Biological background of sustainable maize ( Zea mays L.) production

Abstract

In modern maize production we have enhanced productivity primarily by changing the cropping environment to fit our maize hybrids. This strategy is becoming increasingly expensive, both in cost of inputs and in the environmental impact of these products, particularly when inappropriately applied to the field of production. In sustainable corn production, hybrids are needed that are productive under a range of environmental conditions. There is increasing evidence of the potential for building genetic tolerance into maize hybrids for some major stress conditions such as drought stress, heat stress, cold temperatures and freezing, which can help to maintain productivity under adverse growing conditions. In several cases where genetic differences are simply inherited (controlled by one or a few major genes), they are easily incorporated into hybrids by choosing parents, making appropriate crosses and selections, and testing promising genotypes under stress conditions. Maize is generally grown in Hungary where soils are fertile, but increasing population pressure has pushed production into less favourable areas. In these suboptimal conditions we should genetically adapt maize hybrids to the adverse soil environment; this is receiving most attention by corn breeders who intend to develop hybrids as components of a sustainable agricultural system. Maize lines and hybrids have shown differential responses to nitrogen fertilizer, and lines selected for high nitrogen use efficiently produced higher yields than lines selected for high yield under high nitrogen conditions. As with any breeding programme, the first step in adapting hybrids for sustainable systems is to define objectives carefully and describe the systems in which the hybrids will be produced. The choice of parents in a sustainable breeding programme is a critical initial step. We have found several appropriate traits of interest in high-yielding, well-adapted inbred lines that have superior combining abilities, in contrasts to bringing in those traits from nonadapted introductions. From our point of view, to develop maize hybrids for sustainable systems, it would be desirable to identify genetic combinations that not only tolerate stress conditions but that also respond to favourable growing conditions. On the basis of our results we can conclude that maize breeding will be central to the planning and implementation of more sustainable systems for the future.