Natural selection for grain yield in dry bean populations bred by the bulk method     

Hercules Renato Corte  Magno Antonio Patto Ramalhol  Flávia Maria Avelar Gonçalves  Ângela de Fátima Barbosa Abreu 《Euphytica》2002,123(3):387-393

Three dry bean harvests are possible in some regions of Brazil that differ significantly in temperature, rainfall and day length conditions. Thus in breeding programs, generation advance using the bulk method can be carried out in these three periods. It is questionable whether under conditions such as these the action of natural selection would contribute to an increased frequency of individuals considered superior by breeders. The present study assessed six segregating populations, for up to 17 successive generations to check the effects of natural selection during inbreeding. Six populations were generated from a partial diallel: one group consisting of two early maturity cultivars, ESAL 686 and Manteigão Fosco was crossed to a second group of three cultivars with medium maturity, Carioca MG, Milionario and Ouro. The six populations plus the five parents were assessed in experiments using a randomized complete block design, in three locations: Lavras, where in breeding started from the F₂ generation; Lambari and Patos de Minas, from the F₃ generation. A linear regression equation was fitted to the parents and hybrids mean data in each location, considering grain yield as the dependent variable (y) and generations (F₂ = 1, F₃ = 2, etc.) as the independent variable. Genetic progress was estimated from the differences between the linear regression coefficients of the hybrids (b_i)and the mean of the b coefficient of their respective parents (b_j). The (b_i-b_j) were positive in all cases, showing that natural selection acted in all the segregating populations and contributed to an average increase in grain yield of 2.5% per generation over the mean of the parents.  相似文献   

Identification of citrus hybrids through the combination of leaf apex morphology and SSR markers   总被引：5，自引：0，他引：5  

Antonio Carlos de Oliveira  Aristides Novac Garcia  Mariângela Cristofani  Marcos Antônio Machado 《Euphytica》2002,128(3):397-403

Citrus breeding programs normally face several biological obstacles such as apomixis and polyembryony that result in a cumbersome identification of hybrid seedlings. The main purpose of this work is to describe the combined use of visual selection based on the leaf apex morphology and SSR analysis to differentiate hybrid from nucellar seedlings derived from the cross between the ‘Murcott’ tangor [Citrus reticulata Blanco × Citrus sinensis (L.) Osb.] and ‘Pêra’ sweet orange [Citrus sinensis(L.) Osb.]. A new morphological variable named leaf apex morphometric index is also described as the quantitative basis of the visual selection. The efficiency of visual selection of hybrids was tested under two growth conditions, seedlings germinated in seedbeds and in plastic tubes. Putative hybrid seedlings were also confirmed through the analysis of simple sequence repeats (SSR). The visual selection of hybrid seedlings resulted in an increase of 87.2% (p < 0.01) and 202.2% (p <0.001) in the number of correctly identified hybrids when compared to the method of random picking of seedlings in seedbeds and plastic tubes,respectively. The results indicate that the combination of visual selection and SSR analysis for the identification of hybrids derived from the cross of polyembryonic citrus cultivars will improve the accuracy of the selection,save time, and reduce the costs involved in the use of molecular markers alone in citrus breeding programs. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Dietary addition of the essential oil from Lippia alba to Nile tilapia and its effect after inoculation with Aeromonas spp.     

Renilde Cordeiro de Souza  Elizngela Maria de Souza  Mateus Matiuzzi da Costa  Jos Fernando Bibiano Melo  Bernardo Baldisserotto  Carlos Eduardo Copatti 《Aquaculture Nutrition》2019,25(1):39-45

The objective of this study was to evaluate the effect of dietary addition of the essential oil from Lippia alba (EOLA) on growth performance, biochemical and haematological variables and survival after Aeromonas spp. infection of Nile tilapia juveniles (Oreochromis niloticus). Five diets were evaluated with increasing levels of EOLA (0.0 control; 0.25; 0.50; 1.0; and 2.0 ml/kg diet). After 45 days of feeding, the fish were infected with Aeromonas spp. followed by a 14‐day period of observation. There was no mortality during growth assessment. The addition of 2.0 ml EOLA/kg diet improved feed conversion ratio and condition factor and increased lysozyme activity and haematocrit (Hct), and decreased plasma globulin levels compared to the control group. The survival of fish infected with Aeromonas spp. was higher in those fed with 2.0 ml EOLA/kg diet than in fish fed with 0.0–0.5 ml EOLA/kg diet. We concluded that the inclusion of 2.0 ml EOLA/kg diet is recommended for Nile tilapia juveniles, because it improved feed conversion, Hct and immunological activity, did not provoke metabolic changes, and increased survival after Aeromonas spp. infection.  相似文献   

Structural changes in humic substances after long-term fertilization of a calcareous soil with pig slurries     

Diana E. Jiménez-de-Santiago  Gonzalo Almendros  Àngela D. Bosch-Serra 《Soil Use and Management》2023,39(4):1351-1363

Pig slurries are widely used on calcareous soils in European rainfed systems. Here we assess their impact on the amount of soil organic carbon (SOC) and on the composition of humic-type substances (HTS). Seven doses of slurry (five from fattening pigs and two from sows) ranging from 1.0 to 4.8 Mg ha⁻¹ yr⁻¹ of organic matter were evaluated after a period of 12 years and compared with mineral fertilizer treatment. At the end of the last annual cropping season (September), SOC was quantified, and HTS were isolated by alkaline extraction followed by acid precipitation, and studied by visible spectroscopy (800–400 nm) and Fourier-transformed infrared spectroscopy (4000–400 cm⁻¹). Following the trend in the slurry organic matter applied rates, SOC increased from 9.5 g C kg⁻¹ (mineral treatment) to 13.8 g C kg⁻¹. This SOC increase was equivalent to c. 25.4% of the slurry organic carbon applied. The incorporation of aliphatic structures, mainly polyalkyl, from slurries into the HTS tends to modify the composition of the soil organic matter (SOM), which is reflected in a decrease in the intensity of FT-IR peaks related to aromatic structures. Despite the trend of significant increase in SOC with fattening slurries, mainly from the organic matter rate of 1.6 Mg ha⁻¹ yr⁻¹ (c. 185 kg N ha⁻¹), the composition of the HTS showed an important aliphatic enhancement. The FTIR results showed that using exclusively the relative intensities of specific peaks (alkyl, carboxyl, aromatic and amide groups) as variables for the discriminant analysis, it is possible to identify HA between different groups of soils treated with progressive levels of slurry. Although the new aliphatic components could be considered important to improve soil physical quality, after the incorporation of additional SOM, the spectroscopic characteristics of HTS in soils treated with slurries suggested a weak effect in long-term C sequestration, as the newly incorporated OC forms are not qualitatively similar to the presumably stable native SOM. These potential changes in SOC and SOM composition at field level are constrained by the maximum allowed N rates from organic origin in some agricultural systems.  相似文献