Geraldo Veríssimo de Souza Barbosa

Desenvolvimento vegetativo e produção de variedades de cana-de-açúcar em relação à disponibilidade hídrica e unidades térmicas

Objetivou-se, neste trabalho, avaliar padroes de crescimento e de producao de variedades de cana-de-acucar (Saccharum officinarum L.) com os graus-dias e disponibilidade hidrica, durante os cultivos de cana-planta e cana-soca, na regiao dos Tabuleiros Costeiros Alagoano. O trabalho foi desenvolvido na area experimental de Agrometeorologia da Universidade Federal de Alagoas, Rio Largo-AL, num solo classificado como Latossolo Amarelo coeso argissolico. Utilizou-se o delineamento experimental de blocos cazualizados com cinco repeticoes e quatro tratamentos: variedades RB92579, RB931530, RB93509 e SP79-1011. As variaveis da cultura utilizadas foram: perfilhamento, altura da planta, indice de area foliar (IAF), acumulo de materia seca no colmo e producao final. Foram encontradas diferencas significativas entre as medias de perfilhamento das variedades em todas as epocas amostradas, de forma geral o maior perfilhamento foi observado na variedade RB92579. O crescimento das plantas apresentou curvas de formato sigmoidal, com tres fases distintas. Na fase de estabelecimento da cultura, apesar de ter ocorrido otima disponibilidade hidrica, o crescimento foi lento. Na fase de crescimento vegetativo as plantas nao cresceram em potencial, porque houve deficiencias hidricas. A fase final ocorreu entre 1500 e 2015 GD na cana-planta e 950 e 1800 GD na cana-soca. A variedade RB92579 alcancou valores de IAF superiores a 3, logo aos 600 GD nos dois ciclos, permanecendo o restante dos ciclos acima desse valor, contribuindo para uma melhor eficiencia no uso da agua e para o maior acumulo de materia seca.

Genetic improvement of sugar cane for bioenergy: the brazilian experience in network research with RIDESA

In this paper, it is presented RIDESAs model for sugar cane breeding to ethanol, and its scientific, technological and human resources training contributions. RIDESA is an inter-university network for the development of sugar cane industry in Brazil, and was formed by a technical cooperation agreement between ten public universities. The model of network management is presented in this study, which involves, among other things, the public-private partnership (Universities-Mills) for the development of cultivars. RIDESA has produced 59 cultivars since 1990 and is now responsible for 59% of the total area cultivated with this plant in Brazil. In the last five years, 286 agronomists were trained in breeding programs at universities that comprise RIDESA. In this same period, the network formed 35 professors, 24 doctors and 7 post-docs in researches with this crop. It is also presented a conceptual approach on methods of sugar cane breeding involving families and genome-wide selection.

Photosynthesis and Water Relations in Brazilian Sugarcane

The expansion of sugarcane (Saccharum spp.) in Brazil has been boosted by the growing demand for bio-fuels all over the world and requires the occupation of new agricultural areas, including regions with unfavorable agro-climatic conditions. This observational study makes an analysis of the relationship between stomatal conductance, gas exchange and photosynthesis in sugarcane fields subject to different ambient conditions and growth phases. It was noted that the stomatal conductance had a much higher control on photosynthesis than on transpiration. Even under high stomatal con- ductance, photosynthesis maintained a high correlation to it. Sugarcane had an instantaneous water use efficiency of ap- proximately 4.4 μmol of fixed CO2 for each mmol of H20 expended in transpiration. Lower leaf water potential, besides leading to an internal reduction of CO2, also reduced the instantaneous carboxylation efficiency, indicating that the photo- synthesis apparatus was also affected. The variety RB92579, seems to have good water absorption system, because even under low leaf water potential, it maintained a good stomatal conductance, with a higher transpiration and photosynthesis than the others varieties. These results suggest that this variety has a tolerance mechanism to endure rather than avoid drought.

Genetic similarity among genotypes of sugarcane estimated by SSR and coefficient of parentage

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.

Repetibilidade de características agroindustriais em cana-de-açúcar

Resumo – Os objetivos deste trabalho foram estabelecer estimativas de repetibilidade de caracteristicas agroindustriais em 20 genotipos de cana-de-acucar, determinar a previsibilidade de cada carater e indicar a predicao do valor verdadeiro de cada clone. O delineamento utilizado foi blocos casualizados, com cinco repeticoes. Utilizaram-se a analise de variância com dois fatores de variacao (cortes e genotipos) e a analise dos componentes principais para estimar o coeficiente de repetibilidade , a partir de tres cortes. Foram obtidas estimativas de repetibilidade acima de 0,5 para fibra e toneladas de cana por hectare, em ambos os metodos, com confiabilidade maior que 84% pelo metodo dos componentes principais. As caracteristicas que ficaram abaixo de 0,5, com previsibilidade inferior a 74%, necessitam de um maior numero de avaliacoes. Os metodos dos componentes principais e analise 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 sao os melhores. Termos para indexacao: Saccharum, clones, selecao, analise de variância, componentes principais. Repeatability of agro-industrial characteristics in sugar cane

New Polymorphic EST-SSR Markers in Sugarcane

New polymorphic SSR markers in sugarcane has potential usefulness to studies genetic diversity, genetic mapping, DNA fingerprinting and determination offspring as true hybrids, selfing or contaminant in germplasm from breeding program. SSR markers can be obtained in several ways, and the search for SSR-EST sequences an alternative with significant results. The aim of this study was to develop highly polymorphic SSR markers for germplasm studies in sugarcane. Di- tri- and tetra-nucleotide sequences were mined in the TGI bank and 53 EST-SSR markers developed. These markers were analyzed in five genotypes and showed to be highly polymorphic, with the PIC ranging between 0.48 and 0.95 with a mean of 0.86. The discriminatory power ranged from 0.35 to 0.94 with a mean of 0.82 and the genetic similarity was high in the accessions evaluated.

Production and performance of sugarcane seeds (caryopses) from different hybridizations involving RB92579

A major challenge in sugarcane breeding program is the obtaining of enough number of seeds (caryopses) for the development of new improved cultivars. Genotypes differ in their function as pollen recipient and pollen donor, which also affect the seed performance. Thus, the aim of this study was to verify the production and performance of sugarcane seeds from different hybridizations involving RB92579 as pollen recipient and pollen donor. Twelve bi-parental crossings were carried out involving RB92579 and other different genotypes randomly chosen. Seed production potential was evaluated by percentage of fertile spikelets and caryopsis fresh weight. The seed physiological potential was determined by evaluating germination and vigor (index of germination rate, number of normal seedlings per gram of fuzz, and seedling dry weight). The results showed better performance for RB92579 as pollen donor for all characteristics studied. Therefore, RB92579 sugarcane cultivar should be used as pollen donor during hybridizations, condition that permits a greater production and physiological performance of seeds for the sugarcane breeding programs.