Neotropical mangroves: Conservation and sustainable use in a scenario of global climate change

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How will Mahanarva spectabilis (Hemiptera: Cercopidae) Respond to Global Warming?

The aim of this study was to determine the favorable constant temperature range for Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae) development as well as to generate geographic distribution maps of this insect pest for future climate scenarios. M. spectabilis eggs were reared on two host plants (Brachiaria ruziziensis (Germain and Edvard) and Pennisetum purpureum (Schumach)), with individual plants kept at temperatures of 16, 20, 24, 28, and 32°C. Nymphal stage duration, nymphal survival, adult longevity, and egg production were recorded for each temperature*host plant combination. Using the favorable temperature ranges for M. spectabilis development, it was possible to generate geographic distribution. Nymphal survival was highest at 24.4°C, with estimates of 44 and 8% on Pennisetum and Brachiaria, respectively. Nymphal stage duration was greater on Brachiaria than on Pennisetum at 20 and 24°C but equal at 28°C. Egg production was higher on Pennisetum at 24 and 28°C than at 20°C, and adult longevity on Pennisetum was higher at 28°C than at 20°C, whereas adult longevity at 24°C did not differ from that at 20 and 28°C. With these results, it was possible to predict a reduction in M. spectabilis densities in most regions of Brazil in future climate scenarios.     

Effect of target spot on soybean yield and factors affecting this relationship

The lack of robust estimates of soybean yield losses due to target spot led to this study. The objective was to determine whether soybean yield at stage R8 (W, expressed as kg ha⁻¹) was related to target spot severity at soybean stage R5–R6 (S, expressed as %) and to identify variables that could affect this relationship. Plot-level estimates of mean disease severity and yield from 41 selected Uniform Fungicide Trials carried out in Brazil during 2012–2016 growing seasons were used to estimate linear regression coefficients for the relationship between yield and target spot severity through random-coefficient mixed effects model analysis. The overall estimated mean regression intercept and slope were  = 3564 kg ha⁻¹ (disease-free yield) and  = −17.1 kg ha⁻¹ %⁻¹ (W decrease per percent increase in S), respectively. The model was then refitted with different covariates to determine their effects on model parameters. β₀ was influenced by baseline yield (less than or greater than 3300 kg ha⁻¹) and β₁ was affected by yield response to fungicide treatments. Estimated yield loss at 50% target spot severity ranged from 8% to 42%. Cultivar also had a significant effect on the magnitude of yield reduction due to target spot, which ranged from 11% to 42%, depending on the cultivar.     

Efficiency of low heritability QTL mapping under high SNP density

The efficiency of quantitative trait locus (QTL) mapping methods needs to be investigated assuming high single nucleotide polymorphism (SNP) density and low heritability QTLs. This study assessed the efficiency of the least squares, maximum likelihood, and Bayesian approaches for QTL mapping assuming high SNP density and low heritability QTLs. We simulated 50 samples of 400 F₂ individuals, which were genotyped for 1000 SNPs (average density of one SNP/centiMorgan) and phenotyped for three traits controlled by 12 QTLs and 88 minor genes. The genes were randomly distributed in the regions covered by the SNPs along ten chromosomes. The QTL heritabilities ranged from approximately 1–2% and the sample sizes were 200 and 400. The power of QTL detection ranged from 30 to 60%, the false discovery rate (FDR) ranged from only 0.5–1.2%, and the bias in the QTL position ranged from 4 to 6 cM. The QTL mapping efficiency was not influenced by the degree of dominance. The statistical approaches were comparable regarding the FDR. Regression-based and simple interval mapping methods showed equivalent power of QTL detection and mapping precision. Compared to interval mapping, the inclusive composite interval mapping provided slightly greater QTL detection power and mapping precision only for the intermediate and high heritability QTLs. By maximizing the prior number of QTLs, the Bayesian analysis provided the greatest power of QTL detection. No method proved to be superior.     

Effect of menadione sodium bisulfite,an inducer of plant defenses,on the dynamic of banana phytoalexin accumulation during pathogenesis

Using an authentic sample of 2-hydroxy-9-(p-hydroxyphenyl)-phenalen-1-one, a banana phenalenone-type phytoalexin, we studied its dynamic of accumulation during pathogenesis of banana plants (Musa acuminata (AAA), Grand Nain) inoculated with Fusarium oxysporum f.sp. cubense (FOC), Race 4, the causal agent of Panama disease. The results obtained demonstrate that banana plants treated prior inoculation with menadione sodium bisulfite (MSB), an inducer of plant defenses, are capable of changing the dynamic of accumulation (higher amount and speed of biosynthesis) of this banana phytoalexin, biosynthesized by the banana plant during pathogenesis.     

Standard area diagram set to assess rust severity on eucalyptus leaves

This study aimed to develop and validate a standard area diagram set (SADs) to help assess rust severity caused by Austropuccinia psidii on eucalyptus leaves. The SADs has eight colour images of leaves with severity values ranging from 0.97% to 37.3%. The SADs were validated by 16 raters, who assessed the same set of 50 images twice: the first without the SADs and the second using it as an aid. Accuracy and precision of the estimates were determined based on Lin's concordance correlation coefficient, and the inter‐rater reliability was measured using the coefficient of determination (R²) and intraclass correlation. The estimates of severity of eucalyptus rust were more accurate, precise and reliable using SADs. These results demonstrate the value of SADs for several activities, including epidemiological studies, treatments comparison, disease monitoring, decision‐making in eucalyptus rust management measures, and in breeding programs.     

Serological and molecular comparison of Mannheimia haemolytica and Pasteurella trehalosi strains isolated from wild and domestic ruminants in the French Alps

Over a period of 17 years, 84 bacterial isolates identified as Mannheimia haemolytica or M. glucosida, and 52 isolates identified as Pasteurella trehalosi were detected in the lungs of domestic and wild ruminants in the French Alps. The isolates were serotyped according to their surface capsular antigens, and those sharing common antigens were further characterized by pulsed field gel electrophoresis. The results showed that the bacterial isolates included in the study clustered according to the host species from which they were isolated. These findings indicate that the transmission of serotypes of M. haemolytica, M. glucosida or P. trehalosi from an animal host in which they are common to another species sharing the same geographical space may be a rare epidemiological event.