Chromosome Study Of Local Farmers Varieties Of Opuntia Ficus-indica (l.) Mill. (cactaceae) From Tigray Northern Ethiopia

Opuntia ficus-indica (L.) Mill. is one of the drought resistant plants that play a significantrnrole in rescuing the lives of people and livestock in arid and semiarid regions of the world. InrnEthiopia, particularly in Tigray, it is used as food and forage until cereal crops are harvestedrnas well as during drought seasons. Currently, about thirty-four local farmers’ varieties of O.rnficus-indica are locally identified in the Southern and Eastern Zones of Tigray on the bases ofrntheir fruit characteristics and cladode morphology. The present study tried to assess therncytogenetic variability among these local farmers’ varieties through standard chromosomerncount method. Other three sample plants of opuntia species from Debre-zeyit, Dire Dawarnand Addis Ababa were also included in the study for comparison of their chromosome countrnwith that of the specimens collected from Tigray. The results of the study have shown that allrnthe sample plants chromosomally investigated in the study are polyploids. All the localrnfarmers’ varieties of O. ficus-indica, for which the somatic chromosome spreads werernreliably counted, were found to have an octoploid cytotype, with the same somaticrnchromosome number of 2n = 8x = 88. The two specimens of O. ficus-indica plant, each fromrnDebire-zeyit and Dire Dawa, have also shown the same ploidy level and somaticrnchromosome number with that of the local farmers’ varieties of O. ficus-indica collected fromrnTigray. On the other hand, the specimen of O. cylinderica plant collected from SciencernFaculty Campus of Addis Ababa University was found to have a different ploidy level withrndifferent somatic chromosome number of 2n = 11x = 121.rnThe fact that all the local farmers’ varieties of O. ficus-indica included in the present studyrnbelong to the same ploidy level indicates that the variations among those local farmers’rnvarieties in fruit characteristics and cladode morphology could not be attributed to thernvariation in ploidy level. Further chromosome studies were also recommended to cover widerrnpopulations of O. ficus-indica from different parts of Ethiopia. It was also recommended torninvestigate the polyploidy nature, mode of seed formation and genetic variability of O. ficusindicarnusing appropriate molecular techniques such as ISSR and AFLP.rnKey words: Chromosomes, Local farmers’ varieties, Opuntia ficus-indica,rnPolyploidy, Tigray.

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