Are we ready for back-to-nature crop breeding?

Download : Download video (12MB)     

Pathogen derived resistance to potyviruses: working,but why?

The theory of pathogen-derived resistance suggests that pathogen resistance genes can be developed from a pathogen's own genetic material. For example, transgenic plants expressing plant virus coat protein genes are often virus resistant. Non-structural virus genes also have been expressed in plants, with mixed results. Recent experiments suggest that, at least in some cases, resistance may be RNA-mediated. In all cases the exact mechanism of this resistance remains a mystery. This review discusses examples of pathogen-derived resistance for members of the potyviridae family of plant viruses and offers some possible mechanisms to account for this intriguing phenomenon.     

Are there effective resistance management strategies for vectors of human disease?*

The rotation of insecticides used by the Onchocerciasis Control Programme in West Africa is reviewed and the motives for this rotation are shown to be not only management of temephos resistance in the Simulium vectors but also constraints on what compounds are usable at particular seasons. A computer model indicates that without these seasonal constraints there is unlikely to be an advantage in a pre-planned rotation of insecticides, as compared with the prompt switching of compounds as dictated by detection of build up of resistance and switching back to the original compound if the regression of resistance is found to give the opportunity to do so. The latter sequence of events can hardly be called a ‘strategy’ for resistance management, but is what any well-managed pest control programme would be expected to do. The use of an insecticide mixture is different in principle from the use of rotation and depends on the idea that if the mixture is used from the outset, when resistance to both components of the mixture is likely to be rare, the double resistance combination would be so rare as to be dwarfed in numbers by those insects which avoid exposure altogether. The prospects for successful use of a mixture depend on each component killing a very high percentage of the exposed insects which are genetically susceptible to it. Whether this condition is met could be tested, for example, in the case of exposure of mosquitoes to insecticide-treated bednets.     

ANNEXIN 8 negatively regulates RPW8.1‐mediated cell death and disease resistance in Arabidopsis

Study on the regulation of broad‐spectrum resistance is an active area in plant biology. RESISTANCE TO POWDERY MILDEW 8.1 (RPW8.1) is one of a few broad‐spectrum resistance genes triggering the hypersensitive response (HR) to restrict multiple pathogenic infections. To address the question how RPW8.1 signaling is regulated, we performed a genetic screen and tried to identify mutations enhancing RPW8.1‐mediated HR. Here, we provided evidence to connect an annexin protein with RPW8.1‐mediated resistance in Arabidopsis against powdery mildew. We isolated and characterized Arabidopsis b7‐6 mutant. A point mutation in b7‐6 at the At5g12380 locus resulted in an amino acid substitution in ANNEXIN 8 (AtANN8). Loss‐of‐function or RNA‐silencing of AtANN8 led to enhanced expression of RPW8.1, RPW8.1‐dependent necrotic lesions in leaves, and defense against powdery mildew. Conversely, over‐expression of AtANN8 compromised RPW8.1‐mediated disease resistance and cell death. Interestingly, the mutation in AtANN8 enhanced RPW8.1‐triggered H₂O₂. In addition, mutation in AtANN8 led to hypersensitivity to salt stress. Together, our data indicate that AtANN8 is involved in multiple stress signaling pathways and negatively regulates RPW8.1‐mediated resistance against powdery mildew and cell death, thus linking ANNEXIN's function with plant immunity.     

The role of Schmidt ‘Antonovka’ in apple scab resistance breeding

??Antonovka?? has long been recognised as a major source of scab (Venturia inaequalis) resistance useful for apple breeding worldwide. Both major gene resistances in the form of the Rvi10 and Rvi17 and quantitative resistance, collectively identified as VA, have been identified in different accessions of ??Antonovka??. Most of the ??Antonovka?? scab resistance used in apple-breeding programmes around the world can be traced back to Schmidt ??Antonovka?? and predominantly its B VIII progenies 33,25 (PI 172623), 34,6 (PI 172633), 33,8 (PI 172612) and 34,5 (PI 172632). Using genetic profile reconstruction, we have identified ??common ??Antonovka?? ?? as the progenitor of the B VIII family, which is consistent with it having been a commercial cultivar in Poland and the single source of scab resistance used by Dr. Martin Schmidt. The major ??Antonovka?? scab resistance genes mapped to date are located either very close to Rvi6, or about 20?C25?cM above it, but their identities need further elucidation. The presence of the 139?bp allele of the CH-Vf1 microsatellite marker known to be associated with Rvi17 (Va1) in most of the ??Antonovka?? germplasm used in breeding suggests that it plays a central role in the resistance. The nature and the genetic relationships of the scab resistance in these accessions as well as a number of apple cultivars derived from ??Antonovka??, such as, ??Freedom??, ??Burgundy?? and ??Angold??, are discussed. The parentage of ??Reglindis?? is unclear, but the cultivar commercialised as ??Reglindis?? was confirmed to be an Rvi6 cultivar.     

Marker-based parentage analysis facilitates low input ‘breeding without breeding’ strategies for forest trees

Controlled crosses and progeny testing are important components of tree breeding programs. Recently, a new approach, ‘breeding without breeding’ (BWB), has been proposed to obtain structured pedigrees for the breeding and testing from wind-pollinated progenies; the technique uses high-resolution markers instead of conventional approaches. The BWB approach is attractive for outcrossing conifers where the breeding cycle is long and reproductive maturity is often delayed. For the application of the BWB approach, the accurate assignment of parents is essential. The first step in the application of the BWB approach is to conduct tests into the reliability of paternity and parent-pair exclusion procedures in complex situations. In this study we conducted multi-locus-based empirical and simulation analyses for a Scots pine seed orchard crop, in order to develop the appropriate parentage assignment techniques for BWB and to investigate whether pedigrees from a seed orchard crop can be determined with sufficient accuracy. The results were promising, as 93–97% of the seeds generated by mating among the seed orchard clones were correctly assigned to a parent-pair. When mating occurred with foreign pollen, the success rate of identifying mother clones was 60–78%. Based on these results, we propose three novel low input breeding strategies for forest trees. The principles of the different options and their potential benefits and costs are described and discussed using Scots pine as a case study.     

Plant genome sequencing — applications for crop improvement

1. Download : Download high-res image (182KB)
2. Download : Download full-size image

     

Long‐term effects of agri‐environment schemes on breeding passerine populations in a lowland hay‐meadow system

Capsule Mowing postponement in 25% of a meadow system may lead to improved but instable population dynamics in meadow birds.

Aim To monitor the long‐term effects of mowing postponement on the abundance and territory density of meadow passerines in 25% of a 3000‐ha hay‐meadow area in the Saône Valley (eastern France).

Methods From 1993 to 2009, passerine abundance was measured annually in 78 plots using point counts and territory density was assessed in two study areas by Territory Mapping.

Results The programme of mowing postponement led to substantially increased passerine abundance and territory density, with the highest increase detected in Whinchats Saxicola rubetra. No positive trend was observed in Corn Buntings Emberiza calandra. Immediately after the increase in abundance, bird distribution within the study area was not influenced by the timing of mowing. The hatching success, assessed by the systematic observation of food carrying, was negatively influenced by early mowing (<40% recorded when >60% of the meadow area was already harvested on 1 July) or, in late mown areas, by high meadow passerine territory density (<40% when territory density was >10 per 10 ha). Hatching rate was usually higher in Whinchats than in Corn Buntings.

Conclusion By improving meadow passerine breeding outputs and density, mowing postponement led to instable population dynamics with dominance of certain species and density‐dependent breeding success.     

Does multiple paternity influence offspring disease resistance?

It has been suggested that polyandry allows females to increase offspring genetic diversity and reduce the prevalence and susceptibility of their offspring to infectious diseases. We tested this hypothesis in wild‐derived house mice (Mus musculus) by experimentally infecting the offspring from 15 single‐ and 15 multiple‐sired litters with two different strains of a mouse pathogen (Salmonella Typhimurium) and compared their ability to control infection. We found a high variation in individual infection resistance (measured with pathogen loads) and significant differences among families, suggesting genetic effects on Salmonella resistance, but we found no difference in prevalence or infection resistance between single‐ vs. multiple‐sired litters. We found a significant sex difference in infection resistance, but surprisingly, males were more resistant to infection than females. Also, infection resistance was correlated with weight loss during infection, although only for females, indicating that susceptibility to infection had more harmful health consequences for females than for males. To our knowledge, our findings provide the first evidence for sex‐dependent resistance to Salmonella infection in house mice. Our results do not support the hypothesis that multiple‐sired litters are more likely to survive infection than single‐sired litters; however, as we explain, additional studies are required before ruling out this hypothesis.     

Nitrogen-inputs regulate microbial functional and genetic resistance and resilience to drying–rewetting cycles,with implications for crop yields

Plant and Soil - Waterlogging is a common natural disturbance that has negative impacts on dry-land plant species. However, few studies have focused on how waterlogging influences the invasiveness...     

A biological framework for understanding farmers’ plant breeding

We present a framework for understanding farmer plant breeding (including both choice of varieties and populations and plant selection) in terms of the basic biological model of scientific plant breeding, focusing on three key components of that model: 1) genetic variation, 2) environmental variation and variation of genotype-by-environment interaction, and 3) plant selection. For each of these concepts we suggest questions for research on farmers’plant breeding (farmers’ knowledge, practice, and crop varieties and growing environments). A sample of recent research shows a range of explicit and implicit answers to these questions which are often contradictory, suggesting that generalizations based on experience with specific varieties, environments or farmers may not be valid. They also suggest that farmers’ practice reflects an understanding of their crop varieties and populations that is in many ways fundamentally similar to that of plant breeders; yet, is also different, in part because the details of their experiences are different. Further research based on this framework should be valuable for participatory or collaborative plant breeding that is currently being proposed to reunite farmer and scientific plant breeding.     

Is genetic engineering ever going to take off in forage,turf and bioenergy crop breeding?

Background

Genetic engineering offers the opportunity to generate unique genetic variation that is either absent in the sexually compatible gene pool or has very low heritability. The generation of transgenic plants, coupled with breeding, has led to the production of widely used transgenic cultivars in several major cash crops, such as maize, soybean, cotton and canola. The process for regulatory approval of genetically engineered crops is slow and subject to extensive political interference. The situation in forage grasses and legumes is more complicated.

Scope

Most widely grown forage, turf and bioenergy species (e.g. tall fescue, perennial ryegrass, switchgrass, alfalfa, white clover) are highly self-incompatible and outcrossing. Compared with inbreeding species, they have a high potential to pass their genes to adjacent plants. A major biosafety concern in these species is pollen-mediated transgene flow. Because human consumption is indirect, risk assessment of transgenic forage, turf and bioenergy species has focused on their environmental or ecological impacts. Although significant progress has been made in genetic modification of these species, commercialization of transgenic cultivars is very limited because of the stringent and costly regulatory requirements. To date, the only transgenic forage crop deregulated in the US is ‘Roundup Ready’ (RR) alfalfa. The approval process for RR alfalfa was complicated, involving several rounds of regulation, deregulation and re-regulation. Nevertheless, commercialization of RR alfalfa is an important step forward in regulatory approval of a perennial outcrossing forage crop. As additional transgenic forage, turf and bioenergy crops are generated and tested, different strategies have been developed to meet regulatory requirements. Recent progress in risk assessment and deregulation of transgenic forage and turf species is summarized and discussed.     

Marker-assisted backcross breeding for enhancing β-carotene of QPM inbreds

Molecular Breeding - Molecular breeding is capable of improving important agricultural crop traits by controlling functional genes, aiming to attain high yield, stability and quality. During this...     

Ginsenoside Rh1 potentiates dexamethasone’s anti-inflammatory effects for chronic inflammatory disease by reversing dexamethasone-induced resistance

Introduction

Acquired resistance to glucocorticoids constitutes a major clinical challenge, often overlooked in the search for compounds to improve the effect of classic steroids. We sought to unravel how a plant-original compound, ginsenoside Rh1, potentiates dexmethasone (DEX)’s potential anti-inflammation properties.

Methods

Ginsenoside Rh1 combined with DEX was applied in a short-term and long-term treatment protocol for inflammation. Its potential mechanism on anti-inflammation was explored. In addition, the effect of Rh1 on the side-effect induced by DEX was studied. Furthermore, the in vivo anti-inflammatory effects of Rh1 combined with DEX were evaluated in a collagen-induced arthritis (CIA) mice model.

Results

Ginsenoside Rh1 potentiates DEX’s anti-inflammatory effects even after prolonged DEX treatment. Rh1 could improve the glucocorticoid receptor (GR)’s transrepression on nuclear factor kappa B (NF-κB) and transactivation on dual specificity protein phosphatase 1 (DUSP1), which is responsible for DEX’s anti-inflammatory effects. Parallel Western blot assay and radioligand binding analysis revealed that Rh1 could increase the expression and binding of GR. This is in sharp contrast to DEX alone, showing a direct link among prolonged treatment, decreasing GR and the abolishment of anti-inflammation. Interestingly, Rh1 does not enhance the transactivation of glucocorticoid-responsive elements (GRE) driven genes - gluconeogenic enzyme glucose-6-phosphatase (G6P) and phosphoenolpyruvate carboxykinasee phosphatase (PEPCK) in primary mouse hepatocytes, a mechanism partly held accountable for the metabolic side-effects. Similar results were found in CIA mice.

Conclusion

Rh1 could potentiate DEX’s anti-inflammatory effects and does not cause a hyperglycemic side effect. Ginsenoside Rh1 combined with DEX may be a promising candidate treatment option for chronic inflammatory diseases in need of long-term immunosuppression therapies.     

Soil organic C affected by dry‐season management of no‐till soybean crop rotations in the tropics

Plant and Soil - Cover crop species selection for soybean (Glycine max) production under no-tillage (NT) management may affect soil organic C sequestration by altering the quantity and quality of C...     

How do migratory species stay healthy over the annual cycle? A conceptual model for immune function and for resistance to disease

Migration has fascinated researchers for years and many active areas of study exist. However, the question of how migratory species stay healthy within the context of their annual cycle remains relatively unexplored. This article addresses this question using Red Knots (Calidris canutus) as a model migrant species. We review recent research on immune function in Red Knots and integrate this work with the broader eco-immunological literature to introduce a conceptual model. This model synthesizes earlier ideas about resource allocation and the costs of immunity with recent increases in our knowledge about the vertebrate immune system and then puts these concepts into the context of defense against real pathogens in environments where a myriad of factors change in time and space. We also suggest avenues for further research, which will help to test the model and better link measures of immune function to pressure from pathogens and to optimal defense against disease.