Gene flow among different teosinte taxa and into the domesticated maize gene pool

Maize (Zea mays L. ssp. mays) was domesticated from one wild species ancestor, the Balsas teosinte (Zea mays ssp. parviglumis) about 9000 years ago. Higher levels of gene diversity are found in teosinte taxa compared to maize, following domestication and selection bottlenecks. Diversity in maize can be increased via gene flow from teosinte, which has certainly occurred from various taxa, but the rate of flow from different teosinte taxa and the final impact on maize evolution has been difficult to measure. One hundred populations from six Zea taxa, both domesticated (maize) and wild (teosinte), including domesticated landraces from Asia, Africa, and the Americas, were genotyped with 17 SSR markers using 15 individuals per population. Overall levels of diversity were high, and populations could be distinguished based on markers. Relationships between populations followed most published reports, or can now help resolve previously conflicting reports. Gene flow into maize from different teosinte groups, and gene flow between different teosintes, was estimated. Evidence for contributions from the Balsas teosintes and from Chalco teosintes (Z. mays ssp. mexicana) to the maize gene pool was found, as well as from Chalco into ssp. mexicana race ??Durango?? and Z. mays ssp. huehuetenengensis. These contributions are almost certainly the result of post-domestication (and ongoing) exchanges. This information must give more impetus to in situ conservation of teosinte species, and use of these teosintes to continue to direct the evolution of maize, especially in response to new diseases, insect pests, and other biotic and abiotic stresses.     

Recent rapid changes in the spatio‐temporal distribution of West Nile Neuro‐invasive Disease in Italy

In Italy, the first human case of West Nile Virus (WNV) infection was reported in 2008 and, since then, the number of cases has been steadily increasing. In this study, we describe the temporal and spatial pattern of WNV infection risk among humans in Italy, focusing on the human cases of West Nile Neuro‐invasive Disease (WNND) observed between 2008 and 2017. Incidence rates are estimated for each year and province under study. The incidence temporal trend is estimated using Poisson regression, and a spatio‐temporal cluster detection analysis is performed to detect high‐risk areas. In total, 231 WNND cases were notified in Italy between 2008 and 2017. The annual incidence rates increased during the study period (annual percentage change: 11.7%; 95%CI: ?0.9%; 26.1%). A geographical spread of the disease was observed during the study period throughout Northern Italy, with an increasing number of affected provinces. Provinces close to the Po River (the main river in the north of Italy) and the Oristano province (in the Sardinia Island) experienced the highest incidence rates during the study period. Our study shows a gradual, but rapid spread of WNND across Northern Italy from east to west and suggests the hypothesis that provinces close to Po River might present ecological and climatic conditions favourable to the virus circulation.     

Genetic variability following selection for scrapie resistance in six autochthonous sheep breeds in the province of Bolzano (northern Italy)

Scrapie is an ovine transmissible spongiform encephalopathy, and its susceptibility is associated with polymorphisms in the prion protein gene (PRNP). Genetic selection is currently the most effective mean for eradication of the susceptible VRQ allele in favour of resistant ARR allele. Maintenance of genetic diversity should be one of the major objectives in breeding programmes, especially in endangered breeds, and genetic information are an excellent alternative to pedigree data where these information are missing. The aim of our study was to determine changes of genetic variability in six native sheep breeds from autonomous province of Bolzano, northern Italy, following simulation of scrapie selection scenarios. A total of 684 rams were investigated for PRNP polymorphisms and for 10 microsatellite loci to estimate genetic variability. Across all loci, a total of 163 alleles were detected with a mean of 10.4 alleles per locus. Average observed (Ho) and unbiased expected (uHe) heterozygosity overall loci were 0.74 and 0.78, respectively, showing a statistically significant deviation from Hardy–Weinberg equilibrium (HWE) in all breeds. This heterozygosity deficit was confirmed by a positive fixation index (Fis), determining a moderate inbreeding in each breed. Simulating a soft selection, where only rams having at least a VRQ allele should be excluded from reproduction, Ho, uHe and Fis values remained almost unchanged, indicating that genetic variability should not be affected by the removal of these individuals. With a mild selection scenario, considering only rams with at least one ARR allele, we observed a decrease in the mean alleles per breed (8.9) and the maintenance of heterozygosity deficiency, except for two breeds, where it was any longer significant. These results showed that selection strategies allowing use of heterozygous as well homozygous ARR rams might be the right compromise to improve resistance to scrapie and to do not dramatically affect genetic variability of these breeds.     

Effect of seed phosphorus concentration on nodulation and growth of three common bean cultivars

Abstract

An experiment was conducted in the greenhouse to evaluate the effects of seed phosphorus (P) concentration on growth, nodulation, and nitrogen (N) and P accumulation of three common bean (Phaseolus vulgaris L.) cultivars. Seeds were produced under low or high soil P levels, and soaked, or not, in 200 mM KH₂PO₄ solution. The experiment had a 3×3×2×2 factorial block design: three cultivars (ICA Col 10103, Carioca and Honduras 35), three levels of applied P (15, 30 and 45 mg P kg^?1 soil), two native seed P concentrations, and two seed soaking treatments. Plants were harvested at flowering. Soaked seeds increased the number, dry mass and P content of nodules, but did not affect plant growth. Plants originated from seeds with high native P concentration presented higher shoot dry mass and nodule number and mass at every soil P level, and were less responsive to increased soil P supply, than plants from low seed P. In plants from seeds with high P, soil P levels did not alter significantly root dry mass, while in plants from seeds with low P bean cultivars expressed wider differences in root dry mass. The genotypic variability of nodulation was influenced by soil P levels and seed P concentration. Both higher soil or seed P supply enhanced N and P accumulation in shoots. These results indicate that a high seed P concentration produces plants less dependent on soil P supply, and can enhance nodulation and N₂ fixation of common bean. Seed P supply affected the cultivar performance, and should be considered in evaluation of bean genotypes.     

Biochar as a strategy to manage plant diseases caused by pathogens inhabiting the soil: a critical review

Phytoparasitica - The current agricultural scenario faces a range of challenges, with phytosanitary ones being paramount. In most cases, plant diseases are treated with chemicals; however, they...     

Zinc phosphate protects tomato plants against Pseudomonas syringae pv. tomato

Journal of Plant Diseases and Protection - The purpose of this study was to determine whether zinc phosphate treatments of tomato plants (Solanum lycopersicum L.) can attenuate bacterial speck...     

In vitro antimicrobial activity of different accessions ofSolanum commersonii Dun. from Uruguay

Summary The in vitro antimicrobial activity of extracts from accessions ofSolanum commersonii Dun. collected in the south of Uruguay was investigated against five microorganisms including the pathogenRalstonia solanacearum. A total of 30 extracts corresponding to organic and aqueous extracts were studied. Interestingly, most of the positive results for growth inhibition were againstR. solanacearum. The extracts were also analyzed for the presence of glycoalkaloids and lectins. Six of the ten aqueous extracts showed lectin presence and a wide variation in the type and amounts of glycoalkaloids, was found. Results indicate that there is no clear relationship between the antimicrobial activity against the five microorganisms screened and the presence or amounts of lectins and glycoalkaloids, traditionally regarded as possible antimicrobial metabolites in theSolanum genus, which indicates the presence of as yet unidentified antimicrobial compounds.