DETERMINATION OF OLIVE MILL WASTEWATER TOXIC EFFECTS ON THREE MINT SPECIES GROWN IN HYDROPONIC CULTURE

The effects of two olive mill wastewater (OMW) dilutions upon physiological function and metabolic components of three mint species grown in hydroponic culture were studied. Visible symptoms, chlorosis and stunted growth, were pronounced in peppermint and spearmint; toxicity symptoms in menthe douce were few. Peppermint and spearmint displayed loss of calcium (Ca), magnesium (Mg), and potassium (K); menthe douce revealed accumulation of Ca, sodium (Na), and iron (Fe), under OMW. The loss of Ca negatively affected the development and stability of cell wall and membrane; the Mg deficiency negatively affected the photosynthetic apparatus and carbon fixation. Fv′/ Fm′ was slightly affected under OMW, whereas, Φ_PSII, q _P and Rfd displayed significant reductions. No clear effect of OMW on phenols and carbohydrates among the species were found. Ascorbic acid content in peppermint dropped dramatically; the reduction was lower for spearmint and menthe douce. The OMW resistant species, menthe douce, developed a mechanism to control the physiological and the biochemical status.     

Responses to divergent selection for cob color in maize

Previous studies showed that in materials derived from maize (Zea mays L.) single cross A632 × Mu195 there is association between agronomic traits and cob color (affected by P1 gene). Objectives of this study were to evaluate the responses to divergent selection for cob color in F₂-Syn 0 (obtained by selfing A632 × Mu195), estimate the genetic parameters of the involved putative quantitative trait loci (QTL), and evaluate the responses to divergent selection for cob color in A632 and Mu195 backgrounds. The populations selected in F₂-Syn 0 for red (R0) or white cob (W0) were tested in four trials. Differences between R0 and W0 were found for grain yield (85.0 vs. 75.0 g/plant) and other traits; most of these differences were related to leaf number/plant. Then, population F₂-Syn 1, derived after one random mating generation, was divergently selected for cob color, thus producing R1 and W1. Populations R0, W0, R1, and W1 were tested in two trials, allowing the estimate of genetic effects and recombination frequencies for putative QTL of several traits. Finally, a divergent selection for cob color was conducted in segregating materials of A632 and Mu195 backgrounds. The two pairs of selected populations were compared in two trials; the responses were similar to those detected by comparing R0 and W0. We conclude that divergent selection for cob color in F₂-Syn 0 is effective for several traits, that such responses are due to putative QTL linked to P1, and that selection is also effective in different genetic backgrounds.     

Analysis of meiotic behavior in selecting potential genitors among diploid and artificially induced tetraploid accessions of Brachiaria ruziziensis (Poaceae)

Sexuality is correlated with diploidy and apomixis with polyploidy in the Brachiaria genus. Brachiaria ruziziensis is a key species in Brachiaria breeding due to its obligate sexuality and intrinsic agronomic qualities. Interspecific crosses in the genus became feasible only when a few diploid accessions of B. ruziziensis were artificially tetraploidized and remained sexual. Hybridization has been done since, using natural tetraploid apomictic accessions of B. brizantha or B. decumbens as pollen donors. Twenty two accessions of B. ruziziensis from the Embrapa Beef Cattle germplasm collection (Campo Grande, MS, Brazil) were cytologically analyzed: 16 are natural diploids (2n = 2x = 18) and six are artificially induced tetraploids (2n = 4x = 36). The meiotic behavior in the 16 diploid accessions varied. The mean of meiotic abnormalities per accession ranged from zero to 24.46%. Meiotic behavior in the induced tetraploid accessions also varied with the mean of meiotic abnormalities ranging from 5.20% to 54.71%. The most common abnormalities observed in both the diploid and the tetraploid accessions, were those related to irregular chromosome segregation. In one tetraploid accession, with a high frequency of those, other irregularities involving chromosome orientation at metaphase plate and chromosome convergence to the poles, a meiotic mutation known as divergent spindle, were recorded. Meiotic behavior should be considered in selecting potential genitors for breeding.     

Association mapping reveals loci associated with multiple traits that affect grain yield and adaptation in soft winter wheat

Genome-wide association studies (GWAS) are useful to facilitate crop improvement via enhanced knowledge of marker-trait associations (MTA). A GWAS for grain yield (GY), yield components, and agronomic traits was conducted using a diverse panel of 239 soft red winter wheat (Triticum aestivum) genotypes evaluated across two growing seasons and eight site-years. Analysis of variance showed significant environment, genotype, and genotype-by-environment effects for GY and yield components. Narrow sense heritability of GY (h ²  = 0.48) was moderate compared to other traits including plant height (h ²  = 0.81) and kernel weight (h ²  = 0.77). There were 112 significant MTA (p < 0.0005) detected for eight measured traits using compressed mixed linear models and 5715 single nucleotide polymorphism markers. MTA for GY and agronomic traits coincided with previously reported QTL for winter and spring wheat. Highly significant MTA for GY showed an overall negative allelic effect for the minor allele, indicating selection against these alleles by breeders. Markers associated with multiple traits observed on chromosomes 1A, 2D, 3B, and 4B with positive minor effects serve as potential targets for marker assisted breeding to select for improvement of GY and related traits. Following marker validation, these multi-trait loci have the potential to be utilized for MAS to improve GY and adaptation of soft red winter wheat.     

Control of Cyclohexane Atmospheric Emissions During Soil Remediation

Gaseous effluent from the treatment of contaminated soils must becontrolled to avoid atmospheric emissions of volatile organiccompounds during remediation. The combination of carbonadsorption with catalytic deep oxidation for control ofcyclohexane emissions is analysed in this paper. The activitiesof activated carbons prepared with almond shells and impregnatedwith CoO, Co₃O₄ and CrO₃ were compared, inrelation with carbon structure, catalyst content and catalystspecies. The microcatalytic-chromatographic technique developedwas very suitable for rapid comparison of the catalyticactivities. Carbons with a better development of surface areaand pore volumes showed higher catalytic activities. Theincreasing of catalyst content also increased catalyticactivity. Cobalt is better than chromium to catalyse the deepoxidation of cyclohexane, the oxidation state of cobalt inCo₃O₄ being better than in CoO.     

2n Gamete formation in the genus Brachiaria (Poaceae: Paniceae)

Microsporogenesis of several Brachiaria species of the Brazilian collection at Embrapa Beef Cattle has been analyzed in detail. This paper reports abnormal cytokinesis in three accessions of three different species (Brachiaria humidicola, 2n = 4x = 36, Brachiaria decumbens, 2n = 4x = 36, and Brachiaria dura, 2n = 6x = 54). Chromosomes paired in bi-, tri-, and quadrivalents in these accessions, whereas chromosome segregation at meiosis I was characterized by exclusion of laggards as micronuclei. In a high number of meiocytes, the first sign of cytokinesis appeared only in metaphase II and did not divide the meiocyte into a dyad. Total absence of cytokinesis was also detected among meiocytes in the second division. Since in both cases the two metaphase plates were very close, they favored the rejoining of chromosome sets after anaphase II and formed a restitutional nucleus in telophase II. Second cytokinesis occurred after telophase II in most meiocytes. Monads, dyads, and triads with n or 2n nuclei were observed among meiotic products. The 2n gametes observed correspond to the first division restitution (FDR). The number of affected cells in each accession was variable, but the number of microspores with restitutional nucleus, including those scored in tetrads and the released ones, did not exceed 9%. Although polyploidy is common in the genus Brachiaria, its origin is still unclear. Current results suggest that 2n gametes may have contributed to the evolutionary history of the genus.     

Genetic stability at nuclear and plastid DNA level in regenerated plants of <Emphasis Type="Italic">Solanum</Emphasis> species and hybrids

In this work we detected the extent of variability at nuclear and cytoplasmic DNA level of regenerated plants belonging to Solanum genotypes with a different genetic background and somatic chromosome number. As for the nuclear characterization, a total of 66 (18.5%) polymorphic bands were scored using 13 ISSR primers on 45 randomly selected regenerants. Our results show that the regenerants obtained from clone cmm 1T and, at lower level, those from cph 1C are unstable under in vitro conditions or rather more prone to in vitro-induced stress leading to somaclonal variation than the other genotypes used. Two types of changes were observed: disappearance of parental ISSR fragments, termed “loss”; appearance of novel ISSR fragments, termed “gain”. The most frequent event occurring in the regenerants was the loss of fragments (41 bands). Regenerated plants were analyzed with seven plastid universal primers to determine the cytoplasmic composition at chloroplast level. All cpDNA primer pairs tested produced amplicons of the same size in all genotypes analyzed and no polymorphic fragments were observed with any universal primers used. Our results show that under in vitro culture conditions genotype affects the integrity of the genome. In addition, the absence of polymorphism at plastid level confirms the greater genetic stability of cytoplasmic DNA.     

Allele mining and haplotype discovery in barley candidate genes for drought tolerance

In the present study, allele mining was conducted on a panel of drought related candidate genes in a set of 96 barley genotypes using EcoTILLING, which is a variant of the targeting induced local lesions in genomes (TILLING) technology. Analyzing approximately 1.5 million basepairs in barley a total number of 94 verified unique haplotypes were identified in 18 amplicons designed for 9 genes. Overall, 185 single nucleotide polymorphisms (SNPs) and 46 insertions/deletions (INDELs) were detected with a mean of 1SNP/92 bp and 1INDEL/372 bp genomic sequence. Based on overlapping haplotype sequences, markers were developed for four candidate genes (HvARH1, HvSRG6, HvDRF1, HVA1), which allows distinguishing between the main haplotypes showing either differences in amino acid sequence or which have larger INDELs in the promoter region. As “proof of concept”, the HvARH1 and HvSRG6 haplotypes were tested for the level of abscisic acid-induced gene expression in subsets of genotypes belonging to different haplotype categories. An integrated database was developed to contain information about the genes, genotypes, and haplotypes analyzed in this study. The database supplies profound information about the natural variation in the tested drought related candidate genes providing a significant asset for further mapping studies dealing with this highly polygenic trait.