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Resumo -Os objetivos deste trabalho foram estabelecer estimativas de repetibilidade de características agroindustriais em 20 genótipos de cana-de-açúcar, determinar a previsibilidade de cada caráter e indicar a predição do valor verdadeiro de cada clone. O delineamento utilizado foi blocos casualizados, com cinco repetições. Utilizaram-se a análise de variância com dois fatores de variação (cortes e genótipos) e a análise dos componentes principais para estimar o coeficiente de repetibilidade , a partir de três cortes. Foram obtidas estimativas de repetibilidade acima de 0,5 para fibra e toneladas de cana por hectare, em ambos os métodos, com confiabilidade maior que 84% pelo método dos componentes principais. As características que ficaram abaixo de 0,5, com previsibilidade inferior a 74%, necessitam de um maior número de avaliações. Os métodos dos componentes principais e análise de variância indicaram, em cinco cortes, uma previsibilidade maior que 80% para fibra, porcentagem de pol (sacarose) no caldo da cana, toneladas de cana por hectare e toneladas de pol no caldo da cana por hectare, embora o primeiro tenha sido mais eficiente. Considerando toneladas de cana por hectare e toneladas de pol no caldo da cana por hectare, os clones RB9371, RB9350 e RB9364 são os melhores.Termos para indexação: Saccharum, clones, seleção, análise de variância, componentes principais. Repeatability of agro-industrial characteristics in sugar caneAbstract -The objectives of this work were to establish repeatability estimates for agro-industrial characteristics for twenty genotypes of sugar cane, to indicate the determination coefficient of each character and the prediction of truthful value of each clone. The design consisted of randomized blocks, with five replications. The analysis of variance with two factors of variation (cuts and genotypes) and the analysis of the main components were used to estimate the repeatability coefficient , initiating with three cuts. Estimates of repeatability were obtained over 0.5 for fiber and ton of cane per hectare, in both methods, with confidence over 84% by the method of main components. Characteristics lower than 0.5 and determination lower than 74% need a greater number of measures. The methods of main components and analysis of variance evidenced, in five cuts, determination over 80% for fiber, percentage of pol (sucrose) in the juice of cane, tons of cane per hectare and tons of pol in the juice of cane per hectare, though the first had been most efficient. Considering tons of cane per hectare and tons of pol in the juice of cane per hectare, the clones RB9371, RB9350 and RB9364 are the best.

The aim of this study was to analyze the genetic similarity in commercial cultivars of sugarcane from the breeding program cultivars RB (Republic of Brazil), using SSR markers and coefficient of parentage. Eighteen microsatellite markers were used to estimate genetic similarity in 30 genotypes and coefficient of parentage was estimated in 28 accessions. Eighteen primer pairs produced an average of 3.2 alleles, the level of polymorphism (PIC value) ranged from 0.34 to 0.78 in SMC248CG and SCC2 primers, respectively. The parentage coefficient was high among cultivars, with a mean of 0.14, suggesting high relationship among the cultivars. The results here suggest that to analyzed accessions, there is a high genetic similarity which could reduce the genetic gain in breeding. However, crosses among genotypes of sugarcane produce a high variability in the progenies, suggesting a combination between the genomes of species that originated the current cultivars.

The aim of this report is to depict the proceedings for obtaining new RB varieties of sugarcane in Alagoas, Brazil. This process starts at Sugarcane Flowering and Crossing Station, At Serra do Ouro. Serra do Ouro is located at 9º13'S 35º 50'W, 450m above sea level and 35km from the sea. The Winter (the wet season) extends from March to August. The Summer (the dry season) extends from September to February, and under these conditions the flowering process takes place and the annual cross station activity commences. Field trials and industrial analyses are carried out at sub-stations and sugar mills, respectively. The process for releasing new varieties is accomplished over eleven years. Since 1970 Serra do Ouro has produced and released 51 RB commercial varieties which cover over 50% of the sugarcane-growing area in Brazil.