Cytogenetic and molecular studies of the Egyptian Capsella bursa-pastoris (Brassicaceae)

Abstract

Capsella bursa-pastoris (Brassicaceae) is one of the most successful tetraploid species in the world. It showed high morphological diversity within Egyptian populations. The morphological investigations of herbarium specimens and fresh collected populations grouped them under three distinguished morphotypes (Lobed "L"; Simple "S" and Lobed-Simple "LS") depending mainly on the basal leaves structure. This high degree of phenotypic variation has received our critical attention. Until recently, the previous studies on C. bursa-pastoris attributed its phenotypic variation to environmental factors. But in Egypt, these three morphotypes were traced in mixed populations along with the species geographical range, so the environmental factors have no influence on their distribution or phenotypic variation. Accordingly, our primary concern in this study was to determine the factors controlling this variation. The cytogenetic studies revealed that the three identified morphotypes are three distinct genotypes with three different chromosome numbers: 2n=2x=16 (diploid) for "L"; 2n=3x=24 (triploid) for "S"; 2n=4x=32 (tetraploid) for "LS". The triploid genotype "S" showed rare occurrence among the studied populations and is postulated to be a hybrid newly recorded in Egypt. Karyotyping of the three genotypes showed significant differences in the genome and chromosomes relative lengths. Molecular study using cpSSR technique supported the cytogenetic results and differentiated the three studied genotypes. The retrieved results revealed that the phenotypic diversity within the Egyptian C. bursa-pastoris populations is genetically controlled.

Keywords

• Capsella bursa-pastoris
• cytogenetic studies
• genotypes
• karyotyping
• molecular study
• phenoplasticity