Inheritance of the responses to a defoliation treatment affecting cold tolerance in maize

Previous studies revealed that defoliation can bring about differential responses in maize (Zea mays L.) genotypes for cold tolerance. This research was conducted to study the inheritance of the responses to defoliation for germination at low temperature and for seedling traits in early-sown field trials. Six inbred lines were crossed according to the complete diallel scheme, thus producing 36 geno- types. At milk ripening stage, half of the plants of each genotype were completely defoliated (D) whereas the other half were not (ND). Two experiments were conducted for two years, one in the germinator and one in the field. The response to defoliation was evaluated as (D–ND). Across the two years, the D treatment caused an average kernel weight decrease of - 56 mg ( - 23.1 % as referred to ND), an increase of 2.3 % for germination at 9 C (G9) and a reduction of - 0.3 d for the average time of germination (ATG); in contrast, the defoliation effect was negligible for germination at 25 C. In the field, the defoliation effects were more notable in the first (colder) year and led to an increase of 2.0 % for field emergence (FE) and to a decrease of - 2.7 g for seedling fresh weight (SFW). The genotypic variation for the (D–ND) response was significant for additive, dominance and reciprocal effects for G9, ATG, FE and SFW. There was consistency among lines across traits for additive effects, with Lo1016 and Os420 showing the best and the worst effect, respectively.