Node 1433
RosBREED’s Jewels in the Genome: Self-Fertility
in Cherry
Author:
Dr. Amy Iezzoni
An individual’s genome is the full complement of genetic information inherited from its parents.
Within this vast repertoire of genetic information, individual genes are being discovered that
control critical production and fruit quality traits. As valuable rosaceous gene discoveries are
made and put into breeding applications, we describe them as “Jewels in the Genome.”
Introduction
The S-locus is selected as one of RosBREED’s “Jewels in the Genome," because
knowledge of S-locus variants is leading to more efficient breeding of self-fertile
varieties of cherry, almond, apricot and plum.
Self-Fertility
Self-fertility is the ability to set fruit following self-pollination. Self-fertility contributes to
higher more consistent yields in many Prunus species, because pollen from selfincompatible almond, sweet cherry, tart cherry, plum, and apricot cultivars is unable to
grow the length of its own pistil. In self-fertile selections, pollen borne in a flower is able
to successfully grow down the style, resulting in self-fertilization and fruit set. Selffertile varieties have the advantage of not requiring orchard space for “pollinator”
varieties. Additionally, self-fertile varieties characteristically have higher yields than selfincompatible varieties, as compatible (“self”) pollen is always available at the perfect
time.
Genetic Control of Self-Fertility
For many Prunus species; such as almond, sweet cherry, tart cherry, apricot, and plum;
we know the two major genes that control self-fertility! These two genes reside at the Slocus on stone fruit chromosome 6. One gene is expressed in the style and encodes a
cytotoxic ribonuclease, called the S-RNase. The second gene, expressed in the pollen,
encodes an F-box protein, named SFB,that interacts with the S-RNase in an allele
specific manner. All of the self-fertile alleles described to date in these Prunus species
disrupt either the S-RNase function in the style or the SFB function in the pollen, leading
to self-fertility (Fig.1).
Figure 1: Incompatible versus compatible pollination: If the S-allele in the pollen matches
the S-allele in the style, pollen growth is arrested in the style. When all pollen is
incompatible, fertilization does not occur and the fruit does not develop. However, when
the S-allele in the pollen has a mutation that causes it to be self-fertile (Sf), pollen grows
the length of the style, fertilization is successful, and fruit development follows. Photo
credit: Michigan State University.
Variation and Detection
Knowledge of genetic changes in S-RNase and SFB that lead to self-fertility has resulted
in the development of simple diagnostic tests to screen progeny for self-fertility early in
a breeding program. For example, the S-allele in the self-fertile sweet cherry varieties,
‘Lapins’ and ‘Sweetheart’, is called S4' (Boškovic et al. 2000). This allele has a four base
pair deletion in the S4 SFB gene that results in the production of a shortened nonfunctional SFB protein. Pollen containing non-functional SFB protein is self-fertile and
compatible on styles of all other cherry varieties. The DNA diagnostic test for selffertility simply involves differentiating between S4 and S4', which can be
accomplished by resolving the four base pair difference. Identification of self-fertile
variants enables breeders to select parental combinations that maximize their chances
of obtaining self-fertile offspring.
Reference Cited

Bošković R., Tobutt K.R., Schmidt H., and T. Sonneveld. 2000. Re-examination of
(in)compatibility genotypes of two John Innes self-compatible sweet cherry selections.
Theoretical and Applied Genetics: 101:234-240.
Funding statement
Development of this page was supported in part by the USDA's National Institute of
Food and Agriculture (NIFA). Project title: RosBREED: Enabling marker-assisted
breeding in Rosaceae is provided by the Specialty Crops Research Initiative Competitive
Grant 2009-51181-05808. Any opinions, findings, conclusions, or recommendations
expressed in this publication are those of the author(s)and do not necessarily reflect the
view of the United States Department of Agriculture.