Avaliação de genótipos de milho para semeadura precoce sob influência de baixa temperatura

Abstract

RESUMO -O milho (Zea mays L.) é uma planta de clima tropical que exige calor e umidade para produzir satisfatoriamente e proporcionar rendimentos compensadores. Diversos fatores podem comprometer a germinação das sementes e a emergência de plântulas no campo, merecendo destaque a semeadura em solos com baixas temperaturas. Em regiões que predominam condições de baixas temperaturas, seria importante o uso de sementes mais tolerantes a essa condição de estresse. Sementes de milho apresentam variabilidade genética para a germinação a baixas temperaturas. O objetivo deste trabalho foi classificar genótipos de milho quanto a tolerância das sementes à baixa temperatura de germinação, identificando àqueles com potencial para utilização em semeadura precoce. Avaliaram-se 16 genótipos provenientes do programa de melhoramento de milho da empresa KSP Sementes e Pesquisas Ltda., sendo 10 linhagens em diferentes estádios endogâmicos, seis populações de fecundação aberta e três híbridos simples comerciais, recomendados para semeadura precoce na Região Sul do Brasil. A avaliação da qualidade fisiológica das sementes foi feita pelos testes de germinação, primeira contagem de germinação, comprimento de plântula, biomassa seca, área foliar e radicular nas temperaturas de 25°C e 10°C. Foram realizadas análises eletroforéticas para os sistemas isoenzimáticos da fosfatase ácida, esterase e peroxidase. Os resultados permitiram classificar os genótipos quanto à tolerância das sementes à baixa temperatura, evidenciando que há variabilidade entre eles e potencialidades para serem usados em semeadura precoce na região sul do Brasil.Termos para indexação: Zea mays, baixa temperatura, emergência precoce. EVALUATION OF CORN GENOTYPES FOR USE IN EARLIER SOWING UNDER LOW TEMPERATURESABSTRACT -Corn (Zea mays L.) is a characteristic plant of tropical climates that requires heat and humidity to produce satisfactorily and to provide compensatory incomes. Several factors can compromise seed germination and plant emergence in the field, and it is important to consider sowing in soils with low temperatures. In regions where low temperature conditions predominate, the use of more tolerant seeds to this stress condition would be important. Corn seeds present genetic variability for germination at low temperatures. The objective of this study was to classify corn genotypes for germination at low soil temperatures. Sixteen 16 genotypes from the breeding corn program of the company KSP Sementes and Pesquisas Ltda. were evaluated, 10 lines at different endogamic stages, six cross pollination populations and three 3 single commercial hybrids, recommended for earlier sowing in southern Brazil. The physiological quality was evaluated by the tests of germination, first count of germination, plant growth, dry matter, shoot and root area AT 25°C and 10°C. The eletroforetic patterns of the isoenzimatic systems of the acid phosphatase,

Physiological, isozyme changes and image analysis of popcorn seeds submitted to low temperatures

“…According to Sans and Santana (2005), in low temperature conditions, the emergence of seedlings can take up to fourteen days. Low soil temperatures delay germination, decrease reserve mobilization, and consequently emergence speed (Cruz et al, 2007).…”

Attributes of growth, physiological quality and isoenzymatic expression of common bean seeds produced under the effect of gibberellic acid

“…In addition, in many cases this isoenzyme may be associated with esters hydrolysis reactions, which may lead to peroxidation of membrane phospholipids (Cruz et al, 2007). Thus, the low expression intensity, as well as acid phosphatase isoenzyme bands in both genotypes, shoot and root, may possibly be related to the occurrence of moderate lipid peroxidation in the seeds of this species, thus allowing the maintenance of the high physiological quality of the seeds.…”

Effect of Soil Temperature in the Emergence of Maize Seeds

“…The low soil temperature during sowing contributes to the delay of germination, the transport of seed reserves, and consequently the speed of emergence (Magalhães & Durães, 2006). However, maize presents genetic variability for germination at low temperatures, so it is necessary to select good genotypes for this trait and to use them under these stresses conditions, guaranteeing greater crop success (Cruz et al, 2007).…”

“…According to Cruz et al (2007), low soil temperatures delay germination, decrease reserve mobilization, and consequently the emergence velocity. Temperatures above the optimal value for germination, also lead to the delay of the process, causing the seeds to become less vigorous (Delouche, 2004).…”