Node 1434
RosBREED’s Jewels in the Genome: Crisp
Juicy Apples with Pleasing Acidity
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 Ma locus is selected as one of RosBREED’s “Jewels in the Genome,”
because the Ma locus simultaneously provides predictions for three high priority
traits: acidity, crispness, and juiciness. Identification of Ma locus alleles allows
breeders to make desirable parental combinations and select seedlings with
superior performance prior to field planting.
Apple Texture and Taste
Crisp, juicy apples with pleasing acidity are highly desirable for the fresh market.
However, obtaining the optimum combination of these desirable textural and taste
attributes has been challenging. Soft, mealy, poor tasting apples frequently occur in
breeding populations. A region on linkage group (LG) 16 contains gene(s) that influence
apple crispness and juiciness (King et al. 2001).
Ma Locus
In apple (and many other fruits), malic acid is a major contributor to fruit acidity.
Interestingly, the locus that controls malic acid level in apple, named Ma, is also located
near the top of apple LG 16 (Maliepaard et al. 1998). Alleles for the Ma locus in apple
are associated with a wide range of eating quality. For example, some types appear to
be associated with desirable tart crisp juicy apples, other types with just crisp or tart
apples, and some with poor quality for all these traits. The Ma locus is currently under
detailed investigation in RosBREED (Fig. 1), and is already revealing much wider
diversity in U.S. breeding germplasm than originally reported in European apple
populations
Figure 1. Evaluating crispness with a Mohr Digi-Test. Photo credit: Kate Evans,
Washington State University.
References Cited
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King G.J., Lynn J.R., Dover C.J., Evans K.M., and G.B. Seymour. 2001. Resolution of
quantitative trait loci for mechanical measures accounting for genetic variation in fruit
texture of apple (Malus pumila Mill.). Theoretical and Applied Genetics 101: 1227-1235.
Maliepaard C., Alston F.H., van Arkel G., Brown L.M., Chevreau E., Dunemann F.,
Evans K.M., Gardiner S., Guilford P., van Heusden AW, Janse J, Laurens F, Lynn JR,
Manganaris AG, den Nijs APM, Periam N, Rikkerink E, Roche P, Ryder C, Sansavini S.,
Schmidt H., Tartarini S., Verhaegh J.J., Vrielink-van Ginkel M., and G.J. King. 1998.
Aligning male and female linkage maps of apple (Malus pumila Mill.) using multi-allelic
markers. Theoretical and Applied Genetics 97: 60-73.
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.