**4. Genetics and chromosomal variations of potato**

which gave rise to domesticated diploid species, *Solanum stenotomum*, three otherswild species, namely *S. sparsipilum, Solanum acaule* and *Solanum megistacrolobum* were instrumental in evolution of present day cultivated potatoes. Some authors believed that *S. tuberosum* is a straight tetraploid of *S. stenotomum*but there are stronger evidences in support of the allotetraploid origin of *S. tuberosum* by hybridization between *S. stenotomum* and *S. sparsipilum* [11].

Potato tubers contain about 75% water, 21% carbohydrates (of which about 82% is starch), 2.5% protein and less than 1% fat. Often looked upon as primarily a starchy vegetable, pota-

potato. They also have fair amount of fibers (26% DV), proteins and minerals. The DVs are varied with different types of cultivars, various authors have been reported DVs of 46% for potassium, 33% for manganese, 21% for magnesium and 21% for phosphorus in large baked potato. Potatoes are rich source of essential amino acids which required for proper growth and development, hence it is considered as balanced and complete diet for adults. The flesh color varies according to genotypes and climatic conditions of cultivated area. The most common flesh color is white but other than this variety of flesh color cultivars evident in different countries. The carotenoids (yellow and orange colors) and anthocyanins (red and purple colors) are the two most valuable coloring pigments in potato. White-fleshed potatoes are low in carotenoids (<100 μg/100 g fresh weight) whereas, the carotenoid content of yellowfleshed varieties are higher (about 560 μg/100 g FW) [12]. Intense yellow to near orange flesh color, associated with carotenoid concentrations >2000 μg/100 g FW, have been reported in diploid *Solanum* germplasm [13]. The primary tuber carotenoids in potato tubers are lutein, zeaxanthin and violanxanthin, although some studies have also reported finding neoxanthin and antheraxanthin [13]. In the macula of the human eye, lutein and zeaxanthin are found and it also plays a role in reducing the risk of age-related macular degeneration. In addition, increased intake of zeaxanthin may improve mental acuity in the elderly. The anthocyanin concentration in tubers is 100-fold greater than carotenoids. The red fleshed of tubers is mainly due to the anthocyanin pigment pelogonidin-3-(p-coumaroyltutinoside)-5-glucoside (200–2000 μg/ g FW) and peonidin-3-(pcoumaroyl-rutinoside)-5-glucoside (20–400 μg/g FW) while, petunidin3-(p-coumaroyl-rutinoside)-5-glucoside (1000–2000 μg/g FW) and malvidin-3-(p-coumaroyl-rutinoside)-5-glucoside (2000–5000 μg/g FW) compounds of anthocyanin pigments are responsible for dark purple-fleshed potatoes [14]. There is increasing interest in anthocyanins in potato tubers because of their perceived higher antioxidant content, and ability to combat both prostate cancer and breast cancers. The potatoes with high glycemic index play important role in the diet of persons suffering from diabetes. During digestion, quick breakdown of food with high glycemic index leads to rapid rise of blood sugar level. The two major components of potato starch are amylose (20–25%) and amylopectin (75–80%). While cooking recrystallization of some portion of amylose leads to formation of resistance starch. Resistant starch acts as a dietary fiber. It passes through the small intestines and once in the large intestines microbial fermentation results in the production of small chain fatty acids,

. About 48% daily

are provided by a large (299 g) baked

toes are actually highly nutritious. It is a good source of vitamins C and B6

**3. Nutritional content of potato**

40 Potato - From Incas to All Over the World

values (DV) for vitamin C and 46% for vitamin B6

Breeding of potato is a cumbersome task due to inherent genetic and biological factors. To understand the genetics, we will first outline some important genetic and reproductive aspects of the potato. Potato has basic chromosome number as 12 and right from diploid to hexaploid species. Majority (about 73%) of the species are diploid followed by tetraploids (about 15%), hexaploids (about 6%), triploids (about 4%) and pentaploids (about 2%). The tuber-bearing *Solanum* species include several diploids (2n = 24), triploids (2n = 36) and a few tetraploids (2n = 48), and hexaploids (2n = 72). Many wild species of the series *Tuberosa* are diploid (*S. berthaultii, Solanum canasense, S. sparsipilum, S. vernei,* etc.) and the cultivated diploid (2n = 2× = 24) species*, S. stenotomum*, *S. phureja and S*. *ajanhuri*, of which former two are sexually fertile and the later one is less fertile and does not breed true. Triploid potato species are *S. chaucha* and *S. xjuzepczukii* derived from spontaneous crosses between diploid and tetraploid species. There are 3 cultivated diploid species, *S. stenotonomum, S. phureja* and *S.ajanhuri*. The cultivated potato *S. tuberosum and S. demissum* are autotetraploid species with chromosome number, 2n = 4× = 48 are usually fertile except in a number of highly bred clones outside South America. There is only one pentaploid species (2n = 60), that is, *S. curtilobum* which is reasonably fertile in crosses with *S. tuberosum*, but not in selfings. Nearly all the diploid species are self-incompatible while all the tetraploids and hexaploids are self-compatible [11].

#### **4.1. Genetic diversity for quality traits**

Genetic diversity is a prerequisite for an effective plant breeding program. It is a useful and essential tool for parent's choice in hybridization to develop high yield potential cultivars and to meet the diversified goals of plant breeding [15]. The cultivated potato have narrow genetic base due to limited introduction of germplasm from their natural range in South America [16]. Most of the potato cultivars are auto-tetraploid (2n = 4× = 48), highly heterozygous and out breeding species, which suffer from inbreeding depression. Cultivated potato species have a base chromosome number of n = 12 and may be diploid (2n = 2× = 24), triploid (2n = 3× = 36), tetraploid (2n = 4× = 48) or pentaploid (2n = 5× = 60). There are 7 cultivated potato species [6], whereas only 9 species and 141 intra-specific taxa have been identified [17]. Recent studies suggested that, genotyping of 742 landraces of all cultivated and wild species have been completed with SSR and chloroplast markers [18]. Based on these studies,


**6.** *S. phureja*: this species was cultivated from central Peru to Ecuador, Colombia, and Venezuela since the pre-Spanish era and is believed to have originated from *S. stenotomum* [6].

Breeding Potato for Quality Improvement http://dx.doi.org/10.5772/intechopen.71482 43

**7.** *S. stenotomum*: the species is diploid and cultivated from Central Peru to Central Bolivia. Most primitive form of cultivated potato. *S. stenotomum* shows the diversity within species, suggesting it to be the first domesticated potato derived from diploid wild species

In the field of nutrition, there are several topics such as food and nutritional security, dietary adequacy etc. which have been discussed most vigorously at global level. These all are well defined by the quality of the produce. Potato is the fourth most important food crop of the world. Quality of a potato tuber can be defined as the sum of favorable characteristics of the tuber, which is a subjective and dynamic concept that depends on consumer's tradition life-

Potato considered as an important source of nutrition for human diet. Potato tubers are good source of vitamin C and also having significant amount of 12 various essential amino acids along with minerals. In general, different cultivars have different uses. Red-skinned cultivars with low dry matter content, for example, are used for fresh market, whereas long types are

• **External quality:** this is the first category group which comprising the aspects such as skin color, tuber size and shape, eye depth [23]. Besides, dormancy and greening are additional important quality traits [24]. These traits are deemed very important for fresh consumption

• **Internal quality:** this represents the aspects such as nutritional properties, culinary value, after-cooking properties or processing quality. The traits such as dry matter content, flavor, reducing sugar, protein content, starch quality, type and amount of glycoalkaloids, enzymatic discoloration and other nutritional quality, etc. comprising the internal

The traits which are crucial aspects for consumers are tuber shape, eye depth, skin and flesh color, as these are immediately obvious while making the purchase [24]. Tuber shape is a syndrome of many characters that considers the length/width ratio for describing the overall shape, it varies from compressed/round to long [24]. The round shape of tuber mainly governed by a single locus on chromosome X with a dominant allele *Ro* reported that and other reports mention quantitative

where external traits are most likely to influence consumer's choice.

(**Table 2**).

**5. Quality traits of potato**

suitable for French fries.

quality of tuber [1].

*5.1.1. Fresh market*

**5.1. Inheritance of quality traits**

styles, food habits and the industrial process used.

There are two broad category groups of tuber quality:

**Table 2.** Species for important quality traits.

they reclassified the all cultivated potatoes in following four species: (i) *S. tuberosum*, with two cultivar groups (the *Andigenum* group – diploids, triploids and tetraploids and the *Chilotanum* group – tetraploid); (ii) *S. ajanhuiri* (diploid); (iii) *S. juzepczukii* (triploid) and (iv) *S. curtilobum* (pentaploid) [18].

