Paulo Dejalma Zimmer

Association between genetic distances in wheat (Triticum aestivum L.) as estimated by AFLP and morphological markers

Molecular and morphological data analyses matrices are very informative tools for the estimation of genetic distances. We used AFLP markers, morphological traits and combined analysis to estimate the genetic distances between wheat genotypes and ascertain any associations between the two techneques. Nineteen wheat (Triticum aestivum L.) genotypes were analyzed using amplified fragment length polymorphism (AFLP) markers and field evaluated for two years. The matrices obtained by morphological and molecular marker data analyses revealed a significant but moderate correlation (r = 0.47), indicating that such techniques sample distinct genome regions. The combined analysis was found to be highly correlated with AFLP (r = 0.97) and moderately correlated with morphological (r = 0.59) markers. A possible explanation for such results is a bias caused by the much higher number of AFLP (229) than morphological (17) markers. Thus, it is evident that the combined analysis is not efficient when a very dissimilar number of markers are used in each isolated technique. Therefore, to obtain a better knowledge of the degree of divergence among genotypes it is necessary to consider each analysis separately.

Dissimilaridade genética de linhagens de Trichogramma Westwood (Hymenoptera: Trichogrammatidae) através de marcadores moleculares ISSR

Demands for sustainable agricultural systems have forested the development of biological control techniques, such as the use of the egg parasitoid Trichogramma Westwood. However, the arduous identification of the parasitoid at the species level, due to the tiny size and the morphological similarities is an obstacle to increasing its use. Molecular markers are useful to reach the specimen genome and avoid environmental effects that could misguide identification. Several molecular markers techniques are available and the ISSR technique has been used to differentiate close individuals, due to its high polymorphism level, reproducibility and low cost. The objective of this study was to measure the level of genetic differentiation among five lines of Trichogramma, using ISSR markers: three belonging to the species T. pretiosum Riley, one to T. atopovirilia Oatman & Platner and one to T. bruni Nagaraja. Morphological identification of the parasitoids was conducted at ESALQ/USP - Piracicaba, SP. After DNA removal and standatization, PCR reactions were performed with 26 ISSR primers; 11 of them were selected because they presented greater polymorphism and consistency. Molecular data were converted into a binary matrix and analyzed (NTSYS v. 2.1). The 11 primers produced 172 polymorphic sections. Genetic similarity ranged from 19% to 96%, showing that the ISSR technique can efficiently identify DNA polymorphism in Trichogramma. Results also indicate important inter and intra-specific variations among the parasitoid lines.

Composição química e mobilização de reservas em sementes de soja de alto e baixo vigor

CHEMICAL COMPOSITION AND RESERVE MOBILIZATION IN SOYBEAN SEEDS WITH HIGH AND LOW VIGOR The study of vigour effect on the initial stages of soybean seeds development is important, once it includes the period of crop establishment. Seeds with low vigour may result in reduction of emergence rate and dry matter production, which may affect the crop establishment. The aims of this study were to quantify chemical components and to evaluate the capacity of seed reserve mobilization in germination of soybean seeds with high and low vigour. Three cultivars, BRS 243RR, BRS 246RR and CD 219RR were studied. The characterization of seed vigour was performed by the accelerated aging test. To determine seed chemical composition, soluble sugar, starch and soluble protein were quantified; in addition alpha amylase isoenzyme activity was also evaluated. The capacity of seed reserve mobilization during germination was evaluated by seedling dry matter and length. According to the results of this study, high vigour soybean seeds exhibit higher content of soluble proteins, starch and soluble sugars. Besides, they showed higher capacity of seed reserve mobilization during germination, resulting in a better performance for seedlings development.

Bioprotetores e fungicidas químicos no tratamento de sementes de soja

Several pathogens can damage the soybean seed quality. Seeds treatment offers additional assurance to the establishment of farming at reduced costs, used mainly with the purpose of improving germination in infected seeds, controlling pathogens transmitted by seeds and protecting seeds from soil borne fungi. Significant increase of soybean seed treatment with fungicides demands research on alternative solutions, like bioprotectors, used with the intention of reducing the use of chemical pesticides, risks to operators and possible damages to Bradyrhizobium inoculation. The aim of this research was to evaluate the efficacy of seed treatment with bioprotectors agents and chemical fungicides in soybean emergency and seeds sanity. Biological agents Biotrich (Trichoderma), HFF Turfa Fertil and (Bacillus pumilus) and chemical fungicides carbendazin + thiram, carboxin + thiram and difenoconazole + metalaxyl were tested. Evaluation of products performance was carried out in laboratory, where the seed sanity was evaluated through blotter test, green house, where the plants emergency was evaluated, and in the field, plants emergency and plants height were evaluated. Better results were obtained with chemical fungicides especially benzimidazoles group associated to contact fungicide (thiram). These products promoted an adequate plant stand, even with sowing coinciding with drought periods. According to results obtained in this work, biological protectors do not offer protection to seeds in the soil reducing plant emergency.

Comparação entre medidas de distância genealógica, morfológica e molecular em aveia em experimentos com e sem a aplicação de fungicida

Estimatives of genetic dissimilarity between cultivars can be useful in a breeding program for directing crosses and evaluating the available germplasm. The objective of this work was to estimate the genetic dissimilarity between oat genotypes through AFLP markers and inbreeding coefficient and to intercorrelate these estimate with each other and with an estimate based on agronomical traits in experiments with and without fungicide application. Eleven oat cultivars were used to estimate the molecular genetic distance, from which nine were evaluated in the field to obtain the morphological estimatives. For the estimates of inbreeding coefficients, eight genotypes had known pedigree and were considered for the analyisis. A comparison of the matrices was obtained through a correlation analysis. Among the dissimilarity measures evaluated, the estimated distances based on molecular data and the inbreeding coefficient, were those evidencing the highest correlation (0.45). The second highest correlation was obtained between the morphological distances in experiments with and without fungicide application (0.44), no other correlation obtained was significant. Then, it is evident the presence of high genetic variability among the studied genotypes and the necessity of all three techniques to be used in a joined manner for obtaining a more precise estimate of genetic dissimilarity.

Absorção de P, Mg, Ca e K e tolerância de genótipos de arroz submetidos a estresse por alumínio em sistemas hidropônicos

Soils with high aluminum (Al3+) concentrations can affect the development and nutrient absorption of rice plants. The goals of this study were to evaluate the absorption of P, Mg, Ca and K in 18 rice genotypes and their overall performance when subjected to Al3+ stress in hydroponic systems. The experimental design was randomized blocks with 3 replications and four Al3+ levels (0, 10, 20 and 30mg L-1). Plantlets were treated for 20 days and evaluated for root length (CR) and P, Mg, Ca and K contents. All variables presented significant reductions in their values, and the genotypes presented different performance in nutrient absorption when facing different treatments, with an exception for Mg absorption response in which all genotypes evaluated were similar. Based on the variable CR, the genotypes Felune and Taim were considered the most tolerant and sensitive to Al3+, respectively. Regarding nutrient absorption, the genotypes presented variable responses to each evaluated nutrient, nevertheless the genotype Felune presented also high absorption levels. All the variables presented significant correlations to each other.

Structural differences between soybean seeds coat with contrasting permeability.

A exposicao das sementes de soja a ciclos alternados de elevada e baixa umidades antes da colheita, provocado pela ocorrencia de chuvas frequentes, orvalho ou as flutuacoes diarias da umidade relativa do ar, resulta na deterioracao por umidade, a qual pode ser apontada como a principal causa para a baixa qualidade das sementes. Alguns trabalhos tem evidenciado a existencia de genotipos de soja contrastantes para qualidade fisiologica de sementes. Tais diferencas podem existir em virtude da total ou parcial impermeabilidade do tegumento a penetracao de agua, o que torna as sementes menos susceptiveis aos danos mecânicos, as adversidades climaticas e a deterioracao por umidade. O objetivo desse estudo foi avaliar a qualidade fisiologica das sementes dos genotipos de soja CD-202 (tegumento amarelo, permeavel e susceptivel a deterioracao) e TP (tegumento preto, semi-permeavel e resistente a deterioracao) e identificar diferencas estruturais existentes entre os tegumentos desses genotipos. Na determinacao da qualidade fisiologica das sementes utilizaram-se os testes de germinacao e vigor (condutividade eletrica e envelhecimento acelerado). Para avaliacao da estrutura dos tegumentos, foram coletadas sementes de soja em diferentes estadios de desenvolvimento (25, 40 e 55 dias apos a antese). Essas amostras foram encaminhadas ao Laboratorio de Imunologia e Microscopia Eletronica da Embrapa Clima Temperado, onde os tecidos de tegumento foram visualizados em microscopio otico Olympus BX 51 com aumento de 40x, atraves de cortes histologicos na regiao oposta ao hilo. De acordo com os resultados do trabalho, sementes do genotipo TP apresentaram qualidade fisiologica superior em relacao ao genotipo CD-202. Quanto a caracterizacao morfologica, foram detectadas diferencas entre as estruturas dos tegumentos de soja de coloracao preta e amarela, as quais podem estar relacionadas a qualidade de sementes.

Genetic structure of annual ryegrass (Lolium multiflorum) populations estimated by RAPD

Annual ryegrass is a temperate climate annual foraging grass, grown mostly in the South of Brazil, especially in the state of Rio Grande do Sul. Despite its importance, little is known about its genetic diversity, both within and among the populations cultivated. This knowledge is of fundamental importance for developing breeding and conservation strategies. The aim of this study was to characterize the genetic diversity and structure of four populations of annual ryegrass. Three of the populations were located in Rio Grande do Sul and the fourth in Uruguay. RAPD markers were used to study the genetic diversity and structure of these populations. Analysis of 375 individuals sampled from the populations, using six RAPD primers, generated a total of 82 amplified bands. They included 73 polymorphic bands (89,02%). The value of the total genetic diversity index obtained, (0,71) was high, indicating the presence of wide genetic diversity in the four populations. Genetic structure analysis revealed that 98% of total diversity is intrapopulational, whereas interpopulational genetic diversity was only 2%. These results suggest that before these populations separated, they had gone through a period of gene exchange and, even after the separation event, gene frequency stayed at levels similar to the original levels, with no differential selection for these genes in the different cultivation areas.

Expressão diferencial de isoenzimas durante o processo de germinação de sementes de arroz em grandes profundidades de semeadura

The germination process consists of a complex and regulated group of physiologic and biochemical events that happen in the seed soon after beginning water absorption. The restart of the embryo growth due to water absorption involves the reactivation of many enzymes that will hydrolyze reserve substances, to supply redox potential and energy for germination. Plantlet emergence in monocotyledonous depends, principally, on the sowing depth and other factors such as genetic potential and seed vigor, because the embryo is nurtured by the seed stores along. In this study, isoenzimatic patterns of Esterase (EST), Acid Phosphatase (ACP), Malate Dehydrogenase (MDH), Alcohol Dehydrogenase (ADH) and Glutamate Oxalacetate Transaminase (GOT) were analyzed among germination processes at 20 cm in 34 red rice ecotypes and 5 commercial cultivars with the objective of identifying differential expression variations in the isoenzimatic systems analyzed. The five isoenzimatic systems analyzed showed variations in the enzymatic expression, mainly when compared with the patterns of the dry seed with the developing plantlets. From the results obtained it was concluded that ere is differential expression in the isozyme genes Esterase (EST), Acid Phosphatase (ACP), Malate Dehydrogenase (MDH), Alcohol Dehydrogenase (ADH) and Glutamate Oxalacetate Transaminase (GOT), showing participation in the germination process in rice.

Analysis of Stress-Responsive Gene Expression in Cultivated and Weedy Rice Differing in Cold Stress Tolerance

Rice (Oryza sativa L.) cultivars show impairment of growth in response to environmental stresses such as cold at the early seedling stage. Locally adapted weedy rice is able to survive under adverse environmental conditions, and can emerge in fields from greater soil depth. Cold-tolerant weedy rice can be a good genetic source for developing cold-tolerant, weed-competitive rice cultivars. An in-depth analysis is presented here of diverse indica and japonica rice genotypes, mostly weedy rice, for cold stress response to provide an understanding of different stress adaptive mechanisms towards improvement of the rice crop performance in the field. We have tested a collection of weedy rice genotypes to: 1) classify the subspecies (ssp.) grouping (japonica or indica) of 21 accessions; 2) evaluate their sensitivity to cold stress; and 3) analyze the expression of stress-responsive genes under cold stress and a combination of cold and depth stress. Seeds were germinated at 25°C at 1.5- and 10-cm sowing depth for 10d. Seedlings were then exposed to cold stress at 10°C for 6, 24 and 96h, and the expression of cold-, anoxia-, and submergence-inducible genes was analyzed. Control plants were seeded at 1.5cm depth and kept at 25°C. The analysis revealed that cold stress signaling in indica genotypes is more complex than that of japonica as it operates via both the CBF-dependent and CBF-independent pathways, implicated through induction of transcription factors including OsNAC2, OsMYB46 and OsF-BOX28. When plants were exposed to cold + sowing depth stress, a complex signaling network was induced that involved cross talk between stresses mediated by CBF-dependent and CBF-independent pathways to circumvent the detrimental effects of stresses. The experiments revealed the importance of the CBF regulon for tolerance to both stresses in japonica and indica ssp. The mechanisms for cold tolerance differed among weedy indica genotypes and also between weedy indica and cultivated japonica ssp. as indicated by the up/downregulation of various stress-responsive pathways identified from gene expression analysis. The cold-stress response is described in relation to the stress signaling pathways, showing complex adaptive mechanisms in different genotypes.