Propagation of citrus rootstocks depends upon the production of clonal plants from nucellar seedlings. This makes apomixis one of the host important traits in breeding programs for citrus rootstocks. The genetic control of apomixis was studied in a 50-tree progeny derived from the cross C. volkameriana×P. trifoliata using 69 molecular markers and bulked segregant analysis. The proportion of nucellar seedlings was estimated by isoenzymatic analysis of 25 seedlings per tree for 2 consecutive years. The type of embryony (polyembryonic versus monoembryonic seeds) was also determined for fruit-yielding trees. Separate genetic maps for each parental species were developed. The integration and comparison of these maps could be accomplished using common multiallelic segregant loci. Differences in gene synteny between the two species-specific genetic maps were shown. Important distortions in the segregation of markers at several genomic regions, some of them also involving differences in the C-methylation pattern, have been observed, especially for the pollen parent. Analysis of quantitative trait loci (QTLs) revealed the presence of six genomic positions (two in P. trifoliata and four in C. volkameriana) contributing individually up to 24% of the total variation for apomixis. Within the same species, QTLs with positive and negative allele effects were present, even in the same linkage group. One of the markers associated to apomixis (Apo2) is also associated to embryony type. Therefore, the genetic control of apomictic reproduction found in citrus (nucellar embryony) is quite complex compared to what has been reported for gametophytic apomixis. Molecular markers linked to QTLs governing apomixis will be useful to assist selection of future apomictic rootstocks for citrus varieties.

Chemical composition and in vitro digestibility were determined in stems and leaves hand-separated from grasses and legumes obtained from the first and subsequent cuts of a permanent meadow. Grasses from the first cut were classified in four groups according to their stage of maturity: vegetative, boot, head-bloom and seed stage. Crude protein (CP) content was higher and neutral detergent fibre (NDF) content lower in legumes than in grasses, and in leaves than in stems. CP decreased and NDF increased with maturity in grasses. In general, legumes were more digestible than grasses. The digestibility of grasses harvested in the first cut decreased with increasing maturity. Leaves were more digestible than stems in legumes and grasses, although the relative difference between botanical parts was much larger in grasses than in legumes. The differences in digestibility between leaves and stems became more pronounced with increasing maturity, especially in terms of cell wall digestibility. As for forage quality, early cutting of permanent meadows would be recommended, so that grasses are harvested before they reach an advanced stage of maturity.

No abstract

ABSTRACT. Influence of displacement speed in the performance of a precision no-till planter in northern Rio de Janeiro State. The objective of this work was to evaluate the influence of displacement speed in the performance of a no till planter. The tests were performed in the experimental area of the Universidade Estadual do Norte Fluminense Darcy Ribeiro, located in Campos dos Goytacazes, Rio de Janeiro State, Brazil. The experiment was carried out in a randomized block design, using two speeds of 2.5 and 4.4 km h -1 , with 16 replications. For sowing, the UENF 506-8 hybrid corn, with row spacing of 0.9 m and theoretical 11 cm spacing between seeds was used. When the displacement speed was intensified, there was an increase in planter wheel slippage, effective field capacity, planting depth, plate distribution mechanism speed and the occurrence of doubles. There was a decrease in the number of seeds per meter and exposed seeds with an increase in planter speed. The seeds that did not pass through the plate distribution mechanism reached a germination rate of 98%, while, both in speeds of 2.5 and 4.4 km h -1 they showed 95.3% germination, which represents a reduction of 2.7% due to mechanical damage caused by the planter plate distribution mechanism.

Resumo: O objetivo deste trabalho foi caracterizar os efluentes despejados no Córrego Horizonte, a partir de visita aos locais ao longo do córrego e através de análise de imagens espaciais. Para isso os pontos visitados foram georreferenciados e fotografados. Utilizou-se um aparelho receptor de GPS e as imagens espaciais foram obtidas do processador geográfico Google Earth. As imagens foram coletas pelo satélite GeoEye-1. Como resultado foi possível observar grande ocupação e interferência humana no entorno do curso hídrico, bem como o despejo de efluentes prejudiciais ao longo do córrego. Foi ainda observado que há propriedades no entorno onde são realizadas estratégias de manejo que podem contribuir para a preservação do recurso hídrico. Concluiu-se que a análise espacial e a visita aos locais de interesse para este trabalho permitiram uma visualização mais ampla da ação antrópica sobre o Córrego Horizonte. As informações levantadas podem servir de base para estudos de impacto ambiental e para formulação de estratégias de conservação ambiental.

Currently, Brazil is the world's largest producer of sugar cane. Various factors can interfere in the productivity and technological quality of sugar cane, which in the end, represent the integration of the different conditions to which the culture was exposed. Some of the most relevant aspects for good final yielding or stand of plants are related to planting practices. These practices directly affect the ability of sprouting and tillering of sugar cane. Based on a review of the literature, this article aims to report the various factors that can affect sprouting and tillering of sugar cane.

-The aim of the present study was to investigate the influence of cutting frequency, harvest season and nitrogen fertilization on yield and floristic composition of the herbage harvested from a mountain meadow. The meadow was divided into 22 plots, each receiving a different N P K fertilization treatment. The study lasted seven years, and during the first three years (1985)(1986)(1987) each plot was harvested twice per year (June and September) according to a traditional harvest system, whereas in the years 1989-1991 each plot was harvested three times per year (spring, summer and autumn) following a more intensive harvest system. Nitrogen fertilizer favoured the development of the grasses in spring, thus reducing the proportion of legumes in the two cut harvest system, whereas grasses reached an advanced stage of maturity before the first cut in late June. However, the three cut harvest system entailed an earlier first cut in spring. As a result, the production of legume biomass was significantly increased both in the first cut and in the subsequent regrowths. No significant response in total herbage production to the N fertilizer was observed in the more intensive harvest system. Therefore, the three cut harvest system without nitrogen fertilization seemed to be the most suitable practice for the management of these botanically-complex mountain meadows. These results may contribute to design fertilization and management practices of mountain hay meadows to optimize their productivity and sustainability.Key Words: chemical composition, cutting frequency, floristic composition, herbage yield, nitrogen fertilization Influência da estação da colheita, freqüência de corte e fertilização nitrogenada de prados de montanha sobre o rendimento, a composição botânica e o conteúdo de proteína da forragem RESUMO -O objetivo neste estudo foi investigar a influência da freqüência de corte, da estação de colheita e da adubação nitrogenada no rendimento e na composição botânica da forragem recolhida de um prado de montanha. O prado foi dividido em 22 parcelas, cada uma com nível de fertilização N P K. O estudo durou sete anos e, durante os três primeiros (1985)(1986)(1987), cada parcela foi cortada duas vezes por ano (junho e setembro), seguindo um sistema de aproveitamento tradicional, ao passo que, nos anos 1989-1991, cada parcela foi cortada três vezes por ano (primavera, verão e outono), seguindo um sistema de aproveitamento mais intensivo. O fertilizante nitrogenado favoreceu o desenvolvimento das gramíneas na primavera, reduzindo a proporção de leguminosas no sistema de dois cortes anuais, de modo que as gramíneas alcançaram etapa avançada de maturidade antes do primeiro corte, ao final do mês de junho. No entanto, com o sistema de três cortes anuais, o primeiro corte foi realizado mais cedo, na primavera. Conseqüentemente, a produção da biomassa de leguminosas aumentou significativamente, tanto no primeiro corte como nos rebrotes subseqüentes. Nenhum efeito significativo na produção total de forragem em respost...

One-hundred and ninety-two herbage samples from permanent meadows located in the mountains of León (NW Spain) were analyzed for total nitrogen (total N), nitrogen in trichloroacetic acid precipitated matter (TCAN), borate-phosphate buffer insoluble nitrogen (BPBN), neutral-detergent insoluble nitrogen (NDIN) and acid-detergent insoluble nitrogen (ADIN). These data were used to calculate the partition of nitrogen fractions proposed by the Cornell Net Carbohydrate and Protein System (CNCPS): A (total N − TCAN), B 1 (TCAN − BPBN), B 2 (BPBN − NDIN), B 3 (NDIN − ADIN) and C (ADIN). Near-infrared reflectance spectroscopy (NIRS) technology accurately predicted total N, TCAN and NDIN, as judged by coefficient of determination (R 2 ) and ratio performance deviation (RPD) values greater than 0.90 and 2.5, respectively. The rest of the insoluble N fractions (BPBN and ADIN) were predicted with less accuracy by NIRS. Estimations of CNCPS N fractions (A, B 1 , B 2 , B 3 and C) using visible-NIR spectra of forage samples did not allow accurate predictions (R 2 < 0.90; RPD<2.5).