Pollen flow in a flowering dogwood (Cornus florida L.) orchard: using SSRs to develop a quantitative trait loci mapping population
Flowering dogwood (Cornus florida L.) is an ornamental tree prized for its long-lasting spring blooms, beautiful red fruit, attractive fall color, and graceful architecture. One of the most problematic diseases of C. florida is dogwood powdery mildew (PM) caused by Erysiphe pulchra. One advanced selection in the Rutgers dogwood breeding program, H4AR15P25, shows excellent resistance to PM. The quantitative trait loci (QTLs) underlying this resistance will be investigated and mapped in a pseudo F2 population using genotyping by sequencing-derived single nucleotide polymorphism markers. To expedite population development, open-pollinated seeds were harvested in 2017 from H4AR15P25 grown in an isolated crossing block. The crossing block contained 16 different PM-susceptible C. florida breeding selections and cultivars spaced in various locations from the target tree. The seeds were germinated and 636 of the resulting seedlings were genotyped with 8 simple sequence repeat markers to determine pollen parents and examine pollen flow within the crossing block. Using CERVUS 3.0.7, the pollen parents of 531 seedlings were assigned with 95% confidence and 52 seedlings with 80% confidence. Interestingly, 53 seedlings could not be assigned, with 31 possessing one or more alleles that weren't present in the pollen parents, indicating pollen flow from outside sources. Results showed that distance from the seed parent, H4AR15P25, strongly influenced the proportion of progeny assigned to a given pollen parent. Two hundred and two progenies were identified from H4AR15P25 × H4AR15P28 (closest tree to seed parent) and 196 selected for the QTL mapping population. This study highlights the dynamics of pollen flow in an isolated block of dogwood trees and supports our goal to elucidate the genetics of PM resistance from H4AR15P25 and ultimately develop a means for marker assisted selection to more efficiently breed PM resistant C. florida.
Pfarr, E.L., Vaiciunas, J., Kubik, C., Capik, J., Honig, J. and Molnar, T.J. (2021). Pollen flow in a flowering dogwood (Cornus florida L.) orchard: using SSRs to develop a quantitative trait loci mapping population. Acta Hortic. 1331, 57-62
simple sequence repeats, Cervus, open-pollinated, mapping population development