Ploidy levels of Dioscorea alata L. germplasm determined by flow cytometry

Dioscorea alata L. is a highly important crop, widely distributed in the humid and semi-humid tropics. Flow cytometry was used to determine the ploidy levels of 74 D. alata genotypes collected mainly from West African countries. Sixty three of the genotypes were found to be tetraploid, one was hexaploid and ten were octoploid. The high percentage of tetraploids together with the small percentage of hexaploid individuals and the absence of diploid individuals gives us some more clues on the possible origin of these species. No association between ploidy level and place of cultivation was found for the tested material. The obtained results represent important knowledge for enhancing the breeding methodologies and optimize germplasm management of this species. It also offers further insights to the phylogeny and evolution of Dioscorea species.     

Independent segregation of two isozyme markers and inter-plant differences in nuclear DNA content in the interspecific backcross (Allium fistulosum L. × A. cepa L.) × A. cepa L.

Summary From backcrosses of three interspecific hybrids (A. fistulosum x A. cepa) with a. cepa 14 diploid and 2 triploid plants were recovered.In this BC1 population introgression of A. fistulosum genetic material into the A. cepa nuclear genome was studied using two isozyme markers: Got-1 and Got-2. Both loci carried two alleles. A. cepa was monomorphic for both markers. A. fistulosum was polymorphic for Got-2. Based on their Got isozyme pattern seven out of the 14 diploid BC1 plants had a recombinant genotype. The loci appeared to be unlinked. Differences were observed in nuclear DNA contents between the diploid BC1 plants, indicating that gametes produced by the interspecific hybrids contained different combinations of chromosomal material from A. cepa and A. fistulosum.Abbreviations Adh alcohol dehydrogenase - Got glutamate oxaloacetate transaminase - Idh isocitrate dehydrogenase - Pgi phosphoglucoisomerase - Pgm phosphoglucomutase     

Constraints using the liquid fraction from roadside grass as a bio-based fertilizer

Background

Roadside grass cuttings are currently considered a waste product due to their association with road sweepings as contaminated waste, therefore, their potential as a biofertilizer is understudied.

Aim

This study aimed to determine whether grass liquid fraction (GLF) collected from a roadside verge in Maldegem, Belgium, and pressed using a screw press was suitable as a biofertilizer.

Methods

The characterization of the heavy metal content of the GLF was conducted using an ICP-OES. From May to September 2019, a pot experiment was set up using a randomized block design to compare tomato plant growth, yield, and nutrition for GLF-treated plants to two commercial fertilizers and tap water as a control.

Results

The heavy metal content of the GLF was below the maximum permissible concentrations (MPCs) for organic fertilizers as set out by the European Comission fertilizer regulation 1069/2009 and 1107/2009 (European Comission, 2019). However, despite having a fairly well-balanced nutrient content (0.1% N, 0.04% P₂O₅, and 0.2% K₂O), GLF had a negative effect on the growth, root weight, and yield of the tomato plants, killing six out of ten plants. GLF also promoted mold growth in the soil of some plants. Since the GLF was uncontaminated, heavy metal toxicity did not cause the negative effect.

Conclusions

Previous research showed that liquid fractions from some plants negatively affect the growth of others due to allelopathic chemicals; this, together with the stimulation of fungal growth, could have caused the negative effects observed. Future experiments will investigate the herbicidal property of GLF and possible treatments to potentially recover the nutrients contained within the GLF for application as a biofertilizer.     

Modelling the effect of surveillance programmes on spread of bovine herpesvirus 1 between certified cattle herds

For the eradication of an infectious agent, like bovine herpesvirus 1 (BHV-1), surveillance and certification can be used to reduce the transmission between herds. The goal of surveillance is that a certified herd that becomes infected is detected timely so that infection of several other certified herds is prevented. What counts is whether the reproduction ratio R, i.e. the average number of certified herds infected by one infected certified herd can be kept below 1. To support policy makers in making decisions about the minimal demands for a surveillance programme in an eradication campaign of BHV-1 in cattle, two mathematical models were investigated. With these models, the basic reproduction ratio between herds was calculated. The surveillance programmes were characterised with sample size, sampling frequency, test sensitivity, herd size, vaccination status, and contacts between herds. When R between herds is below 1, then the surveillance programme is sufficiently good to prevent spread of infection, provided that R is estimated well. In the model based on bulk milk testing sample size was replaced by a threshold at which bulk milk can be found positive. The R between herds was mainly influenced by the vaccination status, sampling frequency, and contacts between herds. Herd size moderately affected the outcome. Test sensitivity and sample size, however, were of minor importance. If herds of 50 cows became free of BHV-1 without vaccination, then spread of infection between herds might be prevented when animals within herds are sampled once a year (milk or blood samples). This frequency needs to be intensified, being twice a year, for larger herds and/or herds with extensive contacts with other herds. When bulk milk is sampled instead, sampling should be done at least every 5 months and more intensively, being each month, with larger herd sizes and more contacts between herds.     

Biological characteristics and pathogenicity of avian Escherichia coli strains.

Fifty avian (chicken) pathogenic Escherichia coli strains (APEC) isolated from individuals suffering from omphalitis, septicaemia and swollen head syndrome, and 30 strains isolated from healthy chickens were studied regarding their biological characteristics such as serogroups, haemolysin, colicin, cytotoxin, toxin and siderophore production, adhesion capacity to in vitro cultivated cells, and absorption of Congo red dye. Serotyping demonstrated that most of the omphalitis and normal strains were untypable, whereas most of the septicaemic strains were either untypable or rough. There was no prevalent serogroup among the pathogenic strains studied. The capacity for adhesion and invasion of in vitro cultured cells (HeLa, HEp-2, KPCC), as well as the agglutination of different types of red blood cells and the LD50 of each strain were also evaluated. No correlation was observed between the biological characteristics and pathogenicity, except that colicin was characteristically produced by swollen head syndrome E. coli strains. No correlation was found between adhesion or haemagglutination patterns and pathogenicity. Only six of the 50 strains revealed invasive capacity and the strain that best invaded the cell lines was the one with the lowest LD50.     

Characterization of the functional domain of major surface protein 1a involved in adhesion of the rickettsia Anaplasma marginale to host cells

The major surface protein (MSP) 1a of the genus type species Anaplasma marginale (Rickettsiales: Anaplasmataceae) has been shown to mediate adhesion, infection and transmission of the organism, as well as to contribute to protective immunity in cattle. MSP1a contains a variable number of tandemly repeated peptides in the amino-terminal region, while the remainder of the protein is highly conserved among isolates. The number of repeats varies among geographic isolates of A. marginale but is constant within an isolate and has been used as a stable genetic marker of isolate identity. Because the sequence of the tandem repeats is the most variable part of the protein among isolates, this region of the protein is most likely to be involved in adhesion to host cells, a prerequisite to infection. The purpose of this study was to characterize the organization and function of the MSP1a tandem repeats of A. marginale in adhesion to host cells. We demonstrated by use of recombinant mutant proteins that the tandemly repeated region of MSP1a was necessary and sufficient to mediate adhesion of MSP1a to tick cells and bovine erythrocytes. Synthetic peptides representing the predominant sequences of individual repeats were tested for their adhesive capacity for tick cell extract (TCE). Peptides containing acidic amino acids D or E at position 20 bound to TCE, while peptides with a G as the 20th amino acid were not adhesive to TCE. Antibodies produced in rabbits against a synthetic repeat peptide neutralized A. marginale infection of cultured tick cells, and the neutralization observed was similar to that effected by antibodies produced against the whole MSP1a recombinant protein. Analysis of tandemly repeated MSP1a peptides of several geographic isolates of A. marginale revealed a complex relationship between the msp1alpha genotype and the tick-transmissible phenotype of the isolate and suggested that both the sequence and conformation of the repeated peptides influenced the adhesive properties of MSP1a. These studies demonstrated that the tandemly repeated region of the protein mediates the adhesive function of MSP1a.     

Mapping of QTLs in tomato line FLA456 associated with resistance to a virus causing tomato yellow leaf curl disease

Tomato (yellow) leaf curl disease (TYLCD) is a serious threat to tomato production in the tropics and subtropics. The genetics of resistance to Tomato yellow leaf curl Thailand virus Taiwan strain (TYLCTHV-[TW]) in a highly resistant tomato line FLA456 was studied through quantitative trait loci (QTL) analysis. Four QTLs named qTy4.1, qTy6.1, qTy10.1 and qTy11.1 were detected on chromosomes 4, 6, 10, and 11, respectively, through evaluation of an F₆ recombinant inbred line (RIL) population derived from a cross between FLA456 (resistant) and CLN1621L (susceptible). Gene action of all QTLs was recessive based on disease reaction of the F₁. The markers SINAC1 and SLM4-34 flanked qTy4.1 on chromosome 4, and SLM11-12 and SLM11-17 defined qTy11.1, which co-located with the previously identified Ty-5 and Ty-2 loci, respectively. qTy6.1 was flanked by the markers SLM6-55 and TES-0014, and qTy10.1 by the markers SLM10-80-SLM10-46 on chromosomes 6 and 10. The LOD values of the putative QTLs ranged from 2.79 to 13.76. The phenotypic variance explained by each QTL ranged from 7.1 to 31.9 %. The four QTLs collectively contributed about 60.5 % of the phenotypic variation in resistance against TYLCTHV-[TW]. Group mean severity scores of those RILs possessing three or four qTy were generally lower than RIL groups with only one or no qTy. Given the diversity of begomoviruses that cause TYLCD across the regions, the new QTLs from FLA456 would be valuable in tomato breeding for developing varieties with durable resistance. Two QTL intervals (qTy4.1 and qTy10.1) contained virus resistance candidate genes such as CTV.22 and eukaryotic translation initiation factor 4E.     

A historical analysis of diversity trends in French and Dutch lettuce cultivars

Using historical seed catalogues in combination with molecular fingerprinting data, diversity trends of lettuce, representing an important vegetable with active breeding programmes, were studied. Seed catalogues originating from France and the Netherlands from five different decades, the earliest dating from the 1840s, were checked for the occurence of lettuce cultivars. A total of 225 catalogues, with 7,311 records of lettuce, representing 878 different cultivars were found. The number of unique cultivars on offer by French and Dutch companies showed a small continuous increase until the 1960s, after which the number of cultivars on offer more than doubled to a total of 534 in the 1990s. Only a relatively small overlap between France and the Netherlands in the range of cultivars offered was observed. The 1960s appeared to be a period with many changes: the lowest genetic diversity in lettuce cultivars was found for this decade, whereas after the 1960s the number of companies supplying lettuce seeds reduced dramatically. The percentage of companies in a decade offering an identical cultivar decreased over time, and in the 1990s almost all cultivars were unique to only a single company. The possible relations of the observed trends with the developments in plant variety protection and in the plant breeding industry are discussed.     

Assessing foraging strategies of herbivores in Mediterranean oak woodlands: a review of key issues and selected methodologies

Montados are agro-silvo-pastoral ecosystems, typical of the Southwest Iberian Peninsula, of high socio-economic and conservation importance, where grazing is a dominant activity. Montados are characterized by an open tree canopy of Quercus sp. and a diverse undercover of shrubs and grasslands that constitute the plant food resources for grazing animals. Plant food resources of Montados are highly variable, both spatially and seasonally, in quantity and quality. Reliable and easy to use methods to monitor grazing are necessary to allow proper understanding of foraging strategies of grazing animals and to set sustainable grazing management. We describe the main characteristics of the plant food resources available for grazing animals, striking its variability, and revise the potential of using N-alkanes and saliva proteome methods to assess foraging strategies in Montados. In a scenario of dynamic multiple choices, we discuss the use of n-alkane methodology for the simultaneous estimation of diet composition and voluntary intake and saliva proteome as a mean of increasing the knowledge on diet adjustments.