Major Objectives of IWIN

The general objective of IWIN is to enhance the productivity, yield stability, and end-use quality of wheat production at global level with major emphasis in the developing world.

Specific objectives:

• Develop high yielding and disease and pest resistant wheat genotypes with acceptable grain quality for irrigated and rain-fed production systems

• Identify germplasm for heat and salt tolerance

• Identify, map and pyramid major genes and QTLs for durable disease resistance and drought and heat tolerance

• Distribution of improved germplasm to NARS through the International wheat nursery and system

• Build capacity of NARS through long term and short term training in wheat breeding/genetics

Breeding Methods and Approaches

The wheat breeding program at CIMMYT and ICARDA applies both conventional and molecular breeding approaches and techniques in order to develop high yielding and widely adapted germplasm with resistance/tolerance to the major biotic and abiotic constraints prevailing in the developing world. Some of these strategies and techniques include classification of Mega-Environments (ME) and assembling of targeted crossing blocks, shuttle breeding, utilization of doubled haploids (DH) and marker assisted selection (MAS), key location yield trials, distribution of germplasm to NARS through international nurseries, and partnership & capacity building of NARS (Rajaram et al. 1995; Ferrara et al. 1987; van Ginkel et al. 2002; Ortiz et al. 2007; Tadesse et al. 2012a). As water is becoming scarce even in the irrigated areas, IWIN's germplasm development approach is to identify genotypes with disease resistance, high yield potential and water use efficiency so that wheat genotypes targeted for irrigated areas can cope with temporary drought periods. Similarly, this approach enables to minimize and maximize yield gains during drought and good seasons, respectively, for the rain fed production system.

Principally, high yielding and adapted hall mark wheat cultivars representing each MEs, synthetic wheats and elite lines from CIMMYT/ICARDA breeding programs are used as parents. Physiological and molecular screening techniques in order to increase rates of genetic gains through (a) strategic trait-crossing to combine complementary traits in progeny, (b) high–throughput phenotyping to enrich for desirable alleles in intermediate generations and (c) exploration of genetic resources to broaden the genetic base for hybridization (Reynolds and Tuberosa 2008). Marker-assisted selection using recommended diagnostic markers is used in order to characterize new parental materials for disease resistance genes (yellow rust, leaf rust, stem rust, nematodes); insect resistance (Hessian fly and Russian Wheat Aphid), phenological traits such as photoperiodism (Ppd), vernalization requirement (Vrn); plant height (Rht), grain hardness and other genes (Gupta et al. 1999; Tadesse et al. 2012a). Diagnostic markers are also used for gene pyramiding in the F2, F1 top, and BC1 F1 populations (William et al. 2007). Segregating generations and fixed genotypes are evaluated in key locations using a shuttle breeding approach in order to develop disease resistant, high yielding, widely adapted and photoperiod insensitive genotypes within a short period of time.

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