Early characterization of maize (Zea mays L.) genotypes, as well as the study of the genetic control of traits associated with water deficit tolerance, can provide information to guide breeders in the selection of cultivars adapted to drought environments. The aim of this study was to estimate heterosis and combining ability of maize genotypes under water stress during seed germination and seedling emergence. Four inbred lines previously characterized as water stress tolerant were crossed with four nontolerant lines in partial diallel scheme to obtain 16 hybrids and 16 reciprocals. Seeds were germinated in trays with sand in two environments, with and without water stress, with field capacity adjusted to 10 and 70% of humidity. The traits evaluated were seedling emergence, emergence speed index, shoot length, root length, number of seminal roots, and shoot and root dry weights. The heterosis effect, general combining ability, specific combining ability, and reciprocal effects were estimated for each trait using a partial diallel mixed model. The nonadditive effects were more important, and heterosis was observed in all cases, more expressively for root traits. The reciprocal effects were significant, highlighting the importance of the correct choice of the female parent to obtain maize hybrids tolerant to water stress.
Meloidogyne paranaensis is responsible for considerable losses in coffee production. Because of the distribution of this species in the main Coffea arabica producing regions, there is a need for management practices to ensure the sustainability of coffee production. In this work, we evaluated the agronomic performance of resistant clones of the Conilon coffee cultivar Vitoria Incaper 8142 in areas infested by M. paranaensis in the west region of Minas Gerais, Brazil. Clones 2V, 3V, and 6V presented the lowest number of nematodes per gram of roots and were considered resistant to M. paranaensis. All other clones were considered tolerant to this nematode, and one had good vegetative growth but allowed nematode reproduction. Clones of Vitoria Incaper 8142 of C. canephora represent an alternative to coffee production in areas infested by M. paranaensis including areas traditionally cultivated with C. arabica.
Many maize (Zea mays L.) breeding programs select genotypes considering just grain yield. However, this strategy may not be efficient due to undesirable associations between grain yield and other traits. The breeder's challenge is to combine good characteristics in one genotype. The aim of this study was to propose a new approach to select maize progenies considering multiple traits. One hundred forty‐one half‐sib progenies were evaluated for 14 agronomic traits in a 12 by 12 triple lattice design in two environments. Four progeny selection strategies were performed to increase yield. Strategy 1, considering just yield; Strategy 2, considering all traits in a selection index; Strategy 3, considering only traits that have effect in yield, based on path analysis; and Strategy 4, similar to Strategy 3, but disregarding any trait showing undesirable correlation with other traits. Strategies 2, 3, and 4 considered Smith and Hazel index. The progenies selected by Strategy 4 showed more balanced predicted gains considering all traits. Its predicted gain in all traits related to yield was higher than the of Strategies 2 and 3, and it led to smaller gains in height and flowering time, which breeders want to decrease its means. Strategy 1 showed the best gains in yield, as expected, but obtained undesirable phenotypes for the other traits. The use of path analysis to delineate the Smith and Hazel index is a very appealing approach for selecting maize progenies and the Strategy 4 was the most efficient at accomplishing balanced gains for multiple traits.
The evaluation of breeding lines for prior recommendation in different environments is a step that requires a high level of investment. This evaluation is extremely important, especially when the objective of breeding is to select lines with high homeostasis, adaptability associated with high yield, and stability. Thus, this paper aimed to study the phenotypic plasticity of thirteen upland rice lines for grain yield in multiple environments of Minas Gerais State, Brazil. The experiments were installed in nine different environments corresponding to the combination of locations and agricultural years. Thirteen elite lines were used, originating from a partnership between UFLA (Federal University of Lavras), Epamig (Agricultural Research Company of Minas Gerais) and Embrapa (Brazilian Company of Agricultural Research) Rice and Beans. The experiments were conducted in a complete randomized block design with three replicates. Culture treatments used for conducting were the same as those recommended for culture. The evaluated character was grain yield (kg.ha-1). Adaptability and stability were estimated by the methods Wricke, Annicchiarico, and Lin and Binns. All experiments showed average productivities above average in the state of Minas Gerais. The methods by Anniccchiarico and Lin Binns were efficient for the lines identification with phenotypic plasticity, emphasis on the lines CMG 2097, CMG 1896 and CMG 2089, which obtained superior average performance with productivities higher than 5 t.ha-1. Thus, these lines are promising for the Minas Gerais state recommendation, as well as in similar environments under low fertility natural soil, ferralsol (latosols), with tropical semi-humid and tropical altitude.
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