Sergio Francisco Schwarz

Superação de dormência em sementes de Butia capitata

Aiming to identify efficient conditions to break dormancy in Butia capitata (Mart.) Becc. seeds sown in vitro and in an incubator tests were conducted with mechanical scarification in pre-sowing, by partial or total opening of the seed embryonic cavity, isolated of the endocarps. The embryonic cavity opening accelerated germination significantly, especially when there was total removal of the seed cap, allowing germination on average 90% of embryos, regardless of the provenance of the accessions. The seed dormancy of B. capitata seems to be related to the mechanical barrier imposed by the seed tissues that hamper the embryo development, suggesting mechanical exogenous dormancy.

TESTE DE PATERNIDADE E AVALIAÇÕES AGRONÔMICAS DE POSSÍVEIS HÍBRIDOS DE TANGERINEIRA 'SUNKI'

Citrus production is spread all over the world. In Brazil citrus represent the major volume of fruit production. The rootstock is extremely important to establish a good-quality orchard. At the Estacao Experimental Agronomica of the Universidade Federal do Rio Grande do Sul was established placed a hybrid citrus plants orchard, originated from openpollination with ‘Lee’ tangelo [Citrus clementina Hort. ex Tan. x (C. tangerina Hort. ex Tan. x C. paradisi Macf.)] as female parent. Amongst those hybrids, fourteen plants were selected with characteristics alike to those of the rootstock ‘Sunki’ tangerine (Citrus sunki Hort. ex. Tan.) In order to confirm hybrids paternity, single sequence repeat (SSR) markers were used. The molecular analysis allowed to identify eleven hybrids that did not have ‘Sunki’ tangerine as male parent. The hybrids 49, 77 and 92, potencialy hybrids of ‘Sunki’, stood out for higher poliembriony, higher number of emerged seedling per seed and higher number of seeds per fruit in comparison to ‘Sunki’.

Produção de frutos e incidência de cancro cítrico em laranjeiras "Monte Parnaso" enxertadas sobre sete porta-enxertos

Citrus rootstocks can exert some influences on fruit production and susceptibility of the plants to citrus canker (CC). This research was performed aiming to select rootstocks which induce higher productivity index and lower susceptibility of ‘Monte Parnaso’ navel orange (Citrus sinensis) trees to the bacteria Xanthomonas axonopodis pv. citri. The research was carried out in an experimental orchard, with ten-years-old trees, planted at spacement of 2.5m between trees and 6.0m between rows, located in Butia city, in the Central Depression of Rio Grande do Sul state. It was used an randomized blocks experimental design, with 7 treatments and 4 replications. The treatments consisted of the following rootstoks: Rangpur lime (C. limonia.), ‘Volkameriana’ lemon (C. volkameriana.), ‘Flying Dragon’ trifoliata orange (Poncirus trifoliata), ‘Caipira’ orange (C. sinensis), ‘troyer’ citrange (C. sinensis x P. trifoliata), ‘Sunki’ tangerine (C. sunki.) and ‘Swingle’ citrumelo (C. paradisi x P. trifoliata). The parameters evaluated were: number of fruits and leaves with citrus canker lesions per plant and at two previously selected and marked branches per plant, at different times . The results revealed that the ‘Swingle’ citrumelo and ‘Flying dragon’ rootstocks induced the highest productivity index and, the lowest incidence of citrus canker disease on leaves and fruits. ‘Rangpur’ lime and ‘Volkameriana’ lime rootstocks, promoted a heavy crop load, however, showed higher susceptibility to citrus canker disease.

Caracterização morfológica, determinação do número de embriões e taxa de poliembrionia em três porta-enxertos híbridos de citros

Abstract Due to several phytosanitary problems that affect Brazilian citriculture, diversification of rootstocks is a priority. Hybrid root-stocks are being developed by citrus genetic breeding programs, and those hybrids must be evaluated regarding mor-phological characteristics and yield. Therefore, the objective of the present paper was to characterize leaves and fruits, to determine embryo number per seed and to evaluate polyembriony rates of three hybrid rootstocks: citranges ‘Fepagro C 13’, ‘Fepagro C 37’ and ‘Fepagro C 41’, comparing then to three other rootstocks currently used in citrus orchards Trifoliata, citru-melo ‘Swingle’ and citrange ‘Troyer’. Little morphological variation was found in leaves but, for fruits, some differences were observed, especially in citranges ‘Fepagro C 13’ and ‘Fepagro C 37’ that produced, in average, many seeds per fruit 24.2 and 35.0, many of them viable, 19.2 and 21.2 and with a good number of embryos 5.0 and 3.1, respectively, besides presenting high polyembriony taxes, 84% and 92%, respectively. The results show that these two hybrids have a good potential to be used as seed donor plants to citrus rootstocks.Key words: citriculture, alternative rootstocks, leaves and fruits morphology.

Ploidia e fertilidade de pólen em progênies de citros

PLOIDY AND POLLEN FERTILITY IN CITRUS HYBRIDS This work was performed to estimate pollen fertility and determinate the ploidy level of 11 to 12 years old progenies of crosses of ‘Montenegrina ’ mandarin (Citrus deliciosa Ten.) with ‘King’ mandarin (C. nobilis Lour.) and with ‘Caipira’ sweet orange (C. sinensis (L.) Osb.) maintained at Estacao Experimental Agronomica of UFRGS, in Eldorado do Sul, Brazil. The ploidy level was determined by chromosome countings in meiosis cells and pollen fertility evaluated by staining pollen grains with propionic carmine. All evaluated hybrids are diploid and pollen fertility varied from zero to 98%. C27, a hybrid ‘Montenegrina’ x ‘Caipira’, was found is sterile, and C21, from the same cross, showed 10 % fertility. The lowest observed fertility in the progeny ‘Montenegrina’ x ‘King’ was 42 %.

Emergência de plântulas de Butia odorata (Barb. Rodr.) Noblick em casa de vegetação

Butia odorata is a native palm tree from Rio Grande do Sul State, Brazil, with fruits used as food. The aim of this study was to test the emergence of seeds and diaspores under different procedures to dormancy breaking in greenhouse conditions. Scarification by opening of the embryonic cavity of the seed allowed the emergence of 72% in a mean time of 56 days. The immersion of the seeds in water for 18 h before to sowing increased the emergence but delayed the mean time to 323 days. Seeds isolated from the endocarp and not scarified presented 38% of germination in a mean time of 319 days. The emergence from diaspores submitted to 40 oC for three weeks before sowing was not significantly different to emergence from seeds isolated from endocarp, however the mean time was reduced to 206 days. The opening of the embryonic cavity resulted in higher percentage of emergency, with significant lower mean time.

Propagação de abacateiro via estacas estioladas

This research aimed to test a method of avocado propagation from etiolated cuttings in recipients with different heights. The experiment was carried out in an intermittent mist chamber. The experimental design was in randomized blocks with a 3x4 factorial and three replicates. Two methods of sap obstruction (girdling or strangulation) and four heights of containers (10, 15, 20 or 25 cm) were tested. After 250 days, there was no effect of container heights on the survival, the number of developed leaves, plant height and diameter of the seedlings formed from etiolated cuttings. There was a higher survival rate and number of leaves in girdled cuttings as compared to control plants; cuttings obtained from the strangulation treatment had intermediate behavior. The previous bark girdling or strangulation of etiolated avocado branches increased survival and plant growth for the propagation of selection Viamao cuttings.

Desinfestação de sementes e multiplicação in vitro de guabijuzeiro a partir de segmentos apicais juvenis (Myrcianthes pungens O.Berg) D. Legrand

The guabijuzeiro is an evergreen tree 15-25 meters high. Occurs in Brazil from Sao Paulo to Rio Grande do Sul. Among the wild fruits this species has several characteristics which make it with potential for commercial use, in which the most important are related to fructification. Its propagation is carried out by seed and little information on vegetative propagation. Hence, the objective was to study the disinfection of seeds and in vitro multiplication of guabijuzeiro. The experiments were performed at the Laboratory of Biotechnology in Horticulture, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul. The test began with the disinfestation soaking in 70% ethanol for 1 minute, followed by a solution of sodium hypochlorite at concentrations of 0; 2; 4; 6 and 8%. The culture medium used in experiments was WPM with 30 g.L-1 sucrose and 7 g.L-1 of agar. For the testing of multiplication were used apical segments of seedlings from seeds germinated in vitro. The treatments consisted of BAP concentrations (0; 0,2; 0,4; 0,6; 0,8; 1 and 2 mg.L-1). As a result the concentrations between 4 and 6% sodium hypochlorite are more advantageous, as well as being effective in disinfestation, positively influence the germination. For multiplication, the cultivation of apical segments on medium with BAP at concentrations of up 1mg.l-1 was effective.

Risk analysis of introduction and spread of huanglongbing in citrus groves in Rio Grande do Sul, Brazil

Huanglongbing (HLB), the most damaging disease of the citrus industry, is present in the Brazilian states of São Paulo, Minas Gerais and Paraná. The risks of introduction and spread of this A1 quarantine pest in citrus groves of the Rio Grande do Sul (RS) state were assessed based on a structured questionnaire composed of 27 questions applied to 163 growers in 35 municipalities. The locations were defined according to the economic relevance of citriculture, and the sample size (number of interviewed farmers) was proportional to the cultivated area in each municipality. A multi-criteria method was used to prioritize and assign weights to specific criteria associated with the different risks. Each farm was assigned to one of the four risk categories: low (0 to 0.25), medium (0.25 to 0.50), high (0.50 to 0.75) and very high (0.75 to 1.0). The estimated risks of HLB introduction and spread in RS were mostly medium to high across the regions and farms within regions. Two factors, the presence of HLB in neighbor countries and citrus fruit transport from other regions mostly accounted for the risk of introduction of HLB into RS. Following an eventual introduction, the lack of knowledge about this pathosystem and the little or no use of insecticides were identified as the main contributors of disease spread within the state.

Impacto de las concentraciones de ANA y sacarosa en el enraizamiento in vitro de Butia odorata (Barb. Rodr.) Noblick

The objective of this study was to evaluate the culture medium seeking the development and root formation of pindo palm seedlings for acclimatization. The MS medium were used at a concentration of 70% ammonium nitrate and potassium nitrate, and 0.8% of agar. In the first experiment, concentrations of naphthaleneacetic acid (ANA) added to the medium were tested. In the second, the rooting and growth of the seedlings were evaluated after varying the sucrose concentration (15, 30 and 45 g.L-1) in medium with 0.6 mg.L-1 of ANA. A third experiment was carried out to adjust the ANA concentration, based on the results of the fi rst two tests. The rooting of Butia odorata seedlings were optimized in vitro in medium with 0.3 to 0.9 mg.L-1 of ANA, combined with concentrations of sucrose between 30 and 45 g.L-1.