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Plants grown under flooding stress conditions form reactive oxygen species, both during oxygen deficiency and after reoxygenation. The tolerance of plants under these conditions depends on an efficient antioxidant system, which may be influenced by the higher expression of heat shock proteins, such as mitochondrial MT-sHSP23.6. The objective of the present study was to determine whether the overexpression of this gene increases the antioxidant activity in tomato cv. Micro-Tom plants subjected to flooding during the vegetative stage of four fully expanded leaves. The experiment was performed with three genotypes of tomato plants (Solanum lycopersicum Mill. cv. Micro-Tom), one non-transformed denominated “WT” and two modified for high and low expression of the MT-sHSP23.6 gene, subjected to normal irrigation conditions, 72 hours of flooding, and 24 and 192 hours of recovery after the removal of flooding, consisting a 3x4 split-plot factorial design with four replications. Plants were collected at the vegetative stage of 4 fully expanded leaves to determine superoxide dismutase, ascorbate peroxidase and catalase activities, hydrogen peroxide accumulation and lipid peroxidation. Overexpression of the mitochondrial MT-sHSP23.6 gene in the evaluated plants resulted in higher antioxidant system activity. However, it did not necessarily lead to less damage caused by oxidative stress. Low expression of this gene resulted in lower antioxidant system activity and greater damage caused by reactive oxygen species

Paspalum notatum Flügge (bahiagrass) is one of the most common native grasses found in southern Brazil and have become one of the most promising forage species considering their value for beef cattle production in the tropics and subtropics. The breeding program has been possible through intraspecific hybridization among sexual and apomictic clones, generating progenies with variability for agronomic traits. Hybrid materials with superior agronomic performance can be selected, registered and protected to be made available as a commercial cultivar. The objective of this work was to evaluate 24 intraspecific hybrids and select them for the superior agronomic traits, as well analyze correlations between forage traits that can assist in the selection of genotypes. Based on the three years of evaluation, hybrids KD9, KF1, KF4, and KD5 produced higher total dry mass than other genotypes. The hybrid KF4 too had greater leaf dry matter; KF1 and KF4 were the more cold tolerant. These genotypes were selected for new cycles of hybridization and field evaluations, such as seed production, fertilizer use efficiency and animal performance. The high correlation of the total dry mass with the other forage components might be useful for indirect select criteria in bahiagrass improving strategies.

‘URSBRS Mesclador’ is a red clover cultivar, adapted to southern Brazil with high dry matter production, the genetic material used in the breeding process was a collection from the Department of Fo...

The oat cultivar “URS F Flete” (Avena sativa) registration number 32980 from the Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA), was developed from the cross ‘LA 9339E17 x LAO-591-NZ 0553’ and is the first cultivar bred for the environmental conditions which predominate in southern Brazil. The cultivar hashigh forage production and good resistance to the main diseases that occur in the region.

“BRSURS Entrevero” is a white clover cultivar, indicated for intercropping with winter grasses and for oversowing natural and subtropical pastures in areas with high fertility and humidity. It has high quality and forms a mat of stolons that covers completely the soil, with a prostrate habit with the growth buds close to the surface, resulting in a high grazing aptitude.

Paspalum notatum Flugge (bahiagrass) is the most important forage grass in the native grasslands of southern Brazil; the native germplasm is tetraploid and apomictic. Breeding to produce cultivars has been possible due to chromosome doubling of sexual diploid accessions, allowing hybridizations with apomictic genotypes, generating progenies with variability for agronomic traits and segregating for reproduction mode. The aim of this study was to determine the reproduction mode of selected hybrids derived from intraspecific crosses through cytoembryological analysis and to evaluate the level of apospory expres¬sivity. Eighty one tetraploid hybrids corresponding to 21 families of sexual and apomictic parents were generated and 28 most productive plants based on their superior agronomic performance in the field were evaluated. Sixteen hybrids were reproduced sexually and 12 of them were highly apomictic or facultative apomictic. Sexual hybrids may be used for further crosses in the breeding program while highly apomictic plants produce uniform progeny and become candidates of new cultivars to promote pasture diversification. Key words: Aposporous apomixis, bahiagrass, intraspecific crosses, plant breeding.

Selection of improved genotypes is important for pasture-based feeding systems in subtropical regions. Our goal was to identify hybrids of Paspalum with enhanced forage yield and cold tolerance across 2 sites [Bagé and Eldorado do Sul (ES)], in Rio Grande do Sul, Brazil. We evaluated 19 P. plicatulum × P. guenoarum hybrids, P. plicatulum genotype 4PT, P. guenoarum cultivars Azulão and Baio and, as Control, Megathyrsus maximus cv. Aruana. At both sites, the experimental design was a completely randomized block with 4 replications. Total dry mass (total-DM), leaf-DM and cold tolerance (ColdT) were recorded. At Bagé, hybrid 102069 produced higher total-DM and leaf-DM than the progenitors and cv. Aruana, while at ES, hybrids 102069 and 10308 produced higher total-DM than 4PT, Azulão and Aruana; hybrid 102069 had higher leaf-DM. At Bagé, 16 hybrids displayed ColdT similar to their progenitors and higher than Aruana, while at ES, 12 hybrids showed ColdT similar to Azulão and Baio and higher than 4PT and Aruana. This study demonstrated that hybrids of Paspalum with superior forage yield to their progenitors and Aruana, and hybrids with higher ColdT than 4PT and Aruana are in existence. The hybridization technique shows potential for producing alternative genotypes with higher forage yield and ColdT for sowing in subtropical regions.

Recent efforts placed on breeding Paspalum species made available novel genetic resources for livestock production systems. Nitrogen (N) is an important factor to increase warm‐season grass nutritive value and production, either as anthropogenic supply or in mixture with legumes. Dry matter yield (DMY) and nutritive value in Paspalum plicatulum Michx. × Paspalum guenoarum Arechav. hybrids in response to different rates of N or in mixture with temperate legumes were evaluated for two years. The experiment was a randomized complete block design in split‐plot arrangement with three replications. Treatments were six N supply systems: 0, 60, 120, 240, 480 kg N/ha and grass–legume mixture [white clover (Trifolium repens L.) + birdsfoot trefoil (Lotus corniculatus L.)] as whole plots, and six genotypes (hybrids: 1020133, 102069, 103084, 103061, P. guenoarum ecotype ‘Azulao’ and Megathyrsus maximus cv. ‘Aruana’ used as controls) as subplots. Higher N rates increased DMY and provided variability among genotypes. In general, grass–legume mixture showed greater crude protein and digestibility, and lower neutral and acid detergent fiber than N fertilized grass (p

The native grasslands of southern Brazil have sustained livestock farming for many years; however, decline in pasture areas has led to the loss of genetic diversity of forage species. The development of forage grass cultivars adapted to different environments, will contribute to forming new cultivated pastures or recovering degraded areas. The aim of this study was to assess the herbage accumulation of selected intraspecific hybrid progenies of bahiagrass (P. notatum Flügge) in two different environments (Depressão Central and Campanha region) to estimate their agronomic value. The results indicated variability for the main forage traits studied (leaf dry mass, stem dry mass, inflorescence dry mass, total dry mass, leaf: stem ratio, plant height and population density of tillers). All the hybrids producing more forage mass than the ‘Pensacola’ cultivar in the municipality of Eldorado do Sul and the majority also superior in the municipality of São Gabriel. The production of leaves in the forage was correlated with total dry mass (84%), suggesting that genotype selection for forage mass also selected for production of leaves. The selected hybrids should be indicated for new steps of assessment within the P. notatum breeding program. As pastagens nativas do Rio Grande do Sul (sul do Brasil), sustentam a pecuária há muitos anos; no entanto, o declínio em áreas de pastagens tem levado à perda da diversidade genética das espécies forrageiras e o desenvolvimento de cultivares de gramíneas forrageiras adaptadas a diferentes ambientes contribuirá para a formação de novas áresa de pastagens cultivadas ou recuperação de áreas degradadas. O objetivo deste trabalho foi avaliar o acúmulo de forragem de uma progênie híbrida intraespecífica selecionada de grama forquilha (Paspalum notatum Flügge) em dois ambientes distintos (Depressão Central e Campanha) para estimar seu valor agronômico. Os resultados indicaram variabilidade para as principais características forrageiras estudadas (massa seca das folhas, massa seca do caule, massa seca da inflorescência, massa seca total, relação folha: caule, altura da planta e densidade de perfilhos) com todos os híbridos produzindo mais massa de forragem do que a cultivar ‘Pensacola’ no município de Eldorado do Sul e a maioria também superior no município de São Gabriel. A produção de folhas foi a característica mais correlacionada com a massa seca total (84%), sugerindo que a seleção de genótipos para massa de forragem também selecionou para a produção de folhas. Os híbridos selecionados poderão ser indicados para novas etapas de avaliações dentro do programa de melhoramento de P. notatum.

Paspalum notatum is an important forage native to Southern Brazil and one of the most promising fodder species in terms of productivity, quality, resistance and growth speed. The objective of this study was to evaluate the reproductive mode and fertility of hybrid progenies resulting from artificial crosses among artificially duplicated sexual plants, selected intraspecific hybrids of the UFRGS breeding program and apomictic ecotypes of the species. The resulting F1 progenies were represented by 24 plants with high pollen viability (varying from 82.15 to 99.67%) and 1.2:1 segregation for the sexual: apomictic reproduction mode, indicating predominantly sexual hybrids, due to distorted segregation. In the apomictic plants, most chromosomes paired as bivalents in diakinesis. Since the low presence of abnormalities observed in the meiotic chromosome pairing and the high pollen viability of the hybrids, all plants were confirmed as promising parents for future crosses.

Nitrogen supply and mixtures with legumes affect agronomic performance of pastures, and both practices can guide breeding decisions in Paspalum hybrids. The goals of this study were: (a) quantify herbage accumulation (HA), leaf accumulation (LA), cold tolerance, and N use efficiency (NUE) in P. plicatulum × P. guenoarum hybrids subjected to N fertilization or grown in a mixture with legumes; (b) compare the grass–legume system to a grass–N fertilizer system; and (c) select the best hybrid for future cultivar releases. A randomized complete block design with three replications and a split‐plot treatment arrangement was used for 2 yr, with five N rates (0, 60, 120, 240, and 480 kg N ha−1) and a grass–legume mixture [grass + white clover (Trifolium repens L.) + birdsfoot trefoil (Lotus corniculatus L.)] as whole plots, and six genotypes as subplots (hybrids: 1020133, 102069, 103084, 103061; and controls: P. guenoarum ‘Azulão’ and Megathyrsus maximus ‘Aruana’). Higher N rates increased HA, LA, and cold tolerance. Higher NUE was obtained between 60 and 120 kg N ha−1. In the grass–legume mixture HA was similar to the rates of 60 and 120 kg N ha−1. Hybrid 1020133 had HA similar to the controls, LA greater than Aruana, and greater cold tolerance and NUE at 60 kg N ha−1 than Azulão and Aruana. Hybrid 1020133 should be selected for further animal performance studies. The agronomic performance of perennial pastures can be improved through N management, and NUE should be a selection criterion in forage breeding.

The rational use of N fertilization is essential to increase the recovery efficiency and crop productivity and decrease the cost of production. The objective of this study was to assess forage yield (TDM), tillers population density (TPD) and N use efficiency (NUE) in six Paspalum notatum Flüggé genotypes in response to N fertilization. The experimental design involved randomized blocks on a subdivided plot design. In 2014-2015 the TDM was higher for the C22 and B26 hybrids (P < 0.0001), which were similar to each other, with an average of 6173 kg DM ha-1 yr-1. In 2015-2016 the TDM of the genotypes ranging from 7053 to 13773 kg DM ha-1 yr-1, for pastures fertilized with 0 and 480 kg N ha-1 yr-1, respectively. An interaction was found between Genotype × N fertilization level (P = 0.0155) for TDM in 2016-2017. In the years 2015-2016 and 2016-2017 the C22 hybrid standed out as the genotype with the highest tiller production in response to N fertilization. In the year 2014-2015 NUE was higher (P = 0.0015) in the N fertilization levels N60, being of 15.5 kg DM kg-1 N. In the years 2015-2016 and 2016-2017 the NUE was higher at fertilization level N120 (P < 0.05), being of 21.1 and 31.5 kg DM kg-1 N, respectively. The C22 hybrid was distinct as the genotype with the highest DM yield and superior tillering characteristics. The N fertilization level of 120 kg N ha-1 yr-1 promoted greater NUE in all P. notatum genotypes

Paspalum notatum é uma das mais importantes espécies das pastagens nativas do Sul do Brasil, que é a principal fonte forrageira para a pecuária. Os ecótipos nativos são tetraploides e de reprodução apomítica, o que impede o registro e a proteção de cultivares. Porém, uma variedade cultivada, Paspalum notatum var. saurae (cultivar Pensacola) é diplóide e sexual. O objetivo deste trabalho foi de poliploidizar artificialmente plantas de cv Pensacola, para serem utilizadas como genitores femininos em cruzamentos com genitores masculinos tetraploides e apomíticos. Plântulas e sementes foram tratadas por imersão com soluções de colchicina por tempo de exposição variável. Três plantas confirmaram número cromossômico tetraploide. As plantas polyploides obtidas serão avaliadas quanto ao modo de reprodução; se confirmarem ser sexuais, serão utilizadas nos esquemas de cruzamentos com plantas apomíticas nativas para obtenção de novos híbridos intraespecíficos. Paspalum notatum is one of the most important native grassland species of southern Brazil, and the main forage source for livestock. The native ecotypes are tetraploid and have apomictic reproduction, which prevents the registration and protection of plant varieties. However, the cultivated variety Paspalum notatum var. saurae (cultivar Pensacola) is diploid and sexual. The objective of this study was to artificially produce polyploid cv. Pensacola plants, to be used as female parents in crosses with male tetraploid and apomictic parents. Seedlings and seeds were immersed in colchicine solutions for different periods. A tetraploid chromosome number was confirmed in three plants. The reproduction mode of the resulting polyploid plants will be assessed; if confirmed to be sexual, they can be used in crosses with native apomictic plants to breed new intraspecific hybrids.

For many decades, animal production in southern Brazil has been based on native forage grasses. Paspalum notatum Flügge (bahiagrass) is one of the most frequently used native grass in southern Brazil. The native germplasm of P. notatum is tetraploid and displays apomictic reproduction; hence, chromosome doubling of sexual diploid accessions is required to facilitate hybridization. The main goal of this study was to evaluate forage production and other agronomical evaluation of P. notatum intraspecific hybrids in order to obtain new varieties that could be registered and/or protected and launched as new cultivars in the future. Three tetraploid sexual genotypes were crossed with the ecotypes Bagual and André da Rocha. Biomass production (leaf, stem, and inflorescence fractions), plant growth habit, plant height, number of tillers, and frost damage were evaluated in the resulting hybrids. The general combining ability (GCA) and specific combining ability (SCA) were calculated for the six families generated. We evaluated 196 hybrids and the most productive yielded 42 % more total dry mass than the most productive parent (ecotype Bagual), and Bagual production was seven-fold higher than that of cultivar ‘Pensacola’. The highest GCA values were observed for Bagual and Q4205. No correlation was observed between leaf coloration and the frost effect or regrowth in the following winter. Similarly, no correlation between plant growth habit and dry mass production was observed. The reproduction mode of the most productive hybrids are currently being analyzed in larger plots to identify apomictic and sexual genotypes for future registration and protection.

The Paspalum genus includes several species that are important for livestock in Rio Grande do Sul, such as P. notatum and P. guenoarum , typical of native pastures of the Pampa biome. The aim of this study was to investigate forage production and chemical composition of four ecotypes of these species in relation to the cv. ‘Pensacola’ ( P. notatum ). Ecotypes of P. guenoarum (Azulao and Baio) and P. notatum (Andre da Rocha and Bagual) and the cv. ‘Pensacola’ were evaluated for two years, during which four cuts/year were made. The work was carried out under field conditions at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul (30°05’S; 51°39’W), in a completely randomized design. P. guenoarum stood out for higher productivity and greater tolerance to cold; the Azulao ecotype showed more autumn production in relation to the other ecotypes. Crude protein content ranged from 14 (Baio) to 15% (‘Pensacola’); for neutral detergent fiber, the variation was 68 (Azulao) to 71% (‘Pensacola’) and for acid detergent fiber there was a variation of 38 (‘Pensacola’) to 43% (Baio). The data demonstrates the potential of native genotypes for use as cattle feeding in southern Brazil.

The aim of this study was to determine the mode of reproduction of a hybrid progeny derived from intraspecific crosses of Paspalum notatum through cytoembryological analysis and use of RAPD (random amplification of polymorphic DNA) molecular markers. Cytoembryological analysis allowed identification of the mode of reproduction of 28 plants that were selected after agronomic productivity evaluations. Of these, 19 had embryo sac morphology compatible with an apomictic mode of reproduction and nine had embryo sac morphology compatible with a sexual mode of reproduction. Meanwhile, molecular marker analysis for 194 individuals showed 54 sexual and 140 apomictic plants; of the 28 plants analyzed by the two methods, ten results (35.7%) were in disagreement. In this paper, through cytoembryological analyses, a ratio of 1:2.1 of sexual to apomictic plants was found. The BCU 243 marker showed a stable pattern of amplification, but some results differed with cytoembryological analyses, demonstrating that these analyses are more reliable when determining the mode of sexual reproduction for the plants of P. notatum. Apomictic plants characterized in this work can be tested in the field to check their agronomic value and registration as plant varieties, while the sexual plants can be used as potential parents in future crosses.

The objective of this study was to evaluate, through meta-analysis, the forage characteristics of various species of the genus Paspalum and to use them to select the best ecotypes that can be used in artificial hybridization as parents and hybrids for pasture production and natural pasture recovery systems. Data were obtained from studies conducted by the Department of Forage Plants and Agrometeorology of the Universidade Federal do Rio Grande do Sul. Database comprised tests conducted with ecotypes and/or hybrids of Paspalum spp. in plots for evaluating total dry mass production, leaf dry mass production, and stem dry mass production by means of cuts. Total dry mass production, which included leaves and stems, differed between the ecotypes and hybrids. Hybrid H12 was the most divergent of all evaluated accessions. The greatest genetic divergence occurred due to dry mass production. Hybrids showed high total dry mass production, comprised mainly of leaves. Hybrid H12 and the accession of Paspalum lepton 28E were identified as the most dissimilar based on the generalized Mahalanobis distance using Tocher’s method. Total dry mass production is the characteristic that most contributed to the detection of genetic variability. RESUMO: O objetivo deste trabalho foi avaliar, por meio de meta-análise, a variabilidade dos caracteres forrageiros de espécies do gênero Paspalum e utilizá-los para selecionar os melhores ecótipos para serem utilizados em hibridações artificiais como genitores e híbridos para serem empregados em sistemas de produção a pasto e recuperação de pastagens naturais. Os dados foram obtidos a partir ensaios, do Departamento de Plantas Forrageiras e Agrometeorologia da Universidade Federal do Rio Grande do Sul. A base de dados foi composta por ensaios conduzidos com ecótipos e/ou híbridos do gênero Paspalum, em parcelas, avaliando por meio de cortes a produção de massa seca total, de folhas e colmos. Houve diferença entre ecótipos/híbridos para produção de matéria seca total, de folhas e colmos. O híbrido H12 foi o mais divergente dos acessos avaliados. A maior divergência genética ocorreu devido à produção de massa seca. Os híbridos apresentam elevada produção de massa seca total, sendo esta composta principalmente por folhas. O método de Tocher utilizando a distância generalizada de Mahalanobis identifica o híbrido H12 e o acesso de Paspalum lepton 28E como os mais dissimilares. A produção de massa seca total é o caractere que mais contribui para a detecção da variabilidade genética.

The objective of this study was to evaluate the influence of photoperiod on the forage yield by ecotypes and intraspecific hybrids of P. notatum. Tetraploid ecotypes from the United States Department of Agriculture and the National University of the Northeast in Argentina, in addition to six intraspecific hybrids, totaling 19 ecotypes, were assessed. The materials evaluated were subjected to an extended photoperiod (14 h of light) and natural photoperiod from July 2011 to October 2012. The experimental design was a completely randomized factorial scheme of 19 × 2 (ecotypes × photoperiod) consisting of five replicates. The materials were influenced differentially by the variation in photoperiod, with one group showing high sensitivity, whereas another, smaller group, was insensitive to this factor. The use of materials with differentiated responses to photoperiod in different climatic regions can be an important tool to increase forage yield of Paspalum notatum.

Mimosa scabrella Bentham, popularly known as “bracatinga” in Brazil, is a very important multipurpose tree especially in the southern region of the country, where it occurs naturally in plant associations called “bracatingais”. The species is presently in danger of losing genetic variability as it normally occurs in regions subjected to intense urbanization, industrialization, agriculture and cattle raising. Aiming at broadening the knowledge about the species we have investigated cytogenetic characteristics and genetic diversity among natural populations. The results show that all populations are tetraploid (2n = 4× = 52) and that there is a high genetic diversity among the populations. There is still time to avoid genetic erosion of M. scabrella if the areas where the species occurs are protected.

Tendo em vista inúmeros problemas fitossanitários que vêm acometendo a citricultura brasileira, a diversificação de porta-enxertos é uma necessidade prioritária. Híbridos de porta-enxertos estão sendo desenvolvidos por programas de melhoramento genético de citros, os quais devem ser avaliados quanto a características morfológicas e de produção. Por esse motivo, o objetivo deste trabalho foi caracterizar folhas e frutos, determinar o número de embriões por semente e avaliar a taxa de poliembrionia de três porta-enxertos híbridos: citranges 'Fepagro C 13', 'Fepagro C 37' e 'Fepagro C 41' e compará-los a três porta-enxertos já utilizados na sustentação dos pomares de citros: Trifoliata, citrumelo 'Swingle' e citrange 'Troyer'. Pouca variação foi observada na caracterização morfológica das folhas, porém na caracterização dos frutos foram verificadas diferenças. Destacam-se os citranges 'Fepagro C 13' e 'Fepagro C 37' que produziram, na média, muitas sementes por fruto, ou seja, 24,2 e 35,0, sendo muitas viáveis, 19,2 e 21,2 e estas portando bom número de embriões, 5,0 e 3,1, além de altas taxas de poliembrionia, 84 e 92% respectivamente. Os resultados obtidos com os dois híbridos demonstram que eles possuem bom potencial para serem utilizados como plantas doadoras de sementes para porta-enxertos de citros. 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 morphological 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, citrumelo '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.

As plantas cítricas possuem ampla variação morfológica e citogenética. Neste contexto, análises dessas plantas podem auxiliar na identificação de materiais mais promissores para cruzamentos. Uma população de tangerineiras híbridas oriundas do cruzamento das tangerineiras 'Clementina Fina' (Citrus clementina Hort. ex Tan.) e 'Montenegrina' (Citrus deliciosa Ten.) foi avaliada segundo características morfológicas, época de maturação, número cromossômico e viabilidade de pólen. Foi possível distinguir as 94 plantas da progênie e os genitores através dos dados morfológicos. Verificou-se uma alteração no período de maturação dos frutos nas plantas híbridas. Todas as plantas avaliadas são diplóides com um número cromossômico de 2n=18, bem como, alto grau de viabilidade de pólen, variando entre 79,0% e 98,1%. Citrus plants show morphological and cytogenetic variability and these characteristics can be useful to identify the materials for hybridization. A population of hybrid tangerines, originated from the cross between 'Clementina Fina' (Citrus clementina Hort. ex Tan.) as female and 'Montenegrina' (Citrus deliciosa Ten.) as male parents, was characterized using morphological traits, maturation period, chromosome number and pollen viability. It was possible to distinguish the 94 plants of the progeny and the parents by morphological traits. The time of fruit ripening of the hybrid extended from the beginning of April until the end of August. All plants analyzed are diploid with a chromosome number of 2n = 18 and presented high pollen viability, varying from 79.0% to 98.1%.

A cochonilha Orthezia praelonga e uma importante praga dos citros, atacando as folhas e brotos, sugando continuamente a seiva, introduzindo toxinas que provocam desfolha, enfraquecimento das arvores e queda de ate 50% dos frutos. O fungo Lecanicillium longisporum e patogenico para O. praelonga e ocorre sobre as diferentes fases de desenvolvimento do inseto, exceto ovo. O trabalho teve por objetivo identificar cochonilhas O. praelonga infectadas por Lecanicillium sp. e isolar este fungo para posterior multiplicacao visando a obtencao de colonias puras. Coletou-se 120 insetos com formacao cotonosa sobre os corpos em folhas de laranjeiras Valencia, onde se observaram fungos dos generos Penicillium, Trichoderma, Metarhizium, Beauveria e Lecanicillium. No total foram isolados nove insetos com colonias de Lecanicillium sp. Uma vez que a colonia estava isolada e identificada foram utilizados os postulados de Koch para estabelecer uma relacao causal entre o fungo L. longisporum e a cochonilha O. praelonga. Os insetos coletados das plantas inoculadas com o fungo apresentaram sintomatologia semelhante aos que anteriormente tinham colonias de Lecanicillium sp e confirmaram a relacao causal da doenca, havendo morte de 100% dos insetos apos 10 dias de inoculacao.

Os citros apresentam uma taxonomia muito complexa, principalmente com relação ao número de espécies que constituem o gênero Citrus e os gêneros afins. Genótipos classificados como espécies podem ter sido originados por hibridação interespecífica e preservados por meio da embrionia nucelar. O presente trabalho teve como objetivo caracterizar uma população de tangerineiras híbridas oriundas do cruzamento das tangerineiras 'Clementina Fina' (Citrus clementina Hort. ex Tan.), genitor feminino, e 'Montenegrina' (Citrus deliciosa Ten.), genitor masculino, utilizando marcadores do tipo microssatélites (SSR). Com 12 pares de primers, foi possível diferenciar 93 acessos do estudo e agrupar a F1 em indivíduos mais próximos do genitor feminino e do genitor masculino. O PIC (Conteúdo de Informação de Polimorfismo) dos primers variou de 0,27 a 0,65. Toda a progênie do cruzamento entre 'Clementina Fina' e 'Montenegrina' analisada neste estudo é híbrida, e os SSRs foram eficientes para identificar híbridos com maior similaridade genética em relação aos genitores, mostrando a existência de variabilidade genética entre as plantas da população estudada. Citrus have a very complex taxonomy, especially considering the number of species included in genus Citrus and related genera. What is classified as a species may have originated by interespecific hybridization and preserved through nucellar embryony. This research aimed to characterize a population of hybrid tangerines, originated from the cross of 'Clementina Fina' (Citrus clementina Hort. ex Tan.) as female and 'Montenegrina' (Citrus deliciosa Ten.) as male parents, using microsatellite molecular makers. With 12 pairs of primers it was possible to differentiate 93 of the studied accessions and to group F1 individuals nearer to the male or to the female parent. The primers PIC (Polymorphism Information Content) ranged from 0.27 to 0.65. All the analyzed progeny between 'Clementina Fina' and 'Montenegrina' is hybrid, where SSR were efficient in identifying hybrids more similar to the genitors, showing genetic variability among plants of the studied population.

Este trabalho foi desenvolvido para estimar a fertilidade do pólen e determinar o nível de ploidia em progênies dos cruzamentos da tangerineira 'Montenegrina' (C. deliciosa Ten.) com a tangerineira 'King' (C. nobilis Lour.) e com a laranjeira 'Caipira' (C. sinensis (L.) Osb.). As plantas, de pés-francos e com idade entre 11 e 12 anos, são mantidas na Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul, em Eldorado do Sul. Avaliaram-se o nível de ploidia, através da contagem dos cromossomos em células em meiose, e a fertilidade do pólen, por coloração do pólen com carmim propiônico, em 2005 e 2006. Todos os híbridos avaliados são diplóides e a fertilidade de pólen variou de zero a 98%. C27 - híbrido de 'Montenegrina' x 'Caipira' - revelou-se praticamente estéril, e a fertilidade de C21, do mesmo cruzamento, é de 10%. A menor fertilidade observada no cruzamento da 'Montenegrina' x 'King' foi de 42%.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 Estação Experimental Agronômica 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 %.

The objective of this study was to identify polyploid plants from citrus rootstocks and to evaluate the influence of the genetic constitution and of the environment on the frequency of chromosome duplication. Populations obtained from rootstock seeds of Trifoliata [Poncirus trifoliate (L.) Raf], citrumelo 'Swingle' [C. paradise Macf. × P. trifoliate], citrange 'Troyer' [C. sinensis (L.) Osb. x P. trifoliate] and citranges Fepagro 'C13', 'C37' and 'C41' [C. sinensis (L.) Osb. cv. Pêra x P. trifoliata] were evaluated under field and greenhouse conditions. Flow cytometry analysis of 415 field plants and 435 greenhouse plants identified seven (1.69%) and 29 (6.67%) tetraploids, respectively. Differences in the number of tetraploid plants among genotypes and locations were observed in field progenies of 'C 37' (2.12%) and 'C 13' (2.04%) and in greenhouse progenies of 'C 13' (15.52%) and 'C 37' (6%). The frequency of autotetraploidization events in citrus rootstocks is common and appears to be associated to genetic constitution and environmental conditions.

O objetivo deste trabalho foi confirmar os híbridos obtidos em plantas originadas do cruzamento entre as tangerineiras Citrus deliciosa 'Montenegrina' e C. nobilis 'King', e estimar a similaridade genética entre os híbridos e entre cada híbrido e seus parentais. Vinte e três pares de iniciadores microssatélites foram testados. Quatorze desses pares apresentaram bandas polimórficas entre os parentais. Os iniciadores CCSM 129 e CCSME 52 foram suficientes para identificar os 12 clones nucelares observados na população estudada. A análise da similaridade genética da população (híbridos e parentais) mostrou similaridade média de 0,56. Além dos 12 clones identificados de 'Montenegrina', foram encontrados 25 híbridos, dos quais D18, C32, D06, C05 e D09 são os mais similares a 'Montenegrina'. The objective of this work was to confirm the hybrids obtained in plants originated from the crossing between the mandarins Citrus deliciosa 'Montenegrina' and C. nobilis 'King', and to estimate the genetic similarity among hybrids, and between each hybrid and its parents. Twenty‑three pairs of microsatellite primers were tested. Fourteen of these pairs showed polymorphic bands between parents. Primers CCSM 129 and CCSME 52 were sufficient to identify the 12 nucellar clones observed in the studied population. Genetic similarity analysis of the population (hybrids and parents) showed 0.56 average similarity. Besides the 12 clones of 'Montenegrina' identified, 25 hybrids were found of which D18, C32, D06, C05 and D09 are the more similar to 'Montenegrina'.