Neighborhood analysis in evaluation of sugarcane genotypes

O objetivo deste trabalho foi estudar diferentes covariáveis de competição em análises de vizinhança, e verificar sua eficiência no aumento da precisão experimental e as consequências no ordenamento de genótipos de cana-de-açúcar em termos de potencial produtivo. Foram utilizados dados da rede de ensaios do programa de melhoramento de cana-de-açúcar do Instituto Agronômico, instalados em 2002. O delineamento foi em blocos ao acaso, com três repetições. As parcelas constituíram-se de cinco sulcos de 8 m, espaçados 1,50 m entre si. A produtividade de colmos por hectare (TCH, Mg ha-1) foi avaliada no primeiro e terceiro cortes. As covariáveis "lateral", "ponta" e "quatro vizinhos" foram incluídas nos métodos de Papadakis, em duas variações do método médias móveis. Os métodos de Papadakis e médias móveis 1 não alteraram a precisão experimental em comparação à análise tradicional. O método médias móveis 2 reduziu a variância ambiental, mas alterou as estimativas da variância genotípica e o ordenamento dos genótipos, o que pode induzir a conclusões equivocadas na seleção. Embora a covariável "lateral" tenha sido influente na competição, o efeito em parcelas de cinco sulcos é pequeno.The objective of this work was to study different competition covariates in neighborhood analysis and to check the efficiency of this analysis in the increase of the experimental precision and the consequences in the ranking of sugarcane genotypes in terms of productive potential. Data used were from the state experimental network of the sugarcane breeding program installed in 2002, of the Instituto Agronômico, Campinas, SP, Brazil. The experimental design was in randomized complete blocks, with three replicates. The plots were formed of five 8 m rows with 1.5-m spacing between rows. The stalk productivity (TCH, Mg ha-1) was evaluated in the first and third harvests. The covariates "side", "tip" and "4 neighbors" were included in the Papadakis method and in two variations of the moving average method. The Papadakis and moving average 1 methods did not change the experimental precision in comparison with traditional analysis. The moving average 2 method reduced the environmental variance. However, it changed the estimates of the genetic variance and the genotype ranking, and could lead to erroneous conclusions in the selection. Although the "side" covariate was influential on competition, its effect or on five row-plots was small

Estimates of genetic parameters and expected gains from selection of yield traits in sugarcane families

ABSTRACT It is essential to have basic information on the genetic nature of variation of various metric traits in plantation crops for the proper planning of breeding strategies. The objective of this paper was to estimate the variability for five yield traits in sugarcane (Saccharum spp.) families. Eighteen controlled pollination families were evaluated in a randomized complete block trial having 16 plants per linear plot at Jaú Development and Research Station (DDD/APTA/SAA), in Jau city, Sao Paulo State, Brazil. In the second year, families were assessed and harvested six months after the first ratoon, and evaluated for the following characters: stalk height, stalk diameter, average Brix, stalk number and stalk weight. The results showed highly significant (p<0.01) genetic differences among families for most traits. The genotypic variance component accounted for 4.27, 3.55, 15.87, 3.32 and 51.68% of the phenotypic variance for stalk height, stalk number, stalk diameter, stalk weight and average Brix, respectively. Heritabilities at individual plant level for the above traits were 56.57, 76.59, 67.40, 72.73 and 54.11%, respectively. Negative significant genotypic and phenotypic correlations were found between Brix and stalk height (r g = -0.78**, r p = -0.56**) and stalk diameter (r g = -0.81**, r p = -0.75**). Selecting the best two families out of 18 families would result in a genetic gain of 4.92% and 10.82% for stalk height and stalk diameter, respectively. The best two selected individual seedlings within each family would result in a genetic gain of 18.61% and 16.94% with a total gain of 23.57 % and 27.76 % for these two traits, respectively

Seleção de 39 variedades de cana-de-açúcar para a alimentação animal

It was developed at the Institute of Zootecnia, in Nova Odessa, SP, an experiment to evaluate 39 sugarcanes, for animal feeding. The sugarcanes were evaluated through analysis of main components and grouping. The analysis of grouping was made by the method UPGA (unweighted pair group method with arithimetic average), being taken into account, 4 characters: production of dry matter, percentage of total carbohydrates available, percentage neutral detergent fiber and percentage of effective degradability of dry matter. Being taken into account just the quality and degradability the groups 6, 7, 8, 9 and 10 were selected. Including in the evaluation, the production of dry matter, the selected groups were the one of number 6, 8 and 9.Foi desenvolvido no Instituto de Zootecnia, em Nova Odessa, SP, um experimento para avaliar 39 variedades de canas-de-açúcar, com vistas à alimentação animal. As canas foram avaliadas através de análise sob componentes principais e agrupamento. A análise de agrupamento foi efetuada pelo método UPGA (unweighted pair group method with arithimetic average), levando-se em conta, 4 caracteres, produção de matéria seca, teor de carboidratos totais não estruturais, teor de fibra insolúvel em detergente neutro e degradabilidade efetiva da matéria seca. Levando-se em conta apenas a qualidade e degradabilidade foram selecionados os grupos 6, 7, 8, 9 e 10. Incluindo na avaliação, a produção de matéria seca, os grupos selecionados foram os de número 6, 8 e 9

Atributos químicos de subsuperfície de latossolos e produtividades da cana- de-açúcar

In spite of the great homogeneity found in the morphological characteristics of Oxisols, there is great chemical diversity in subsurface layers of these soils. Studies indicate that crop yield presents significant correlation with the chemical attributes of the subsurface, which, are more stable than attributes found in the plough layer, subject to greater alterations as a consequence of agricultural exploration. This work evaluated the effects of subsurface chemical attributes of Oxisols of the South Central region of Brazil, on the yield of sugarcane clones and of variety RB72454, during the first, second and third cropping cycles. Productivity data were obtained between 1993 and 1998. Soils were characterized in terms of their mechanical analysis and chemical traits at 0.8 to 1.0 m; correlation studies between these attributes and mean daily productivity as well as multiple regression analysis were also carried out; variables were selected based on their R² values by means of the stepwise procedure. The subsurface chemical traits of the Oxisols influenced sugarcane productivity, especially the 3rd harvest; the clone productivity model for the 3rd harvest as a function of base saturation and phosphorus content presented R² = 0.31, i.e., 31% of the variation in sugarcane yield (t ha-1 day-1) can be explained by these two attributes. For variety RB72454, 47% of that variation is explained by the sum of bases and contents of calcium and organic matter. Variations on productivity at 1st and 2nd harvests can be better explained by pHwater.Embora haja homogeneidade nas características morfológicas na classe dos Latossolos, existe grande diversidade química na subsuperfície. Trabalhos indicam que a produção agrícola apresenta correlação significativa com atributos químicos de subsuperfície, que são mais estáveis que na camada arável, sujeita a alterações decorrentes da exploração agrícola. Pelo exposto, o presente estudo avaliou os efeitos dos atributos químicos de subsuperfície de Latossolos da região Centro-Sul do Brasil na produtividade agrícola dos três primeiros cortes de clones de cana-de-açúcar e da variedade RB72454. Utilizaram-se os dados de produtividade agrícola correspondentes ao período de 1993 a 1998. Os solos foram caracterizados sob o ponto de vista granulométrico e químico na profundidade entre 0,8 e 1,0 m e foram feitos estudos de correlação entre tais atributos e as médias de produtividade agrícola diária durante o ciclo dos clones de cada ensaio e da variedade RB72454 e análise de regressão múltipla, com as variáveis selecionadas pelo procedimento "stepwise" em função do R². As características químicas de subsuperfície dos Latossolos influenciaram na produtividade agrícola da cana-de-açúcar, principalmente no 3º corte. Para as médias dos clones, o modelo de produtividade do 3º corte em função de saturação por bases e fósforo, mostra R² = 0,31, ou seja, que 31% da variação de TCH dia-1 pode ser explicada por esses dois atributos. No caso da variedade RB72454, essa mesma variação no 3º corte é explicada em 47% pelos atributos soma de bases e teores de cálcio e matéria orgânica. As variações de produtividade de 1º e 2º cortes foram melhor explicadas pelo pHágua

Biometric and physiological responses to water deficit in sugarcane at different phenological stages

O objetivo deste trabalho foi avaliar as respostas biométricas e fisiológicas de cana-de-açúcar (Saccharum spp.) ao deficit hídrico (DH), em diferentes fases fenológicas. Os genótipos IACSP 94-2094 e IACSP 96-2042 foram submetidos a DH nas fases de crescimento inicial, crescimento máximo e de acúmulo de sacarose no colmo. O delineamento experimental foi inteiramente casualizado. A suscetibilidade ao DH foi determinada pela redução de matéria seca do colmo e do conteúdo de sólidos solúveis no caldo. O deficit hídrico causou redução nas trocas gasosas, nas três fases fenológicas, em ambos os genótipos. Foi observada menor altura das plantas, menor acúmulo de matéria seca do colmo e de sólidos solúveis, e redução no número e comprimento de entrenós, apenas na fase de crescimento inicial, no clone IACSP 96-2042. Na fase de crescimento inicial, observou-se tolerância ao DH no genótipo IACSP 94-2094, com evidências de aclimatação fisiológica, e redução na produção de fitomassa e de sólidos solúveis no genótipo IACSP 96-2042, como resposta à menor condutância estomática e à menor eficiência aparente de carboxilação da fotossíntese. Independentemente da fase fenológica, o genótipo IACSP 94-2094 foi tolerante ao deficit hídrico, pois manteve a produção de fitomassa mesmo com redução das trocas gasosas.The aim of this work was to evaluate the biometric and physiological responses of sugarcane (Saccharum spp.) to water deficit (WD), during different phenological phases. Genotypes IACSP 94-2094 and IACSP 96-2042 were subjected to WD conditions during the initial, maximum and sucrose accumulation phases. The experiment was carried out in a completely randomized design. Susceptibility to WD was established by reduction in stalk dry matter and soluble solids. Water deficit reduced leaf gas exchange in all phenological phases of both genotypes. Lower plant height, less stalk dry matter and soluble solids, and reduction in number and length of internodes were only observed during the initial growth phase of the IACSP 96-2042 clone. In the initial growth phase, tolerance to WD was observed for IACSP 94-2094, with evidence of physiological acclimation, and for IACSP 96-2042 in reduction phytomass production and its soluble solid content, caused by lower stomatal conductance and lower apparent carboxylation efficiency which limit photosynthesis. Regardless of the phenological phase, genotype IACSP 94-2094 was tolerant to WD, since its phytomass production was maintained even with impairment of leaf gas exchange

Composição bromatológica e digestibilidade de cana-de-açúcar colhida em duas épocas do ano

Objetivou-se com este estudo avaliar o efeito da época de corte sobre a composição bromatológica e digestibilidade in vitro de genótipos de cana-de-açúcar, comparar a composição bromatológica e digestibilidade in vitro das frações colmo e folhas, e estabelecer possíveis correlações entre composição química e digestibilidade in vitro da planta inteira de genótipos da cana-de-açúcar. Nove genótipos foram colhidos em maio e setembro de 2006. Em maio, somente a fração planta inteira foi analisada, em setembro foram separados em colmos, folhas ou planta inteira para determinação da composição bromatológica, sacarose (POL) e digestibilidade in vitro. Colmos apresentaram menor teor de fibra em detergente neutro (FDN) e lignina na MS, e maior digestibilidade in vitro da matéria seca (DIVMS) do que folhas. Em contrapartida, apresentaram menor digestibilidade in vitro da FDN (DIVFDN), maior teor de lignina na FDN e menor concentração de proteína bruta (PB). Houve redução no teor e digestibilidade da FDN com o avanço da maturidade, enquanto que DIVMS, POL e lignina aumentaram. A DIVMS se mostrou negativamente correlacionada com FDN e FDN/POL, porém não houve correlação entre DIVFDN e FDN ou FDN/POL. Conclui-se que o avanço da maturidade promoveu redução na DIVFDN e aumento na DIVMS, não existindo correlação genética entre acúmulo de açúcar e digestibilidade in vitro da fibra. Os dados deste artigo indicam não ser esperado que a seleção de genótipos com maior DIVFDN do colmo altere o teor de açúcar do mesmo.The objectives of this study were to evaluate the effect of time of harvest on chemical composition and in vitro digestibility of sugarcane genotypes, to compare chemical composition and in vitro digestibility of the stem and leaf fractions, and to determine possible correlations between chemical composition and in vitro digestibility of the whole plant in sugarcane genotypes. Nine genotypes were harvested in May and September of 2006. In May, only the whole-plant fraction was analyzed, in September the genotypes were separated in stems, leaves or whole-plant for determination of chemical composition, sucrose (POL) and in vitro digestibility. Stems had lower neutral detergent fiber (NDF) and lignin in the DM, and greater in vitro dry matter digestibility (IVDMD) than leaves. However, stems had lower in vitro NDF digestibility (IVNDFD), higher lignin in the NDF and lower crude protein (CP). The NDF and IVNDFD were reduced with advanced maturity, while IVDMD, POL and lignin were increased. IVDMD was negatively correlated with NDF and NDF/POL, however there was no correlation between IVFDND and NDF or NDF/POL. It can be concluded that with the advance in maturity the IVNDFD was reduced and IVDMD was increased, and there was no genetic correlation between accumulation of sugar and in vitro fiber digestibility. Data from this study indicate that it is not expected that selection of genotypes with greater stem IVNDFD would alter the sugar content of the plant

Gene Duplication in the Sugarcane Genome: A Case Study of Allele Interactions and Evolutionary Patterns in Two Genic Regions

Sugarcane (Saccharum spp.) is highly polyploid and aneuploid. Modern cultivars are derived from hybridization between S. officinarum and S. spontaneum. This combination results in a genome exhibiting variable ploidy among different loci, a huge genome size (~10 Gb) and a high content of repetitive regions. An approach using genomic, transcriptomic, and genetic mapping can improve our knowledge of the behavior of genetics in sugarcane. The hypothetical HP600 and Centromere Protein C (CENP-C) genes from sugarcane were used to elucidate the allelic expression and genomic and genetic behaviors of this complex polyploid. The physically linked side-by-side genes HP600 and CENP-C were found in two different homeologous chromosome groups with ploidies of eight and ten. The first region (Region01) was a Sorghum bicolor ortholog region with all haplotypes of HP600 and CENP-C expressed, but HP600 exhibited an unbalanced haplotype expression. The second region (Region02) was a scrambled sugarcane sequence formed from different noncollinear genes containing partial duplications of HP600 and CENP-C (paralogs). This duplication resulted in a non-expressed HP600 pseudogene and a recombined fusion version of CENP-C and the orthologous gene Sobic.003G299500 with at least two chimeric gene haplotypes expressed. It was also determined that it occurred before Saccharum genus formation and after the separation of sorghum and sugarcane. A linkage map was constructed using markers from nonduplicated Region01 and for the duplication (Region01 and Region02). We compare the physical and linkage maps, demonstrating the possibility of mapping markers located in duplicated regions with markers in nonduplicated region. Our results contribute directly to the improvement of linkage mapping in complex polyploids and improve the integration of physical and genetic data for sugarcane breeding programs. Thus, we describe the complexity involved in sugarcane genetics and genomics and allelic dynamics, which can be useful for understanding complex polyploid genomes

Sugarcane (Saccharum X officinarum): A Reference Study for the Regulation of Genetically Modified Cultivars in Brazil

Global interest in sugarcane has increased significantly in recent years due to its economic impact on sustainable energy production. Sugarcane breeding and better agronomic practices have contributed to a huge increase in sugarcane yield in the last 30 years. Additional increases in sugarcane yield are expected to result from the use of biotechnology tools in the near future. Genetically modified (GM) sugarcane that incorporates genes to increase resistance to biotic and abiotic stresses could play a major role in achieving this goal. However, to bring GM sugarcane to the market, it is necessary to follow a regulatory process that will evaluate the environmental and health impacts of this crop. The regulatory review process is usually accomplished through a comparison of the biology and composition of the GM cultivar and a non-GM counterpart. This review intends to provide information on non-GM sugarcane biology, genetics, breeding, agronomic management, processing, products and byproducts, as well as the current technologies used to develop GM sugarcane, with the aim of assisting regulators in the decision-making process regarding the commercial release of GM sugarcane cultivars