Variabilidade genética de isolados de Fusarium oxysporum f. sp. cubense obtidos de bananais do norte de Minas Gerais

A banana é uma das frutas tropicais mais consumidas no mundo, respondendo por, aproximadamente, 10% do comércio mundial de frutas. O mal-do-panamá, causado por Fusariumoxysporum f. sp. cubense (E.F. Smith), é uma das principais doenças da bananeira. Os marcadores moleculares RAPD têm sido extremamente úteis para estudos de identificação taxonômica, análise de variabilidade da virulência em fungos fitopatogênicos, caracterização de raças e variabilidade inter e intraespecifica de populações de diferentes regiões. O objetivo do trabalho foi avaliar a variabilidade genética de 36 culturas monospóricas de isolados de F. oxysporum f. sp. cubense por meio de marcadores moleculares do tipo RAPD. Foram selecionados 13 primers RAPD, e a análise de dados foi realizada utilizando-se do coeficiente de similaridade de Nei e Li. A partir da amplificação dos primers, foram obtidas 178 bandas, sendo que 167 (93,82%) apresentaram polimorfismo entre, pelo menos, dois isolados e apenas 11 (6,18%) apresentaram monomorfismo, demonstrando alta variabilidade entre os isolados. As distâncias genéticas variaram de 5,7 a 54,6%, sendo a distância média de 30,2%, e a distância média relativa, de 55,3%. De acordo com a análise de agrupamento (UPGMA), não foram observadas correlações entre os isolados estudados. Os resultados sugerem alta variabilidade genética entre os isolados avaliados, não ocorrendo agrupamento de acordo com a origem geográfica de coleta

Nitrogen symbiotically fixed by cowpea and gliricidia in traditional and agroforestry systems under semiarid conditions

The objective of this work was to estimate the amounts of N fixed by cowpea in a traditional system and by cowpea and gliricidia in an agroforestry system in the Brazilian Northeast semiarid. The experiment was carried out in a randomized complete block design, in a split-plot arrangement, with four replicates, in the semiarid region of the state of Paraíba, Brazil. Plots consisted of agroforestry and traditional systems (no trees), and split-plots of the three crops planted between the tree rows in the agroforestry system. To estimate N fixation, plant samples were collected in the fourth growth cycle of the perennial species and in the fourth planting cycle of the annual species. In the agroforestry system with buffel grass and prickly-pear cactus, gliricidia plants symbiotically fix high proportions of N (>50%) and contribute with higher N amounts (40 kg ha-1 in leaves) than in the traditional system (11 kg ha-1 in grain and 18 kg ha-1 in straw). In the agroforestry system with maize and cowpea, gliricidia plants do not fix nitrogen, and N input is limited to the fixation by cowpea (2.7 kg ha-1), which is lower than in the traditional system due to its lower biomass production

Robust and coordinated tuning of power system stabiliser gains using sequential linear programming

This study presents a linear programming (LP)-based multivariable root locus following technique for coordinating the gain settings of power system stabilisers (PSSs). The stabiliser robustness is accounted for in the design problem by simultaneously considering the state-space representations and multivariable root loci corresponding to different operating scenarios. The proposed technique computes a curve in the PSS gain parameter space such that when the PSS gains move along this curve to their optimal values, the branches of the corresponding multivariable root loci terminate at satisfactory points in the complex plane. The curve in the gain parameter space is computed via a linear program that successively minimises the Euclidean distance between the unsatisfactory and satisfactory eigenvalue locations. The design method is demonstrated on a 39-bus test system with 14 operating scenarios. A comparison is carried out between the coordination results of two PSS structures, one involving two phase-lead blocks and the other comprised of two phase-lead blocks and a phase-lag block. © 2010 The Institution of Engineering and Technology.Ben-Tal A, 2001, LECT MODERN CONVEX O; Cai LJ, 2005, IEEE T POWER SYST, V20, P294, DOI 10.1109-TPWRS.2004.841177; CIGRE Task Force, 2000, 380216 CIGRE TASK FO; daCruz JJ, 1997, INT J ELEC POWER, V19, P519, DOI 10.1016-S0142-0615(97)00023-9; do Bomfim ALB, 2000, IEEE T POWER SYST, V15, P163, DOI 10.1109-59.852116; DOI A, 1984, IEEE T POWER AP SYST, V103, P1473, DOI 10.1109-TPAS.1984.318486; Ferraz J.C.R., 2001, IEEE POW ENG SOC WIN, V3, P1154; FERRAZ J.C.R., 2007, IEEE POW ENG SOC GEN, P1; FERRAZ JCR, 2004, IEEE PES POW SYST C, V2, P1164; GIBB WRG, 1991, MOVEMENT DISORD, V6, P2, DOI 10.1002-mds.870060103; GIBBARD MJ, 1988, IEE PROC-C, V135, P276; Kamwa I, 2005, IEEE T POWER SYST, V20, P903, DOI 10.1109-TPWRS.2005.846197; Kamwa I, 2000, IEEE T POWER SYST, V15, P1084, DOI 10.1109-59.871737; Kundur P., 1994, POWER SYSTEM STABILI; MARTINS N, 1999, IEEE PES SUMM M 18 2, V1, P58; Nagurka M. L., 1993, Transactions of the ASME. Journal of Dynamic Systems, Measurement and Control, V115; Pai M. A., 1989, ENERGY FUNCTION ANAL; Pal B., 2005, ROBUST CONTROL POWER; Pal BC, 2002, IEE P-GENER TRANSM D, V149, P739, DOI 10.1049-ip-gtd:20020659; Pal BC, 2000, IEEE T POWER SYST, V15, P356, DOI 10.1109-59.852144; Pourbeik P, 1998, IEEE T POWER SYST, V13, P473, DOI 10.1109-59.667371; ROGERS G, POWER SYSTEM TOOLBOX; Rogers G., 2000, POWER SYSTEM OSCILLA; Rommes J, 2006, IEEE T POWER SYST, V21, P1471, DOI 10.1109-TPWRS.2006.881154; Rommes J, 2006, IEEE T POWER SYST, V21, P1218, DOI 10.1109-TPWRS.2006.876671; Rommes J, 2010, IEEE T POWER SYST, V25, P929, DOI 10.1109-TPWRS.2009.2036822; Sturm JF, 1999, OPTIM METHOD SOFTW, V11-2, P625, DOI 10.1080-10556789908805766; XU XM, 1986, 25 IEEE C DIC CONTR, V25, P713; Zanetta LC, 2005, IEEE T POWER SYST, V20, P895, DOI 10.1109-TPWRS.2005.84611119191