Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The experiment was carried out in the southern of Brazil, by direct sowing ryegrass (Lolium multiflorum Lam.), white clover (Trifolium repens L). birds foot trifolium (Lotus corniculatus L.) and red clover (Trifolium pratense L.) on native pasture. Herbicide Glyfosate was previously applied. The treatments were T1 -seed sowing in row with half fertilizer in row and half broadcasting; T2 – seed sowing in row with all fertilizer in row; T3 – seed sowing in row and all fertilizer broadcasting; T4 – seed and fertilizer broadcasting. The evaluation period was in 1998 and 1999. Considering cut means for two years, treatments T1 and T2 produced the highest dry matter yield and no difference were observed between them, however, both treatments differed (P<0.05) from T3 and T4. The fast pasture establishment and the best legume-grass mixture were obtained in the treatments T1 and T2 where soil available phosphorus was close to the critical level for pasture growth.

The nutritive value of round bales hay from natural pasture from the Campanha area of Rio Grande of Sul stocked under field conditions were evaluated over a three months period. Three samples from different places in the bale were taken every 28 days: one from the outside of the bale; one from the center and one from the middle space between those two. The following constituents were analyzed: dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, neutral detergent insoluble protein (NDIP) and acid detergent insoluble protein (ADIP). It was observed an increase in the concentration of NDIP and ADIP (P < 0.05), indicating a decrease in the concentration of available protein of the hay. The samples taken from the outer layer showed higher values for ADIP (P < 0.05). The values of NDIP did not show a variation in relation to the positions in the bale (P > 0.05). It was concluded that the outer layer was more negatively influenced by the period of storage.

The objective of this study was to evaluate the reproductive performance of heifers mated at 14, 18 and 26 months of age. The study was based on data collected from 2003 to 2005 from 270 heifers (Aberdeen Angus, Devon and cross-breeds) and mated at 14 (A14, n = 70), 18 (A18, n = 36) and 26 months old (A26, n = 164). The attributes analyzed among the different groups were age at mating (AM), average weight gain from birth to mating (AWG-BM), weight at mating (WM) and pregnancy rate (PR). The PR was tested using Qui-square test and the average weight gains and weight at mating were tested using the test t of Student. The WM was 312.0 kg for the A14 group, 333.0 kg for the A18 and 297.4 kg for the A26 group, where the A18 was different than A14 and A26 (P < 0.01). The AWG-BM was 0.658 kg, 0.507 kg and 0.353 kg for the A14, A18 and A26 groups, respectively, showing significance differences (P < 0.01). The PR was 84.3% for the A14 group, 94.4% for the A18 and 90.9% for the A26 animals group (P > 0.05). Thus, it is possible to conclude that the different ages at mating did not influence on the pregnancy rate.

With the purpose to evaluate the effects ethephon sprays to control alternate bearing and ameliorate fruit quality of ‘Montenegrina’ mandarins (Citrus deliciosa Tenore), grafted on ‘Caipira’ Orange, a experiment was conducted in a seven-year old comercial orchard, located in Butiá-RS, southern Brazil (29°57’S - 51°40’W). The experiment evaluated the effects as chemical thinner of different concentrations of ehtephon: 0, 200, 300 and 400 mg L-1. The treatments were applied in a randomized block design with four replicates and 3 plants as experimental unit. The number of flowers and fruitset, fruit development, number, weight and average weight of fruits, fruit classification in first, second and third category Were analyzed. Ethephon sprays only have a thinning effect with concentrations up to 200 mg L-1, which shoved effect resulting in leaf yellowing and abscission.

The natural grasslands of Rio Grande do Sul (RS) have been deteriorated due to widespread overgrazing, use of fire, soil tillage, erosion and by the invasion of the south african grass Eragrostis plana (capim-annoni-2), accidentally introduced in the 1950’s. Seed multiplication and use as a forage crop favored its dispersion establishment in roadsides and in the natural grassland vegetation. The invaded area in RS is estimated to be one million hectares. Integrated control, regulations of animal transport, weeding of sale yard areas, and the elimination of weed nursery will help to reduce the spreading of this species. Preventive grassland management practices might avoid invasion of new fields. The evaluation of the effects of management systems over the vegetation dynamics and the animals performance may reveal new tools capable to decrease or retain the abun- dance of this invasive species and improve biodiversity and productivity of the natural grassland.

Nowadays the black sigatoka is the major fitosanitary constrain of the banana cultivation in the world. In this context, the knowledge of the environmental factors related to the disease is essential for proposing management techniques and damage reductions. This paper presents some aspects of black Sigatoka disease, environmental factors related to the disease, and possibi- lities of management. Besides, it infers about the behavior of the disease at the extreme South of Brazil. Regarding the banana plantations of Rio Grande do Sul, the black Sigatoka dissemination should be avoided and the disease management should be integrated, considering aspects of soil, cultural practices, and the use of resistant cultivars. Agroforestry systems are also alterna- tives to the banana plantations as they can promote shading, and concomitantly produce other crops, in a diversified and sustaina- ble way.

It was evaluated the development of Citrus rootstock on substrates composed of burn rice husk. The experiment was carried out in the Fepagro Fruticultura, Taquari – RS, using three substrates (mix, comercial substrate and burn rice husk) and two rootstocks seeds (Poncirus trifoliata and Citrus sunki ), placed in plugs (50 cm3) and cultived in a greenhouse. The experimental design was completely randomized, in a factorial (3x2), with 4 replicates and 8 seeds per plot. The seeds germination and seedlin- gs diameter were not affected by the substrate type. The seedlings reached the biggest height in the mix substrate. The burn rice husk is a alternative in the composition of substrates to seeds germination of Citrus rootstocks.

In ordcr to verify the occurrence and distribution of biovars of Ralstonia solanacearum in vegetable crops under crop in the Statc of Rio Grande do Sul, Brazil. samples of tomato, eggplant and tobacco showing symptoms of bacterial wilt were collectcd in the spring of 2004, in 12 fanes from four citics: Maquiné, Caxias do Sul, Sobradinho and Santa Cruz do Sul. The identification of the bacterial species was carried out by the immunological test of ELISA and thc classification in biovar was based on the oxidative metabolism of alcohols and sugars and in the PCR fingerprinting. All thc 54 isolatcs were identificd as biovar 1. l-lowever, the amplification of DNA with the primas T3A and T5A resulted in a profile different from that expectcd for R. solanacearum strains, showing the amplification of an additional product with 650 bp. Dueto its dimane conditions and according to previous surveys in potato flelds, it was cstablished thc predominante of the biovar 2 of R. solanacearum. This study demonstrated that conditions of climate and soil in Rio Grande do Sul State pennit the occurrence of both biovars I and 2 and that the predominante of one or other is determined by the host spccics.

Potato Field Guide, Insects, Diseases and Defects

A protocol for disinfection and in vitro regeneration of Spartina argentinensis was developed. The lowest percentage of contamination was obtained after treating caryopses with 90° ethanol for 60 s and 20 min immersion in 2.5% sodium hypochlorite (NaOCl) plus 0.1% Tween 20. Murashige and Skoog (MS) media was used for callus induction, supplemented with 0.5 mg·L-1 of 2, 4 dichlorophenoxy acetic (2,4-D) and 1 mg·L-1 of indole-3-acetic acid (IAA). The highest proportion (20%) of shoot regeneration was achieved with MS media plus 0.25 mg·L-1 of bencyl aminopurine (BAP), whereas 0.5 mg·L-1 naphtalenacetic acid (NAA) was used for root induction. Plants were regenerated via organogenesis. To our knowledge, this is the first report of a protocol for in vitro plant regeneration of S. argentinensis, and it is the initial stage required for obtaining somaclonal variations. Se desarrolló un protocolo de desinfección y regeneración in vitro deSpartina argentinensis. El menor porcentaje de contaminación se obtuvo tratando los cariopses por 60 s en etanol 90° y 20 min de inmersión en hipoclorito de sodio al 2,5% con Tween 20. La inducción de callos se realizó en medio Murashige y Skoog (MS) suplementado con 0,5 mg·L-1de ácido diclorofenoxi acético (2,4-D) y 1 mg·L-1 de ácido indol acético (AIA). La mayor (20%) regeneración de vástagos se logró con igual base salina y 0,25 mg·L-1 de bencilamino purina (BAP). Se utilizó 0,025 mg·L-1 de ácido naftalen acético para la regeneración de raíces. Las plantas se regeneraron vía organogénesis. Este protocolo es la primera mención de regeneración de plantas de S. argentinensis utilizando cultivo in vitro y constituye la etapa inicial para obtener variantes somaclonales. La metodología de desinfección se puede hacer extensiva a otras especies.