Adriano Delly Veiga

Influência do potássio e da calagem na composição química, qualidade fisiológica e na atividade enzimática de sementes de soja

A composicao quimica das sementes pode ser influenciada por fatores geneticos, ambientais e pela disponibilidade de nutrientes no solo durante a producao e, como consequencia, terem o seu vigor afetado. O potassio pode influenciar a atividade de varias enzimas presentes nas plantas, necessarias em varias reacoes envolvidas na utilizacao de energia, sintese de amido, metabolismo do nitrogenio e respiracao. Avaliou-se o efeito da adubacao potassica e da calagem na composicao quimica, qualidade fisiologica e na atividade de enzimas de sementes de soja. A pesquisa foi desenvolvida nos laboratorios de analises e biotecnologia de sementes do Departamento de Agricultura e no Laboratorio de Producao Vegetal do Departamento de Ciencias dos Alimentos da Universidade Federal de Lavras (UFLA). Em sementes de soja do cultivar Msoy 8001, produzidas sob 2 niveis de saturacao por base (48% e 85%) e quatro doses de K2O por hectare (0, 50, 100 e 200 kg), foram avaliados teores de oleo e proteina, germinacao, envelhecimento acelerado e atividade das enzimas envolvidas nos processos de germinacao e deterioracao de sementes. A adubacao potassica nao afeta a germinacao e o vigor das sementes, enquanto a elevacao da saturacao por base, proporciona maior vigor de sementes de soja. Ha aumento no teor de oleo e reducao no teor de proteina em sementes de soja a medida que a dose de K2O e aumentada. Ocorre aumento de teor de proteinas em sementes de soja, produzidas sob maiores niveis de saturacao por base. A atividade das enzimas piruvato quinase, esterase e alcool desidrogenase em sementes de soja e afetada pela concentracao de potassio e saturacao por base no solo.

Armazenabilidade de sementes de cafeeiro colhidas em diferentes estádios de maturação e submetidas a diferentes métodos de secagem

The harvesting time and drying methods may influence the quality of coffee seeds during storage. This work was conducted with the objective of understand the effects of maturation stages and drying methods on the physiological quality and storability of coffee seeds. The experiments were performed at the Seed Analysis and Electrophoresis Laboratory of the Department of Agricultural of UFLA. The fruits of the cultivar Rubi were harvested, depulped and the mucilages removed by fermentation and the seeds washed and let on paper for removal of the water. The seeds were submitted to conventional drying (under shade) and drying in stationary drier at temperature of 35oC. As a control, seeds with no drying were analyzed. The evaluations were done soon after the drying treatments and after four and eight months of storage. The seeds were stored at 10oC in air-tight plastic packages. The germination test, radicle protrusion, seedling dry matter, emergence index speed, electric conductivity, electrophoresis analyses of heat-resistant proteins and quantification of endo-â-mannanase activity were the parameter evaluated. The design was completely randomized with 2 (maturation stages) x 3 (dryings) x 3 (storage time) factorial scheme with four replications. Seeds harvested in the cherry stage have greater storage potential than in the green-yellow stage. Reduced germination and vigor occur in the coffee seeds harvested in the green yellow stage, when submitted to fast drying. The presence or intensity heat-resistant protein bands is associated with seed drying. Greater activity of endo-s-mananase enzyme occurs in seeds harvested in the cherry stage than in the green yellow stage. Increase of the activity of endo-s-mananase enzyme occurs during storage.

Tolerância de sementes de soja à dessecação

A colheita antecipada de sementes, apos a maturidade fisiologica, permite a obtencao da melhor qualidade fisiologica e sanitaria, rotacao de culturas e otimizacao das estruturas de processamento. Sementes nao toleram a secagem durante todos estadios e adquirem tolerância em estadios especificos. Durante a maturacao, esta aquisicao da tolerância a dessecacao pode coincidir com a maturidade fisiologica e, em sementes de soja, ocorre no estadio R7, com umidade ao redor de 45% a 50%. Assim, a presente pesquisa teve como objetivo avaliar a tolerância a dessecacao de sementes de soja. As sementes foram colhidas em tres estadios fenologicos, R6, R6/R7 e R7 e foram submetidas a secagem artificial a 35oC ate 20% de teor de agua e a 42oC ate 13%. Uma quarta colheita foi realizada com sementes secadas no campo, sendo estas utilizadas como testemunha. A qualidade das sementes foi avaliada pelos testes de germinacao, de condutividade eletrica, de frio, de peso seco de plântulas e eletroforese de proteinas lea. O delineamento experimental foi inteiramente casualizado em esquema fatorial com quatro repeticoes. A testemunha foi comparada individualmente com cada tratamento. Com os resultados, concluiu-se que a germinabilidade e a tolerância a dessecacao de sementes de soja aumentam com a perda natural de agua no campo; sementes colhidas no estadio R7 apresentam maior qualidade fisiologica, padrao diferenciado de proteinas lea e maior tolerância a dessecacao do que nos estadios R6 e R6/R7; secagem de sementes colhidas proximo a maturidade induz a sintese de lea proteinas; e sementes colhidas no estadio R7 apresentam qualidade fisiologica e padrao de proteina lea similares aos de sementes secadas no campo ate 14% de teor de agua.

Inibição do desenvolvimento in vitro de embriões de Coffea por cafeína exógena

Caffeine, the alkaloid known as 1,3,7 - trimetilxantina, is found in quiescent coffee seeds, amounting to a total of 1.1 to 1.7% in Coffea arabica L. and 2 to 3% in Coffea canephora Pierre, mostly localized in theo endosperm, in the free cytoplasm of cells or complexed with chlorogenic acids. With the physiological function in plants not yet completely understood, caffeine causes an allelophatic effect, either inhibiting germination of a number of species or as an anti-herbivore or a natural pesticide agent. The slow germination of coffee seeds has not yet been elucidated and several causes are pointed to, such as the presence of the endocarp, low water and O2 uptake and presence of natural inhibitors and hormonal balance. Although suggested, studies on coffee seed inhibition by the action of endogenous or exogenous caffeine are scarce. Thus, the present study was designed to investigate the effect of exogenous caffeine on both germination and embryo development of Coffea arabica L. and Coffea canephora Pierre. The experiment was conducted by utilizing seeds from red ripe berries of the cultivars Rubi and Apoata IAC-2258. After disinfecting the berries for 30 minutes by soaking in sodium hypochlorite (2% a.i.) and washing three times in distilled water and autoclaved, the embryos were removed and inoculated in a aseptic manner, in Petrri dishes with 50% MS medium with the addition of sucrose and supplemented with different of concentrations of caffeine (0.00; 0.05; 0.10; 0.15; 0.20; 0.25; 0.30 and 0.40%). The embryos were maintained in a growth room at 27±20oC and photon flow density of 13µmol.m-2.s-1 for 23 days, when shoot length, root length and seedling fresh mass were evaluated. Five days after cultivation, the percentage of radicle emission and that of cotyledons were evaluated, calculating the embryos with open cotyledons and with expanded radicles. A complete randomized experimental design was used six replications per treatment, each replicate consisting of five embryos. It follows that germination and in vitro development of embryos of Coffea arabica L. and of Coffea canephora Pierre are affected by exogenous caffeine. The detrimental effect of exogenous caffeine on Coffea embryos is greater on the radicles than on the cotyledons. Coffea arabica L. embryos are more sensitive to the negative effects of exogenous caffeine than embryos of Coffea canephora Pierre. Caffeine can contribute to the slow seed germination and slow coffee seedling development.

Physiological quality and amylase enzyme expression in maize seeds

The physiological quality of maize seeds is affected by the genotype. Thus, the study of expression of genes associated with this characteristic is important in the genotype selection process in breeding programs. The aim of this research was to study the expression of amylase enzymes associated with physiological quality of maize seeds with different genotypes and seed sizes. We further sought to assess the expression of these enzymes in dry and soaked seeds The experiment was conducted in the experimental area and the Central Seed Laboratory of the Department of Agriculture of the Universidade Federal de Lavras. Seeds of four maize inbred lines were used, classified in two sizes. The physiological quality of the seeds was evaluated by means of germination, seedling emergence, seedling emergence speed index and accelerated aging test. Expression of the alpha amylase enzyme was evaluated by the electrophoresis technique and expression of the alpha amylase B73, alpha amylase (LOC542522) and beta amylase 5 (amyb5) genes was studied by the qRT-PCR technique in dry and soaked seeds of the inbred lines. There is differentiated expression of amylase enzymes in maize seeds of inbred lines with different levels of physiological quality. higher expression of amylase enzymes is observed in soaked maize seeds. The expression of transcripts is higher in smaller as wellas in soaked maize seeds of inbred lines.

Quantitative trait loci associated with resistance to gray leaf spot and grain yield in corn

A incorporacao de resistencia genetica a doencas e o aumento na produtividade de graos estao entre os principais objetivos dos programas de desenvolvimento de hibridos. A identificacao de locos de caracteres quantitativos (QTL) por meio de analises estatisticas associadas a marcadores moleculares possibilita a rapida obtencao de hibridos resistentes e produtivos. Nesta pesquisa, objetivou-se identificar locos de caracteres quantitativos (QTL) associados com resistencia a cercosporiose e com producao de graos em germoplasma de milho tropical. Foram utilizadas duas linhagens contrastantes em niveis de reacao a doenca (genotipos pertencentes a GENESEEDS - Ltda), seu hibrido F1 e a populacao segregante F2. Essas plantas foram fenotipadas quanto a resistencia a doenca e quanto a producao de graos e genotipadas com 94 marcadores de microssatelites. A associacao dos marcadores ao QTL foi realizada por meio de analises de marcas individuais, utilizando as metodologias de regressao linear e analise da maxima verossimilhanca. Observou-se que o tipo de efeito predominante no controle genetico da resistencia a cercosporiose foi o aditivo e para o controle genetico da producao de graos foi de dominância. Os marcadores microssatelites mais promissores para serem utilizados em estudos de selecao assistida para resistencia a cercosporiose sao umc2082 na posicao 4.03 e umc1117 na posicao 4.04 e para producao de graos, umc1042 e umc1058 nas posicoes 2.07 e 4.11.

Minimum period to assess the potential of germination of coffee seeds 1

In recent research, early stages of coffee seedling development were identified, after radicle protrusion, in which all the essential parts of the seedling can be assessed to demonstrate the potential of seed germination to generate normal plants. Thus, the objective of this research was to develop studies to reduce the time on the germination test. Ten seed lots of coffee were assessed through the germination test, every two days, from the tenth day of sowing, according to the morphological criteria of the seedlings. The data were compared to the standard germination test and analyzed by means of regression analysis and segmented nonlinear regression and planteau response model. It was concluded that the assessment of coffee seedlings at 16 days, in stage S1, provides the similar result of the pattern germination test, allowing a significant reduction of time in order to demonstrate the germination of the seed lots; the seedling assessment coffee in stage S2 does not have reduction of the time for assessing the coffee germination, in relation to the pattern.