AFLP and RAPD analyses of genetic diversity of wild and/or weedy Guizotia (Asteraceae) from Ethiopia

摘要

The genus Guizotia is a small Afro-montane endemic genus (Baag?e 1974) that belongs to the family Asteraceae, tribe Heliantheae. Baag?e (1974) reduced the number of species in the genus to six in her taxonomic revision, of which one was further classified into two subspecies. These species are: G. abyssinica (L.F.) CASS., G. arborescens I. FRIIS, G. reptans HUTCH., G. scabra (VIS.) CHIOV. ssp. scabra,G. scabra (VIS.) CHIOV. ssp. schimperi (SCH. BIP. in WALP.) J. BAA?GE stat. nov, G. villosa SCH.BIP. in WALP., G. zavattarii LANZA in CHIOV. Two decades after the taxonomic revision, two new populations of Guizotia were discovered by K. Dagne who called them ‘Chelelu’ and ‘Ketcha’, respectively, by the name of the place from where they were collected first (Dagne 1995).All the taxa are diploids with 2n=2×=30 chromosomes (Hiremath and Murthy 1986, 1992; Dagne 2001). Based on the fact that all taxa of the genus, except G. reptans, are found in Ethiopia, Baag?e (1974) indicated that the genus has its center of distribution, genetic diversity and perhaps its center of origin in Ethiopia. The crossability between several taxa of the genus (Murthy et al. 1993; Dagne 1994) is an indication for the outcrossing nature of the genus and cross compatibility between species. These taxa have close phylogenetic affinity as determined by hybridization between taxa, meiotic analysis and oil content and fatty acid composition (Dagne 1994, 1995, 2001; Dagne and Jonsson 1997).All Guizotia species are wild and/or weedy except G. abyssinica, which is cultivated mainly for its edible oil, particularly in Ethiopia but also in India and some other African and Asian countries (Baag?e 1974; Murthy et al. 1993; Getinet and Sharma 1996). G. arborescens is a shrubby perennial endemic to southwest Ethiopia and mountain Imatongs in Sudan and Uganda (Friis 1971; Baag?e 1974). This species is different from the other Guizotia taxa mainly in having an arborescent habit and petiolate leaves (Friis 1971; Baag?e 1974). G. scabra ssp. scabra is a perennial taxon of wide distribution in east Africa, Cameron and Nigerian highlands (Baag?e 1974; Hiremath and Murthy 1986). G. scabra ssp. schimperi is an erect, annual, terrestrial, moderately branching herb (Baag?e 1974). This subspecies is native to the Ethiopian highlands and is a common weed of crops in mid and high altitude areas.G. villosa is an erect, annual, and a terrestrial, much branching, herb restricted in distribution to the northern and northwestern part of the Ethiopian highland, and can be easily distinguished from other Guizotia species by its small heads and nearly square ray florets (Baag?e 1974). G. zavattarii is an erect, perennial, terrestrial plant restricted to southern Ethiopia around mount Mega, Arero and Yabelo; and the Hurri Hills in northern Kenya (Hiremath and Murthy 1992; Dagne and Jonsson 1997). Chelelu and Ketcha populations do not exactly fit to any of the recognized taxa of the genus Guizotia and the taxonomic status of these populations has not yet been determined (Dagne 1995, 2001). We treated each of them as a separate “taxon” for the sake of simplicity. The geographic distribution of these populations has not been fully explored.The economic use of the wild and/or weedy Guizotia taxa is not well known. However, G. scabra ssp. scabra was reported to be used for human consumption (seeds) in Nigeria, and to make fishing nets (stem) in Congo (Baag?e 1974). G. scabra ssp. schimperi was reported to be used as a substitute of G. abyssinica and also as herbal medicine in some places in Ethiopia (Baag?e 1974). The fatty acids of G. scabra ssp. schimperi are identical to that of G. abyssinica (Dagne and Jonsson 1997), thus the use of G. scabra ssp. schimperi seeds for human consumption is encouraging.In spite of their biological and potential economic importance, almost no information is available on the extent and distribution of genetic variability in wild and/or weedy Guizotia species. In ord