Chapter 5 Genetic Analysis of Apomixis - cimmyt

Feedlog rIoo World io tltt 2111 ''''.ry: Pl••IB,eedi.g. 8Io1....oIogy, IIIId Iitt Pot..tlol KIlt of Aponi.1s 3broadly applicable across such diverseagronomic and socio-economic conditions,and plant breeders are just beginning toprovide improved varieties tailored to a fewof the multitude of niche environments foundin the region.Of the major developing regions, improvedvarieties have had the least impact in sub­Saharan Africa; food production there haslagged behind rapid population growth. InAfrica as a whole, more than 168 millionpeople are chronically undernourished, and,alarmingly, nearly a fourfold increase inpopulation, from 740 million in 1996 to 2.8billion by the end of the 21st century, is nowprojected (FAa 1992, 1998; Bongaarts 1994).The defining characteristics of Africanagriculture are its complexity andheterogeneity. Most farmers have smallholdings on which they grow a variety ofcrops, often intercropped with one another. Ineach of the continent's countries, soils andclimate are highly diverse and variable.Economic realities limit the development ofirrigation and other forms of yield enhancingand risk averting infrastructure. As in muchof Latin America, no elite breeding lines arebroadly applicable and improved varietieswith specific characteristics need to bedeveloped for many different types ofagronomic and socioeconomic niches. Suchniche breeding has been successful in a fewlocations and has potential for expansion, butit is a slow process when based onconventional breeding technology. Notably,while there is no such thing as low input/highoutput agriculture, average yields in Africa areso low (often less than It/ha) that a doublingor tripling of production should be possiblewith locally well-adapted varieties using justminimal inputs. Undoubtedly, bettermanagement practices would help boostyields (the use of nutrient and SOil-enhancingcrop rota tions and associa tions looksespecially promising), but over the long term,greater use of inputs, particularly fertilizer,will be necessary.BiotechnologyModem plant breeding, which revolutionizedagriculture in the 20 th century, is now on theverge of significantly extending itstechnological potential. New geneticmonitoring and manipulation tools, inaggregate commonly referred to asbiotechnology, are becoming available as aresult of advances in molecular and cellularbiology. As indicated in Figure 1.1, these newtools are contributing to both phases of planteo:o...r:::0.....Foreign genes and modified genesI IG,"" J..l "'------+IRelated wild speciesWide hybrids Samati, hybridsI I Existing (fOp germplasmsomJclonalvatlionWider primary gene pool 14------'1Traditian,1 crossingBreeding linesc Anther culture Genotype selectionoo::>""6.1;Marker-aided assesment ofpest/pathogen papulationMarker-aided selection ofprogeny with desired genesI Improved (fOp varieties IFigure 1.1 Biote(hology tools for strengthening plant breeding.