Breeding wheat cultivars better adapted to conservation agriculture

Conservation agriculture has improved the productivity and sustainability of cropping systems and reduced the costs of production. These more sustainable crop management strategies have changed the disease spectrum in some environments and plant breeders have responded by developing cultivars with a broader range of disease resistance. Nevertheless, the potential for yield improvement in the absence of diseases in farming systems where residues are retained and tillage is minimized is unclear. The genetic improvement of crops for specialized agronomic practices is dependent upon a genotype x practice interaction. Without such an interaction crops could be developed under full tillage and expected to adapt to zero-tillage systems where crop residues are retained. A diverse set of cultivars were sown in two contrasting environments under two tillage regimes in Mexico between 2003 and 2005 and grain yield and grain quality estimated. Highly significant genotype x tillage practice interactions for grain yield and many grain quality attributes were noted, including protein content, SOS sedimentation and some mixographic properties. The results suggest that wheat cultivars with improved adaptation to conservation agriculture could be developed with more relevant market quality. A mapping population of 150 entries derived from a cross between Berkut, one of the parents tested in Mexico and the Australian cultivar Krichauff, was then evaluated in Australia under contrasting tillage regimes. These parents were chosen for their contrasting response to tillage. A QTL analysis identified several QTL associated with specific adaptation to tillage regimes. Two regions were located on chromosome 2D (wPt3728-cfd44 and gmw484-wmc27) and one on 5B (wmc99-wPt2373) which explained 9, 9 and 12% of the variation for yield under zero-tillage, respectively. A major QTL on 5A (cfa2155-wPt1370), overlapping the Vrn1A locus, explained up to 25% of the variation for yield within this cross, but was not tillage regime specific. Clearly it is possible to breed cultivars with specific adaption to conservation agriculture although the genetic control of adaptation appears highly complex and greatly influenced by environment, soil type, planting method and crop rotation. (C) 2011 Elsevier B.V. All rights reserved.