Response of maize inbred lines to a defoliation treatment inducing tolerance to cold at germination

Abstract

Defoliation during maize (Zea mays L.) kernel development has been observed to induce tolerance to cold of germinating seeds in responsive genotypes. The objectives of this study were to evaluate the response to defoliation of immature embryo and mature seed germinability at cold and to verify if the response was influenced by the developmental stage at which the treatment was applied. In three environments, six inbred lines (B73, IABO78, Lo1016, Lo964, Mo17, Os420) were defoliated (D) approximately 20 days after pollination (DAP) or not defoliated (ND). Immature embryos were excised three days after defoliation and germinated in vitro at 9 or 25 • C. At maturation, kernel germination was tested at the same temperatures. Defoliation improved cold tolerance and mean time to germination (MTG) at 9 • C of both embryos and kernels of Lo1016. To study the effect of kernel developmental stage on response to defoliation, plants of B73, Lo1016 and Lo964 were defoliated at 15, 18, 21, 24, 27, 30, 33, 36, and 39 DAP, or not defoliated. At the same DAP, immature grains were analyzed for dry weight, water and abscisic acid (ABA) content. In Lo1016, low amounts of kernel ABA were detected at all stages, while in Lo964 and B73 ABA increased during development. Lo1016 mature kernels showed an improvement of cold tolerance due to defoliation at all times, while the other genotypes did not. In conclusion inbred lines showed variability for mature seed and immature embryo tolerance to cold at germination and for the ability to acquire tolerance after defoliation.

Direct and Joint Effects of Genotype, Defoliation and Crop Density on the Yield of Three Inbred Maize Lines

“…In one of the initial studies within this field [16], the response of six maize (Zea mays L.) inbreds was evaluated to 50% and 100% defoliation at the 14-leaf stage regarding grain yields and yield components. Frascaroli et al [17] studied the response of six inbred lines of maize (B73, IABO78, Lo1016, Lo964, Mo17 and Os420) to different defoliation treatments in three environments. Raza et al [9] investigated the effects of four-leaf excision treatments (T 1 -0; T 2 -2; T 3 -4 and T 4 -6 leaves excised from the top of maize plants) on grain yield of maize through two-year field experiments.…”

Influência do despendoamento e da eliminação de plantas dominadas na qualidade de sementes e na produtividade de milho

“…Conforme observado por Frascaroli et al (2005), a desfolha diminui a matéria seca de grãos na colheita, sendo as perdas maiores quando a desfolha se realizou nos estádios iniciais de desenvolvimento dos grãos, como verificado nesse experimento. (1) Tratamento: 1 (sem folhas acima da espiga); 2 (1 folha acima da espiga); 3 (2 folhas acima da espiga); 4 (3 folhas acima da espiga); 5 (4 folhas acima da espiga); 6 (apenas inflorescência masculina retirada).…”