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Wild tomato species have been widely used for improvement of tomato disease resistance but have not been extensively explored for health-related traits. In this work, three interspecific populations derived from backcrosses between cultivated tomato and Solanum pimpinellifolium (LA1589), S. habrochaites (LA1223), and S. peruvianum (LA2172) were analyzed for water-soluble antioxidant activity, phenolic content, vitamin C content, and basic agronomic traits including fruit weight, shape, and color. The wild species accessions significantly exceeded S. lycopersicum for all three antioxidant traits with only one exception: vitamin C content in S. habrochaites LA1223. Several populations and traits showed transgressive segregation indicating that the backcross populations contained individuals with allele combinations that allowed antioxidant activity/content to exceed that of both parents. The S. habrochaites LA1223 population provided the best starting material for improvement of water-soluble antioxidant activity and phenolics content with 20% and 15% of the population, respectively, significantly exceeding the parental values for these traits. Moreover, the S. habrochaites population contained individuals that had nearly 2-fold more water-soluble antioxidant activity and phenolic content than cultivated tomato. The S. peruvianum LA2172 population was best for improvement of vitamin C content with 3-fold variation for the trait and individuals, which had twice as much vitamin C as cultivated tomato. Tomato, Solanum lycopersicum (syn. Lycopersicon esculentum), is a member of the Solanaceae, a plant family of more than 3000 species including the economically important crops potato, eggplant, pepper, and tobacco. Tomato ranks second after potato as the most consumed vegetable of this family. Currently, tomato is grown in almost all countries worldwide. However, the origins of tomato are believed to be in western South America: Chile, Bolivia, Ecuador, and the coastal region of Peru (Razdan and Mattoo, 2007) where wild tomato species, including S. pimpinellifolium, S. pennellii, S. habrochaites, S. peruvianum, S. chmielewskii, and S. chilense, are still found (Peralta et al., 2006). Wild tomato species are sources of both desired and undesired traits. S. peruvianum (syn. L. peruvianum) is genetically and morphologically the most diverse of the wild tomatoes (Peralta et al., 2005). It is so polymorphic that S. peruvianum was divided into varieties including dentatum (Dunal) and humifusum (M€uller). S. peruvianum has green fruits, is typically self-incompatible, and allogamous. This species is also known for its virus, bacteria, fungi, aphid, and nematode resistances and has been widely used to introduce these traits into cultivated tomato (Robertson and Labate, 2007). S. habrochaites (syn. L. hirsutum) is another wild species used in the improvement and breeding of tomatoes. It has green fruits like S. peruvianum and is self-incompatible. S. habrochaites has a wide range of biotic and abiotic stress tolerances such as bacterial (Francis et al., 2001; Kabelka et al., 2002), fungal (Zhang et al., 2003), viral (Momotaz et al., 2005), insect (Musetti and Neal, 1997; Snyder et al., 1993), and cold (Veneema et al., 2000) resistances. Many of these resistances have been incorporated into cultivated tomato by backcross breeding (Hajjar and Hodgkin, 2007; Kalloo, 1991). S. pimpinellifolium (syn. L. pimpinellifolium) is a self-compatible tomato with red fruit. It is autogamous and facultatively allogamous. It is closely related to S. lycopersicum (Peralta and Spooner, 2007) and has been used in breeding to improve fruit color and quality (Causse et al., 2007). To date, most of the work using wild species for improvement of tomato has focused on biotic stress resistance. In comparison, only superficial and partial assessment of genetic variation for abiotic stress and nutritional factors such as antioxidant compound content has been made in wild tomato species (Causse et al., 2007). Tomato is rich in various vitamins, antioxidants, and secondary metabolites (Adalid et al., 2004). The most abundant of these molecules are vitamin C, lycopene, b-carotene, and phenolics. These compounds are all known antioxidants, which are reported to be important for human health as well as a plant defense to abiotic and biotic stresses (Khachik et al., 2002). However, during domestication and later breeding, farmers and plant breeders focused on agronomically important traits of tomato such as fruit weight, color, shape, and disease resistance. Now that we know the genetic mechanisms of some of these phenotypic traits, it is possible to breed agricultural plants with more precision for what is needed. Often the best source for improvement of a crop plant is its wild species (Tanksley and McCouch, 1997). Wild species retain allelic (trait) diversity, which has been lost during domestication and breeding. In this work, antioxidant and agronomic traits of three wild tomato species accessions, S. peruvianum LA2172, S. habrochaites LA1223, and S. pimpinellifolium LA1589, were compared with cultivated tomato. Antioxidant traits are of interest to consumers and plant breeders for their health-related contributions as well as their importance in plant resistance to biotic and abiotic stresses. The main aim of this work was to determine the potential of these wild species accessions for improvement of different traits. These results can be used in designing a breeding program to improve elite tomato lines for antioxidant characteristics. Materials and Methods The S. peruvianum advanced backcross BC2F2 population was obtained by crossing S. lycopersicum (TA496) as the cultivated recurrent parent with S. peruvianum (LA2172) as the wild donor parent. TA496 is the processing tomato line E6203 with the addition of tomato mosaic virus resistance. Because crossability barriers between S. peruvianum LA2172 and S. lycopersicum prevent normal development of F1 seeds, ovule culture was used to rescue the hybrids as described in Doganlar et al. (1997). F1 hybrids were then backcrossed to TA496 for two generations with no further need for ovule culture. Self-pollination of the BC2F1 families resulted in the BC2F2 families that were used in this work. Overall, the Peruvianum population contained 88 lines. For the Habrochaites studies, a BC2F2 population was developed by crossing S. lycopersicum (TA1166) as the recurrent parent and S. habrochaites (LA1223) as the donor parent. TA1166 is a fresh-market inbred line (5TSS802 from Harris Moran). Population development was the same as for the Peruvianum population except that ovule culture was not necessary. The Habrochaites population contained 151 lines. Received for publication 13 Feb. 2014. Accepted for publication 5 June 2014. This project was supported by grants from Izmir Institute of Technology (BAP projects 2002-IYTE-29 and 2004-IYTE-38). We are grateful to Öykum Kırsoy Bektas x, Mehmet Ali Kec xeli, Hasan Özg€ur Sxığva, and Yeliz T€umbilen for assistance with antioxidant trait measurements. We also thank MultiTarim Seed Co. and the Aegean Agricultural Research Institute for growth of plant materials. To whom reprint requests should be addressed; e-mail samidoganlar@iyte.edu.tr. HORTSCIENCE VOL. 49(8) AUGUST 2014 1003 The Pimpinellifolium studies were performed with a BC2F9 population that was developed by crossing recurrent parent S. lycopersicum (TA209) and S. pimpinellifolium (LA1589), the wild donor parent. TA209 is processing line E6203 without virus resistance. One F1 hybrid was selected from the interspecific cross and backcrossed to TA209. A total of 27 BC1 plants were then selected based on presence of the sp locus on chromosome 6 so that all progeny plants had determinate growth. These selected individuals were backcrossed to TA209 to produce the BC2 population. BC2F1 individuals were then selfed for eight generations to produce the BC2F9 population. The Pimpinellifolium population contained 109 lines. The Peruvianum population and parental lines were grown in the field at MultiTarim Seed Co., Antalya, Turkey, from late March to June 2006. The Habrochaites population and parents were also field-grown in Antalya from early April to July 2007. During the growing season, mean minimum temperature ranged from 11 to 22 C, whereas mean maximum temperature ranged from 21 to 34 C. Ten plants of each population and parental line were grown and were transplanted in double rows with 140-cm wide rows and 50-cm narrow row spacing. Double-row spacing is common in coastal regions and provides shade for fruit. Plants were spaced at 40 cm within rows. Soil was loamy and well-drained and fertilized with 15:15:15 fertilizer and 50 t composted manure per hectare before transplanting. Plants were drip-irrigated with fertigation (1.4 dS·m electrical conductivity value) during the growing season (1:2:1 until first fruit set, 2:1:1 until first ripe fruit, 1:1: 2 after first ripe fruit). The Pimpinellifolium population was grown in the field at the Aegean Agricultural Research Institute, Izmir, Turkey, from late April to early Aug. 2006. During the growing season, mean minimum temperature ranged from 11 to 22 C, whereas mean maximum temperature ranged from 21 to 33 C. Ten plants of each population and parental line were grown in single rows with 140 cm between rows and 40 cm between plants within rows. The soil at the Izmir site was sandy loam and was fertilized with 30 kg·d potassium sulfate, 25 kg·d di-ammonium phosphate, and 10 kg·d ammonium sulfate before transplanting. Plants were drip-irrigated with 30 kg·d ammonium nitrate and 10 kg·d potassium nitrate fertilizer. Plants were treated three times with 2% calcium nitrate to prevent blossom-end rot during fruit development. At both locations, fruit were harvested at the normal ripe market stage with samples bulked from the different plants for each line. Total water-soluble a

Exploration of Three Solanum Species for Improvement of Antioxidant Traits in Tomato