Moso Bamboo Invasion Reshapes Community Structure of Denitrifying Bacteria in Rhizosphere of Alsophila spinulosa

The uncontrolled invasion of moso bamboo (Phyllostachys pubescens) dramatically alters soil nitrogen cycling and destroys the natural habitat of Alsophila spinulosa. Nevertheless, no clear evidence points out the role of denitrifying bacteria in the invasion of bamboo into the habitat of A. spinulosa. In the present study, we found that low (importance value 0.0008), moderate (0.6551), and high (0.9326) bamboo invasions dramatically altered the underground root biomass of both P. pubescens and A. spinulosa. The root biomass of A. spinulosa was maximal at moderate invasion, indicating that intermediate disturbance might contribute to the growth and survival of the colonized plant. Successful bamboo invasion significantly increased rhizospheric soil available nitrogen content of A. spinulosa, coupled with elevated denitrifying bacterial abundance and diversity. Shewanella, Chitinophaga, and Achromobacter were the primary genera in the three invasions, whereas high bamboo invasion harbored more denitrifying bacteria and higher abundance than moderate and low invasions. Further correlation analysis found that most soil denitrifying bacteria were positively correlated with soil organic matter and available nitrogen but negatively correlated with pH and water content. In addition, our findings illustrated that two denitrifying bacteria, Chitinophaga and Sorangium, might be essential indicators for evaluating the effects of bamboo invasion on the growth of A. spinulosa. Collectively, this study found that moso bamboo invasion could change the nitrogen cycling of colonized habitats through alterations of denitrifying bacteria and provided valuable perspectives for profound recognizing the invasive impacts and mechanisms of bamboo expansion.

A toolkit to rapidly modify root systems through single plant selection

Background The incorporation of root traits into elite germplasm is typically a slow process. Thus, innovative approaches are required to accelerate research and pre-breeding programs targeting root traits to improve yield stability in different environments and soil types. Marker-assisted selection (MAS) can help to speed up the process by selecting key genes or quantitative trait loci (QTL) associated with root traits. However, this approach is limited due to the complex genetic control of root traits and the limited number of well-characterised large effect QTL. Coupling MAS with phenotyping could increase the reliability of selection. Here we present a useful framework to rapidly modify root traits in elite germplasm. In this wheat exemplar, a single plant selection (SPS) approach combined three main elements: phenotypic selection (in this case for seminal root angle); MAS using KASP markers (targeting a root biomass QTL); and speed breeding to accelerate each cycle. Results To develop a SPS approach that integrates non-destructive screening for seminal root angle and root biomass, two initial experiments were conducted. Firstly, we demonstrated that transplanting wheat seedlings from clear pots (for seminal root angle assessment) into sand pots (for root biomass assessment) did not impact the ability to differentiate genotypes with high and low root biomass. Secondly, we demonstrated that visual scores for root biomass were correlated with root dry weight (r = 0.72), indicating that single plants could be evaluated for root biomass in a non-destructive manner. To highlight the potential of the approach, we applied SPS in a backcrossing program which integrated MAS and speed breeding for the purpose of rapidly modifying the root system of elite bread wheat line Borlaug100. Bi-directional selection for root angle in segregating generations successfully shifted the mean root angle by 30° in the subsequent generation (P ≤ 0.05). Within 18 months, BC2F4:F5 introgression lines were developed that displayed a full range of root configurations, while retaining similar above-ground traits to the recurrent parent. Notably, the seminal root angle displayed by introgression lines varied more than 30° compared to the recurrent parent, resulting in lines with both narrow and wide root angles, and high and low root biomass phenotypes. Conclusion The SPS approach enables researchers and plant breeders to rapidly manipulate root traits of future crop varieties, which could help improve productivity in the face of increasing environmental fluctuations. The newly developed elite wheat lines with modified root traits provide valuable materials to study the value of different root systems to support yield in different environments and soil types.

GO WIDE TO GO DEEP: AFFORDABLE, REPLICABLE ROBOTIC MINIRHIZOTRON SAMPLING FOR PHENOLOGY STUDIES

Minirhizotrons (paired camera systems and buried observatories) are the best current method to make repeatable measurements of fine roots in the field. Automating the technique is also the only way to gather high resolution data necessary for comparison with phenology-relevant above-ground remote sensing, and, when appropriately validated, to assess with high temporal resolution belowground biomass, which can support carbon budgets estimates. Minirhizotron technology has been available for half a century but there are many challenges to automating the technique for global change experiments. Instruments must be cheap enough to replicate on field scales given their shallow field of view, and automated analysis must both be robust to changeable soil and root conditions because ultimately, image properties extracted from minirhizotrons must have biological meaning. Both digital photography and computer technology are rapidly evolving, with huge potential for generating belowground data from images using modern technological advantages. Here we demonstrate a homemade automatic minirhizotron scheme, built with off-the-shelf parts and sampling every two hours, which we paired with a neural network-based image analysis method in a proof-of-concept mesocosm study. We show that we are able to produce a robust daily timeseries of root cover dynamics. The method is applied at the same model across multiple instruments demonstrating good reproducibility of the measurements and a good pairing with an above-ground vegetation index and root biomass recovery through time. We found a sensitivity of the root cover we extracted to soil moisture conditions and time of day (potentially relating to soil moisture), which may only be an issue with high resolution automated imagery and not commonly reported as encountered when training neural networks on traditional, time-distinct minirhizotron studies. We discuss potential avenues for dealing with such issues in future field applications of such devices. If such issues are dealt with to a satisfactory manner in the field, automated timeseries of root biomass and traits from replicated instruments could add a new dimension to phenology understanding at ecosystem level by understanding the dynamics of root properties and traits.

Root mass vertical distribution of perennial cool-season grasses grown in pure or mixed swards

ABSTRACT: In this study we tested whether the root biomass of mixtures composed by grass species is greater than their respective monocultures. The treatments were monocultures of Arrhenatherum elatius, Festuca arundinacea, Dactylis glomerata, and a mixture of them, cultivated in a rich-soil environment. Root biomass was evaluated on a single evaluation per season at three soil depths (0-5, 5-10, and 10-20 cm). Mixed swards presented the greatest root biomass, and this was explained by a greater concentration in the topsoil layer (0-5 cm). These findings reinforce the need for permanent soil conservation practices to not jeopardize the benefits of the more abundant root biomass reported in the mixed swards.

Mineral Fertilization Influences the Growth, Cryptolepine Yield, and Bioefficacy of Cryptolepis sanguinolenta (Lindl.) Schlt.

Cryptolepis sanguinolenta (Lindl.) Schlt., the main source of cryptolepine alkaloid, is intensively exploited in the wild to treat malaria and Lyme disease. In this study, the influence of four inorganic fertilizers (supplying N, P, K, or NPK) and four growth periods (3, 6, 9, and 12 months after transplanting) on the herb’s root biomass, cryptolepine content and yield, and biological activities were investigated in a pot and field trial. The results showed the application of N (in the form of Urea or NPK) increased root biomass yield, cryptolepine content, and cryptolepine yield compared to unfertilized plants. The 9-month-old plants recorded the maximum cryptolepine content (2.26 mg/100 mg dry root) and cryptolepine yield (304.08 mg/plant), indicating the perfect time to harvest the herb. Plant age at harvest had a more significant influence (50.6–55.7%) on cryptolepine production than fertilizer application (29.2–33.3%). Cryptolepine extracts from 9- to 12-month-old plants had the highest antiplasmodial activity (IC50 = 2.56–4.65 µg/mL) and drug selectivity index (2.15–3.91) against Plasmodium falciparum Dd2. These extracts were also cytotoxic to Jurkat leukaemia cell lines (CC50 < 62.56 µg/mL), indicating the possible use of cryptolepine for cancer management. Growing the herb in the field increased cryptolepine yield 2.5 times compared to growth in a pot, but this did not influence the antiplasmodial activity of the extract. Commercial cultivation of C. sanguinolenta for 9 months combined with N application could be a promising solution to the sustainable use of this threatened medicinal species.