Ecology and Development Series No. 10, 2003 - ZEF
Ecology and Development Series No. 10, 2003 - ZEF Ecology and Development Series No. 10, 2003 - ZEF
Current state of knowledgekapakata, C. liberica and C. stenophylla. On the other hand, Raina et al. (1998), usinggenomic in-situ hybridization (GISH) and fluorescent in-situ hybridization (FISH),confirmed the allopolyploid nature of C. arabica and suggested that it originates from twodiploid species: C. congensis and C. eugenioides. A more recent study using trnL-trnFsequence of chloroplast DNA revealed that C. eugenoides is the maternal progenitorspecies of C. arabica (Cros et al. 1998). Lashermes et al. (1999) applied restrictionfragment markers (RFLP) in combination with GISH and reached the conclusion that C.arabica is an amphidiploid formed by hybridization between C. eugenioides and C.canephora, or ecotypes related to these diploid species.It has been suggested that the search for the origin of C. arabica should include adiploid ‘race’ C. arabica in the rain forests of Ethiopia (Meyer 1965) and the intergenericlevel relationships between Coffea and Psilanthus (Charrier and Berthaud 1985). From thestudies reported to date, it seems that more research work needs to be done to gainknowledge on the putative diploid progenitors of C. arabica. Further investigation based onthe materials from the wild populations in SW Ethiopia and the relationship of C. arabicawith closely related taxa can be of great help in this regard. As Meyer (1965) speculated, C.arabica may also have been derived as a result of allotetraploid hybrid from parents nowextinct.Although C. arabica is economically very important, few investigations havebeen carried out on its genetics (Raina et al. 1998). This is especially true when it comes tothe populations of the species in Ethiopia. Botanists and genetists who visited Ethiopia inthe 1960s and before observed the presence of high phenotypic variability among the wildcoffee populations and landraces (Sylvain 1955, 1958; Meyer 1965; Monaco 1968). Recentstudies using modern molecular techniques indicate that there is higher genetic diversityamong wild populations of Coffea arabica than among its cultivars (Lashermes et al. 1996,1999; Montagnon and Bouharmont 1996; Anthony et al. 2001, 2002; Esayas et al.submitted). These studies indicate high levels of polymorphism especially among thepopulations from the southwestern part of Ethiopia. However, these studies were based ona limited number of accessions collected in the 1960s during the FAO (FAO 1968) and theOSTROM (now IDR) coffee missions (Charrier and Berthaud 1988). In most cases, no17
Current state of knowledgedistinction was made between whether the plant material was collected from wildpopulations in forests and landraces. To avoid this problem, authors have usually used theterm "subspontaneous" to described the origin of plant material (e.g., Lashermes et al.1996; Anthony et al. 2002).2.2.3 Reproductive biologySeveral authors have dealt with the reproductive biology of C. arabica (e.g., Carvalho1988; Carvalho and Monaco 1969; Charrier and Berthaud 1985; Meyer 1965; van derVossen 1985; Purseglove 1968). Coffee flowers first appear when the young plant attainsan age of two to three years. Flowering remarkably coincides with the onset of a rainyseason. A rain shower of a minimum of 20 mm following an extended dry season isrequired to break the dormancy of flower buds. Flowering may occur once or twice a yeardepending on whether the rainfall is uni- or bi-modal. Buds that will develop into flowersare usually induced four to five months before anthesis. The time between breaking of thedormancy and anthesis may vary from 4 to 10 days depending on temperature andatmospheric humidity. Flower buds open on sunny days in the early morning, and begin towither after 2 days. A few days later all floral parts drop away except the ovaries.Flowers have a short corolla tube, long style and exerted stamens. Although suchflowers morphologically permit natural cross pollination, C. arabica is largely autogamous.Double fertilization occurs on the day the flower opens. The outer cells of the integumentmultiply actively giving rise to the perisperm. The first division of the endosperm occursfrom 21 to 27 days after flower opening, and the first division in the zygote occurs 60 to 70days after anthesis, when the endosperm is already multinucleated (Carvalho andMonaco1969; Carvalho1988).Studies on the cultivars of Coffea arabica Brazil (Carvalho and Krug 1949) andKenya (Van der Vossen 1974) show that on average about 11.9% of pollination takes placethrough natural cross-pollination (also in Carvalho 1988). The percentage of crosspollinationis influenced by environmental conditions, which may affect the main crosspollinatingagents, namely insects and wind. The rate of out-crossing may vary in the rangeof 7-15%. The rate of out-crossing is expected to be higher in its center of origin than in the18
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Current state of knowledgekapakata, C. liberica <strong>and</strong> C. stenophylla. On the other h<strong>and</strong>, Raina et al. (1998), usinggenomic in-situ hybridization (GISH) <strong>and</strong> fluorescent in-situ hybridization (FISH),confirmed the allopolyploid nature of C. arabica <strong>and</strong> suggested that it originates from twodiploid species: C. congensis <strong>and</strong> C. eugenioides. A more recent study using trnL-trnFsequence of chloroplast DNA revealed that C. eugenoides is the maternal progenitorspecies of C. arabica (Cros et al. 1998). Lashermes et al. (1999) applied restrictionfragment markers (RFLP) in combination with GISH <strong>and</strong> reached the conclusion that C.arabica is an amphidiploid formed by hybridization between C. eugenioides <strong>and</strong> C.canephora, or ecotypes related to these diploid species.It has been suggested that the search for the origin of C. arabica should include adiploid ‘race’ C. arabica in the rain forests of Ethiopia (Meyer 1965) <strong>and</strong> the intergenericlevel relationships between Coffea <strong>and</strong> Psilanthus (Charrier <strong>and</strong> Berthaud 1985). From thestudies reported to date, it seems that more research work needs to be done to gainknowledge on the putative diploid progenitors of C. arabica. Further investigation based onthe materials from the wild populations in SW Ethiopia <strong>and</strong> the relationship of C. arabicawith closely related taxa can be of great help in this regard. As Meyer (1965) speculated, C.arabica may also have been derived as a result of allotetraploid hybrid from parents nowextinct.Although C. arabica is economically very important, few investigations havebeen carried out on its genetics (Raina et al. 1998). This is especially true when it comes tothe populations of the species in Ethiopia. Botanists <strong>and</strong> genetists who visited Ethiopia inthe 1960s <strong>and</strong> before observed the presence of high phenotypic variability among the wildcoffee populations <strong>and</strong> l<strong>and</strong>races (Sylvain 1955, 1958; Meyer 1965; Monaco 1968). Recentstudies using modern molecular techniques indicate that there is higher genetic diversityamong wild populations of Coffea arabica than among its cultivars (Lashermes et al. 1996,1999; Montagnon <strong>and</strong> Bouharmont 1996; Anthony et al. 2001, 2002; Esayas et al.submitted). These studies indicate high levels of polymorphism especially among thepopulations from the southwestern part of Ethiopia. However, these studies were based ona limited number of accessions collected in the 1960s during the FAO (FAO 1968) <strong>and</strong> theOSTROM (now IDR) coffee missions (Charrier <strong>and</strong> Berthaud 1988). In most cases, no17
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