Genetic divergence among maize hybrids and correlations with heterosis and combining ability - doi: 10.4025/actasciagron.v34i1.11979

Twelve corn hybrids recommended for cropping in the south-central region of the Paraná State and 66 crossings obtained among these hybrids were evaluated for agronomic and morphological traits. These genotypes were evaluated in three experiments performed in Laranjeiras do Sul, Guarapuava and Cantagalo, Paraná State, Brazil. Heterosis and specific combining ability (SCA) were estimated for yield of husked ears. Data from measuring 22 morphological/agronomical traits of the parents were subjected to a multivariate joint analysis of variance and cluster analysis to group the parental hybrids via the neighbor method, using the generalized Mahalanobis distance. Pearson correlation coefficients between heterosis, SCA, D2 and yield of husked ears were obtained. The cross P30F44 x Sprint displayed a high mean and a high heterosis for yield of husked ears, but a moderate estimate of genetic divergence. Estimates of genetic divergence were not effective at predicting the most heterotic crossings, as Pearson correlation coefficients between D2 and heterosis and D2 and CEC were not significant. Positive significant correlations were observed between yield means and CEC and heterosis.

Produtividade e rendimento comercial de bulbos de cebola em função da densidade de cultivo Productivity and commercial yield of onion bulbs in function of growth density

A distribuição adequada das plantas de cebola (Allium cepa L.) na lavoura torna-se necessária devido a influência sobre a competição por água, luz e nutrientes, determinando o tamanho dos bulbos e a produtividade total. Objetivou-se, no trabalho, avaliar a produtividade e os padrões comerciais de bulbos de cebola, em função da densidade de plantio adotada. As mudas de cebola foram produzidas em bandejas de poliestireno de 200 células, com substrato comercial Plantimax®. O experimento foi instalado em delineamento experimental de blocos casualizados (DBC) com 4 repetições, com parcelas de 2 m². Utilizou-se a cultivar Buccaneer, nas densidades de 50, 75 e 100 plantas m-2. Foram avaliadas a produção comercial, a produção total e a massa média de bulbos. Observou-se que a densidade de 100 plantas m-2 proporcionou a maior produtividade (92,20 t ha-1). No entanto, a menor densidade de plantas avaliada proporcionou bulbos com a maior massa média (171g). As densidades de 50 e 75 plantas m-2 apresentaram os maiores valores distribuídos na classe 4 (> que 70 até 90 mm de diâmetro) e 3 cheio (> que 60 até 70 mm de diâmetro), respectivamente. A densidade de 100 plantas m-2 proporcionou uma maior quantidade de bulbos na classificação 3 cheio. Os resultados obtidos demonstraram que o aumento na densidade de plantas proporcionou uma maior produtividade, uma menor massa média de bulbos e uma maior produção na classificação comercial 3 cheio, considerada ideal para comercialização em função da preferência pelos consumidores.The adequate distribution of onions (Allium cepa L.) within a crop becomes necessary due to their influence on the competition for water, light, and nutrients, which determines the size of the bulbs and the total yield. The goal of this work was to evaluate the yield and commercial pattern of onion bulbs as a function of the crop density employed. The onion seedlings were produced on polystyrene trays with 200 cells filled with commercial substrate Plantimax®. The experiment was carried out according to a randomized block design (RBD), with four replications and 2-m² plots. The cultivar Buccaneer was evaluated in densities of 50, 75, and 100 plants m-2. The commercial bulb yield, the total yield, and the average mass of bulbs were evaluated. The density of 100 plants m-2 provided the greatest yield (92.20 t ha-1). However, the lower density of plants provided bulbs with the greatest average mass (171g). Densities of 50 and 75 plants m-2 presented the greatest values distributed in class 4 (> 70 up to 90 mm of diameter) and 3 full (> 60 up to 70 mm of diameter), respectively. Density of 100 plants m-2 provides a larger amount of bulbs in the 3-full classification. The results obtained in this experiment showed that an increase in the density of plants provided greater yield, smaller average mass of bulbs and greater production in the commercial 3-full classification, which is considered ideal for the market due to the consumers' preference

Performance and stability of maize topcross hybrids from partly inbred lines

Commercial hybrids are viable to generate base populations for obtaining new superior lines. Therefore, this study aimed to evaluate the performance and stability of maize topcross hybrids and select superior partly inbred lines. We evaluated 155 topcross hybrids of partly inbred lines crossed with an elite inbred line (tester) together with 14 commercial hybrids (2B688, AG7088, AS1575, DKB390, GNZ2005, GNZ8132, GNZ9501, GNZ9505, GNZ9548, GNZ9623, P30F35, P30F53, P30R50, and Penta) in Guarapuava-PR, Candói-PR, Guarda-Mor-MG, and Paracatu-MG (Brazil). The assessed variable was grain yield (GY), in kg ha-1, at 13% moisture, being the plant stand corrected by covariance method. A variance analysis was carried out, testing both stability and adaptability. There were significant differences for all sources of variation. By considering the GY means of the genotypes in each environment, Candói (10,985 kg ha-1) and Paracatu (10,917 kg ha-1) were in the first group, while Guarda-Mor (10,448 kg ha-1) was allocated in the intermediate group, and Guarapuava (10,159 kg ha-1) formed the group of lower GY means. None of the topcrosses stood out in any of the four environments, which may be related to the differences in climate and altitude between environments. Despite of this fact, lines 9, 13, 39, 40, 60, 93, 108, 179, 184, 189, 194, 211, 212, 213, 216, 217, 235, 243, 245, and 253 excelled as promising and should follow the process of inbreeding, in addition to the topcrosses 87, 144, 179, and 211, which also stood out for stability and adaptability in these environments