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Abstract: Perennial ryegrass (Lolium perenne) is an important source of protein and energy for dairy cattle. To improve the protein/energy ratio of this forage, focus is now on improving its cell wall digestibility. The in vitro assessment of the digestible fraction of the neutral detergent fibre (NDFD) is a superior method for determining the cell wall digestibility, but requires the use of ruminal fluid, which has a highly variable composition and is often not readily available. As lignin is considered the main cell wall component that impedes NDFD, we investigated whether this “subtrait” could serve as alternative breeding selection criterion to improve NDFD. Therefore, we assessed the accuracy of two lignin quantification methods: van Soest (ADL) and Klason lignin (KL). We also considered KL estimates corrected for the solubilized lignin (total lignin or TL) and non‐solubilized protein (TL'). Although the latter is considered the truest possible lignin content, it was not always the most correlated to NDFD, due to the limited accuracy of protein quantification on lignin residue. TL is most correlated to NDFD and we therefore recommend it for use in conventional breeding if NDFD determination is not a possibility. However, NDFD is still a superior selection criterion, as it combines the effect of several subtraits and not just lignin. For marker–trait association studies, a more accurate estimate of lignin content is more important than a high correlation with NDFD, but also here, TL performs best. [ABSTRACT FROM AUTHOR]

To assess the incidence of early blight/brown spot (EB/BS) in Flanders (Belgium), potato fields in 22 locations were monitored and scored over the duration of the growing seasons 2014 and 2015. The average disease incidence was shown to be higher in 2014 than in 2015. Soil type, rainfall and temperature were also analysed in relation to disease incidence. In 2014, potato plants grown in sandy soils had more EB/BS disease than those grown in clay or loamy soils. However, the low disease incidence in 2015 meant that differences in disease levels between soil types could not be discerned for that growing season. A windowpane analysis demonstrated that rainfall and humidity accounted for the differences in disease incidence between the two growing seasons. During the course of the survey, the species composition in leaves with symptoms was assessed using real‐time PCR. Remarkably, small‐spored Alternaria species, such as A. alternata and A. arborescens, rather than the more virulent A. solani were the predominant species on potato leaves throughout the growing season. As the disease progressed, the proportion of A. solani increased. In view of these results, the virulence of a collected set of Alternaria isolates was assessed by an in vitro assay. Despite A. solani being more virulent than A. alternata or A. arborescens, the most abundant species isolated from potato leaves with symptoms was A. arborescens. [ABSTRACT FROM AUTHOR]

The relevance of particular architectural characteristics for a good regrowth has not been elucidated yet in red clover. Here, we present the shoot architecture and regrowth of six red clover genotypes analysed under controlled and field conditions, with and without competition from perennial ryegrass. Among the genotypes investigated, Lemmon and Crossway displayed the highest number of nodes and branches, the highest increase in the number of nodes in the basal 7 cm and the highest outgrowth capacity of the nodes in this zone resulting in the highest dry-matter yields. Our results indicate that selecting genotypes with a high number of first-order branches, short internodes and the ability to resume growth from the nodes that remain in the uncut zone will allow the development of cultivars with good regrowth. [ABSTRACT FROM AUTHOR]

In monocots, lignin content has a strong impact on the digestibility of the cell wall fraction. Engineering lignin biosynthesis requires a profound knowledge of the role of paralogues in the multigene families that constitute the monolignol biosynthesis pathway. We applied a bioinformatics approach for genome-wide identification of candidate genes in Lolium perenne that are likely to be involved in the biosynthesis of monolignols. More specifically, we performed functional subtyping of phylogenetic clades in four multigene families: 4CL, COMT, CAD and CCR. Essential residues were considered for functional clade delineation within these families. This classification was complemented with previously published experimental evidence on gene expression, gene function and enzymatic activity in closely related crops and model species. This allowed us to assign functions to novel identified L. perenne genes, and to assess functional redundancy among paralogues. We found that two 4CL paralogues, two COMT paralogues, three CCR paralogues and one CAD gene are prime targets for genetic studies to engineer developmentally regulated lignin in this species. Based on the delineation of sequence conservation between paralogues and a first analysis of allelic diversity, we discuss possibilities to further study the roles of these paralogues in lignin biosynthesis, including expression analysis, reverse genetics and forward genetics, such as association mapping. We propose criteria to prioritise paralogues within multigene families and certain SNPs within these genes for developing genotyping assays or increasing power in association mapping studies. Although L. perenne was the target of the analyses presented here, this functional subtyping of phylogenetic clades represents a valuable tool for studies investigating monolignol biosynthesis genes in other monocot species. [ABSTRACT FROM AUTHOR]

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Triticale is the intergeneric hybrid between wheat and rye. With the expansion of the triticale growing area, powdery mildew has emerged and become a significant disease on this new host. Recent research demonstrated that this 'new' powdery mildew on triticale has emerged through a host range expansion of powdery mildew of wheat. Moreover, isolates sampled from triticale still infect their previous host, wheat, but isolates sampled from wheat hardly infect triticale. Race-specific and adult-plant resistance have been identified in triticale cultivars. The main objective of this study was to characterize the cellular basis of powdery mildew resistance in triticale. Commonalities with resistance responses in other cereals such as wheat, barley and oat are discussed. A detailed comparative histological study of various resistance responses during cross-inoculation of either virulent or avirulent wheat and triticale isolates on both hosts was carried out. The present data provide evidence that for incompatible interactions, the formation of non-penetrated papillae is the predominant resistance response, while the hypersensitive response ( HR) acts as a second line of defence, to cut the fungus off from nutrients, if penetration resistance fails. It is not clear yet what causes the slower growth and reduced colony size of triticale isolates when inoculated on wheat. Possibly, post-penetration resistance mechanisms, other than HR, are switched on during these (semi-) compatible interactions. Molecular studies on gene expression and gene function of defence-related genes might reveal further insights into the genetic basis of these resistance responses. [ABSTRACT FROM AUTHOR]

Deoxynivalenol ( DON) is one of the most prevalent toxins in Fusarium-infected wheat samples. Accurate forecasting systems that predict the presence of DON are useful to underpin decision making on the application of fungicides, to identify fields under risk, and to help minimize the risk of food and feed contamination with DON. To this end, existing forecasting systems often adopt statistical regression models, in which attempts are made to predict DON values as a continuous variable. In contrast, this paper advocates the use of ordinal regression models for the prediction of DON values, by defining thresholds for converting continuous DON values into a fixed number of well-chosen risk classes. Objective criteria for selecting these thresholds in a meaningful way are proposed. The resulting approach was evaluated on a sizeable field experiment in Belgium, for which measurements of DON values and various types of predictor variables were collected at 18 locations during 2002-2011. The results demonstrate that modelling and evaluating DON values on an ordinal scale leads to a more accurate and more easily interpreted predictive performance. Compared to traditional regression models, an improvement could be observed for support vector ordinal regression models and proportional odds models. [ABSTRACT FROM AUTHOR]

The effect of humic substances on the nutrient uptake, herbage production and nutritive value of herbage from sown grass pastures was studied in six field experiments. Commercial humic substances were applied in combination with mineral fertilizer or slurry, either as a solution (HF liquid; 8·3 kg humic substances ha−1) or incorporated into the mineral fertilizer (HF incorporated; 3·6 to 6·4 kg humic substances ha−1). A series of cuts, ranging from two to five cuts, was taken during the growing season. The general response in herbage production to application of humic substances was an increase in herbage mass of dry matter (DM) at the first cut although this was only significant in two experiments for the HF incorporated treatment. Total herbage production of DM over the growing season, however, was similar for treatments with or without application of humic substances. The overall effect of HF incorporated and HF liquid on the herbage mass of DM at the first cut across the experiments was calculated using a meta-analysis technique and it was shown that there was a significant proportional increase of 0·14 ( P < 0·05) with the HF incorporated treatment and a non-significant increase of 0·08 with the HF liquid treatment compared to the control treatment. The nutritive value of the herbage at the first cut was similar across all treatments. In general nitrogen, phosphorus and potassium uptake at the first grass cut was higher after application of humic substances but only in one experiment was this increase statistically significant. [ABSTRACT FROM AUTHOR]

The transition to sustainable agriculture and horticulture is a societal challenge of global importance. Fertilization with a minimum impact on the environment can facilitate this. Organic fertilizers can play an important role, given their typical release pattern and production through resource recovery. Microbial fertilizers (MFs) constitute an emerging class of organic fertilizers and consist of dried microbial biomass, for instance produced on effluents from the food and beverage industry. In this study, three groups of organisms were tested as MFs: a high-rate consortium aerobic bacteria (CAB), the microalga Arthrospira platensis ('Spirulina') and a purple non-sulfur bacterium (PNSB) Rhodobacter sp. During storage as dry products, the MFs showed light hygroscopic activity, but the mineral and organic fractions remained stable over a storage period of 91 days. For biological tests, a reference organic fertilizer (ROF) was used as positive control, and a commercial organic growing medium (GM) as substrate. The mineralization patterns without and with plants were similar for all MFs and ROF, with more than 70% of the organic nitrogen mineralized in 77 days. In a first fertilization trial with parsley, all MFs showed equal performance compared to ROF, and the plant fresh weight was even higher with CAB fertilization. CAB was subsequently used in a follow-up trial with petunia and resulted in elevated plant height, comparable chlorophyll content and a higher amount of flowers compared to ROF. Finally, a cost estimation for packed GM with supplemented fertilizer indicated that CAB and a blend of CAB/PNSB (85%/15%) were most cost competitive, with an increase of 6% and 7% in cost compared to ROF. In conclusion, as bio-based fertilizers, MFs have the potential to contribute to sustainable plant nutrition, performing as good as a commercially available organic fertilizer, and to a circular economy., (© 2020 The Authors. Microbial Biotechnology published by Society for Applied Microbiology and John Wiley & Sons Ltd.)

Purple non-sulphur bacteria (PNSB) are phototrophic microorganisms, which increasingly gain attention in plant production due to their ability to produce and accumulate high-value compounds that are beneficial for plant growth. Remarkable features of PNSB include the accumulation of polyphosphate, the production of pigments and vitamins and the production of plant growth-promoting substances (PGPSs). Scattered case studies on the application of PNSB for plant cultivation have been reported for decades, yet a comprehensive overview is lacking. This review highlights the potential of using PNSB in plant production, with emphasis on three key performance indicators (KPIs): fertilization, resistance to stress (biotic and abiotic) and environmental benefits. PNSB have the potential to enhance plant growth performance, increase the yield and quality of edible plant biomass, boost the resistance to environmental stresses, bioremediate heavy metals and mitigate greenhouse gas emissions. Here, the mechanisms responsible for these attributes are discussed. A distinction is made between the use of living and dead PNSB cells, where critical interpretation of existing literature revealed the better performance of living cells. Finally, this review presents research gaps that remain yet to be elucidated and proposes a roadmap for future research and implementation paving the way for a more sustainable crop production., (© 2019 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.)