RESUMO O algodoeiro de fibra natural colorida tem recebido atenção dos programas de melhoramento na região semiárida do Nordeste brasileiro devido ao aumento no interesse por este tipo de fibra. Com isso, o objetivo deste trabalho foi selecionar genótipos de algodoeiro de fibra colorida quanto às características agronômicas e tecnológicas da fibra para as condições da região semiárida brasileira. O experimento foi realizado em dois ambientes (Patos-PB e Apodi-RN), na safra de 2016. O delineamento foi blocos ao acaso com quatro repetições. Foram utilizados 11 genótipos de fibra colorida e três testemunhas (BRS Topázio, BRS Rubi e BRS Verde), constituindo 14 tratamentos. As características avaliadas foram: Produtividade de algodão em caroço (PROD, kg.ha-1), Porcentagem de fibra (PF, %), Comprimento de fibra (COMP, mm), Resistência (RES, gf.tex-1) e Finura (FIN, µg.in-1). Os dados foram submetidos à análise de variância individual e conjunta e as médias foram agrupadas pelo teste de Scott e Knott (1974) a 0.05 de probabilidade. Os genótipos apresentaram variabilidade para as características estudadas com possibilidade de ganhos genéticos em ciclos posteriores de seleção. BRS Topázio, CNPA 2002 10245 e CNPA 2002 10327 apresentaram as melhores estimativas para as características avaliadas, sendo selecionados para futuros trabalhos de melhoramento do algodoeiro para o semiárido.

ABSTRACT Naturally-colored cotton fiber has received attention from breeding programs in the semiarid region of northeastern Brazil due to an increased interest in its fibers. Therefore, this study aimed to select genotypes of colored cotton fiber for agronomic and technological fiber characteristics for the Brazilian semi-arid conditions. The experiment was carried out in two environments (Patos-PB and Apodi-RN) in Brazil during the 2016 growing season. The experimental design was in randomized blocks with four replications. Treatments consisted of eleven colored fiber genotypes and three controls (BRS Topázio, BRS Rubi, and BRS Verde). The following traits were assessed: seed cotton yield (SCY, kg ha-1), lint percentage (LP, %), lint length (LEN, mm), lint strength (STR, gf tex-1), and lint micronaire (MIC, µg in-1). The data were submitted to individual and joint variance analyses, and means were grouped by the Scott and Knott (1974) test at 0.05 probability. Genotypes showed variability in all traits, which allows genetic gains in subsequent cycles of selection. The genotypes BRS Topázio, CNPA 2002 10245, and CNPA 2002 10327 presented the best estimates for the assessed traits, thus they can be selected for future studies in cotton breeding programs in the semiarid region.

RESUMO: O aprimoramento das características tecnológicas da fibra de algodão é uma demanda constante da indústria têxtil. Este trabalho teve como objetivo identificar o potencial de materiais melhorados com alta porcentagem de plumas para contribuir com alelos que aumentam a porcentagem de plumas com fibra extra longa (ELS) no algodão de terras altas. Dois materiais contrastantes para porcentagem de fibra (LP) e comprimento de fibra (FL) foram usados, um com fibra longa e uma baixa porcentagem de fibra (pai A) e outro com alta porcentagem de fibra e comprimento médio (pai B). As seguintes variáveis foram avaliadas: porcentagem de fibra (LP), comprimento médio da metade superior (UHML), uniformidade da fibra (FU), resistência da fibra (FS) e alongamento (EL). A análise dialélica foi realizada utilizando o Método 4 de Griffing adaptado para dialelo parcial. Os efeitos aditivos foram predominantes em relação aos efeitos não aditivos. O LP médio foi maior quando se usou o pai B. O oposto ocorreu para o UHML. Uma correlação negativa foi detectada entre LP e UHML, mostrando a dificuldade de obter ganho genético para ambas as características ao mesmo tempo.

ABSTRACT: Technological traits improvement of cotton fiber is a constant demand by textile industry. This research aimed to identify the potential of improved materials with high lint percentage to contribute with alleles that increase the lint percentage in Extra long staple fiber (ELS) upland cotton. Two contrasting materials for lint percentage (LP) and fiber length (FL) were used, one with long fiber and a low lint percentage (parent A) and another with high lint percentage and medium length (parent B). The following variables were evaluated: lint percentage (LP), upper half mean length (UHML), fiber uniformity (FU), fiber strength (FS), and elongation (EL). Diallel analysis was performed using the Griffing’s Method 4 adapted to partial diallel. Additive effects were predominant over non-additive effects. The mean LP was higher when using parent B. The opposite occurred for UHML. A negative correlation was detected between LP and UHML, showing the difficulty of obtaining genetic gain for both traits at the same time.

ABSTRACT Cotton provides about 90% of the world textile fiber, and is one of the crops of greater industrial relevance. The objectives of this study were to estimate the inbreeding depressionand the genetic effects involved in the control of the agronomic andfiber quality traits in F1 and F2 generations and to identify promising hybrids for obtaining superior cotton genotypes. Two cultivars of upland cotton and two moco (Brazilian endemic) cotton were crossed using a half-diallel scheme. The following traits were evaluated: percentage of fibers and weight of one boll, fiber length, fiber uniformity, short fiber index, fiber strength, and micronaire index. The additive genetic effects are predominant in the evaluated agronomic and fiber quality traits. Cultivar FM 966 is the most suitable parent to compose crossing blocks for the improvement of cotton agronomic and fiber quality traits. The hybrids FM 966 × CNPA 7MH and FM 966 × BRS 286 are the most promising for obtaining segregating populations aiming to select superior genotypes. Inbreeding depression is more pronounced in the agronomic traits than in the fiber quality traits.

ABSTRACT The objective of this work was to estimate the predicted genetic gains with the simultaneous selection of agronomic and technological traits from elite cotton lines using selection indexes. Data from the evaluation of 36 elite lines were evaluated in three trials located in Apodi-RN in 2013 and 2014 and Santa Helena, GO, Brazil in 2013, in a randomized block design with two replicates. The agronomic traits evaluated were: plant height (PH), average boll weight (ABW), percentage of fibers (PF) and seed cotton yield (YIE). In 20 bolls from each experimental unit, the following technological fiber traits were evaluated: fiber length (UHM), fiber uniformity (UNIF), short fiber index (SFI), fiber strength (FS), elongation (ELON), micronaire (MIC), reflectance (RD) and degree of yellowing (+b). Smith and Hazel, Pesek and Baker and Mulamba and Mock selection indexes were tested for selection of the seven superior genotypes, assigning the coefficients of genetic variation (CVg) as economic weight. There were no interaction between genotypes and environments for any of the evaluated traits. Smith and Hazel index resulted in negative gains for fiber length and positive for the traits whose reduction is of interest, such as plant height, micronaire and degree of yellowing. Pesek and Baker index provided positive predictive gains for all traits of interest. However, it promoted reduction only to the degree of yellowing. Mulamba and Mock presented satisfactory gains, being the most suitable for selecting genotypes aiming at simultaneous gains in yield and fiber technological components.

Abstract Fiber length is the main trait that needs to be improved in cotton. However, the presence of genotypes x environments interaction for this trait can hinder the recommendation of genotypes with greater length fibers. The aim of this study was to evaluate the adaptability and stability of the fibers length of cotton genotypes for recommendation to the Midwest and Northeast, using artificial neural networks (ANNs) and Eberhart and Russell method. Seven trials were carried out in the states of Ceará, Rio Grande do Norte, Goiás and Mato Grosso do Sul. Experimental design was a randomized block with four replications. Data were submitted to analysis of adaptability and stability through the Eberhart & Russell and ANNs methodologies. Based on these methods, the genotypes BRS Aroeira, CNPA CNPA 2009 42 and CNPA 2009 27 has better performance in unfavorable, general and favorable environment, respectively, for having fiber length above the overall mean of environments and high phenotypic stability.

RESUMO. Dentre os caracteres tecnológicos que ainda precisam ser melhorados no algodoeiro, destaca-se o comprimento das fibras. Deste modo, os objetivos com este trabalho foram quantificar as inter-relações entre caracteres agronômicos e tecnológicos de fibras e identificar caracteres que possam ser utilizados para a seleção indireta de genótipos de algodoeiro com maior comprimento de fibras. Foram avaliados caracteres agronômicos e tecnológicos em 36 linhagens elite de algodoeiro cultivadas em três ambientes. Foram estimadas as correlações canônicas entre dois grupos de caracteres: agronômicos e tecnológicos. Realizou-se análise de trilha considerando o comprimento de fibras como variável dependente principal. Os genótipos apresentaram variabilidade para todos os caracteres avaliados e não houve interação genótipos x ambientes significativa para nenhum caráter. É possível melhorar os principais caracteres tecnológicos do algodoeiro a partir da seleção indireta em caracteres agronômicos. A seleção de genótipos de algodoeiro com menor porte e maior peso médio de capulhos pode ser uma estratégia para aumentar o comprimento de fibras e melhorar os demais caracteres tecnológicos. Índices de seleção contendo altura de plantas, peso de capulhos, resistência e uniformidade de fibras é uma das principais estratégias para selecionar genótipos de algodoeiro com alta produtividade de algodão em caroço e fibras longas.

ABSTRACT. Fiber length stands out among technological traits as one that still needs to be improved in cotton. Thus, the objectives of this work were to quantify the interrelations between agronomic and technological fiber traits and to identify traits that could be used for the indirect selection of cotton genotypes with longer fiber lengths. Agronomic and technological traits were evaluated in 36 elite lines of cotton that were cultivated in three environments. Canonical correlations were estimated between two groups of traits: agronomic and technological. Path analysis was performed that considered fiber length as the primary dependent variable. The genotypes presented variability in all the evaluated traits, and no significant genotype vs. environmental interaction was observed for any of them. The main technological traits of cotton crops can be improved by an indirect selection of agronomic traits. The selection of cotton genotypes with a smaller size and a higher mean boll weight can be used to increase fiber length and improve other technological traits. Selection indices containing plant height, mean boll weight, fiber strength, and fiber uniformity can be one of the main strategies for the selection of cotton genotypes with a high yield of cotton bolls and long fibers.

Resumo: O objetivo deste trabalho foi avaliar o teor de óleo e os caracteres relacionados à qualidade e ao rendimento de fibra em linhagens de algodão (Gossypium hirsutum), para selecionar materiais com alto teor de óleo e níveis aceitáveis dos demais caracteres. Vinte e duas linhagens F6 e três testemunhas foram cultivadas em três ensaios de campo - dois em Apodi, RN, e um em Barbalha, CE. Os parâmetros genéticos e o ganho com a seleção de 20% das linhagens foram estimados de acordo com suas médias em cada ambiente e no conjunto de ambientes. Quanto ao teor de óleo, há variabilidade genética, e a seleção com base na média geral é indicada, pois esse caráter apresentou elevada herdabilidade, com ganho esperado de 4,58%. As linhagens selecionadas por este critério apresentam teores de óleo entre 23,52 e 24,51%, superiores aos da cultivar brasileira BRS Aroeira com maior teor de óleo no grão (22,04%).

Abstract: The objective of this work was to evaluate the oil content and characters related to fiber quality and yield in cotton lines (Gossypium hirsutum), in order to select genotypes with high oil content and acceptable levels of the other characters. Twenty-two F6 lines and three checks were cultivated in three field trials - two in the municipality of Apodi, in the state of Rio Grande do Norte, and one in the municipality of Barbalha, in the state of Ceará, both in Brazil. The genetic parameters and the genetic gain from selecting 20% of the lines were estimated according to their means in each environment and in the group of environments. Regarding oil content, there is genetic variability, and the selection based on the overall mean is indicated, since this character showed high heritability, with 4.58% expected gain. The lines selected with this criterion have oil contents between 23.52 and 24.51%, which are higher than those of the Brazilian cultivar BRS Aroeira with the highest grain oil content (22.04%).

Abstract In cotton breeding programs, it is necessary to identify genotypes with predictable behavior on the length of fibers, and which are responsive to environmental variations, in specific or broad conditions. The aim of this study was to employ the methodology of mixed models for simultaneous selection of cotton genotypes with greater length of fibers, adaptability and stability. It was evaluated 36 lines in three trials located in Apodi (2013 and 2014) and Santa Helena (2013,) in a randomized block design with two replications. Genetic parameters were estimated by the restricted maximum likelihood/best linear unbiased predictor method (REML/BLUP) and the selection was based on the method of harmonic mean of the relative performance of genetic values. The genotypes CNPA 2012-55, CNPA 2012-58, CNPA 2012-62 and CNPA 2012-64 can be grown in all tested environments, since they gather greater length of fibers, stability and adaptability.

RESUMO A metodologia máxima verossimilhança restrita/melhor preditor linear não viesado (REML/BLUP) tem sido utilizada para interpretação da estabilidade genotípica e da adaptabilidade de culturas como feijão, canade-açúcar, cajueiro, eucalipto e arroz, porém pesquisas com o algodão ainda são limitadas. O objetivo deste trabalho foi selecionar genótipos de algodoeiro, via modelos mistos, que reúnem simultaneamente adaptabilidade e estabilidade produtiva e verificar se essa metodologia pode ser utilizada nos programas de melhoramento genético do algodoeiro. Foram avaliadas 36 linhagens em três ensaios localizados em Apodi, RN (2013 e 2014), e Santa Helena, GO (2013), em delineamento de blocos casualizados com duas repetições. Os parâmetros genéticos foram estimados pela metodologia REML/BLUP, e a seleção baseou-se no método da média harmônica da performance relativa dos valores genéticos (MHPRVG), com três estratégias: seleção com base no valor genético predito, tendo-se considerado o desempenho médio dos genótipos em todos os ambientes (sem efeito de interação); o desempenho em cada ambiente (com efeito da interação); e seleção simultânea quanto à produtividade de algodão em caroço, adaptabilidade e estabilidade. Os genótipos CNPA 2012-60 e CNPA 2012-65 podem ser cultivados em ambientes similares aos testados, pois reúnem alta adaptabilidade e estabilidade produtiva de algodão em caroço. Houve concordância entre as estatísticas utilizadas na discriminação dos genótipos mais produtivos e com alta adaptabilidade e estabilidade, o que indica que as mesmas podem fazer parte de critérios seletivos na rotina dos programas de melhoramento do algodoeiro.

ABSTRACT The restricted maximum likelihood/best linear unbiased predictor methodology (REML/BLUP) has been used for the interpretation of genotypic stability and adaptability of crops such as common bean, sugarcane, cashew, eucalyptus and rice, but researches with cotton are still limited. The aim of this work was to select cotton genotypes, via mixed models, which simultaneously meet adaptability and stability and verify if this methodology can be used in genetic improvement programs in cotton. Thirty-six strains were evaluated in three trials located in Apodi, Rio Grande do Norte (2013 and 2014), and Santa Helena, Goiás (2013), in a randomized block design with two replications. The genetic parameters were estimated by REML/ BLUP methodology, and the selection was based on the method of the harmonic mean of the relative performance of the genetic values (MHPRVG), with three strategies: selection based on the predicted genetic value, considering the average performance of genotypes in all environments (without interaction effect); performance in each environment (with interaction effect); and simultaneous selection as to cotton yield, stability and adaptability. The CNPA 2012-60 and CNPA 2012-65 genotypes may be grown in environments similar to those tested, since they present high adaptability and productive stability of cotton. There was agreement among the statistics used in discrimination of the most productive genotypes with high adaptability and stability, indicating that they can be part of selective criteria in the routine of cotton breeding programs.

RESUMO: Objetivou-se avaliar a produtividade, o rendimento e a qualidade de fibras de cultivares de algodoeiro herbáceo submetidas a diferentes lâminas de irrigação. Durante dois anos consecutivos foi conduzido um experimento de campo na região de Apodi (RN) disposto em parcelas subdivididas com quatro lâminas de irrigação (130, 100, 70 e 40% da evapotranspiração da cultura - ETc) e quatro cultivares de algodoeiro (FiberMax 993, BRS 286, BRS 336 e BRS 335), em delineamento de blocos casualizados com quatro repetições. Foram avaliadas a produtividade, a percentagem e a qualidade das fibras do algodoeiro. Houve diferença significativa para as características avaliadas entre as cultivares e as lâminas de irrigação. A rega com déficit (70 e 40% ETc) ocasionou declínio na produtividade de algodão em caroço, na percentagem e qualidade das fibras. As cultivares FiberMax 993 e BRS 286 apresentaram as maiores produtividades e percentagem de fibras entre as cultivares avaliadas. Com a lâmina de 40% da ETc as cultivares de fibra média (FiberMax 993, BRS 286 e BRS 335) apresentaram fibras curtas, e a cultivar de fibra longa (BRS 336) apresentou fibra média. De forma geral, a redução na qualidade da fibra não foi severa, haja vista a fibra produzida está dentro da faixa de qualidade aceitável pela indústria têxtil nacional, mesmo em condições de déficit hídrico. Dessa forma, a decisão em irrigar o algodoeiro com ou sem déficit hídrico dependerá dos custos da irrigação e do valor de mercado do produto.

ABSTRACT: This study was conducted to evaluate seed cotton yield, fiber yield, and fiber quality traits of cotton cultivars grown under different irrigation levels in Brazil. The experiment was conducted over two years in the region of Apodi - RN, with sprinkler irrigation. Treatments comprised of 4 irrigation levels i.e., 130, 100, 70 and 40 % of the crop evapotranspiration (ETc) and 4 cotton cultivars i.e., FiberMax 993, BRS 286, BRS 336 and BRS 335. The experimental design was factorial with randomized complete block design and four replicates. Yield, lint percent and fiber quality traits determined were evaluated. Different responses were observed for cultivars at various irrigation levels. Cultivars grown under limited irrigation exhibited a decline in the seed cotton yield, lint percent, and fiber quality. Cultivars with the highest yield and lint percent were FiberMax 993 and BRS 286. Within irrigation level of 40 % ETc, the medium fiber cultivars produced short fibers whereas the long fiber cultivar, BRS 336, produced medium fiber length. Overall, the different levels of water deficits did not significantly affect fiber quality of the four cultivars tested as all fiber quality traits remained acceptable for the domestic textile industry.

O objetivo deste trabalho foi verificar a presença de interação genótipo x ambiente (G x A) e determinar a adaptabilidade e estabilidade fenotípica de linhagens de algodão de fibra marrom, utilizando o modelo de Ebehart & Russell. Foram conduzidos sete experimentos nos estados de CE, GO, MS e RN, em 2010 e 2011, em regime irrigado e de sequeiro. O delineamento utilizado foi blocos casualizados com quatro repetições. Foram avaliados 11 genótipos, segundo sete caracteres relativos à fibra. A interação G x A foi significativa para a maioria dos caracteres. As linhagens 1, 2, 3, 4, 5 e 7 demonstraram capacidade de resposta à melhoria de ambiente, sendo 1 e 5 os genótipos que apresentaram comportamento previsível para todas as características. O índice de fibras curtas mostrou ser uma característica de alta previsibilidade

The objective of this study was to verify the presence of genotype x environment (G x E) interaction and determine the adaptability and phenotypic stability of strains of brown cotton fiber using the model of Ebehart & Russell. Seven experiments were conducted in the states of CE, GO, MS and RN, in 2010 and 2011 under irrigated and rain fed conditions. The experimental design was randomized blocks with four replications. Eleven genotypes were assessed according to seven characters on the fiber. The G x E interaction was significant for most characters. The lines 1, 2, 3, 4, 5 and 7 showed better responsiveness to the environment, being 1 and 5 genotypes showed all predictable behavior characteristics for all characteristics. The content of short fibers proved to be a characteristic of high predictability

A maioria das fibras de algodão (Gossypium hirsutum) produzidas no mundo é de cor branca, apesar do línter e da fibra dos algodões tetraplóides (G. barbadense) apresentarem tonalidades de verde e de marrom. A cor da fibra é uma característica geneticamente herdada, resultante da presença de pigmentos entremeados à celulose. A herança da coloração é relativamente simples e a herdabilidade elevada, porém nos acessos silvestres, esta ainda é desconhecida. Estudou-se a herança da cor de fibra em acessos de G. barbadense que apresentam tonalidades de marrom. Acessos silvestres de G. barbadense e cultivares de G. hirsutum de fibra branca foram cruzados e obtidas as gerações F2 e de retrocruzamentos (RC1 e RC2). As cores de fibra são todas governadas por um gene, sendo a cor marrom parcialmente dominante sobre o branco, com exceção da cor acinzentada do material PI 435267 que mostra ser o branco parcialmente dominante.

Most of cotton (Gossypium hirsutum) fibers produced in the world are white, in spite of the lint and fiber of tetraploid cottons (G. barbadense), exhibiting various shades of green and brown. Cotton fiber color is a genetically inherited trait resulting from the presence of pigments intermingled with cellulose. Inheritance of fiber color is relatively simple, with high heritability, but in wild accessions it is still unknown. The objective of this study was to determine the inheritance of fiber color in G. barbadense accessions representing different shades of brown. We crossed wild G. barbadense accessions and G. hirsutum cultivars (with white fiber) and obtained the F2 generations, and BC1 and BC2 backcrosses. It may be concluded that fiber color is controlled by one gene, with partial dominance of the brown color over white, except for the grayish color of the PI 435267 accession, which showed the white to be partially dominant.

O Nordeste brasileiro engloba o bioma Caatinga (900 mil km²) onde se encontra a região Semiárida com sistemas de produção dependentes de chuva e irrigação. Dentre os programas de melhoramento que tiveram sucesso destacam-se o do cajueiro e do algodoeiro. O primeiro produziu aumento substancial na produção de castanhas no Ceará, Rio Grande do Norte e Piauí e o segundo resultou em fibra colorida processada em pequenas indústrias de confecção na Paraíba, com exportação para 11 países. No Submédio São Francisco, a cebola cultivada foi substituída pelas variedades melhoradas, cultivadas em 90% da área de produção, e o tomate industrial, introduzido pela pesquisa em 1972, foi cultivada em mais de 80% da área, na época. A participação do setor privado e a continuidade dos programas de melhoramento foram determinantes para o sucesso dos mesmos. Esperam-se mais casos de sucesso com o estabelecimento de cursos de pós-graduação em Ciências Agrárias no Semiárido.

The Northeastern region of Brazil comprises the Caatinga biome (900,000 km²) part of which is a semiarid region with rainfed and irrigated production systems. Among the successful breeding programs are cashew and cotton. The first led to a substantial increase in nut production in Ceará, Rio Grande do Norte and Piauí and the second bred a naturally colored cotton fiber, now processed in small clothing industries in Paraiba, exporting to 11 countries. In the lower-middle São Francisco valley, the previously grown onion was replaced by improved varieties, on 90% of the production area, and by industrial tomato, introduced by research in 1972, which came to be used on more than 80% of the area at the time. The participation of the private sector and continuity of breeding programs were crucial for the success. More examples of success are expected with the establishment of postgraduate courses in Agricultural Sciences in the Semiarid region.

Objetivou-se identificar variáveis fisiológicas para distinguir genótipos de algodoeiro tolerantes e sensíveis ao déficit hídrico. O experimento foi conduzido no delineamento inteiramente casualizado em arranjo fatorial, sendo testados quatro genótipos (BRS 187 8H e ACALA SJ-4 - tolerante ao déficit hídrico; CNPA 7H e SU-0450/8909 -sensíveis ao déficit hídrico) e dois regimes hídricos (controle - sempre irrigado e com déficit hídrico imposto na emissão da primeira flor. Na emissão da primeira flor, a irrigação foi suspensa para o grupo a ser submetido ao déficit hídrico. O potencial hídrico foliar foi monitorado na antemanhã até que as plantas dos cultivares em estudo atingissem -3,0 MPa, ponto no qual coletaram-se amostras foliares para análises fisiológicas. Após, irrigou-se as plantas até a obtenção de valor superior a 50% do potencial hídrico foliar (-1,50 MPa). Avaliaram-se a eficiência fotoquímica máxima (Fv/Fm), o conteúdo de clorofila via índice SPAD, o conteúdo relativo de água (CRA), o extravasamento de eletrólitos, a composição isotópica do carbono (δ13C), o rendimento de algodão em caroço por planta e a qualidade da fibra. A disruptura de membrana via extravasamento de eletrólitos e a δ13C apresentaram-se como potenciais indicadores fisiológicos visando a seleção de genótipos de algodoeiro tolerantes ao déficit hídrico.

The objective of this study was to identify physiological traits that could distinguish between cotton genotypes that were tolerant or sensitive to water deficits. The experiment was conducted in a completely randomized design through a factorial combination to analyze four genotypes (BRS 187 8H and ACALA SJ-4 - water deficit tolerant; CNPA 7H and SU-0450/8909 - water deficit sensitive) and two water regimes (watered/always irrigated and stressed/with a water deficit imposed at flowering). Irrigation was suspended for the plants in the water deficit treatment groups when their first flowers appeared. Leaf water potential (ψpd) was monitored until the plants reached -3.0 MPa predawn, at which point leaf samples were collected for analysis. The plants were re-irrigated and monitored for a recovery to 50% of leaf water potential. The maximum photochemical efficiency (Fv/Fm), chlorophyll content (SPAD index), relative water content (RWC), disruption of the cell membrane via membrane leakage, carbon isotope composition (δ13C), seed cotton yield and fiber quality were evaluated. The trends in membrane leakage and carbon isotope composition were different between the tolerant and sensitive genotypes under a water deficit, which makes these physiological traits suitable for screening for tolerance to water deficits in cotton.

O objetivo deste trabalho foi analisar a estabilidade e a adaptabilidade, e agrupar ambientes de cultivo, com dados de produtividade de oito genótipos do algodoeiro, avaliados em 16 ambientes localizados no Cerrado de Mato Grosso e Mato Grosso do Sul, na safra 1998/1999. O delineamento utilizado foi em quadrado latino 8x8. As análises individual e conjunta foram realizadas, considerando-se os efeitos de genótipos e ambientes fixos. Os parâmetros foram avaliados pelo método da ecovalência e pelo modelo AMMI. A linhagem CNPA 94773 foi a mais estável e adaptada às condições ambientais. Houve adaptabilidade específica e interação positiva de genótipos a grupos de ambientes: ITA 90 (Campo Novo dos Parecis, Chapadão do Sul, Sorriso, Itiquira e Sapezal); ITA 96, FMT Fetagri e FMT Saturno (Rondonópolis e Pedra Preta); BRS 197 (Nova Mutum, Primavera do Leste e Campo Verde); BRS FACUAL (Quatro Marcos e Campo Verde); CNPA 94773 (Ponta Porã, Sapezal, Alto Taquari e Lucas do Rio Verde) e BRS Antares (Ponta Porã, Alto Taquari e Lucas do Rio Verde).

The objective of this work was to analyze stability and adaptability, and to group environments with productivity data of eight cotton genotypes in 16 environments of Cerrado of Mato Grosso and Mato Grosso do Sul, Brazil, in 1998/1999 harvest. Statistical model used was the simple square 8x8. The individual and combined statistical analysis were performed by considering genotype and environment effects fixed. Parameters of the cultivars or lines were evaluated by the covalence, method and by the AMMI procedure. The lineage CNPA 94773 was the stablest and most adapted to environmental conditions. There was a positive specific adaptability and interaction of the genotypes with the environments: CNPA ITA 90 cultivar (Campo Novo dos Parecis, Chapadão do Sul, Sorriso, Itiquira and Sapezal); ITA 96, FMT Fetagri and FMT Saturno (Rondonópolis and Pedra Preta); BRS 197 (Nova Mutum, Primavera do Leste and Campo Verde); BRS FACUAL (Quatro Marcos and Campo Verde); CNPA 94773 (Ponta Porã, Sapezal, Alto Taquari and Lucas do Rio Verde) and BRS Antares (Ponta Porã, Alto Taquari and Lucas do Rio Verde).