A Unique Cytoplasmic-Nuclear Interaction in Sunflower ( Helianthus annuus L.) Causing Reduced-Vigor Plants and the Genetics of Vigor Restoration.

WildHelianthusspecies are an important genetic resource for sunflower improvement, but sometimes there are adverse interactions between the wild and cultivated sunflowers. This study reports the inheritance of reduced vigor and its restoration resulting from an interaction of perennialHelianthuscytoplasms with nuclear genes of cultivated sunflower lines. The large number of vigor restoration (V) genes identified in cultivated lines are all located at the same locus, designatedV(1), suggesting a common origin of these genes. AdditionalVgenes derived from the wild perennial speciesH. giganteusL. andH. hirsutusRaf. are located at a different locus thanV(1), designatedV(2). A major difference between the wild annualHelianthuscytoplasms and perennial cytoplasms is the lack of the vigor-reducing cytoplasms, but surprisinglyVgenes were observed in wild annualH. annuusL. andH. petiolarisNutt. which were at the same locus asV(1). A common vigor-reducing cytoplasmic effect of the perennialHelianthusspecies and the existence of a common vigor restorationVgene in most perennialHelianthusspecies could be explained as a result of vigor selection duringHelianthusspeciation.V(1)was mapped on linkage group (LG) 7 of the sunflower genome, using an F(2)population derived from MOL-RV/HA 821.V(1)co-segregated with an InDel marker ZVG31, with three single-nucleotide polymorphism (SNP) markers, SFW01024, SFW07230, and SFW00604, located above it on the map at a genetic distance of 0.8 cM, and another SNP marker, SFW08671, below it at a distance of 0.4 cM. The physical distance between the two closest flanking SNP markers corresponds to 0.56 and 1.37 Mb on the HA 412-HO and XRQ assemblies, respectively. The tightly linked markers will help select normal vigor progenies when using perennialHelianthuscytoplasms in a breeding program, which will also provide a basis for studying the mechanism of the cytonuclear interaction, and the speciation of annual and perennialHelianthusspecies.