Jairo Vidal Vieira

Seleção de progênies de meio-irmãos de cenoura baseada em características de sementes

A menor germinacao e emergencia de plântulas em campo de cenoura obtida nas sementes de cultivares nacionais em relacao as importadas, aumenta o custo de producao alem de impossibilitar a otimizacao do estande final atraves do emprego de semeadeiras de precisao. Setenta e quatro progenies de meio-irmaos oriundas de uma populacao de cenoura tipo Brasilia foram avaliadas quanto a germinacao, vigor e peso de sementes com o objetivo de verificar a variabilidade e as relacoes geneticas entre os referidos caracteres. Evidenciou-se a existencia de diferencas significativas entre as progenies de meio-irmaos em relacao a todos os caracteres avaliados. Os altos valores de herdabilidade e variabilidade genetica entre progenies para os caracteres avaliados sugerem que metodos de melhoramento simples combinados com metodos de selecao tendo por base a teoria de indice podem ser aplicados visando a melhoria da qualidade fisiologica das sementes de cenoura.

Verificação da adaptabilidade e estabilidade de populações de cenoura pelos métodos AMMI, GGE biplot e REML/BLUP

O objetivo desse estudo foi verificar a adaptabilidade e estabilidade de populacoes de cenoura diante de ambientes com cultivo orgânico e convencional e realizar a comparacao entre as metodologias estatisticas utilizadas. O trabalho foi desenvolvido em 2007 e 2008, em cinco locais. Em Sao Gotardo (MG); Irece (BA) e Gama (DF) foi realizado cultivo convencional e em PAD (DF) (Programa de Assentamento Dirigido do Distrito Federal) e Gama (DF) foi utilizado o sistema de cultivo orgânico. O delineamento experimental utilizado foi o de blocos ao acaso com tres repeticoes e parcelas de 1 m2. Foram avaliadas sete populacoes de cenoura do grupo Brasilia: 0912545, 0912532, 0912520, BRS Planalto, Esplanada, Brasilia e Alvorada. Aos cem dias apos a semeadura, foi determinada em cada parcela, em gramas, a massa das raizes com padrao comercial. Para a avaliacao da adaptabilidade e estabilidade foram aplicados os metodos AMMI, GGE Biplot e REML/BLUP. As analises AMMI e GGE Biplot foram bastante semelhantes na verificacao da adaptabilidade e estabilidade das populacoes de cenoura, e GGE Biplot agrupou de maneira mais clara os ambientes mais favoraveis e desfavoraveis. A analise REML/BLUP se destacou das demais e apesar de nao informar sobre o agrupamento de locais mais semelhantes, apresenta os resultados em funcao de valores genotipicos levando em consideracao os parâmetros de adaptabilidade e estabilidade. As populacoes com melhor adaptabilidade e estabilidade foram 0912532, BRS Planalto e 0912520.

Produtividade, florescimento prematuro e queima-das-folhas em cenoura cultivada em sistema orgânico e convencional

Four experiments were carried out with carrots genotypes during summer season in Distrito Federal, Brazil, to evaluate yield, bolting and leaf blight under organic and conventional conditions. The experiments were carried out in two locations and in each one two experiments were established, considering both crop systems. The experimental design was a random block with eight treatments and five replicates. The treatments consisted of the cvs. Alvorada, Brasilia RL, Brasilia Bionatur, Kuronan, Nantes 3 Tip Top, Carandai AG 106, Brazlândia and Pop. 0212246. The soil was fertilized with organic compost for the organic trial and with chemical fertilizer for the conventional trial. Plants were evaluated for leaf blight incidence, 70 days after sowing date, through visual observation. Roots were harvested 95 days after sowing, washed, classified and weighted. Bolting was more frequent in Brasilia Bionatur, under conventional condition, in Brazlândia. A difference of susceptibility to leaf blight among genotypes was observed in plants cultivated in the organic system. Nantes was the most susceptible while Pop. 0212246 was the most resistant. Alternaria dauci was observed more frequently at Brazlândia, while Cercospora carotae was observed at both locations, similarly, under organic conditions. For commercial and total yield, commercial and total root number, Pop. 0212246 and Brazlândia were the best materials in both crop systems. Total and commercial yield, total and commercial root number, number and weight of refused roots were higher in the conventional area, compared to the organic area. Brasilia and Brazlândia can be recommended for Distrito Federal, independently of crop system, during summer season. Pop. 0212246 showed desirable agronomical characteristics and can be, in the future, available for farmers in Distrito Federal.

Adaptabilidade e estabilidade de populações de cenoura

In the process of developing new cultivars, it is imperative to know the performance of carrot populations in final breeding phase for the possible environments to which they may be indicated; this can be verified testing the adaptability and stability. In this study the adaptability and stability of carrot genotypes from the Brasilia group were verified. The experiment was carried out during the 2007/2008, 2008/2009 and 2009/2010 crop years at five different places, three being in conventional growing at Sao Gotardo (Minas Gerais state), Irece (Bahia state) and Gama (Federal District), and two in organic growing at Managed Settlement Program of the Federal District (PAD-DF) and Gama. A randomized block design with three replications with 1 m2 plots was used. Four carrot genotypes from the Brasilia group: 0912532, 0912520, BRS Planalto and Brasilia were evaluated. 100 days following sowing, fresh mass of commercial root value was determined in grams, in each plot. Regarding adaptability and stability assessment, the REML/BLUP methodology was applied. BRS Planalto and 0912520 were the genotypes with better adaptability and stability; BRS Planalto was preeminent mainly in 2009-2010 crop years; and 0912520 was preeminent in 2007/2008 and 2008/2009. Brasilia had the worst performance in most places, but good performance and specific adaptability to Irece.

Evaluation of watermelon genotypes for resistance to Papaya ringspot virus, type watermelon

The aim of this study was to assess the resistance of nine watermelon genotypes against three PRSV-W isolates originated from three Brazilian States (Sao Paulo, Goias and Pernambuco). The experiment was carried out at Embrapa Hortalicas, Brasilia, Brazil, in April 2004. Nine watermelon genotypes were appraised, in a randomizated block design with four replications. Each plot was comprised of one 5 kg pot and five watermelon plants per pot. Ten to 13 days after sowing, inoculation was carried out with three PRSV-W isolates. Twenty-seven and 37 days after sowing, virus symptoms were evaluated. Virus presence or absence in the inoculated plants was confirmed by Das-Elisa. The results comprised variance analysis, heritability estimation, correlations among the characters, and genotype comparisons. Based on the different behavior of the genotypes in relation to each PRSV-W isolate, it is concluded that different isolates should be used in watermelon breeding programs. The high heritability values for most of the characters indicated that the characteristic in study is under the control of a few loci and, therefore, the possibility of selection of resistant watermelon accesses is high. The evaluated genotypes showed higher virus tolerance compared to the most planted cultivar in the country (Crimson Sweet), as it can be verified by the average values. The results suggest that the selected watermelon accesses are a good source of resistance to new watermelon cultivars tolerant to PRSV-W.

Componentes genéticos e fenotípicos para caracteres de importância agronômica em população de cenoura sob seleção recorrente

The objective of this work was to estimate the genotypic and phenotypic parameters for traits of carrot populations among characters in carrot populations, in order to guide the choice of selection strategies. The experiments were performed at two locations (Lapao, Bahia State and Brasilia, Brazil) in the summer of 2004. Nine carrot hybrid populations were evaluated in randomized complete block design with 4 replications and 2 m2 treatments. 90 days after sowing, 15 competitive plants per plot were harvested and evaluated individually for the characters yield, root length, green shoulder length, tip type, shoulder type, root diameter, xylem root diameter, relationship among xylem diameter/root diameter, and both xylem and phloem a* color (color parameter determined by colorimetry, varying from green to red). The data were submitted to variance analyses and the heritability in the wide sense of plot average was estimated by medium square and the correlation among the characters. According to the heritability values, for the characters xylem diameter (0.92 and 0.87), color of a* xylem (0.96 and 0.95) and ratio among xylem diameter and root diameter (0.87 and 0.91), strong selection pressure can be applied in the two evaluation places. Larger root yield was associated with larger root diameter and larger xylem diameter, as well as by larger values of the ratio among xylem diameter and root diameter. Thicker roots are associated with smaller a* (content of β-carotene), mainly in relation to the part constituted by the xylem. Therefore, through the correlation values, there exist an indication that selection for larger carotene content cannot be carried out without considering the characters of root diameter, which are important yield components.

Herdabilidade e correlações genotípicas entre caracteres de folhagem e sistema radicular em famílias de cenoura, cultivar Brasília

The present work was conducted aiming to estimate genetic parameters associated with traits of importance to carrot breeding, including: number of leaves per plant (NL), length of the longest leaf in the plant (LL), root length (RL), root weight (RW), root diameter (RD), and xylem diameter (XD). This experiment was carried out during the rainy summer season (1999/2000) using 69 half-sib families derived from cultivar Brasilia. Progenies were evaluated using a complete randomized block design with two replications and 2 m2 plots, with four 20-plant rows. The broad-sense heritability (ha2) values ranged from 29.9% (for RD) to 77.6% (for LL). Genotypic, phenotypic, and environmental correlations displayed a large variation in magnitude with the highest genotypic correlation (0.85) being observed between the traits RW and RD. Negative genotypic correlation was observed between RL and XD, which indicates that the development of new cultivars suitable for processing as baby-carrots is feasible using populations derived from cultivar Brasilia. High negative environmental correlation values were obtained between the traits RW and XD, as well as between RD and XD. This information would be of extreme importance aiming to optimize the selection process when using segregating populations derived from the tropical-adapted cultivar Brasilia.

Heritability and gain from selection for field resistance against multiple root-knot nematode species (Meloidogyne incognita race 1 and M. javanica) in carrot

AbstractHeritability and gain from selection of traits associated with field resistance to multiple root-knot nematode species were estimated in carrot (Daucus carota L.). Experimental plots were uniformly and simultaneously infested with Meloidogyne incognita race 1 and M. javanica. Forty-seven half-sib families derived from the cv. ‘Brasília’ were evaluated for: (1) percentage of commercial roots with non-galling symptoms (%RNG); (2) percentage of commercial roots with gall symptoms (%RGS) and (3) percentage of non-commercial roots (%NCR). The cultivars ‘Brasília’ (resistant), ‘Carandaí’ (intermediate) and ‘Nova Kuroda’ (susceptible) were employed as standards. Broad-sense heritability estimates were 61.9 % for %RNG; 30.6 % for %RGS and 67.9 % for %NCR. However, the gains from selection were very small for all traits. The genotypic correlation between %RGS and %NCR was –0.38 and the correlation between %RNG and %RGS was 0.13. Selection on increasing %RNG resulted in a negative correlated response on %NCR (genotypic correlation = –0.99) indicating repulsion phase linkage(s) between the genetic factor(s) controlling these traits. The phenotypic correlation of –0.88 between %RNG and %NCR suggested that incomplete penetrance and dosage effects might be involved in the expression of these traits. Selection of superior genotypes (i.e. high %RNG, low %RGS, and low %NCR) can be achieved. ‘Brasília’ was among the genotypes selected for the following cycle of recombination reinforcing the notion that this cultivar is one of the most promising sources of stable, wide-spectrum field resistance to Meloidogyne species in D. carota.

Tamanho mínimo de parcela para avaliação de caracteres de raiz em cenoura

The estimate of the optimal number of plants per plot for the evaluation of carrot populations is important in order to reduce the experimental error and to enhance the accuracy of the information obtained in breeding experiments. Additionally, it contributes to reduce the research costs. The objective of the present work was to estimate the minimum number of plants per plot for evaluation of root characters in carrot populations using the modified maximum curvature and the stabilization of the average and genetic variance methods. The essays were conducted in the summer of 2004 at three representative areas for carrot production in Brazil, respectively: Brasilia, DF; Sao Gotardo, MG and Lapao, BA, in randomized blocks design with four replications, and plots with 2 m2. Harvesting took place 90 days after sowing. In each plot of nine populations, 15 competitive plants were harvest and roots evaluated for mass, length, green shoulder length, tip shape, shoulder shape, diameter, xylem diameter, relationship among xylem diameter / root diameter and the L* a* b* color caracters for the xylem and phloem. The procedures of re-sampling and the modified maximum curvature method were used to estimate the minimum plant number to represent each plot. The results obtained for each procedure indicated that a sample of 13 plants per plot is enough to guarantee an appropriate evaluation of carrot populations for the group of studied characters.

Resistência de populações de cenoura à queima-das-folhas com diferentes níveis de germoplasma tropical

A queima-das-folhas e responsavel por perdas significativas na producao de cenoura e a resistencia genetica e uma das formas mais eficientes de controle da doenca. Objetivou-se com este trabalho avaliar a resistencia de progenies de populacoes de cenoura a queima-das-folhas com diferentes niveis de germoplasma tropical. Foram avaliadas as populacoes 561, 586 e 587 e como testemunhas as cultivares comerciais, Juliana e BRS Planalto. Foi utilizado o delineamento de blocos casualizados, com duas repeticoes e parcela de 1,2 m2. A doenca ocorreu de forma natural no campo e foi avaliada a cada cinco dias, a partir dos 72 dias apos a semeadura. As populacoes 561, 586 e 587 e a cultivar BRS Planalto apresentaram severidades semelhantes e inferiores as cultivares Brasilia e Juliana, as quais nao diferiram entre si. Nao foram observadas diferencas significativas na producao comercial e total de raizes. Nas analises realizadas entre as progenies dentro de cada populacao e as testemunhas nao foram observadas diferencas na producao comercial e total de raizes. Com relacao a severidade, as progenies da populacao 561 e 586 e BRS Planalto nao diferiram entre si e apresentaram maiores niveis de resistencia que Brasilia e Juliana. Contudo, uma progenie da populacao 586 apresentou resistencia intermediaria. Dez de 15 progenies da populacao 587 apresentaram niveis de resistencia semelhantes a BRS Planalto, enquanto cinco apresentaram resistencia semelhante a Brasilia e Juliana. Esta maior variabilidade fenotipica indica seu potencial para a obtencao de ganho genetico para resistencia a queima-das-folhas. A producao de raizes comerciais e totais das populacoes 561 e 586 apresentaram correlacao negativa com a severidade da doenca. Tais resultados indicam que a resistencia a queima-das-folhas atribui-se, majoritariamente, ao germoplasma tropical, observado em maior quantidade na populacao 561, cerca de 87,5%.