BP Singh

20 Bhag Singh3. Establish the distribution of genetic diversity anddetermine the geographical centres where this is atmaximum, especially those centres with endemic forms Icharacters.4. Determine the centre where diversity of geneticallyallied species is concentrated.5. Correlate the above centres with the areas ofconcentration of nearest wild relatives.6. Compare centres of origin of group of cultivated plantswith certain specialized parasite(s).7. Support the above with the evidences from archae,ologylinguistics and history.Transformation of concept of originThere has been considerable chan~{n the concept of originever since Vavilov (1951) propounded it.It was considered later that the presence of wild relatives wasessential for designating the centre of origin. Subsequently, severalworkers revised the boundaries supported with the conceptsdeveloped by them.Schiemann(1951) criticised the Vavilovian gene centre theoryspecially in relation to Ethiopean and central Asian centres whichwere considered by Vavilov as the centres of origin of durumwheat (Triticum durunt) and barley (Hordeum vulgare) and that ofhexaploid wheat (T. aestivum) on the other. The criticism isprimarily based on the fact that none of wild progenitors werepresent in these centres, hence termed them as /I Accumul~tiQnCentres". Zohary (1970) also criticized the Vaviiovian"~oncept ofcentres of origin. Similarly Ku.ckuck (1963) criticised the Vavilovianconcept as he did not find the dominant alleles in the centres oforigin and recessives in the periphery, e.g., bread wheat andsorghum as claimed by Vavilov.Megagene centresZhukovsky (1965), a dose associate of Vavilov, proposed 12megagene centres of crop-plant diversity. The new areas addedto Vavilov's eight centres were Australia, Africa, and Siberia