Since spontaneous mutation rates are very low, artificially induced mutations have been used more frequently to raise the frequency of mutations and variations, which can be amplified through chemical mutagens as for instance alkylating agents (ethyl- methanesulfonate and methyl-methanesulfonate), as much as physical mutagens, such as ionizing radiations (Predieri 2001). The latter is the most commonly used mutagen to create mutant varieties (Waugh et al. 2006). The determination of mainly the target population size, the mutagen type and dose rate, along with appropriate selection methods of mutants need more in-depth research (Scossiroli 1977, Coimbra et al. 2004). The main strategy of improvement by mutation must be to alter one or two traits that restrict the yield or grain quality of a well adapted cultivar, e.g. vegetative cycle (Ahloowalia and Maluszynski 2001).
The Brazilian commercial broodstocks of L. vannamei shows clear signals of limited inbreeding. However, the overall L. vannamei geneticvariability found among nine of the largest national hatcheries can be considered high. These findings stress the necessity of adequate management of this valuable genetic resource. Moreover, the results suggest that a genetic improvement program based on the available germoplasm is feasible. Finally, the recent level of global interest in L. vannamei aquaculture indicates that the creation of a standardized database of molecular markers would be highly useful for the shrimp industry, providing information for localized management, higher level of breeding control and traceability. There are currently no molecular marker standards for the shrimp industry. The creation of such a database would also be relevant for conservation purposes, since L. vannamei has been introduced in many different ecosystems and seems likely to have an impact on natural populations of marine shrimp in the near future.
The present study, part of the integrated project “Aspects of Fauna and Flora on the Tibagi River Basin” carried out by Universidade Estadual de Londrina for the restoration of the basin, conflicts with government projects to construct five hydro-electric plants along the Tibagi River. These plants may be barriers to the dispersion of fresh water organisms, specially migratory species. Besides the impact caused by water flow control, they jeopardize survival, successful mating, and gene flow, which surely will alter the genic frequencies in the fish species. Thus, the maintenance of the environmental heterogeneity of the Tibagi River is important for the preservation of aquatic organisms. The construction of hydro-electric plants will lead to a reduction in the geneticvariabilityof migratory species, such as L. friderici, perhaps reaching levels lower
The PROT content in oats is higher than in other ce- reals. It presents high digestibility and a balanced amino acid composition (Biel et al., 2014; Doehlert et al., 2013; Hawerroth et al., 2013; Klose and Arendt, 2012). For the PROT content, an absence in heterosis gain in both popu- lations was observed (Table 1), which can be an indicative of low combining ability between the parents, possibly due to the presence of similar loci that expresses reduced average performance for the trait, even after genetic re- combination. An absence of hybrid vigor in F 1 does not mean that the populations had to be discarded, since dis- tinct phenotypic classes can occurr in F 2 .
Didelphis albiventris is a well- known and common marsupial. Due to its high adaptability, this very widespread gen- eralist species occurs under various environmental conditions, this even including protected regions and disturbed urban areas. We studied a 653 bp fragment of cytochrome oxidase c (COI) from 93 biological samples from seven Brazilian localities, with linear distances ranging between 58 and about 1800 km to analyze the effects of geographic distances on variability and genetic differentiation. The haplotype network presented nine haplotypes and two ge- netic clusters compatible with the two most distant geographic areas of the states of Minas Gerais, in the southeast, and Rio Grande do Sul, in the extreme south. As each cluster was characterized by low nucleotide and high haplotype diversities, their populations were obviously composed of closely related haplotypes. Surprisingly, moder- ate to high F ST differentiation values and a very weak phylogeographic signal characterizes interpopulation compari-
Abstract – The objective of this work was to evaluate the population structure and the genetic and phenotypic progress of Nelore cattle in Northern Brazil. Pedigree information concerning animals born between 1942 and 2006 were analyzed. Population structure was performed using the Endog program. Out of the 140,628 animals studied, 67.7, 14.52 and 3.18% had complete pedigree record of the first, second and third parental generation, respectively. Inbreeding and average relatedness coefficients were low: 0.2 and 0.13%, respectively. However, these parameters may have been underestimated, since information on pedigree was incomplete. The effective number of founders was 370 and the genetic contribution of 10, 50 and 448 most influent ancestors explained 13.2, 28 and 50% of the geneticvariabilityin the population, respectively. The geneticvariability for growth traits and population structure demonstrates high probability of increasing productivity through selective breeding. Moreover, management strategies to reduce the currently observed age at first calving and generation intervals are important for Nelore cattle genetic improvement.
The Maydeae tribe contains several genera, including the genus Zea, which presents a high economic importance including cultivated species of corn and teosinte. This genus has several species of teosinte, such as Z. diploperennis (Iltis, Doebley and Guzman), Z. perennis (Hitda), Z. luxurians (Durieu and Aschersonia) and Zea mays, which includes the subspecies maize (Z. mays L. ssp. mays) and teosintes Z. mays L. ssp. parviglumis (Iltis and Doebley), Z. mays L. ssp. Huehuetenangensis, and Z. mays L. ssp. mexican (Schrader) (Iltis and Doebley 1980, Molina and Narang 1987). Teosinte has been considered a genetic source for the improvement of agronomic characteristics of maize (Reeves 1950, Cohen and Galinat 1984, Lubberstedt et al. 1998). Spontaneous hybrids have occurred between these
Gonçalves et al. (2014) evaluated 10 lines of popcorn maize from different origins and reported a significant effect of GCA and SCA for GY and PE. On the other hand, Moterle et al. (2012) evaluated GY and PE of nine lines of popcorn, eight of temperate and one of tropical climate, and found a significant effect of GCA and SCA only for GY. Scapim et al. (2002) recommended using populations with high GCA estimates to obtain new varieties with high GY and PE. However, according to Wu and Matheson (2001), only GCA and SCA estimates do not allow obtaining information on when parents are used as either male or female. Cabral, Amaral Júnior, Freitas, Ribeiro, and Silva (2016) reported reciprocal effect on popcorn for GY and recommended alternating the parents in the crosses. Andrade, Cruz, Scapim, Silverio, and Tonet (2008) reported a negligible reciprocal effect for the PE trait. Rodovalho et al. (2014), using Bayesian reference, reported predominance of non-additive effects for these two traits whereas Miranda et al. (2008) found additive effects only for PE.
ABSTRACT: The study of the genetic evaluation of residual feed intake adjusted for fat (RFIFat) is important for the appropriate use of feed efficiency in selection programs. The objective was to analyze the influence of selection for RFIF at on carcass and performance traits by estimating various genetic parameters. Data were analyzed from five tests of feed efficiency, which were conducted with 677 Nellore males. Genetic evaluation was performed by Bayesian inference using an animal model via single- and two-trait analyses. Variables analyzed were dry matter intake, average daily gain, RFIFat, rib eye area, back fat thickness, rump fat thickness, marbling score, and subcutaneous fat thickness. The posterior mean distributions estimated at each analysis were used to estimate heritability of the traits and to perform various correlations. The studied traits showed high heritability estimates, and they should respond well to selection. The RFIFat presented a phenotypic correlation with carcass traits (which was next to zero), and there was also a negative genetic correlation. Additive geneticvariability for RFIFat showed that selection for this trait can promote genetic gains in future generations, resulting in animals that are efficient in terms of nutrient use, and according to the genetic and phenotypic correlations, with no significant negative changes to carcass traits.
Begomoviruses are whitefly-transmitted single-stranded DNA viruses of great economic importance in the tropics and subtropics. Several begomovirus species have been reported in tomatoes in Brazil, but only a few predominate in the field, for unknown reasons. In this study begomovirus-infected tomato samples were collected in Viçosa, State of Minas Gerais, in Nov/2009 and Dec/2010. Viral genomes were amplified, cloned and sequenced. A total of 36 DNA-A components were obtained. Sequence comparisons indicated the presence of a single begomovirus, Tomato severe rugose virus (ToSRV), with pairwise identities between isolates ranging from 97.3 to 100%. Subdivision tests indicated the existence of a single population. The analysis ofvariability descriptors indicated that the ToSRV population has a geneticvariability similar to other begomovirus populations described in Brazil infecting tomato. Neutrality tests suggested the occurrence of purifying selection acting upon the population. Recombination analysis identified recombination events with begomoviruses from the weed species Sida micrantha. The wide distribution of ToSRV in the field and the detection of recombination indicate that continuous monitoring of viral populations in the field will be required to enable an efficient resistance-based control strategy for begomoviruses.
Abstract – The objectives of this study were to evaluate the resistance of maize inbred lines to anthracnose leaf blight (Colletotrichum graminicola Ces.), and to estimate genetic parameters associated with resistance. Sixteen lines (S 5 ) were evaluated for resistance to anthracnose leaf blight in three experiments, in a randomized block design with four replications. From three evaluations of severity, it was estimated the area under the disease progress curve (AUDPC), and the genetic parameters associated with resistance. Results showed the existence ofgeneticvariability for resistance to anthracnose leaf blight in the set of studied lines. Five lines stood out for the high resistance pattern to anthracnose leaf blight, presenting the lowest AUDPC values in the three experiments, and thus were considered important sources of C. graminicola resistance genes. Estimates ofgenetic parameters indicated low participation of the environment and highlighted the possibility ofgenetic gains with artificial selection for resistance in this pathosystem.
Computer techniques have great relevance in the simulation and optimization in various areas (Krug et al., 2015; Barbosa et al., 2016). Simulation models are essential in the identification of factors that influence agricultural production and more- efficient managements (Mello & Caimi, 2008; Leal et al., 2015). Artificial intelligence (AI) techniques have emerged as an alternative in the development of simulation and optimization models (Leal et al., 2015; Soares et al., 2015). Among AI techniques, artificial neural networks (ANNs) present a mathematical model inspired in the neural structure of intelligent organisms, capable of performing computer learning and pattern recognition (McCulloch & Pitts, 1943; Çelebi et al., 2017). Genetic algorithm is also an AI technique inspired in the mechanisms of evolution of living organisms, which promote agility in the formulation and solution of optimization problems (Bento & Kagan, 2008; Zheng et al., 2017).
The breeding program for recurrent selection of upland rice of Embrapa aims to genetically improve the populations for a geographic region that is characterized by diverse soils and climatic conditions (Breseghello et al., 2011; Colombari Filho et al., 2013). Therefore, in the next selection cycles, even if geneticvariability is maintained for GY and PH in the CNA6 population due to the strong effect of the G×L interaction, it is still necessary to increase the number of replications and locations in order to obtain selection gains superior to those of previous cycles (Morais Júnior et al., 2015), even when satisfactory selection gains are reached. The reason do to this is to increase the heritability among the averages of progenies and, consequently, the expected response to selection (Bernardo, 2010). In addition, changing locations should be avoided during selection cycles, since indirect selection may make null or reduce genetic gain due to the low correlation among genotype performance and locations.
The organic farming of their own local seeds was one strategy used by farmers to enable production, which initially aims at meeting the demand for animal feeding and secondly, to generate income through the sale of grain or its products. In fact, LMV production by small-scale farmers in western SC is consumed mainly (≈90 %) on their own farms as animal and human feed. Moreover, other maize-derived products, including ar- tisanal wares and other artifacts made with straw and grains, have also been marketed (Ogliari et al., 2013). This is particularly the case in the city of Anchieta (SC) (26º31'27" S; 53º23'14" W), where a group of farmers perceived an opportunity to improve their incomes by purchasing a small industrial mill through their associa- tion in order to process the surplus production of organic maize into flour. The sale of this special flour to specific market niches that value health foods offers an increase
Regardless of the goals and methods of improvement and the inherent self-incompatibility of yellow passion fruit, leading to allogamy and therefore the existence ofgeneticvariability, the selection of genotypes with greater phenotypic uniformity will always narrow the genetic base. Depend- ing on the origin of the genetic material and the degree of selection, the loss of alleles can negatively affect the main- tenance of the productive potential of improved genotypes. Comparative studies between improved genotypes and germplasm accessions are essential to verify the distribution ofgeneticvariability, changes in allele frequencies and the direction of allelic losses, to outline the best strategy of crop improvement. The purpose of this study was to evaluate the potential of ISSR markers in yellow passion fruit breeding and to assess the effect ofgenetic diversity in two sets of genotypes obtained by different breeding methods (massal selection, hybrids and half-sib progenies), in comparison to unimproved germplasm accessions.
The genus Begomovirus (family Geminiviridae) contains viral species with ssDNA genomes, affecting dicotyledonous plants and transmitted by the whitefly Bemisia tabaci. Viral diseases caused by begomoviruses are of economic importance due to their adverse effects on the production of tropical and subtropical crops. In Ecuador, despite reports of significant infestations of Bemisia tabaci in the late 1990's, only very recently has a begomovirus, Tomato leaf deformation virus (ToLDeV, also present in Peru), been reported in tomato. ToLDeV is the first monopartite begomovirus originated in the Americas, and its presence in Ecuador highlights the need for a wider survey of tomato- infecting begomoviruses in this country. The study of ToLDeV populations may provide insights into the evolution of this monopartite virus and its ongoing adaptation to a new host. Tomato and weed samples were collected in 2010 and 2011 in six provinces of Ecuador, and begomovirus genomes were cloned and sequenced using a rolling-circle amplification-based approach. No begomovirus-positive samples were detected in the provinces of Chimborazo and Galapagos. Most begomovirus-positive tomato samples from the provinces of Guayas, Loja, Manabi and Santa Elena were infected with ToLDeV. One sample from Manabí had a triple infection with ToLDeV, Rhynchosia golden mosaic Yucatan virus (RhGMYuV) and a recombinant isolate between the two. A new begomovirus species was detected in another tomato sample from Manabí. Samples of Rhynchosia sp. from the provinces of Guayas and Manabi were infected by RhGMYuV.
The number of monomorphic loci was high by ac- counting that each primer pair that did not allow detection of polymorphism was adjacent to regions containing a high number of repeats, these ranging from 19 (Ap32) to 58 (Ap35) repeats. Among the ones that did not detect any polymorphism four are described in this paper and two (Ap32 and Ap38) were previously used in three studies on geneticvariabilityin Arachis (Bravo et al., 2006; Hoshino et al., 2006; Angelici et al., 2008), all with similar results. We tested the latter two primer pairs because Hoshino et al. (2006) studied only one accession of each species of sec- tion Caulorrhizae, whereas Bravo et al. (2006) and Ange- lici et al. (2008) used these two primers in other sections of genus Arachis. Thus, we expected additional information from these primers by using samples of the species from which they had been isolated. It may be that the areas tar- geted by the two primer pairs are within conserved regions of the genome. There was no similarity between the se- quences used to design primers for these six microsatellites and any nucleotide or protein sequence in GenBank.
Biodiversity is composed of ecological and genetic variation, and its evaluation is an essential step towards planning conservation strategies for endangered or vul- nerable species (Schwartz et al., 2006). Birds are known to have lower gene variation when compared to other ver- tebrates (Ward et al., 1992). Considering only Amazon parrots studies, is noteworthy to observe the lack ofgenetic diversity reported by Faria and Miyaki (2006) on A. pretrei and A. brasiliensis analyses using highly polymorphic genetic markers. Although the vulnerable status of both species may explain the results, it shows how difficult is to find cross-species polymorphic genetic markers for population studies in this genus. The alloz- yme markers standardized here can be an alternative, fast, and easy approach toward evaluating the intraspecific and interspecific genetic diversity of these three Amazon par- rot species as well as other vulnerable or endangered spe- cies that belong to sister groups. The application of these markers can also be useful to conservation follow-up pro- grams, such as the successful reintroduction of captive- raised Yellow-shoulder Amazon parrots (A. barbadensis Gmelin, 1788) on Margarita Island in Venezuela (Sanz and Grajal, 1998), which is a model that can be pro- posed for vulnerable and endangered species in Brazil. Allozyme analysis has been increasingly replaced by DNA markers, but its use remains justifiable when it can contribute on additional information, mainly when rapid screening is required for a species from one genus and when hybridization is one of the hypotheses to be tested.