RESUMO A estimativa da área foliar na couve é importante, pois medidas diretas são difíceis e imprecisas, devido ao tamanho da folha, a irregularidade da superfície foliar de alguns genótipos, a necessidade de equipamentos caros e de muita mão-de-obra. Objetivou-se verificar a eficiência da estimação da área foliar de couve por meio de RNAs e constatar a eficiência desta estratégia em comparação com o uso da área foliar observada. O experimento foi conduzido em delineamento de blocos casualizados com três repetições, 22 acessos e quatro plantas por parcela. Desenvolveram-se perceptrons de multicamadas utilizando 50 folhas por acesso, destinando-se 70% para treinamento, 15% para a validação cruzada (early-stop) e 15% para teste. Foram testadas 39 configurações de rede perceptron de multicamadas. As RNAs foram eficientes para estimar a área foliar da couve a partir do comprimento e largura do limbo foliar. A área foliar estimada pela RNA é indicada para a seleção de plantas por ser de fácil obtenção, ser um método não destrutivo, apresentar alta correlação fenotípica e genética com a área foliar observada e maior herdabilidade.
This research was installed to study plant growth of sweet potato and identify the most favorable harvest time for both roots and the aboveground part (stems). The experiment was carried out at the JK campus of the Federal University of the Vale do Jequitinhonha e Mucuri, in Diamantina, MG, complete blocks at random, with four replications. Three plants in the central part of the experimental plots were collected in twelve consecutive harvests at 15-day intervals. Plants were fractionated in roots, stems, and leaves to determine the dry matter of each part. Leaf area was also measured and growth rates were calculated. Data were analyzed by means of regression. Plants reached the highest dry matter accumulation between 75 and 156 days after transplanting (DAT), which corresponded to the phase of greatest growth. Plants should be harvested between 60 and 87 DAT to achieve the highest stem yield. For the highest root yield, the harvest should be carried out 180 DAT. The period from 80 to 118 DAT was the most adequate for reaching simultaneously the highest yields for both roots and stems. Therefore, the ideal harvest time for sweet potatoes depends on the use intended for the plant and on the physiological indexes associated with it.
The estimation of repeatability coefficient provides support to define the number and the appropriate period of genotype evaluations, obtaining better success in breeding programs, in order to lower labor costs. Therefore, knowing repeatability and heritability parameters is relevant. Thus, the aim of this study was to estimate the repeatability and heritability coefficients and accurately determine the number of measurements. Eight strawberry cultivars were analyzed in a randomized block design with four replicates and eighteen plants per plot, being harvested twice a week over a period of six months (May to October, 2012), totalizing six evaluations. Among the evaluated traits, the estimated heritabilities ranged from 3.13% (number of fruits) to 40.20% (average fruit mass) whereas the repeatability ranged from 9.00 to 42.06% for the same characters. The minimum number of evaluations, to reach a coefficient of determination with an accuracy of about 80%, ranged from the maximum of 40 for fruit number and the minimum of 6 for average fruit mass. In order to be considered commercially important marketable fruit mass, minimum of 20 evaluations are required, it means, at least, 20 months.
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