O caráter "stay-green" (permanência da cor verde nas plantas) tem sido utilizado para reduzir a senescência em trigo, resultando no aumento funcional da área foliar, e, conseqüentemente, na elevação da taxa e da duração do enchimento da semente. O objetivo deste trabalho foi analisar a taxa de acúmulo de matéria seca e a duração do período de enchimento da semente de linhas quase-isogênicas de trigo diferenciadas quanto à presença e ausência do caráter "stay-green". O experimento foi conduzido no Centro Experimental da Palma, Pelotas, RS. Foram utilizadas quatro linhas quase-isogênicas: F6-SG e F6-SZ, no ano de 2000 e F7-SG e F7-SZ no ano 2001, com cinco repetições. O caráter "stay-green" permitiu maior deposição de reservas na semente na fase próxima do ponto de maturidade fisiológica. A duração do período de enchimento da semente esteve associada ao acúmulo de matéria seca na semente, promovendo um maior peso médio da semente. Assim, o progresso do caráter taxa de enchimento da semente poderá ser obtido por meio de seleções de plantas com maior peso médio da semente.

O objetivo deste trabalho foi avaliar a eficiência de coeficientes de similaridade em genótipos de feijão por meio de marcadores RAPD. A eficiência dos coeficientes de similaridade de Jaccard, Sorensen-Dice, Russel e Rao, Ochiai, Coincidência Simples, Rogers e Tanimoto, Hamann, Kulczynski 2, Yule e Phi no agrupamento de 35 cultivares locais e comerciais de feijão foi analisada com base em 104 marcadores RAPD. Os coeficientes foram comparados por dendrogramas, pela eficiência da projeção no espaço bidimensional e por grupos formados pelo método de otimização de Tocher. Os diferentes coeficientes de similaridade apresentaram variação quanto à eficiência de projeção no espaço bidimensional e quanto ao número de grupos formados pelo método de otimização de Tocher. Os coeficientes de Russel e Rao e de Yule são os mais discordantes, e os coeficientes de Sorensen-Dice, Ochiai e Kulczynski 2 são mais eficientes que os demais. O coeficiente de Russel e Rao não tem a capacidade de agrupar as cultivares em seus respectivos centros de domesticação.

O objetivo deste trabalho foi caracterizar a diversidade genética dentro e entre cultivares locais e comerciais de feijão, por meio de marcadores RAPD, e avaliar a capacidade destes em agrupar genótipos de feijão de acordo com o centro de domesticação e coloração de semente. Foram avaliadas 35 cultivares, 13 comerciais e 22 locais, de diversas regiões do Rio Grande do Sul. As distâncias genéticas foram obtidas pelo complemento do coeficiente de similaridade de Sorensen-Dice e a representação simplificada destas distâncias realizada mediante um dendrograma. Marcadores RAPD foram eficientes ao agrupar cultivares de acordo com o centro de domesticação, mas não foram capazes de separar as cultivares de acordo com a coloração da semente. Cultivares locais e comerciais, mesoamericanas, foram agrupadas separadamente. Cultivares comerciais, em cultivo no Rio Grande do Sul apresentam alto grau de similaridade.

Development of physiological maturation was studied on cedro (Cedrela fissilis Vell.) seeds in order to determine the best harvesting time. The reserch conducted at the Palma Farm and Seed Laboratory of the Federal University of Pelotas, included eight periods of fruit collect at 25 weeks after anthesis. The evaluation of the quality was made by determination of seed water content, dry weight, germination and electric conductivity of the seeds, and emergence velocity test and dry weight of seedlings. Also fruit color and dehiscence both were taken in consideration. Results showed that the physiologic maturity in cedro seeds occurs before dehiscence, within 29 and 31 weeks after anthesis, with seed water content ranging from 50 to 60% and, at the time, the fruits present a brown-greenish color or brown-clear. The best harvesting time of cedro seeds were obtained at 32 weeks after anthesis, with fruits present a brown color and initial dehiscence.

Com o objetivo de testar a hipótese de polimorfismo intracultivar para vigor em pimentão (Capsicum annuum L.), sementes de um único lote da cv. Ikeda foram submetidas a quatro testes de vigor, respectivamente: teste de frio sem solo, velocidade de germinação, envelhecimento precoce e classificação do vigor de plântula. As plântulas vigorosas e fracas, selecionadas em cada teste, junto com testemunhas (lote original, sem seleção) foram transplantadas para casa de vegetação até a produção de sementes S1. Posteriormente, comparou-se o desempenho das sementes S1 dentro do mesmo teste que possibilitara a seleção das plantas que lhes deram origem. Avaliou-se também o desempenho das sementes em relação à velocidade de emergência das plântulas em campo. Finalmente, conduziu- se por mais uma geração somente as plantas vigorosas e fracas oriundas do teste de frio sem solo e testemunha -- para confirmar, ou não, a existência de ganhos de seleção. Os resultados obtidos permitiram as seguintes conclusões: a) há variação quanto ao vigor individual das sementes na cultivar de pimentão utilizada; b) a variação encontrada tem, no mínimo, um componente genético passível de ser explorado, não só para aumentar a qualidade das sementes em si como para, possivelmente, melhorar o comportamento da cultivar em condições de campo; e c) o teste de frio foi o mais eficiente para detectar as diferenças comportamentais dos indivíduos dentro da população estudada.

This study aimed at erradicating seed-borne fungi on carrot, Daucus carota L., seeds, cv. Brasilia, by thermotherapy (dry heat) without any damage to its viability. The study was carried out in 1994/95, at Faculdade de Agronomia Eliseu Maciel, Federal University of Pelotas, RS, Brazil. Four seed lots, two harvested in 1993/94 and two harvested in 1994/95, were heated at 70 degrees C for periods of: 0, 3, 6, 9, 12 and 15 days. The following parameters were used to evaluate the seeds: seed health test (blotter-test), standard germination test and vigor tests (cold test and accelerated aging test). The results showed that: dry heat at 70 degrees C for 15 days eliminated seed-borne fungi of high quality carrot seeds, without reducing germination and vigor; high quality carrot seeds can be dehydrated to 1% moisture content without damage to it; and the seed quality or age affects its performance in heat treatments.

To assess nitrogen movement from the soil into the plant and within the plant, studies of dry matter and N accumulation are necessary. The objective of this experiment was to study the effect of 30, 60, 90 and 120 kg of N/ha on dry matter and N accumulation by four standard height-semi-dwarf normal mutant malting barley isotype pairs (Morex, Hazen, Norbert, Andre) and two check cultivars: Steptoe and Klages. Considerable differences among genotypes on dry matter accumulation until anthesis and dry matter lost during grain filling period were observed. Genotypic differences for pre-anthesis (range: 36.6 to 52.9 mg N/plant) and post-anthesis (range: -2.3 to 10.8 mg N/plant)N accumulation and in total N accumulation (range: 69 to 149.2 mg N/plant in 1987 and 41.3 to 56.5 mg N/ha in 1989) were observed. Within the isotype pairs, consistent differences were detected for post-anthesis and total N accumulation both favoring the standard isotypes. These differences were not affected by fertilizer N levels. Genotypic differences in N remobilization into the grain were also observed. Relationship between N and dry matter partitioning are discussed.

Considering that a substantial amount of N applied in cereal production may be lost by leaching or erosion, the development of cultivars with increased efficiency to utilize N and more efficient N management practices are desirable. The objective of this experiment was to study the effect of 30, 60, 90 and 120 kg of N/ha on N use by four standard height semi-dwarf normal-mutant malting barley isotype pairs (Morex, Hazen, Norbert, Andre). Genotypic differences in N remobilization in the grain, remobilization efficiency, utilization efficiency and uptake efficiency and N use efficiency were observed. The standard isotypes with few exceptions had higher values for all of these N traits. Nitrogen remobilization in the grain increased with increasing N fertilization while N utilization and N use efficiency decreased in both standard and semi-dwarf isotypes. Nitrogen use and grain yield relations are discussed.

The objective of this study was to evaluate the effect of seed size, protein content and N application timing on barley seedling vigor and grain yield. Two seed sizes, three protein levels and two genotypes (Hazen and Hazen semi-dwarf, SD, isotype pair) were used in a laboratory and in a field study. In a greenhouse study with Hazen only, N application timing (at sowing and 20 days after emergence) treatments were added to the other treatments. High seed protein content and large seed positively affected coleoptile length, root dry weight and seedling dry weight at early stages of plant development, but had no effect on emergence rate index and plant and root dry weights at 40 days after emergence. Both the standard height and semi-dwarf isotypes responded similarly. The delay of N supply until 20 days after emergence negatively affected the initial seedling growth, but had no effect on plant dry weight 40 days after emergence in the greenhouse. Grain yield and yield components were not affected by seed protein content nor seed size under field conditions.

In 1992 and 1993, at the National Wheat Research Center (CNPT-EMBRAPA), this study was carried out to evaluate the genetic improvement of wheat (Triticum aestivum, L.) cultivars. Fifteen genotypes released between 1940 acid 1992 were evaluated on two nitrogen levels. Linear regression of grain yield means on number of years elapsed since 1940, showed increases of 17 kg/ha(-1)/year(-1) in grain yield, and the newer genotypes showed to be more responsive to higher nitrogen fertilization. The newer genotypes showed a slight increase in the biological yield over the old ones, but the harvest index contributed with 83.6% of the overall yield. There was a significant and positive correlation between grain yield, spikes/m(-2), grain/spike(-1), biological yield and plant dry weight at anthesis. The newer genotypes were shorter in height and grain filling period and had a longer emergence-anthesis period.

Introduction of certain semidwarf genes into wheat ( Triticum spp.) has improved N‐use efficiency, particularly at high N supply. This study was conducted to determine whether yield and grain quality differ between standard height (STD) and mutant semidwarf (SD) malting barley ( Hordeum vulgare L.) isotypes with varying levels of N supply. Isotype pairs (‘Morex’, ‘Hazen’, ‘Norbert’, and ‘Andre’) and check cultivars (Steptoe, Klages) were grown with 30, 60, 90, and 120 kg N ha −1 in 1987 and 1989. Yield, grain characteristics, and malting quality parameters were evaluated. The STD isotypes had higher yield (6781 vs. 5642 and 5202 vs. 4504 kg ha −1 in 1987 and 1989, respectively) and generally higher values for yield components and harvest index, as well as better grain quality than their respective SD isotypes; however, two‐row SD isotypes had better malting quality than their STD isotypes. The generally superior performance of STD isotypes in part may be due to the SD isotypes being raw induced mutants that had not been improved by crossing. Malting quality parameters, such as total malt protein and malt extract, were affected negatively by N >60 kg ha −1 , when the preceding crop was pea ( Pisum sativum L.; high N); however, for yield and some malt quality parameters such as diastatic power, all genotypes responded significantly and positively to N fertilization when the preceding crop was barley (low N). In general, the response to N was similar for both barley types. As SD malting barley cultivars are developed to control lodging, they may not utilize more N or yield more than STD types.