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Maize forage is commonly used as silage in milk and beef cattle livestock production systems. Despite the wide variety of maize hybrids with high potential for grain production, few available hybrids have been developed exclusively for forage aptitude. The present study aimed to select S3 maize progenies derived from the single hybrid AS1572 based on the combining ability of forage traits in topcrosses with testers AG8025, 70.H26.1, and MLP102. The 135 resulting topcross hybrids were assessed in partial diallel in Guarapuava and Rio Bonito do Iguaçu, Paraná State, Brazil. Were evaluated the contents of neutral detergent fiber (NDF, %DM) and acid detergent fiber (ADF, %DM), forage dry matter yield (DMY, t ha-1), and in situ digestibility of forage dry matter (DIG, %DM). For all evaluated traits, the variability allowed us to select superior progenies. Progenies 3.1, 22.1, and 39.1stood out in terms of NDF, ADF, and DIG, whereas progenies 47.1, 73.1, 79.1, and 90.2 were efficient in increasing the forage dry matter yield. The testers AG8025 and 70.H26.1, of narrow genetic base, are the best to explore genetic variability among progenies.

Resistance of maize inbred lines to major leaf diseases should be characterized for the development of new hybrids in breeding programs. Thus, this study aimed to assess the severity of leaf diseases in maize inbredlines with different kernel hardnessand two sowingseasons. We assessed four inbred lines and one check hybrid with dent kernels and four inbred lines and a check hybrid with flint kernels. Treatments were conducted in two sowing seasons, one in October, and another in December 2013. The symptoms of gray leaf spot (Cercospora zeae-maydis), northern leaf blight (Exserohilum turcicum), and white leaf spot (a complex of Phaeosphaeria maydis and Pantoea ananatis) were assessed every 10 days from flowering. The area under the disease progress curve was also calculated. Severity level of the diseases was higher in inbred lines when compared to the check hybrds (AG8041 PRO and P30R50YH), regardless of kernel hardness. Dent-kernel inbred lines showed a higher severity of northern leaf blight symptoms when compared to flint-kernelones. It is worth mentioning that disease severity increased as sowing was delayed.

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.

A caracterização de linhagens de milho quanto à resistência às principais doenças é fundamental para o desenvolvimento de novos híbridos em programas de melhoramento. Assim, o objetivo deste trabalho foi avaliar a severidade de doenças foliares em linhagens de milho com diferentes texturas de grãos em duas épocas de semeadura. Foram avaliadas quatro linhagens e um híbrido testemunha com grãos dentados e quatro linhagens e um híbrido testemunha com grãos duros. Os tratamentos foram conduzidos em duas épocas de semeadura, em outubro e em dezembro de 2013. A partir do florescimento, a cada 10 dias, foram avaliadas as doenças foliares cercosporiose (Cercospora zeae-maydis), helmintosporiose (Exserohilum turcicum) e mancha branca (complexo Phaeosphaeria maydis/Pantoea ananatis). Foi calculada a área abaixo da curva do progresso das doenças (AACPD). A severidade das doenças foi maior nas linhagens, comparativamente aos híbridos testemunhas AG8041 PRO e P30R50YH, independentemente da textura dos grãos. As linhagens de textura dentada apresentaram maior severidade de sintomas da helmintosporiose, quando comparada às linhagens de grãos duros. Houve aumento da severidade das doenças avaliadas com o atraso da semeadura.

The objective of this study was to evaluate the relative performance of 74 partially inbred lines (S4) from crosses between the commercial hybrids P30P70 and Dow8460 in topcrosses with the commercial single cross hybrid P30F53 (tester), and checks (hybrids Dow8460, P30F53 and Status). The grain yield (GY) was evaluated in two environments in Guarapuava-PR. The effects of genotypes, environments and genotypes x environments interaction were significant for grain yield (GY). Among the topcrosses hybrids (TCH) the GY ranged from 8,302 (TCH 123, in the environment 2) to 14,809 kg ha-1 (TCH 11, in the environment 1). In the environment 1 we evaluated agronomic characteristics of the forage and bromatologic characteristics of the silage. The green mass productivity (GMP) of forage ranged from 49,857 (TCH 208) to 80,642 kg ha-1 (TCH 22) and the dry mass productivity (DMP) ranged from 11,072 (TCH 217) to 24,143 kg ha-1 (TCH 22). The contents of neutral detergent fiber (NDF) ranged from 45.39 (TCH 80) to 56.71% (TCH 77) and the contents of acid detergent fiber (ADF) ranged from 25.45 (TCH 80) to 35 60% (TCH 99). The relative value of the silage (RVS) presented average ratios ranged from 103 (TCH 148) to 142 (TCH 80). For all the characteristics many topcrosses did not differ from the best checks. TCH 22 and 53 were higher considering the set of all characteristics of forage and silage and, also, it showed high grain yield, therefore, these inbred lines should be advanced in the breeding program.

Um sistema destinado à secagem de produtos agrícolas, do tipo camada fixa, foi construído e o seu desempenho testado. O sistema é composto de um depósito formado por painéis modulados, cujo número pode variar em função da capacidade necessária, dois ventiladores axiais para movimentação do ar e dois geradores de calor, a lenha. Os geradores são de fluxo descendente, com ar primário para combustão sob baixa pressão, impulsionado por pequeno ventilador. Os testes realizados com amendoim (Leguminosae-Faboideae), levaram a resultados que comprovam a praticidade do sistema proposto, e que pode ser construído e operado nos próprios locais de produção