Intraspecific Variability of Spinacia Aleracea L. by Phenotypic and Genotypic Markers

Abstract

Assessment of genetic diversity is the basis for crop improvement. A number of taxonomic markers could be used to assess this diversity. It is hypothesized that rather than a single marker, an integrated approach of various markers can give clearer genetic understanding of the crop. Spinacia oleracea L. (spinach) is a nutritionally and medicinally important leafy vegetable. The study was carried out to explore its intraspecific variability by morphological, nutritional, cytological and molecular markers. The experiments were performed in Molecular Taxonomy Lab of Lahore College for Women University, Lahore, Pakistan and field experimentations were done in Ayub Agriculture Research Institute, Faisalabad, Pakistan. The genetic variability of 200 spinach accessions was explored by twenty-one morphological markers. These markers included 6 quantitative (percentage germination, plant height, petiole length, petiole thickness, leaf length and width) and 15 qualitative traits (stem shape, petiole anthocyanin, petiole attitude, leaf color, anthocyanin, blistering, lobing, glossiness, apex, margin undulation, bolting speed, seed size, color, surface and ornamentation). Significant variation was observed among seed germination, plant height, leaf lobing, anothocyanin, petiole attitude and seed surface of accessions. Multivariate analytical techniques showed the importance of seed surface, ornamentation, plant height, leaf shape and anthocyanin presence towards the overall variability of accessions. Based on the diversity of these characters, 30 most diverse accessions were screened out for further analyses. Proximate and mineral analysis was performed for nutritional profiling of selected thirty accessions. Few Asian accessions from Pakistan, India, Iran and China were found to be rich in minerals, fibers and proteins. Flow cytometry analysis of accessions was also performed to assess the endopolyploidy level variation among the accessions. The level of endopolyploidy varied from 2C to 32C. Maximum cycle value (1.4-1.8) showing greater endopolyploidy level was represented by accessions of Pakistan, India, Hong Kong and Mongolia. The genetic diversity of 30 accessions was also assessed by 110 functional molecular markers related to seven genes involved in oxalate biosynthesis (i.e., glycolate oxidase, malate dehydrogenase, ascorbate peroxidase, iso-citrate lyase, malate synthase, citrate synthase and ascorbate oxidase), three genes involved in oxalate degradation (i.e., oxalyl CoA synthetase, formate dehydrogenase and oxalate CoA ligase) and one gene related to downy mildew resistance (i.e., glucose-6-phosphate dehydrogenase). High level of polymorphism was observed among the accessions represented with 115 polymorphic bands out of 130 bands. Polymorphism information content (PIC) of functional markers ranged from 0.5 to 0.92. Results indicated that the accessions from Asian countries (Pakistan, India, Iran and China) were the most variable in its phenotype and genotype. Moreover, the accessions from Pakistan (19339) and Iran (227383) were the best in terms of morphology, nutrition, disease resistance and oxalate metabolism. The obtained information could be helpful as a prerequisite for future breeding program. However, further studies are required to improve the understanding about key roles of these functional genes in various metabolic pathways.