Analysis of karyotype, chromosome characteristics, variation in mucilage content and grain yield traits in Plantago ovata and P. psyllium species

Plantago ovata and P. psyllium are of the most abundant and widely distributed Plantago species in the world. World-wide, it is an important and growing industrial and medicinal crop for dry land agriculture. In spite of this, basic characterization for economically important traits of these species is lacking for many accessions. In particular, there are gaps in our knowledge about accession identity and ploidy levels and the effects of agronomic practices of yield. This study is aimed at determining mitotic chromosome number, karyotype characteristics, morphological and mucilage character variation of wild accessions of Plantago species collected from a wide geographic range in Iran. Chromosome numbers were determined by a modification of conventional root tip squash method and karyotypes were digitally analysed. Morphological characters were evaluated under experimental field condition. Three replications of morphological and mucilage characters were also measured in the wild in situ natural habitats. The analysis of the karyotype indices showed that all P. ovata accessions were diploid (2n = 8) with small, homogeneous chromosomes. Likewise, P. psyllium accessions were diploid (2n = 12) and had symmetrical karyotype demonstrating P. psyllium as a primitive species. Results showed significant differences in accessions and environments with respect to seed yield, thousand grain weight, mucilage yield, mucilage content, days to flowering and plant height. P. ovata accumulated higher mucilage than P. psyllium. Mucilage content was higher in samples collected from natural habitats compared with those grown under experimental field conditions whereas mucilage yield was lower under field evaluation in natural habitats. Genotype by environment analysis revealed that the most stable accessions were G2 (P. ovata) and G6, G7 and G8 (P. psyllium) for seed yield, and G2 and G4 (P. ovata) and G8 (P. psyllium) for mucilage content, G4 (P. ovata) and all P. psyllium for grain weight. All accessions tested showed stability for mucilage yield, flowering stalk height and days to flowering. The outcome of karyotype analysis and field evaluations in this study provides information important to Plantago breeders focused on crop improvement.