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. 2011 May;156(1):275-85.
doi: 10.1104/pp.110.167577. Epub 2011 Mar 25.

Distribution of SUN, OVATE, LC, and FAS in the Tomato Germplasm and the Relationship to Fruit Shape Diversity

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Free PMC article

Distribution of SUN, OVATE, LC, and FAS in the Tomato Germplasm and the Relationship to Fruit Shape Diversity

Gustavo R Rodríguez et al. Plant Physiol. .
Free PMC article

Abstract

Phenotypic diversity within cultivated tomato (Solanum lycopersicum) is particularly evident for fruit shape and size. Four genes that control tomato fruit shape have been cloned. SUN and OVATE control elongated shape whereas FASCIATED (FAS) and LOCULE NUMBER (LC) control fruit locule number and flat shape. We investigated the distribution of the fruit shape alleles in the tomato germplasm and evaluated their contribution to morphology in a diverse collection of 368 predominantly tomato and tomato var. cerasiforme accessions. Fruits were visually classified into eight shape categories that were supported by objective measurements obtained from image analysis using the Tomato Analyzer software. The allele distribution of SUN, OVATE, LC, and FAS in all accessions was strongly associated with fruit shape classification. We also genotyped 116 representative accessions with additional 25 markers distributed evenly across the genome. Through a model-based clustering we demonstrated that shape categories, germplasm classes, and the shape genes were nonrandomly distributed among five genetic clusters (P < 0.001), implying that selection for fruit shape genes was critical to subpopulation differentiation within cultivated tomato. Our data suggested that the LC, FAS, and SUN mutations arose in the same ancestral population while the OVATE mutation arose in a separate lineage. Furthermore, LC, OVATE, and FAS mutations may have arisen prior to domestication or early during the selection of cultivated tomato whereas the SUN mutation appeared to be a postdomestication event arising in Europe.

Figures

Figure 1.
Figure 1.
Tomato fruit shape categories adapted from UPOV (2001) and IPGRI (1996). Each fruit is identified by variety name (information available at http://solgenomics.net/) and presence of mutation in the SUN, OVATE, LC, and/or FAS genes (abbreviated as S, O, LC, and F, respectively).
Figure 2.
Figure 2.
Population structure of 116 tomato accessions using STRUCTURE software and 29 markers (25 randomly distributed markers and SUN, OVATE, LC, and FAS). The coefficients of estimated ancestry per accession in each cluster were represented by an individual bar, where each color refers to a distinct cluster. The name of the accession is below the bar whereas the notation above the bar indicates germplasm class. CA, Contemporary U.S.; Ce, cerasiforme; RI, regional Italian; CI, contemporary Italian; LA, regional Latin American; S, regional Spanish; He, U.S. Heirloom; and Ot, other. The black squares indicate accessions carrying OVATE; the white circles indicate accessions carrying LC; the stars indicate accessions carrying FAS; and accessions carrying SUN are listed in red. The fruit shape category is written on each bar. Ov, Obovoid; R, rectangular; Ro, round; H, heart; Ox, oxheart; L, long; F, flat; and E, ellipsoid.
Figure 3.
Figure 3.
Model of the evolution of fruit shape variation in tomato. The tomato domestication most likely occurred in Latin America starting with round wild-type tomato var. cerasiforme accessions. LC arose first in the cerasiforme background, resulting in round or flat tomatoes. The OVATE mutation arose in a different ancestral population than LC but also in the cerasiforme background, resulting in ellipsoid fruit. FAS arose in the cerasiforme LC background around the same time as OVATE, resulting in flat and highly loculed fruit. The presence of OVATE, LC, and FAS mutant alleles in the Latin American germplasm suggest they arose early or prior to domestication of tomato. The SUN mutation arose postdomestication in Europe, most likely in the LC background of a cultivated tomato and resulting in long fruit. It is also possible that SUN arose in the LC and FAS mutant background, resulting in an oxheart fruit. [See online article for color version of this figure.]

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