Effects of domestication on structural polysaccharides and dietary fiber in nopalitos (Opuntia spp.)

• Published in: Genetic resources and crop evolution 2012-08, Vol.59 (6), p.1015-1026
• Main Authors: López-Palacios, Cristian, Peña-Valdivia, Cecilia Beatriz, Reyes-Agüero, J. Antonio, Rodríguez-Hernández, Adriana Inés
• Format: Article
• Language: English
• Subjects: Agriculture; analysis of variance; artificial selection; Biological evolution; Biomedical and Life Sciences; Cacti; Cellulose; Cellulose fibers; cladodes; consumer preferences; Cultivation; Dietary fiber; Domestication; Drought; Extreme environments; fiber content; genotype; Genotypes; Hemicellulose; Life Sciences; mucilages; Opuntia; Opuntia ficus-indica; Organic chemistry; Pectin; pectins; Plant Genetics and Genomics; Plant Physiology; Plant Sciences; Plant Systematics/Taxonomy/Biogeography; Polysaccharides; principal component analysis; Principal components analysis; Research Article; Saccharides; Species; Variance analysis; vegetables; wild plants
• ISSN: 0925-9864; 1573-5109
• DOI: 10.1007/s10722-011-9740-3

Domestication is an evolutionary process that modifies morphological, physiological, chemical and genetic features of wild plants, and is a product of artificial selection. A gradient of domestication can be appreciated in species of the Opuntia genus. There are wild species like O. streptacantha, others semi-domesticated like O. hyptiacantha O. megacantha and O. albicarpa, or other like O. ficus-indica with the highest degree of domestication. At the same time, some structural polysaccharides have been associated with plant drought and freeze resistance. This study aimed at quantify five groups of structural polysaccharides in 14 variants of nopalitos (edible young cladodes of flat-stemmed spiny cacti consumed as vegetables) of Opuntia spp. in a domestication gradient. Given that extreme environment is less frequent under cultivation than in the wild, we hypothesized that structural polysaccharides in nopalitos are reduced throughout the domestication process. The experiment was conducted as a completely randomized design with a 5 × 14 two-factor factorial treatment structure, with four replications. Mucilages, pectins, hemicelluloses and cellulose were extracted and dietary fiber content was calculated. ANOVA of data was performed, pair wise comparisons of species and variants were conducted by Tukey test and principal components analysis was carried out. Mucilages were higher in O. ficus-indica (12% of total dry mass) and pectins, loosely and tightly bound hemicelluloses in O. streptacantha (2.5, 9 and 3%, respectively). All five species had similar content of cellulose (5.1% dry mass); but, O. streptacantha presented more dietary fiber. Higher pectins and both loosely and tightly bound hemicelluloses content in wild species can be related to genotype and the persistence of reaction to a wild environment. Mucilages which are one of the main characteristics of consumer preference and loosely bound hemicelluloses could have impact for selection during Opuntia domestication.