Genotypic Variation for Cold Tolerance among Twelve Maize (Zea mays L.) Populations

The objectives of this study were (1) to ascertain the genetic differences for cold-tolerance traits in a series of diallel crosses among 12 maize populations grown in field experiments, and (2) to compare, in controlled environment rooms, the modification of various metabolic parameters of two sets of four F1 variety crosses which, according to the field experiments, differed largely in seedling early vigour (cold-tolerant Ct] vs cold-sensitive Cs] Fl sets). Under field conditions, cold-tolerance adaptability, as monitored by shoot dry matter accumulation, appeared genetically controlled; moreover, considerable differences existed among genotypes. Field data suggested that shoot dry weight was a good indicator of plant adaptability to periods of unfavorable cool conditions. The growth-chamber experiments showed that shoot dry weights of the two sets of hybrids (Ct vs Cs), were more uniform at the highest temperature regimes than under suboptimal temperatures. Moreover, the laboratory study indicated that the interval of time of attain a specific stage of development provided a meaningful and useful criterion for differentiating the capacity of maize plants to grow at low temperatures. Although a clear association between a particular metabolite and the capacity of plants to grow at low temperatures was not observed, it was of interest to note that the total N concentration in the shoot was significantly higher in the Ct plants compared to the Cs ones.