Repositório RCAAP

Aiming to delimit areas showing climate aptitude for growing com, an agroclimatic zoning based on growing degrce-days and water deficit as agroclimatic indexes, at different sowing dates, was generated for the State of Rio Grande do Sul, Brazil. The zoning was established for sowing dates 8/1, 9/1, 10/1, 11/1,12/1, and 1/1, and six maps (1:750,000), which are presented in a reduced forre in this papei, were obtained. The zoning areas were classified as Preferential I and II. Tolerable. Marginal, and Not Recomended for com. Planalto, Serra do Nordeste, Serra do Sudeste, and Alto Vale do Uruguai are the regions showing higher potential for com in the state. Additionally, Médio and Baixo Vale do Uruguai, Missões, Depressão Central, Litoral Sul, and Campanha regions, though also showing potential for com, have the highest values of water deficit and, by using irrigation, are clssified through the temperature index. The main limitation to high com yields in the state is linked to water deficit that normaly occurs in southwestern and southeastern state arcas and in part of Depressão Central region in 9/1 to 1/1 sowing dates. Low temperaturas and frost occurrence are the most limiting factors in the sowings centered in 8/ 1. The results obtained show that climate aptitude for com in Rio grande do Sul varies according to the sowing date and region, evidencing the importante of carrying out the zoning by sowing dates. 

This paper deals with allocative changes in the production of rice in the State of Rio Grande do Sul, Brazil, during the period 1970-1996. Therefore, it was possible to obtain, through a descriptive statistical method, that involves interconnected analyses of proportions of land use, among other indicators, the Dislodgement Index (DI) and the Rice Allocative Effect (RAE). Results, that embody recent structural changes surveyed in the agricultural census of 1995-96, support either basic and specific hypotheses formulated in this paper. The Dislodgement Index (DI), a proxy indicator for agricultural output growth rate, decreased along time, a movement apparently of pro- cyclical content. Although, it has to be put in perspective with yield increases in agricultural production as well as with changes of relative weights in all the links of the production chain, that must have been increasing participation of processing industries, services sector and so on. Therefore, rice production has been increasingly nettcd by agribusiness links and by systems of institutional support that made it possible to generate changes, in an environment that helped increase scale, complexity and scope for rice production in Rio Grande do Sul. The trends observed for results obtained regarding RAE in the analysed periods reflected allocative changes. once farmers privileged investment decision in favour of rice, making that activity one of important specific weight in the economy of State of Rio Grande do Sul, and stabilizing the original impacts of soybeans, that has "migrated" to midwestern region, on a very concentrated farm size structure. The expansion of rice in State of Rio Grande do Sul was, for its turn, highlighted as a phenomenon occurred largely on biggcr farms. Mass production, found in Europe and in the United State.% canal "fordism", that consists in a increasing concentration in a reduced number of agricultural and processing units, on larger scale of operation, has been a new tendency for rice production in State of Rio Grande do Sul. However, even larger scales cannot avoid the increasing segmenting trend in demand, patterns that have been observed more recently, as opposed to the mass production. It is the so-called demand-pull influente, that may significantly alter the conformation of rice production in State of Rio Grande do Sul.

Exploitation of heterosis has been the main point to increase maize productivity in this century. However, the varieties use this phenomenon in a different way. This work was designed to compare the performance of open pollinated populations, their crossings and commercial hybrids in two different locations. The results demonstrated that the environment is important for the expression of the genetic potential of the plants. In the favorable environment the crossings performed better than the populations and the commercial hybrids outperformed both. In the unfavorable environment ali genotypes presented low grain yield. This fact demonstrated that superior genotypes could not express their genetic potential in environments with limitations for plant development. As a consequence, the choice of the commercial variety to be acquired by the farmers should take into account the environment and the management level that will be adopted in the crop.

Cultivation in plastic greenhouses is an incipient activity in the State of Rio Grande do Sul, in the south of Brazil, specially for melon. Studies in adaptation of cultivars, period of cultivation and greenhouse management are essential to the improvement of this activity. In order to evaluate the productivity, in protected environment, of four cultivars of melon – Hy Mark, Acclaim, AI-522 and Sunrise – an experiment was carried out, in four seedling periods, in the region of Serra do Nordeste, in the State of Rio Grande do Sul, Brazil. The treatments were laid out in a randomized block arranged in a split plot design with three replicates, where seedling period was assigned to the main plot and cultivar of melon was assigned to the sub-plot effect. The cultivars Hy Mark, Acclaim, AI-522 and Sunrise productivities varied from 36,7 to 77,3 t of melons per hectare. The cultivars Hy Mark and Acclaim presented the more stable productivities among the periods of seedling. The cultivar Sunrise is the most prolific and productive, while AI-522 shows the lowest productivities and the most extensive period of conservation after harvest.

The research evaluates the vegetative and productive behavior of five cultivars and one selection ofpersimmon cultivated in Veranópolis, RS, Brazil. In general, the flowering of persimmon cultivars and selectionoccurred in October, while the fruit’s ripening began in March and finished in April or May. ‘Kaoru’, ‘Rama Forte’,‘Micado’ and ‘Regina’ showed the longest cycles (period between the beginning of the flowering and the beginningof the ripening), while ‘Fuyu’ and ‘Chocolate 3’ the shortest cycles. The cvs. Fuyu, Kaoru and Micado exhibitedalternation of production. Regina persimmon was the best, with an average yield of 83,10 kg/plant; ‘Kaoru’ and‘Fuyu’ also showed good yields. The cv. Micado showed the highest mean fruit weight (368,43 g), while the cv.Rama Forte showed the lowest (140,25 g).

This work was designed to investigate the possible existence of genetic variability for speed of germination in bean seeds. Hundred and one genotypes, three of them green beans and the remainder dry beans, were evaluated in greenhouse. Greenhouse produced seeds were sowed in plastic boxes at depths of 2.5 and 8.0 cm. A randomized complete block design with two replications and six seeds per plot, was performed. Analysis of speed of germination, evaluated through an Emergente Index, indicated significant differences for seed placement depth and no significant differences for seed placement depth x cultivar interaction. A superior group comprised 98 genotypes. whereas the inferior one, comprised the three others, two of which are green bean types. The conclusions are: low variability was detected for the character germination speed within this germplasm; green beans might be improved; germplasm collected from different locations presented different • behavior suggesting that natural selection might act differently in different environments.

In order to evaluate the effect of nitrogen supply in black oat (Avena strigosa) and the quantity of oat straw as a soil cover on initial growth of maize plants, a trial was conducted in greenhouse conditions, in Porto Alegre/Rio Grande do Sul, Brazil. Treatments consisted of three nitrogen level (0, 15 and 40 kg/ha) applied at the beginning of the tillering stage of oat and two amounts of oat straw as soil cover ( 3 and 6 t/ha). One treatment without oat straw was included. Nitrogen fertilization in oat increased dry matter yield and nitrogen uptake by plant and decreased carbon/nitrogen ratio of oat straw. The increase of the nitrogen level applied on oat and the oat straw quantity used as soil cover increased height, dry matter production and nitrogen uptake by com plants. The variables analysed in com plants were higher in the treatments with soil cover than in the check without soil cover.

The objective of this study was to investigate the genetic variability for grain water absorption capability in 219 genotypes of different commercial common bean groups, as an indicator of cooking time. Grains were obtained from the bean crop breeding program at the Santa Maria Federal University, RS, harvested in January 2002 and adjusted to 12,15% grain humidity. The experiment was conducted in a completely randomized design with three replications of 50g of seeds of each genotype. Samples were placed in a recipient with 200 ml of distilled water during 12 hours. Percentages of normal (soft) and hardshell grains were estimated. The majority of genotypes evaluated showed from 95 to 100 % of water absorption by the grains. A minority presented grains without hydration capacity (hardshell grains). The results showed that there is genetic variability for water absorption in commercial common bean genotypes.

This experiment was performed in Lages, Santa Catarina, to determine the moment of wheat tiller emission through the addition of red and far red light. Treatments involved the application of red (R) and far red (PR) light during the day time, at different growth stages (from emergence to emission of the 2° leaf on the main stem; between the emission of 2° and 3' leaf; 3° and 4° leaf; and 4° and 5° leaf ). The definition about the emission of tiller AO was set between emergence and the emission of wheat's second leaf. For A I, A2 and A3, this decision was made between plant emergence and the emission of the fourth leaf.

The objective of this research work was to test two improved populations of alfalfa for tolerance to acid soils, one selected for two cycles in soil and one for two cycles in solution culture, in five levels of pH. The aluminum tolerance was assessed by measuring the plants height and the roots length. Results indicated progress in alfalfa's tolerance to acid soils, evaluated by plants height and roots lenght by both methodologies of selection. The productive potential of the selected populations was not reduced in the absence of aluminum. The solution culture selection was as efficient as the soil selection for alfalfa's tolerance to acidity. Correlation between plants height and roots lenght was positive and significant.

Two experimenta were performed at the Rice Experimental Farm of IRGA, in the county of Cachoeirinha-Rio Grande do Sul, Brazil, in the 1997/98 and 1998/99 growing seasons, with objective to evaluate soybean grain yield grown in flooded soil. In the 1997/98 growing season, 20 cultivars were evaluated, under 774 mm of precipitation and two flooding irrigation at the reproductive stage. The medium grain yield was of 2598 kg/ ha, the cultivar FT-Abyara (3727 kg/ha) produced the highest yield, and did not differ of other 17 cultivars. The cultivar BR-4 had the lowest grain yield (1555 kg/ha). In 1998/99 growing season, were evaluated 30 cultivars, under 346 mm of precipitation and two flooding periods: one of eight days when plants had six developed leaves and another of two days in the seed-formation begin. The medium grain yield was of 1010 kg/ha, with the highest yield in the cultivar FT-2004 (2065 kg/ha), although it did not differ of other 14 cultivars. These results demonstrated the existente of genetic variability in soybean cultivars under excess of soil water.

In order to indicate the most favorable regions for the cultivation of tomatoes in greenhouse, the monthly average of global solar radiation and the number of days with radiation equal and lower than 8,4 MJ.m -2 d-' was measured based on the lower criticai trophic limit of this crop and the probability of monthly ocurrence of averages equal or lower than that value, from April to September in the State of Rio Grande do Sul . Data collected from 24 meteorological stations of the Fundação Estadual de Pesquisa Agropecuária — FEPAGRO/SCT, located at different climatic regions were, utilized considering the1957 - .1997 period. In general the monthly average for the Depressão Central, Campanha, Serra do Nordeste, and Litoral regions was lower than 8,4 Mim -3 d' in June and July and for the Serra do Sudeste, Missões, Planalto, and Vale do Uruguai the average for the winter months stayed above the criticai limit. 

Grain yield was used to perform a phenotypic stability analysis in maize. The yield data were obtained from a group of maize trials classified as very early, early and normal cycles. Data were analyzed within each maturity group and phenotypic stability was done using the unbalanced discontinuous bi-segmented model (STORCK, 1989). A total of` 18, 20, and 19 environments (1994/95 and 1995/96 growing seasons) and 34, 44, and 19 cultivars were used in the analysis for very early, early and normal maturity groups, respectively. Cultivars were ranked from intermediate, maximum, higher than intermediate, diverse and lower environment to not recommend. The cultivars Agromen 3050. C 969. AGX 6272, Dina 170, Dina 771, P 3063, AG 672 and AG 9023 are those that performed well in a diverse environmental conditions. The cultivars AG 9012, AG 9014, Dina'766, AG 521 and AG 951 are only recommended for environmental conditions relatéd to high yield expectation.

 Populational dynamics of Geophagus brasiliensis (Quoy & Gaimard, 1824) was studied from September/ 1995 to August/1996, through bi monthly samples at the Águas Belas reservoir, Viamão, Rio Grande do Sul, Brazil (30°02'22"S and 51°01'11.5'W). Individuais were captured using a beach reine 10 m long, 2 m high and a circular fishing net, both with 5 mm of mesh size. The reproductive period begins in October, with maximum reproduction activity in November and February, ending on march. The absolute fecundity was estimated 566 ± 142 oocytes, in females ranging from 7.28 to 13.17 cm. The size at the first maturation was between 8 and 9 cm. 

This experiment was carried out in order to determine physical injuries caused by artificial drying of corn kernels using drying air temperatures of 40oC, 70oC and 100oC) and harvested at moisture contents of 18%, 25% and 35% and to correlate them to breakage susceptibility. A stationary fixed bed drier with an air flow of 15 m3/min/ m2 was used. Lots of 1,400 kg, using three replications, were dried for each combination of harvest moisture content and drying temperature level. Hectoliter weight, 1,000-kernels weight, percentage of kernels with one, two and multiple cracks, stress cracks index and breakage susceptibility were evaluated. Stress cracks index of corn kernels increases when harvest moisture and driyng temperature increase in a stationary fixed bed drier. Occurrence of broken kernels during pre processing is affected by stress cracks severity. Stress cracks index and percentage of kernels with multiple cracks are fairly correlated to breakage susceptibility.

The seasonal variations and composition of the diet of Leporinus obtusidens in Lake Guaíba were studied. Specimens were captured between August/1994 and August/1995 with gill nets and trotlines in several different placas of Guaíba Lake. A total of 187 stomachs was examined for fullness and the diet composition of 68 individuais with full or partially full stomachs was investigated. Frequency of occurrence and an index of diet importance were used to analyze the data. Plant matter and sediments were the most abundant items, so that L. obtusidens can be considered a herbivorous-geophagus species. Other less frequent and abundant items included bivalves, gastropods and insect larvae. The large number of empty stomachs (63.6 %) may be an indication that this species regurgitates the contents in its stomach when submitted to stress due to the sampling procedure or that the period of feeding activity is not coincident with the sampling period.

Feeding is omnivorous type. The gonadotrofic hormones existing in commercial forms (Pregnyl) or in carp hypofisis were employed to induce spawning in L. friderici, Lpiau, L obtusidens and L elongatus females. Hormonal dosage were between 0,25 mg/kg and 5.0 mg/kg for females and 0,25 and 3,3 mg/kg for males. L elongatus females were crossed with Schizodon fasciatus males. The Liou for the genus was 12 until 21 cm. L friderici youngs was catched in reservoirs. This denotes the possibility for species of genus spawn in closed environment.

Apomixis is a method genetically determined of reproduction in plants, in which embryo is formed without the union of male and female gametes. There are three basic mechanisms of apomixis: apospory, diplospory and adventitious embryony. In most apomictic species, the pseudogamy is necessary for the endosperm development and consequent embryo viability. Apomixis can be detected through several techniques as embryo sac cytological analysis, progeny tests, callose deposition analysis in cell walls, auxin tests, among others. Apomixis represents an advantage for plant improvement because it allows the fixation of superior genotypes by succeeding generations. The available information about the genetics of apomixis suggests that this characteristic is controlled by few dominant genes, which favors the manipulation of this characteristic in breeding programs.

This study was conducted at the Santa Terezinha do Salto district (Lages, SC, Brazil) during the 1998/1999 growing season. The main objective of this trial was to evaluate the effects of increasing rates of nitrogen (0, 50, 100 and 200 kg/ha) fertilization (Urea form) in combination with com (Zea mays) hybrids (AG 12, AG 28, AG 303, and AG 9012) on the incidence and severity of common rust (Puccinia sorghi) and stalk rots (Gibberella zea and Pythium sp.). The experimental design was a completely randomized block (four replications) with split-plots. Hybrids were located on the main plots and nitrogen rates on the split plot of each block. The results showed that common rust severity increased with the increasing rates of nitrogen. The hybrids AG 303 and AG 9012 were more affected by rust than the hybrids AG 12 and AG 28. The hybrids AG 28 and AG 303 presented more incidence of stalk rot than the other hybrids. Despite of being one of the most affected by the diseases, the hybrid AG 9012 was the most productive. 

 Soil fertility and yield was evaluated on a typical dystrophic Red Latosol (Typic Haplorthox) located in Passo Fundo, State of Rio Grande do Sul, Brazil, after eight years under mixed production systems (1993 to 2000). Five production systems were evaluated: system I (wheat/soybean, common vetch/corn, and white oat/soybean); system II (wheat/soybean, grazed black oat + grazed common vetch/corn, and white oat/soybean); system III [perennial cool season pastures (fescue + white clover + red clover + birdsfoot trefoil)]; system IV [perennial warm season pastures (bahiagrass + black oat + rye grass + white clover + red clover + birdsfoot trefoil)]; and system V (alfalfa as hay crop), which was established in replicated plots in an adjacent area in 1994. The treatments were arranged in a randomized complete block design, with four replications. Exchangeable Al, exchangeable Ca + Mg, organic matter, extractable P, and exchangeable K levels displayed differences among crop production systems, whereas the production systems raised the corresponding contents, chiefly in the 0-5 cm layer. Organic matter, exchangeable Al, extractable P, and exchangeable K levels decreased from the 0-5 cm soil layer to the 15-20 cm layer, while the opposite occurred with the pH and exchangeable Ca + Mg contents.