Effects of maize genotypes, nitrogen rates and sources in yield, nutritional status, and fumonisins incidence.

The maize yield, nutritional status, and grain fumonisins concentration were evaluated in different genotypes, doses, and nitrogen sources (N) in two years and three locations. Two experiments were carried out in each area and year in an experimental design of a subdivided plot with four replications. One experiment involved a 4x2 factorial treatment: four nitrogen (N) doses (0, 80, 160, and 240 kg ha-1) in coverage and having urea as a source of N and two genotypes. Another experiment involved a 4x2 factorial treatment: four N sources: urea, urea covered with polymer, ammonium nitrate, and ammonium nitrate + urea (UAN), at a dose of 160 kg ha-1, in two genotypes. The genotype generally influenced maize yield more than N doses and sources, mainly due to the bushy stunt/corn stunt tolerance of AG7098 PRO2 and AG8677 PRO2. The N doses linearly increased the N leaf content. However, the N sources did not affect the N leaf content. The N doses and sources had no significant effect on the content of fumonisins, which was affected only by the genotypes in Sete Lagoas in 2016 (N doses experiment) and 2017 (N sources experiment). The hybrids, P3630H and AG8677PRO2 (Sete Lagoas, 2016, N doses experiment and 2017, N sources experiment, respectively) exceeded the Brazilian legislation for Maximum Tolerance Limit for fumonisins in corn grains, which is 5,000 µg kg-1. The best result was obtained with AG7098 PRO2, with yields (above 10,000 kg ha-1) and fumonisins consistently below 5,000 µg kg-1. Therefore, the selection of corn hybrids is a strategy to reduce the occurrence of fumonisins in the grains.

Novel strategies for genomic prediction of untested single-cross maize hybrids using unbalanced historical data.

KEY MESSAGE: Weighted outperformed unweighted genomic prediction using an unbalanced dataset representative of a commercial breeding program. Moreover, the use of the two cycles preceding predictions as training set achieved optimal prediction ability. Predicting the performance of untested single-cross hybrids through genomic prediction (GP) is highly desirable to increase genetic gain. Here, we evaluate the predictive ability (PA) of novel genomic strategies to predict single-cross maize hybrids using an unbalanced historical dataset of a tropical breeding program. Field data comprised 949 single-cross hybrids evaluated from 2006 to 2013, representing eight breeding cycles. Hybrid genotypes were inferred based on their parents' genotypes (inbred lines) using single-nucleotide polymorphism markers obtained via genotyping-by-sequencing. GP analyses were fitted using genomic best linear unbiased prediction via a stage-wise approach, considering two distinct cross-validation schemes. Results highlight the importance of taking into account the uncertainty regarding the adjusted means at each step of a stage-wise analysis, due to the highly unbalanced data structure and the expected heterogeneity of variances across years and locations of a commercial breeding program. Further, an increase in the size of the training set was not always advantageous even in the same breeding program. The use of the two cycles preceding predictions achieved optimal PA of untested single-cross hybrids in a forward prediction scenario, which could be used to replace the first step of field screening. Finally, in addition to the practical and theoretical results applied to maize hybrid breeding programs, the stage-wise analysis performed in this study may be applied to any crop historical unbalanced data.

Multi-trait multi-environment quantitative trait loci mapping for a sugarcane commercial cross provides insights on the inheritance of important traits.

Breeding trials typically consist of phenotypic observations for various traits evaluated in multiple environments. For sugarcane in particular, repeated measures are obtained for plant crop and one or more ratoons, such that joint analysis through mixed models for modeling heterogeneous genetic (co)variances between traits, locations and harvests is appropriate. This modeling approach also enables us to include molecular marker information, aiding in understanding the genetic architecture of quantitative traits. Our work aims at detecting QTL and QTL by environment interactions by fitting mixed models with multiple QTLs, with appropriate modeling of multi-trait multi-environment data for outcrossing species. We evaluated 100 individuals from a biparental cross at two locations and three  years for fiber content, sugar content (POL) and tonnes of cane per hectare (TCH). We detected 13 QTLs exhibiting QTL by location, QTL by harvest or the three-way interaction. Overall, 11 of the 13 effects presented some degree of pleiotropy, affecting at least two traits. Furthermore, these QTLs always affected fiber and TCH in the same direction, whereas POL was affected in the opposite way. There was no evidence in favor of the linked QTL over the pleiotropic QTL hypothesis for any detected genome position. These results provide valuable insights into the genetic basis of quantitative variation in sugarcane and the genetic relation between traits.

A mixed model QTL analysis for sugarcane multiple-harvest-location trial data.

Sugarcane-breeding programs take at least 12 years to develop new commercial cultivars. Molecular markers offer a possibility to study the genetic architecture of quantitative traits in sugarcane, and they may be used in marker-assisted selection to speed up artificial selection. Although the performance of sugarcane progenies in breeding programs are commonly evaluated across a range of locations and harvest years, many of the QTL detection methods ignore two- and three-way interactions between QTL, harvest, and location. In this work, a strategy for QTL detection in multi-harvest-location trial data, based on interval mapping and mixed models, is proposed and applied to map QTL effects on a segregating progeny from a biparental cross of pre-commercial Brazilian cultivars, evaluated at two locations and three consecutive harvest years for cane yield (tonnes per hectare), sugar yield (tonnes per hectare), fiber percent, and sucrose content. In the mixed model, we have included appropriate (co)variance structures for modeling heterogeneity and correlation of genetic effects and non-genetic residual effects. Forty-six QTLs were found: 13 QTLs for cane yield, 14 for sugar yield, 11 for fiber percent, and 8 for sucrose content. In addition, QTL by harvest, QTL by location, and QTL by harvest by location interaction effects were significant for all evaluated traits (30 QTLs showed some interaction, and 16 none). Our results contribute to a better understanding of the genetic architecture of complex traits related to biomass production and sucrose content in sugarcane.

Stigmatization of schizophrenia as perceived by nurses, medical doctors, medical students and patients.

Stigmatization of schizophrenia is widespread and its genetic explanation may potentially increase the stigma. The present study investigated whether seeing schizophrenia as a genetic or environmental disorder might influence perceived beliefs towards people with schizophrenia and whether social stigmatizing attitudes were differently perceived the 202 subjects who were recruited. Perceived social stigmatizing attitudes were compared among participants who read two vignettes depicting a person with schizophrenia. Then, the Standardized Stigmatization Questionnaire (SSQ) was administered. A genetic explanation of schizophrenia was more frequently associated with stigmatizing attitudes. Also, there were higher levels of perceived stigmatization in medical students and medical doctors than in other groups based on their social experience or background. However, the sample size was small and this was a non-experimental design; also the SSQ would benefit from more cross-validation. About half of the participants perceived stigmatizing social attitudes. Finally, considering schizophrenia as a genetic disorder influenced participants perception of other people's beliefs about dangerousness and unpredictability and people's desire for social distance.

Development of an integrated genetic map of a sugarcane (Saccharum spp.) commercial cross, based on a maximum-likelihood approach for estimation of linkage and linkage phases.

Sugarcane (Saccharum spp.) is a clonally propagated outcrossing polyploid crop of great importance in tropical agriculture. Up to now, all sugarcane genetic maps had been developed using either full-sib progenies derived from interspecific crosses or from selfing, both approaches not directly adopted in conventional breeding. We have developed a single integrated genetic map using a population derived from a cross between two pre-commercial cultivars ('SP80-180' x 'SP80-4966') using a novel approach based on the simultaneous maximum-likelihood estimation of linkage and linkage phases method specially designed for outcrossing species. From a total of 1,118 single-dose markers (RFLP, SSR and AFLP) identified, 39% derived from a testcross configuration between the parents segregating in a 1:1 fashion, while 61% segregated 3:1, representing heterozygous markers in both parents with the same genotypes. The markers segregating 3:1 were used to establish linkage between the testcross markers. The final map comprised of 357 linked markers, including 57 RFLPs, 64 SSRs and 236 AFLPs that were assigned to 131 co-segregation groups, considering a LOD score of 5, and a recombination fraction of 37.5 cM with map distances estimated by Kosambi function. The co-segregation groups represented a total map length of 2,602.4 cM, with a marker density of 7.3 cM. When the same data were analyzed using JoinMap software, only 217 linked markers were assigned to 98 co-segregation groups, spanning 1,340 cM, with a marker density of 6.2 cM. The maximum-likelihood approach reduced the number of unlinked markers to 761 (68.0%), compared to 901 (80.5%) using JoinMap. All the co-segregation groups obtained using JoinMap were present in the map constructed based on the maximum-likelihood method. Differences on the marker order within the co-segregation groups were observed between the two maps. Based on RFLP and SSR markers, 42 of the 131 co-segregation groups were assembled into 12 putative homology groups. Overall, the simultaneous maximum-likelihood estimation of linkage and linkage phases was more efficient than the method used by JoinMap to generate an integrated genetic map of sugarcane.

Surgery for esophageal achalasia. long-term results with three different techniques.

BACKGROUND/AIMS: In surgery for achalasia, the length of the myotomy and the opportunity of associating an antireflux procedure are still debated. Prospective and comparative studies on different techniques are few. The aims of this work is to compare the long term results of three different techniques successively adopted by the same surgical group. MATERIALS AND METHODS: Between January 1955 and December 1991, 185 achalasic patients were submitted to myotomy by using in temporal sequence three different techniques. The first technique utilized (1955-1972) was a long esophagogastric abdominal myotomy (83 patients), secondly (1973-1978) a limited transthoracic myotomy (30 patients) and at last (1979-1991) a long esophagogastric abdominal myotomy associated to the Dor gastroplasty (72 patients). Since 1972, patients were prospectively followed up according to a protocol which included a clinical interview, x-rays, manometry and endoscopy at given dates. Post-operative esophagogastric transit and gastro-esophageal reflux were assessed to verify the therapeutical outcome. Results obtained with the three different techniques were analyzed and compared by using the actuarial Kaplan-Meier curves. RESULTS: The mean follow up was 193.3 months for the patient group that underwent abdominal myotomy (62/83 patients), 137.3 months for the thoracic myotomy group (30/30 patients) and 86.9 months for the abdominal myotomy plus Dor gastroplasty group (69/72 patients). Long-term results in the abdominal myotomy and in the thoracic myotomy groups were respectively poor in 51.6% and in 46.6% of patients. Major causes of failure were insufficient myotomy (6.5%), periesophageal scarring (9.6%) and reflux esophagitis (22.6%) for the abdominal myotomy group; insufficient myotomy (20%) and reflux esophagitis (23%) for the thoracic myotomy group. In the abdominal myotomy plus Dor gastroplasty group long-term results were excellent or good in 87% of patients and poor in 13%. Reflux esophagitis (10% of cases) was the principal cause of failure. CONCLUSIONS: The comparison of the actuarial curves shows a significantly better long term outcome for the abdominal myotomy plus Dor antireflux procedure than for the abdominal myotomy (p = 0.01) and for the thoracic myotomy (p = 0.002) techniques.

Duodenogastric and non acid gastro-oesophageal reflux in patients with reflux oesophagitis.

BACKGROUND/AIM: The role and the identification criteria of non acid gastro-oesophageal reflux (GOR) are still debated. Moreover, the relationship between nonacid GOR and gastric alkalinizations, particularly if secondary to duodeno-gastric reflux is yet to be defined. MATERIALS AND METHODS: One hundred and forty one patients affected by GORD symptoms and oesophagitis entered the study. Oesophagitis was divided into four categories, according to a modified Savary and Miller classification. Acid (pH<4), alkalacid (47), alkaline (pH>7) GOR and duodenogastric reflux were measured by means of ambulatory three channel esophago-gastric pH monitoring with a combined analysis of the pH traces recorded in the oesophagus fundus and antrum. RESULTS: Total time percentage (T%) of acid GOR was significantly greater in patients than in healthy volunteers (HV) and between groups of patients in direct relation with the severity of the oesophagitis. Alkaline GOR was hardly detectable in every class of esophagitis. Alkalacid GOR increased with the grade of severeness of oesophagitis. Alkalacid GOR occurred prevalently in the postprandial period; it was only 8% of the time in patients with mild reflux oesophagitis and even less in patients with moderate or severe oesophagitis. The 24 hr total time percentage of duodenogastric reflux was similar in the patients and healthy volunteer groups. The frequency distribution in 0.1 intervals of fundic and antral pH samples showed a greater number of them in the acid range (0.8-1.2) in the patients than in healthy volunteer group (0.00067) samples was similar in patients and in healthy volunteers. CONCLUSIONS: Our findings demonstrate that alkaline GOR is rare in GORD patients and that non acid GOR has a minor role in the pathophysiology of reflux esophagitis.

Indications for 24-hour gastric pH monitoring with single and multiple probes in clinical research and practice.

The methodology of prolonged gastric pH monitoring has not yet been standardized with regard to the number and position of pH probes. Twenty-seven healthy volunteers and 11 patients affected by nonulcer dyspepsia have been submitted to 24-hr ambulatory simultaneous pH monitoring of the distal esophagus, fundus, and antrum. Fundic and antral pH profiles have been compared and causes of pH variations (pH > 4) identified. Both in healthy volunteers and dyspeptic patients, percentile curves of fundic and antral pH were statistically different in more than one of the daily periods considered (24-hr, postprandial, interdigestive, nocturnal). Percent time of duodenogastric reflux is significantly higher in the antrum than in the fundus in both groups. Modalities of gastric alkalinization secondary to food or duodenogastric reflux were different for the fundus and for the antrum both in healthy and dyspeptic subjects and between the two groups. These differences suggest that single and multiple pH monitoring of the stomach have different indications, and the position of the probes should vary according to the purpose of the test.

[Definition of a normal tracing in pH monitoring]. / Definizione di normalità di un tracciato pH-metrico.

The adoption of specific criteria for the reading of tracings, together with a comparison of the results obtained during the course of patient tests with the thresholds of normality calculated in groups of healthy volunteers, are required to determine the normality or abnormality of pH monitoring. From such comparisons performed among groups of healthy volunteers, selected especially on the basis of age or nationality, it was found that age bears no significant influence in calculating the parameters pertinent to pH monitoring. On the other hand, different dietary and life habits could be responsible for a few, albeit limited, discrepancies, such as, for instance, the number of recorded occurrences of gastro-esophageal acid reflux. Use of esophago-gastric pH monitoring, which makes it possible to identify both acid and non-acid gastro-esophageal reflux (mixed and alkaline), authorizes the diagnosis of that limited number of patients in whom this latter component of reflux only exceeds normal limits (3.3%) and an improved definition of the clinical picture in a larger share of patients (20%). Use of different statistical methods to calculate the thresholds of normalcy does not substantially improve the sensitivity of the examination, changing the thresholds by a few tenths of a unit and the fact that the examination is slightly over, or slightly under, the threshold being of ineffectual clinical significance. The study of the correlation between symptoms and pH monitoring events seems a valid interpretative criterion of these tests and capable of improving the diagnostic efficiency of the examination (0.88) when combined with mathematical evaluation.