resistance to both apple scab and fire blight. Six replicates of each of 190 GMAL4593 seedlings were grafted to seedling rootstock and phenotyped for fire blight resistance in the greenhouse. When vigorously growing shoot tips of the grafted plants were scissor-inoculated with Erwinia amylovora Ea273, the percent of the current season’s shoot length necrotic for individual members of the population ranged from 4 to 94%. Four replicates of each of the 190 GMAL4593 seedlings were established in the field and are currently being phenotyped for fire blight resistance. To enable QTL analysis of this and other important traits in Ms, we have undertaken the construction of a genetic framework map for the 190 seedlings of GMAL4593 using Joinmap® 3.0. Of 187 SSR primer combinations screened, 104 SSRs were polymorphic within the family. Fifty-nine segregated in both Ms and RG, 16 segregated in Ms only and 29 in RG only. Additionally, approximately 500 SNPs were screened in a subset (96) of the population of which approximately 300 SNPs were informative for mapping. Forty SNPs segregated in both Ms and RG, 218 in RG only and 36 in MS only. The current RG map consists of 170 molecular markers (117 SNPs and 53 SSRs) assigned to 17 linkage groups, and the Ms map consists of 118 molecular markers (57 SNPs and 61 SSRs) assigned to 17 linkage groups. A significant association was found between markers on linkage group 8 and fire blight resistance using MapQTL® 6.0. To better define this putative QTL, additional markers are being added to the map.