Selection on uniformity and yield stability in maize

Abstract

Historically speaking, both the introduction of double-cross hybrids and use of single crosses have caused the increase in grain yield and significantly improved agricultural practice. Nowadays, the uniformity of crops is regarded as an advantage of modern agriculture, since the uniformity of products is crucial in global market. Thus, uniformity of crop maturation provides both planning and efficient mechanized harvest. F1 single-cross hybrids of maize, which is an allogamous species, not only exploit heterosis, but also impose homogeneity. Basically, the uniformity of hybrids has been regarded as their crucial advantage. There are two aspects of hybrid maize uniformity: (i) genetic homogeneity and (ii) genetic stability. Genetic homogeneity refers to presence of identical genotypes, whereas genetic stability refers to phenotypic uniformity (homeostasis) in different environments. At present, yield performance of inbreds has not advanced as rapidly as performance of hybrids, especially in stressful environments. Focusing on inbred productivity combined with stability may be more appropriate strategy in the future. Poor farmers are not able to employ superior genotypes because they require considerable financial investment and farmers survive not due to high yield in good seasons, but due to enduring extreme ones. Breeding process may create genotypes in favorable seasons when genetic variance is maximal and environmental influence is minimal, which should be followed by breeding for different environments. The aim of such breeding are, most probably, genotypes intended for a specific set of conditions which, in fact, represents a convergence of two strategies of plant breeding. One should probably bear in mind the strategy of both yield improvement and survival of farmers in extreme conditions without decreasing yield of best genotypes, especially those adapted only to favorable conditions. Solution to this problem should be: financial (best possible loans), social (education), and technological (breeding improved genotypes and advanced agricultural production).