The Impact of Seed Polymorphism of Plant Genetic Resources on the Collection Strategy of Gene Banks

Seed morphs of Calendula officinalis were investigated in order to examine the genetic variability which correlates with seed polymorphism and its impact on collection strategy of gene banks. The basic parameters to get the evidence were obtained from morphological data, karyotype analysis, electrophoretic pattern of seed proteins as well as nucleic acid analysis. Seven seed morphs were observed from every inflorescence as follows: curve, winged, insect leg, balloon rough, balloon smooth, worm and open worm. All seed morphs were diploid, with thirty-two chromosomes observed in somatic cells. Karyotype studies showed that the seed forms have different karyotype formulae. However, the chromosome type nearly submetacentric (-) and nearly metacentric are representing in all karyotype formulae of all seed forms.Where as Nearly submetacentric (+) was represented in all forms except in both insect leg and balloon smooth forms and nearly subtelocentric (-) was represented only in the insect leg form. Not only the dissimilarity was found in the morphology of chromosomes but also in the mean chromosome length (MCL) and diploid chromosome length (DCL).The types and proportions of abnormalities observed at mitotic division were analysed. The electrophoretic analysis revealed the presence of eleven bands of molecular weight ranging from 70.50 to 15.00 KD. Four bands were common to all seed types: 35.00, 31.50, 21.00 and 20.00 KD. However, some bands were more restricted to particular seed types thus; band 70.50 KD was present only in winged and insect leg whereas 15.00 KD only found in open worm and worm. The nuclear DNA content was ranged from 0.007 mg/g to 0.013 mg/g, while RNA content from 2.257 mg/g to 17.662 mg/g. A compiling of all data recorded, cluster analysis was conducted to generate a dendrogram to show possible relationships among seven seed morphs of C. officinalis. The heteromorphic phenomena in C. officinalis might be due to genetic variations during the formation period of seeds. Seed morphs of balloon smooth and balloon rough as well as worm could be collected in the same accession. While seed morph of open worm and insect leg and winged could be collected as one accession. Seed morph curve has to be in separate accession in gene bank. It is recommended that seed polymorphism should be considered during collection mission for conservation of plant genetic resources in gene banks.