RESUMO

Vegetative canopy architecture, and plant population density, has a direct influence on the growth and production of crops. The objective of this study was to evaluate the growth of four cassava cultivars of contrasting canopies, in four population densities, during two vegetative cycles. A randomized complete block design was used in a subdivided plot scheme, with two replications, with the population densities in the plots and harvesting times in the subplots. 'Branca de Santa Catarina' (BSC), 'IAC 13', 'IAC 14-18' and 'Fibra' were collected every four months, beginning at 120 and ending at 720 days after planting (DAP). Primary data on dry matter and leaf area were calculated. The total dry mass (Wt), leaf area ratio (La), leaf area index (L), relative growth rate (Rw), and net assimilation rate (Ea) were calculated based on the primary data. All cultivars accumulated more total dry mass (Wt) at lower planting densities. The plants reached a higher leaf area ratio (La) 120 days after planting. In the second vegetative cycle, the four cultivars, independently of the population, presented a reduction of assimilate translocation to the leaves. Relative growth rate (Rw) of the cultivars varied strongly with the plant population only in the second cycle. 'IAC 14-18' showed greater dependence on spacing, and 'Fibra' less dependence. Growth (Rw) and assimilatory (Ea) rates decreased at the end of the first cycle, then increased slowly until the end of the second cycle of vegetation.(AU)

A arquitetura do dossel vegetativo e a população das plantas têm influência direta no crescimento e na produção das culturas. O objetivo desta pesquisa foi avaliar o crescimento de quatro cultivares de mandioca de dosséis contrastantes em quatro densidades populacionais por dois ciclos vegetativos. Utilizou-se o delineamento em blocos casualizados no esquema de parcelas subdivididas, com duas repetições, sendo as densidades populacionais nas parcelas e épocas de colheita nas subparcelas. Foram estudadas 'Branca de Santa Catarina' (BSC), 'IAC 13', 'IAC 14-18' e 'Fibra' colhidas quadrimestralmente, com início aos 120 e finalizando aos 720 dias após o plantio (DAP). Foram determinados os dados primários massa seca e área foliar. A partir dos dados primários foi aplicada a análise de crescimento e calculada a massa seca total (Wt), razão de área foliar (Fa), índice de área foliar (L), taxa de crescimento relativo (Rw) e a taxa assimilatória liquida (Ea). Todas as cultivares acumularam mais massa seca (Wt) nas menores densidades de plantio. As plantas atingiram maior razão de área foliar (Fa) aos 120 dias após o plantio. No segundo ciclo vegetativo, as quatro cultivares, independentemente da população, apresentaram redução da translocação de assimilados para as folhas. As taxas de crescimento relativo (Rw) das cultivares variaram de maneira mais acentuada com a população de plantas apenas no segundo ciclo. A ‘IAC 14-18 apresentou maior dependência dos espaçamentos e ‘Fibra menor dependência. As taxas de crescimento (Rw) e assimilatórias (Ea) decrescem no final do primeiro ciclo, depois crescem lentamente até o final do segundo ciclo vegetativo.(AU)

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RESUMO

Vegetative canopy architecture, and plant population density, has a direct influence on the growth and production of crops. The objective of this study was to evaluate the growth of four cassava cultivars of contrasting canopies, in four population densities, during two vegetative cycles. A randomized complete block design was used in a subdivided plot scheme, with two replications, with the population densities in the plots and harvesting times in the subplots. 'Branca de Santa Catarina' (BSC), 'IAC 13', 'IAC 14-18' and 'Fibra' were collected every four months, beginning at 120 and ending at 720 days after planting (DAP). Primary data on dry matter and leaf area were calculated. The total dry mass (Wt), leaf area ratio (La), leaf area index (L), relative growth rate (Rw), and net assimilation rate (Ea) were calculated based on the primary data. All cultivars accumulated more total dry mass (Wt) at lower planting densities. The plants reached a higher leaf area ratio (La) 120 days after planting. In the second vegetative cycle, the four cultivars, independently of the population, presented a reduction of assimilate translocation to the leaves. Relative growth rate (Rw) of the cultivars varied strongly with the plant population only in the second cycle. 'IAC 14-18' showed greater dependence on spacing, and 'Fibra' less dependence. Growth (Rw) and assimilatory (Ea) rates decreased at the end of the first cycle, then increased slowly until the end of the second cycle of vegetation.

A arquitetura do dossel vegetativo e a população das plantas têm influência direta no crescimento e na produção das culturas. O objetivo desta pesquisa foi avaliar o crescimento de quatro cultivares de mandioca de dosséis contrastantes em quatro densidades populacionais por dois ciclos vegetativos. Utilizou-se o delineamento em blocos casualizados no esquema de parcelas subdivididas, com duas repetições, sendo as densidades populacionais nas parcelas e épocas de colheita nas subparcelas. Foram estudadas 'Branca de Santa Catarina' (BSC), 'IAC 13', 'IAC 14-18' e 'Fibra' colhidas quadrimestralmente, com início aos 120 e finalizando aos 720 dias após o plantio (DAP). Foram determinados os dados primários massa seca e área foliar. A partir dos dados primários foi aplicada a análise de crescimento e calculada a massa seca total (Wt), razão de área foliar (Fa), índice de área foliar (L), taxa de crescimento relativo (Rw) e a taxa assimilatória liquida (Ea). Todas as cultivares acumularam mais massa seca (Wt) nas menores densidades de plantio. As plantas atingiram maior razão de área foliar (Fa) aos 120 dias após o plantio. No segundo ciclo vegetativo, as quatro cultivares, independentemente da população, apresentaram redução da translocação de assimilados para as folhas. As taxas de crescimento relativo (Rw) das cultivares variaram de maneira mais acentuada com a população de plantas apenas no segundo ciclo. A ‘IAC 14-18’ apresentou maior dependência dos espaçamentos e ‘Fibra’ menor dependência. As taxas de crescimento (Rw) e assimilatórias (Ea) decrescem no final do primeiro ciclo, depois crescem lentamente até o final do segundo ciclo vegetativo.

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Background and Aims: Amazonia is a major world centre of plant domestication, but little is known about how the crops were dispersed across the region. Manioc (Manihot esculenta) was domesticated in the south-western Amazon basin, and is the most important staple food crop that originated in Amazonia. Current contrasting distributions may reflect distinct histories of dispersal of bitter and sweet manioc landraces. To produce new insights into the evolutionary history of the crop, we investigated the contemporary genetic diversity and structure of bitter and sweet manioc along major Amazonian rivers. Methods: The patterns of genetic structure and diversity of wild and cultivated sweet and bitter manioc with four chloroplast and 14 nuclear microsatellite markers were evaluated. Results were interpreted in terms of the crop's dispersal. Key results: No phylogeographic patterns among rivers were detected, and genetic structure among rivers was confounded by the bitter-sweet divergence. However, differences in the distribution of nuclear diversity and somewhat distinctive patterns of genetic structure across rivers were observed within bitter and sweet manioc. Conclusions: Various pre-Columbian and post-European conquest events in the history of Amazonian occupation may explain the absence of clearer patterns of genetic structure. However, the wide distribution of the most common chloroplast haplotype agrees with an early dispersal of manioc across Brazilian Amazonia. Furthermore, differences in genetic structure and in the spatial distribution of genetic diversity suggest that bitter and sweet manioc had distinct dispersal histories. Knowledge about how prehistoric and contemporary Amazonian peoples manage their crops is valuable for the maintenance and conservation of the impressive diversity of their native crops.

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Pornunça is a species of the genus Manihot that has been cultivated as an option for animal feeding in the Brazilian semi-arid. Leaf area (LA) is important to determine forage plant growth, whose evaluation model has to meet the following characteristics: practicality, precision and low cost. The objective of this study was to set a model to determine the leaf area in Pornunça (Manihot sp.) from morphometric measurements of the leaf. The experimental design was in randomized blocks with three methods for determination of leaf area, and three blocks, with 144 replicates (leaves). For the determination of LA, the direct method (FAReal), treadmill leaf area meter (Li-Color 3100©) and linear dimensions were used. Data were subjected to regression analysis. There was a relationship between the actual leaf area (FAReal) for small, medium, large and total leaves, and the leaf area determined by the treadmill leaf area meter (FALi-Cor©) with a high coefficient of determination for linear fit. The Pornunça leaf area obtained by the Li-Cor3100© meter is approximately 10% lower compared to the FAReal method. The model that best fit the Ponunça leaf area estimation was the potential.

A Pornunça é uma espécie do gênero Manihot que está sendo cultivada como opção para alimentação animal no semiárido do Brasil. A área foliar (AF) é importante para determinar o crescimento de planta forrageira, e a avaliação tem que reunir as seguintes características: praticidade, precisão e baixo custo. O estudo objetivou estabelecer um modelo para determinar a área foliar da Pornunça (Manihot sp.) a partir de medidas morfométricas da folha. O delineamento experimental foi realizado em blocos ao acaso, com três tratamentos (métodos de determinação de área foliar) e três blocos, com o total de 144 repetições (folhas). Para determinação da AF, utilizou-se o método direto (AFReal), medidor de área foliar tipo esteira (Li-Cor 3100©) por meio das dimensões lineares. Os dados foram submetidos à análise de regressão. Houve uma relação entre a área foliar real (AFReal) para folhas pequenas, médias, grandes e total, e a área foliar determinada pelo medidor de área foliar tipo esteira (AFLi-Cor©) apresentou coeficiente de determinação elevado para o ajuste linear. A área foliar da Pornunça obtida pelo medidor Li-Cor3100© é de aproximadamente 10%, inferior, em comparação ao método AFReal. O modelo que melhor se ajustou para a estimativa da área foliar da Pornunça foi o potencial.

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RESUMO

Pornunça is a species of the genus Manihot that has been cultivated as an option for animal feeding in the Brazilian semi-arid. Leaf area (LA) is important to determine forage plant growth, whose evaluation model has to meet the following characteristics: practicality, precision and low cost. The objective of this study was to set a model to determine the leaf area in Pornunça (Manihot sp.) from morphometric measurements of the leaf. The experimental design was in randomized blocks with three methods for determination of leaf area, and three blocks, with 144 replicates (leaves). For the determination of LA, the direct method (FAReal), treadmill leaf area meter (Li-Color 3100©) and linear dimensions were used. Data were subjected to regression analysis. There was a relationship between the actual leaf area (FAReal) for small, medium, large and total leaves, and the leaf area determined by the treadmill leaf area meter (FALi-Cor©) with a high coefficient of determination for linear fit. The Pornunça leaf area obtained by the Li-Cor3100© meter is approximately 10% lower compared to the FAReal method. The model that best fit the Ponunça leaf area estimation was the potential.(AU)

A Pornunça é uma espécie do gênero Manihot que está sendo cultivada como opção para alimentação animal no semiárido do Brasil. A área foliar (AF) é importante para determinar o crescimento de planta forrageira, e a avaliação tem que reunir as seguintes características: praticidade, precisão e baixo custo. O estudo objetivou estabelecer um modelo para determinar a área foliar da Pornunça (Manihot sp.) a partir de medidas morfométricas da folha. O delineamento experimental foi realizado em blocos ao acaso, com três tratamentos (métodos de determinação de área foliar) e três blocos, com o total de 144 repetições (folhas). Para determinação da AF, utilizou-se o método direto (AFReal), medidor de área foliar tipo esteira (Li-Cor 3100©) por meio das dimensões lineares. Os dados foram submetidos à análise de regressão. Houve uma relação entre a área foliar real (AFReal) para folhas pequenas, médias, grandes e total, e a área foliar determinada pelo medidor de área foliar tipo esteira (AFLi-Cor©) apresentou coeficiente de determinação elevado para o ajuste linear. A área foliar da Pornunça obtida pelo medidor Li-Cor3100© é de aproximadamente 10%, inferior, em comparação ao método AFReal. O modelo que melhor se ajustou para a estimativa da área foliar da Pornunça foi o potencial.(AU)

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ABSTRACT The objective of this study was to determine predictor models of leaf area of ​​cassava from linear leaf measurements. The experiment was carried out in greenhouse in the municipality of Botucatu, São Paulo state, Brazil. The stem cuttings with 5-7 nodes of the cultivar IAC 576-70 were planted in boxes filled with about 320 liters of soil, keeping soil moisture at field capacity, monitored by puncturing tensiometers. At 80 days after planting, 140 leaves were randomly collected from the top, middle third and base of cassava plants. We evaluated the length and width of the central lobe of leaves, number of lobes and leaf area. The measurements of leaf areas were correlated with the length and width of the central lobe and the number of lobes of the leaves, and adjusted to polynomial and multiple regression models. The linear function that used the length of the central lobe LA = -69.91114 + 15.06462L and linear multiple functions LA = -69.9188 + 15.5102L + 0.0197726K - 0.0768998J or LA = -69.9346 + 15.0106L + 0.188931K - 0.0264323H are suitable models to estimate leaf area of ​​cassava cultivar IAC 576-70.

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Genetic variability of cassava (Manihot esculenta Crantz) in Brazil is wide, being this the result of natural and cultural selection during pre- and post-domestication of the species in different environments. Given the number of species of the genus found in the region (38 of a total of 98 species), the central region of Brazil was defined as the primary center of cassava diversity. Therefore, genetic diversity characterization of cassava accessions is fundamental, both for farmers and for plant breeders, because it allows the organization of genetic resources and better utilization of available genetic diversity. This research aims to assess genetic divergence of cassava accessions from the south-central region of the State of Mato Grosso, based on multi-categorical morphological traits. For this purpose, 38 qualitative and quantitative morphological descriptors were used. Genetic diversity was expressed by the genetic similarity index, with subsequent clustering of accessions by the modified Tocher's procedure and UPGMA. Of 38 descriptors, only growth habit of stem showed no variability. Tocher and UPGMA methods were efficient and corroborated on group composition. Both methods were able to group accessions of different localities in distinct group consistency.

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RESUMO

The objective of this study was to determine predictor models of leaf area of ​​cassava from linear leaf measurements. The experiment was carried out in greenhouse in the municipality of Botucatu, São Paulo state, Brazil. The stem cuttings with 5-7 nodes of the cultivar IAC 576-70 were planted in boxes filled with about 320 liters of soil, keeping soil moisture at field capacity, monitored by puncturing tensiometers. At 80 days after planting, 140 leaves were randomly collected from the top, middle third and base of cassava plants. We evaluated the length and width of the central lobe of leaves, number of lobes and leaf area. The measurements of leaf areas were correlated with the length and width of the central lobe and the number of lobes of the leaves, and adjusted to polynomial and multiple regression models. The linear function that used the length of the central lobe LA = -69.91114 + 15.06462L and linear multiple functions LA = -69.9188 + 15.5102L + 0.0197726K - 0.0768998J or LA = -69.9346 + 15.0106L + 0.188931K - 0.0264323H are suitable models to estimate leaf area of ​​cassava cultivar IAC 576-70.

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Cassava is an important culture in Brazil and in the North of the country, and soft root rot has affected root production. The aim of this work was to identify root morphoanatomic and histochemical characters associated with root rot resistance. In areas with no occurrence of the disease, nine cassava genotypes were tested, four of which were resistant, and five were susceptible to root rot. Root harvest was carried out twelve months after sowing, and thickness of suber, suber and cortex, and secondary xylem were measured. Moreover, texture, suber cell layers, lignin content, and lignin monomers content of the portion suber and cortex were analyzed. Also, histochemical tests and scanning electron microscopy (SEM) analyses of the roots were performed. Results were subjected to analysis of variance, and means were compared by the Scott-Knott test (p < = 0.05). The characters thickness of suber and cortex at proximal and medium portions, thickness of secondary xylem at medium and apical portions, number of cell layers of suber, thickness of suber, and root texture showed differences among genotypes; however, the characters could not be associated with resistance or susceptibility. There were no differences for: vessel elements, lignin and lignin monomers, and for the histochemical tests with Sudan IV and Lugol. Images of SEM showed differences among genotypes, which could not be associated with resistance or susceptibility. Thus, the characters evaluated cannot be used in selection for cassava resistance to soft root rot in genetic breeding programs.(AU)

A mandioca é uma cultura importante no Brasil e no Norte do país, e a podridão mole da raiz tem afetado a produção. O objetivo deste trabalho foi identificar caracteres morfoanatômicos e histoquímicos da raiz associados à resistência à podridão da raiz. Em áreas sem ocorrência da doença, nove genótipos de mandioca foram testados, quatro resistentes e cinco suscetíveis. A colheita da raiz foi realizada doze meses após o plantio e medidas de espessura do súber, súber e cortex e xilema secundário foram realizadas. Além disso, foram analisados a textura, as camadas de célula do súber, o conteúdo de lignina e os monômeros de lignina da porção súber e cortex. Ainda, testes histoquímicos e microscopia eletrônica de varredura (MEV) das raízes foram realizados. Os resultados foram submetidos à análise de variância e as médias foram comparadas pelo teste de Scott-Knott (p < = 0.05). Os caracteres: espessura de súber e córtex nas porções mediana e proximal, espessura do xilema secundário nas porções mediana e apical, número de camadas de células do súber, espessura do súber e textura da raiz apresentaram diferenças entre os genótipos, mas não associadas à resistência ou suscetibilidade. Não houve diferenças para: elementos de vaso, lignina e monômeros de lignina para os testes histoquímicos com Sudan IV e Lugol. Imagens de MEV apresentaram diferenças entre os genótipos, mas não associadas à resistência ou suscetibilidade. Assim, os caracteres avaliados não podem ser usados na seleção de mandioca com resistência à podridão mole da raiz em programa de melhoramento genético.(AU)

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Ten cassava cultivars were grown in the field and evaluated to identify the most adapted to the Coastal Tablelands of northeast Brazil. The cultivars showed differences in proline and chlorophyll contents, plant height, number of leaves and branches, canopy area and root production, however they did not differ on photosynthetic rates. Cultivars 'Tianguá' and '9783-13' presented lower root yield, whereas 'BRS Tapioqueira' and 'Irará' had the highest root yield. Few leaves coupled with the highest water use efficiency for CO2 assimilation was found in 'BRS Kiriris' in contrast to 'BRS Jarina' and '9783-13'. 'BRS Caipira' had high proline content in both Umbaúba and Frei Paulo areas, traits usually associated to drought tolerance, that contribute to the adaptation. It is also important to consider that cultivar 'BRS Caipira' was the first to present increase in chlorophyll content after extended period of drought, that indicates a faster recovery after dry season. Furthermore, the results indicated that the most adapted cultivars for cultivation in this area are 'Irará', 'BRS Tapioqueira', 'BRS Kiriris' and 'BRS Caipira'.(AU)

Dez cultivares de mandioca foram cultivadas no campo e avaliadas para identificar a mais adaptada aos Tabuleiros Costeiros do Nordeste do Brasil. As cultivares apresentaram diferenças nos teores de prolina e clorofila, altura, número de folhas e ramos, área de copa e produção de raízes, no entanto, não diferiram quanto às taxas fotossintéticas. As cultivares 'Tianguá' e '9783-13' apresentaram menor rendimento de raízes e 'BRS Tapioqueira' e 'Irará' maior rendimento. Poucas folhas e maior eficiência no uso da água para a assimilação de CO2 foi verificado em 'BRS Kiriris', em contraste com 'BRS Jarina' e '9783-13'. 'BRS Caipira' teve alto teor de prolina em Umbaúba e em Frei Paulo, características geralmente associadas à tolerância à seca, que contribuem para adaptação. Também é importante considerar que a cultivar 'BRS Caipira' foi a primeira a apresentar aumento no teor de clorofila após longo período de seca, o que indica recuperação mais rápida após período seco. Além disso, os resultados indicam que as cultivares mais adaptadas ao cultivo nessa área são 'Irará', 'BRS Tapioqueira', 'BRS Kiriris' e 'BRS Caipira'.(AU)

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In this study, we describe the petiole anatomy of six wild cassava (Manihot) species, one hybrid, and two cultivars of Manihot esculenta, in order to identify their dominant anatomical patterns and relate them to possible adaptations to abiotic factors in the Cerrado biome. The median parts of several petiole samples were transversally and longitudinally sectioned and stained. The results include data for the taxonomic classification of the genus, including distinctive anatomical characteristics of hybrid varieties of cassava and wild species, such as the presence/absence of trichomes and a hypodermis, layer type and number in the cortex, number of vascular bundles, cell types in the pith, and type of organization. Morphological analysis revealed differences in length and shape of the petiole insertion. The presence of trichomes, a hypodermis, the amount and type of supporting tissue in the cortex, as well as gelatinous fibers, may be related to drought tolerance.

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PREMISE OF THE STUDY: Morphologically diverse clades are useful for detecting adaptive morphological evolution. Each of their variants may have evolved once or several times, suggesting that their repeated appearance may be due to environmental pressures. The North American Manihot species are an excellent system to detect possible adaptations and to assess the effect of mono- or polyphyly on classification. With 20 species, this group includes growth forms from tuberous herbs to trees. The monophyly of this group and its relationship with the economically important M. esculenta were tested for the first time with complete sampling of North American species. METHODS: We carried out maximum likelihood and Bayesian phylogenetic analyses on a matrix of 3662 bp from chloroplast (psbA-trnH, trnL-trnF) and nuclear loci (PEPC and two paralogous copies of G3pdh). We included all North American Manihot species, Manihotoides pauciflora, and published sequences from 34 South American species. KEY RESULTS: Our results support monophyly of the North American Manihot group. Its taxonomic sections are paraphyletic, and three to four growth forms evolved repeatedly. Manihotoides pauciflora is nested within North American Manihot species. Some PEPC and G3pdh clones grouped with clones of other species and not with clones from their own species. CONCLUSIONS: North and South American Manihot species are sister clades. Paraphyly of North American sections suggests that taxonomic revision is warranted. The position of Manihotoides pauciflora confirms that Manihotoides should remain subsumed within Manihot. Most growth forms likely evolved repeatedly in this group. The behavior of PEPC and G3pdhNA clones is probably due to incomplete lineage sorting.

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Cassava periclinal cytochimeras, cultivars, and interspecific hybrid and polyploid types were studied in relation to embryonic, cytogenetic, and anatomical behavior. Their apical shoots, pollen grains, male and female buds, roots, stomata, and flowering period were analyzed. Chimeras exhibited increased size of L1 and L2 cells. Polyploidy led to enlargement of stomata in chimeras whereas L2 gave tetraploid chromosome configurations, tetrad irregularity, decrease of pollen viability, and increase in frequency of polyembryo sacs. The chimeric composition of tetraploids L1 and L2 and diploid L3 expressed a notable epigenetic effect seen in a marked enlargement of edible roots compared to total diploid. One of the chimeric types was accompanied by complete flowering inhibition. Pollen viability and diameter appeared to be reliable markers to determine ploidy levels.

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The objective of this research to evaluate the behavior of cassava cultivated under irrigation and nitrogen levels. The experimental design was a randomized complete block in factorial arrangement (7 x 4), seven water slides (394.28, 333.16, 279.20, 213.00, 209.00, 169.16 and 116.60mm) and four levels of nitrogen (absence, 50, 100 and 150kg/ha) with two replications. Evaluations were performed at 60 and 120 days of regrowth. At 60 and 120 days there was no interaction between water slides and nitrogen for all morphological characteristics. The nitrogen and water slides separately exerted positive linear effect on the variables plant height, number of leaves, number of bifurcations, stem diameter and canopy area at 60 days. Just for the characteristic number of leaves and nitrogen use efficiency were detected significant interactions between factors at 120 days. Nitrogen rates exerted positive linear effect on the morphological characteristics of plant height, number of bifurcations, stem diameter, canopy area, fresh matter yield, dry matter yield and water use efficiency at 120 days. Similar effect was observed for the factor water slides, however no significant difference was observed for the characteristic canopy area. The morphological characteristics and production of cassava are increased with the use of nitrogen fertilizer and irrigation.(AU)

Objetivou-se com este ensaio avaliar o comportamento da maniçoba cultivada sob irrigação e doses de nitrogênio. O delineamento experimental utilizado foi o de blocos completos casualizados em arranjo fatorial (7 x 4), sendo sete lâminas totais de água (394,28, 333,16, 279,20, 213,00, 209,00, 169,16 e 116,60mm) e quatro doses de nitrogênio (ausência, 50, 100 e 150kg/ha), com duas repetições. As avaliações foram realizadas aos 60 e 120 dias após corte de uniformização. Aos 60 e 120 dias não houve interação entre os fatores lâminas hídricas e doses de nitrogênio para todas as características morfológicas. As doses de nitrogênio e lâminas hídricas separadamente exerceram efeito linear positivo sobre as variáveis altura de plantas, número de folhas, número de bifurcações, diâmetro de caule e área de copa aos 60 dias. Apenas para a característica número de folhas e eficiência de utilização do nitrogênio foram detectadas interações significativas entre os fatores aos 120 dias. As doses de nitrogênio imprimiram efeito linear positivo sobre as características morfológicas altura de plantas, número de bifurcações, diâmetro de caule, área de copa, produção de massa fresca e produção de massa seca e eficiência de utilização da água aos 120 dias. Observou-se efeito semelhante para o fator lâmina hídrica, no entanto não foi observada diferença significativa para as características área de copa. As características morfológicas e produtivas da maniçoba são incrementadas com a utilização da adubação nitrogenada e irrigação.(AU)

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The objective of this research to evaluate the behavior of cassava cultivated under irrigation and nitrogen levels. The experimental design was a randomized complete block in factorial arrangement (7 x 4), seven water slides (394.28, 333.16, 279.20, 213.00, 209.00, 169.16 and 116.60mm) and four levels of nitrogen (absence, 50, 100 and 150kg/ha) with two replications. Evaluations were performed at 60 and 120 days of regrowth. At 60 and 120 days there was no interaction between water slides and nitrogen for all morphological characteristics. The nitrogen and water slides separately exerted positive linear effect on the variables plant height, number of leaves, number of bifurcations, stem diameter and canopy area at 60 days. Just for the characteristic number of leaves and nitrogen use efficiency were detected significant interactions between factors at 120 days. Nitrogen rates exerted positive linear effect on the morphological characteristics of plant height, number of bifurcations, stem diameter, canopy area, fresh matter yield, dry matter yield and water use efficiency at 120 days. Similar effect was observed for the factor water slides, however no significant difference was observed for the characteristic canopy area. The morphological characteristics and production of cassava are increased with the use of nitrogen fertilizer and irrigation.

Objetivou-se com este ensaio avaliar o comportamento da maniçoba cultivada sob irrigação e doses de nitrogênio. O delineamento experimental utilizado foi o de blocos completos casualizados em arranjo fatorial (7 x 4), sendo sete lâminas totais de água (394,28, 333,16, 279,20, 213,00, 209,00, 169,16 e 116,60mm) e quatro doses de nitrogênio (ausência, 50, 100 e 150kg/ha), com duas repetições. As avaliações foram realizadas aos 60 e 120 dias após corte de uniformização. Aos 60 e 120 dias não houve interação entre os fatores lâminas hídricas e doses de nitrogênio para todas as características morfológicas. As doses de nitrogênio e lâminas hídricas separadamente exerceram efeito linear positivo sobre as variáveis altura de plantas, número de folhas, número de bifurcações, diâmetro de caule e área de copa aos 60 dias. Apenas para a característica número de folhas e eficiência de utilização do nitrogênio foram detectadas interações significativas entre os fatores aos 120 dias. As doses de nitrogênio imprimiram efeito linear positivo sobre as características morfológicas altura de plantas, número de bifurcações, diâmetro de caule, área de copa, produção de massa fresca e produção de massa seca e eficiência de utilização da água aos 120 dias. Observou-se efeito semelhante para o fator lâmina hídrica, no entanto não foi observada diferença significativa para as características área de copa. As características morfológicas e produtivas da maniçoba são incrementadas com a utilização da adubação nitrogenada e irrigação.

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RESUMO

We provide the first report on the synthesis of a very productive interspecific periclinal chimera of cassava, with large and edible roots. The epidermal tissue of the chimera was formed by the cultivated species Manihot esculenta (E), and the subepidermis and internal tissue were formed by the wild species, Manihot fortalezensis (F). We used cytogenetics and morphological analyses to determine the origins of all tissues. These results may offer potential for the development of new lines for crop improvement based on the use of chimera composed of different combinations of wild species and cultivars.

Assuntos

RESUMO

An anatomical study of roots was conducted on two wild Manihot species, namely M. glaziovii and M. fortalezensis, and two cassava varieties, M. esculenta Crantz variety UnB 201 and M. esculenta variety UnB 122, to identify taxonomic differences in primary growth. Anatomical characters of cassava roots have been rarely investigated. Their study may help cassava breeders to identify varieties with economically important characters, such as tolerance to drought. We investigated tap and lateral adventitious roots of two specimens of each clone or species. Free-hand cross-sections of roots were drawn; these had been clarified with 20% sodium hypochlorite solution, stained with 1% safranin-alcian blue ethanolic solution, dehydrated in ethanol series and butyl acetate and mounted in synthetic resin. Anatomical differences among Manihot species and varieties were found in the epidermal and exodermal cell shape and wall thickness, content of cortical parenchyma, and number of xylem poles. Wall thickness of the epidermis and exodermis of tap root were similar in all species, while in the lateral root there were differences in cell shape and wall thickness. Epidermal cells with thick walls were found in the tap root of all species and in lateral roots of cassava varieties. This character is apparently associated with tolerance to drought and disease. The variation in the number of xylem poles of cassava varieties was larger (4-8) than in wild species (4-6), and appears to support the hybrid origin of cassava.

Assuntos

RESUMO

A molecular, anatomical and cytogenetic study of an interspecific hybrid between Manihot esculenta (cassava) and the wild species M. oligantha was carried out. Cytogenetics revealed relatively complete chromosome pairing and high viability of the pollen grains. Ovule structure examined by the clearing method showed polyembryony in 2.7% of the ovules. Doubling of the chromosome number resulted in an increase in polyembryony of up to 18% and a reduction in pollen viability. Multivalent formation was also observed. An anatomical study of stems of diploid and tetraploid hybrids showed a larger number of vascular bundles in the tetraploid type.

Assuntos

RESUMO

Information on anatomical structure is needed by breeders working on improvement for drought tolerance. For studying the effect of polyploidy on cassava anatomy and its significance to tolerance to drought, we induced a polyploidy type of a selected clone (UnB 530) by applying an aqueous solution of 0.2% colchicine on lateral buds for a period of 12 h. The stem identified as tetraploid was propagated to produce the whole plant. Free-hand cross-sections of the median portion between stem internodes were made. They were clarified using 50% sodium hypochlorite solution, stained with 1% safranin-alcian blue, passed through an ethanol series and butyl acetate and mounted in synthetic resin. The tetraploid type showed more prismatic and druse crystals in the cortical parenchyma, and its pericycle fibers had thicker walls. The secondary xylem of tetraploid types was wider than diploid ones, having thinner walls and less starch.

Assuntos

RESUMO

A total of 98 Manihot species have been recognized in the genus. All of them are native to the tropics of the New World, particularly Brazil and Mexico. The cultigen, Manihot esculenta Crantz (cassava), grows throughout the lowland tropics. Wild species vary in growth habit from acaulescent or short shrubs to tree-like. Because of their adaptations to different conditions, they are gene reservoirs for tackling many abiotic and biotic stresses such as improving root quality and resistance to diseases. They have been used successfully by the first author for improving protein content, seed-fertility, apomixis, resistance to mealy bug, and tolerance to drought. A table of the most important species from an economic viewpoint is presented.

Assuntos