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Title: Variation in microanatomy and enzyme profiles in the Trifolieae
Author: Karam, M. F.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1991
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This investigation was primarily taxonomic and was centred on two legume genera which provide forage crops of great importance in temperate agricultural systems, Medicago and Trifolium. The core of the investigation was a study of variation in isozyme patterns and in the SEM characters of seeds and pollen within and among the species of these genera, in order to assess the value of these characters for achieving a better understanding of relationships among the species in each genus. In addition, preliminary surveys were made of SEM characters of some species in other genera in the Trifolieae (Melilotus and Trigonella) and in related or similar tribes (Ononis, Lotus, Dorycnium, Coronilla, Ornithopus, Lathyrus and Vicia. Isozyme characters were investigated at a maximum number of 13 isozyme loci in a total of 32 populations from seven species of Medicago, divided between four sections of the genus. The isozyme characters were found to be valuable indicators of relationships within species and among closely related species, but not at the intersectional level. Intraspecific variation was generally low in annuals but relatively high in the outbreeding perennial M. sativa. The tetraploid annual M. rugosa showed fixed heterozygosity at several loci. Three of the four species in the section Spirocarpos were closely related isozymically, but the fourth was distant, suggesting that its position needed reassessment. In Trifolium, isozyme characters were investigated at a maximum number of 12 loci in a total of 23 populations of seven annual species from four sections. One species, T. angustifolium, appeared to consist of two isozymically distinct taxa. As in Medicago, isozyme characters were valuable indicators of relationships within species and among closely related species, but not at intersectional or higher levels. Intraspecific variation was generally low. The SEM characters of the seeds were investigated in 19 species of Medicago, divided between five sections. The SEM surface micromorphology of the seed coat was found to provide valuable additional taxonomic characters, with six main types and additional subtypes which were closely correlated with existing taxonomic classification at the sectional level. In Trifolium, seed characters were investigated in 29 species from six of the eight sections of the genus. As in Medicago, SEM seed surface micromorphology provided valuable additional taxonomic characters, generally closely correlated with existing classifications in most sections but suggesting possible reassessments of relationships within the large and variable Section Trifolium. SEM studies of seeds in other genera in the Trifolieae and in Ononis showed that SEM seed surface characters were potentially valuable at both intratribal and intertribal levels, and a pilot study of the seeds of the tribe Viceae showed striking surface structures and significant intrageneric variation in Vicia and Lathyrus. Studies of the SEM characters of pollen indicated that they were probably of limited value for taxonomic comparisons within or between genera, but showed some differences between tribes. Pollen characters were studied in 18 species from seven genera, four in the Trifolieae (Medicago, Trifolium, Melilotus and Trigonella), one (Ononis) in the closely related Ononideae, one (Lotus) in the tribe Loteae, and one (Lathyrus) in the tribe Vicieae.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available