Reproductive fitness in common bean (Phaseolus vulgaris L.) under drought stress is associated with root length and volume

Variability in drought stress response in a panel of 100 faba bean genotypes

Faba bean is an important protein crop for food and feed worldwide and provides a range of advantages in crop rotations. Its limited use in modern agriculture is mainly due to the high fluctuations in yield. A well known limiting factor in most legumes, and particularly in faba bean, is the high sensitivity to water shortage, which is further aggravated by climate change. The present study was undertaken to exploit the genetic variation in drought stress response in a faba bean collection of 100 accessions with diverse origins and to assess selection criteria for identifying drought tolerant genotypes. Physiological, phenological and yield related traits evaluated under drought or water-sufficient conditions responded significantly to the end-terminated drought stress. Comparison of yield relations showed the advantage of using a stress tolerance index (STI) to identify genotypes combining high yield potential with high stress yield. With regard to physiological traits, SPAD (chlorophyll content) values were significantly related to yield as well as to STI, while the other traits also contributed to different extents to variation in yield formation. Among the yield related traits, seeds per plant proved to be the most important trait followed by pods per plant. Interestingly, the eight genotypes with the best STI performance use different strategies to cope with drought stress.

Response characteristics of root to moisture change at seedling stage of Kengyilia hirsuta

Kengyilia hirsuta is an important pioneer plant distributed on the desertified grassland of the Qinghai-Tibet Plateau. It has strong adaptability to alpine desert habitats, so it can be used as a sand-fixing plant on sandy alpine land. To study the response mechanisms of root morphological and physiological characteristics of K. hirsuta to sandy soil moisture, 10%, 25% and 40% moisture levels were set up through potted weighing water control method. The biomass, root-shoot ratio, root architecture parameters, and biochemical parameters malondialdehyde, free proline, soluble protein, indole-3-acetic acid, abscisic acid, cytokinin, gibberellin, relative conductivity and antioxidant enzyme activities were measured in the trefoil stage, and the response mechanisms of roots at different moisture levels were analyzed. The results showed that with the increase of soil moisture, root morphological indexes such as root biomass, total root length, total root volume and total root surface increased, while the root topological index decreased continuously. The malondialdehyde content, relative conductivity, superoxide dismutase activity, peroxidase activity, catalase activity, free proline content, soluble protein content, abscisic acid content and cytokinin content at the 25% and 40% moisture levels were significantly decreased compared with the 10% level (P< 0.05). Thus, the root growth of K. hirsuta was restricted by the 10% moisture level, but supported by the 25% and 40% moisture levels. An artificial neural network revealed that total root length, total root surface area, root link average length, relative conductivity, soluble protein, free proline and moisture level were the key factors affecting root development. These research results could contribute to future agricultural sustainability.

Root Trait Variation in Lentil (Lens culinaris Medikus) Germplasm under Drought Stress

Drought is the most critical environmental factor across the continents affecting food security. Roots are the prime organs for water and nutrient uptake. Fine tuning between water uptake, efficient use and loss determines the genotypic response to water limitations. Targeted breeding for root system architecture needs to be explored to improve water use efficiency in legumes. Hence, the present study was designed to explore root system architecture in lentil germplasm in response to drought. A set of 119 lentil (Lens culinaris Medik.) genotypes was screened in controlled conditions to assess the variability in root traits in relation to drought tolerance at seedling stage. We reported significant variation for different root traits in lentil germplasm. Total root length, surface area, root volume and root diameter were correlated to the survival and growth under drought. Among the studied genotypes, the stress tolerance index varied 0.19–1.0 for survival and 0.09–0.90 for biomass. Based on seedling survival and biomass under control and drought conditions, 11 drought tolerant genotypes were identified, which may be investigated further at a physiological and molecular level for the identification of the genes involved in drought tolerance. Identified lines may also be utilised in a lentil breeding program.

Response of common bean (Phaseolus vulgaris L.) growth to soil contaminated with microplastics

Although concerns surrounding microplastics (MPs) in terrestrial ecosystems have been growing in recent years, little is known about the responses of plant growth to MPs pollution. Here, we conducted a pot experiment in a net house under natural condition by adding two types of MPs, low-density polyethylene (LDPE-MPs) and polylactic acid (PLA) mixed with poly-butylene-adipate-co-terephthalate (PBAT, Bio-MPs), to sandy soil at 5 doses (0.5%, 1.0%, 1.5%, 2.0%, 2.5% ω/ω dry soil weight). The effects of LDPE-MPs and Bio-MPs on common bean (Phaseolus vulgaris L) were tested. Compared to control (no MPs addition), LDPE-MPs showed no significant effects on shoot, root and fruit biomass while ≥1.0% LDPE-MPs showed significant higher specific root nodules (n·g^-1 dry root biomass) and only 2.5% LDPE-MPs showed significant higher specific root length (cm·g^-1 dry root biomass). 1.0% LDPE-MPs caused significant higher leaf area and 0.5% LDPE-MPs caused significant lower leaf relative chlorophyll content. For Bio-MPs treatment, compared to control, ≥1.5% Bio-MPs showed significant lower shoot and root biomass. ≥2.0% Bio-MPs showed significant lower leaf area and fruit biomass. All Bio-MPs treatments showed significant higher specific root length and specific root nodules as compared to control. The results of the current research show that both MPs induced the responses of common bean growth, and ≥1.5% Bio-MPs exerted stronger effects. Further studies of their ecological impacts on soil-plant systems are urgently needed.

Effect of sire population on the genetic diversity and fitness of F1 progeny in the endangered Chinese endemic Sinocalycanthus chinensis

Sinocalycanthus chinensis Cheng et S. Y. Chang (Calycanthaceae), which has a unique systematic status, is listed as a national second-class protected plant of China. In this study, the genetic diversity, performance, and fitness of F1 progeny from crosses between the Damingshan (DMS) population of S. chinensis and pollen parents from the Daleishan (DLS) and Longxushan (LXS) populations were examined. The DLS population has a relatively small population size, low genetic diversity, and considerable geographical and genetic distances from the DMS population relative to the LXS population. Compared with naturally occurring seeds, DLS-sired seeds had the highest thousand-seed weight, starch content, fat content, germination rate, germination index, and emergence rate, but the lowest protein content. Naturally occurring, open-pollinated seeds had the lowest thousand-seed weight, starch content, and fat content, but the highest protein content. Compared with natural F1 progeny, DMS × DLS seedlings had the highest genetic diversity, photosynthetic parameters, and growth characteristics, except for leaf mass ratio and stem mass ratio. Under strong light, DMS × DLS seedlings exhibited a F v/F m value of 0.75, while the other two seedling types exhibited F v/F m values of 0.65. DLS-sired seeds had the most vigorous growth characteristics except for leaf mass ratio and stem mass ratio. These results suggest that genetic rescue by transplanting seedlings from the DLS population or hand pollination with pollen from the DLS population would be effective methods to reduce inbreeding depression and obtain strong offspring with high genetic diversity and fitness in the DMS population.

Alien chromosome segment from Aegilops speltoides and Dasypyrum villosum increases drought tolerance in wheat via profuse and deep root system

BACKGROUND

Recurrent drought associated with climate change is a major constraint to wheat (Triticum aestivum L.) productivity. This study aimed to (i) quantify the effects of addition/substitution/translocation of chromosome segments from wild relatives of wheat on the root, physiological and yield traits of hexaploid wheat under drought, and (ii) understand the mechanism(s) associated with drought tolerance or susceptibility in wheat-alien chromosome lines.

METHODS

A set of 48 wheat-alien chromosome lines (addition/substitution/translocation lines) with Chinese Spring background were used. Seedling root traits were studied on solid agar medium. To understand the influence of drought on the root system of adult plants, these 48 lines were grown in 150-cm columns for 65 d under full irrigation or withholding water for 58 d. To quantify the effect of drought on physiological and yield traits, the 48 lines were grown in pots under full irrigation until anthesis; after that, half of the plants were drought stressed by withholding water for 16 d before recording physiological and yield-associated traits.

RESULTS

The alien chromosome lines exhibited altered root architecture and decreased photochemical efficiency and seed yield and its components under drought. The wheat-alien chromosome lines T5DS·5S#3L (TA5088) with a chromosome segment from Aegilops speltoides (5S) and T5DL.5 V#3S (TA5638) with a chromosome segment from Dasypyrum villosum (5 V) were identified as drought tolerant, and the drought tolerance mechanism was associated with a deep, thin and profuse root system.

CONCLUSIONS

The two germplasm lines (TA5088 and TA5638) could be used in wheat breeding programs to improve drought tolerance in wheat and understand the underlying molecular genetic mechanisms of root architecture and drought tolerance.

Research Progress and Perspective on Drought Stress in Legumes: A Review

Climate change, food shortage, water scarcity, and population growth are some of the threatening challenges being faced in today's world. Drought stress (DS) poses a constant challenge for agricultural crops and has been considered a severe constraint for global agricultural productivity; its intensity and severity are predicted to increase in the near future. Legumes demonstrate high sensitivity to DS, especially at vegetative and reproductive stages. They are mostly grown in the dry areas and are moderately drought tolerant, but severe DS leads to remarkable production losses. The most prominent effects of DS are reduced germination, stunted growth, serious damage to the photosynthetic apparatus, decrease in net photosynthesis, and a reduction in nutrient uptake. To curb the catastrophic effect of DS in legumes, it is imperative to understand its effects, mechanisms, and the agronomic and genetic basis of drought for sustainable management. This review highlights the impact of DS on legumes, mechanisms, and proposes appropriate management approaches to alleviate the severity of water stress. In our discussion, we outline the influence of water stress on physiological aspects (such as germination, photosynthesis, water and nutrient uptake), growth parameters and yield. Additionally, mechanisms, various management strategies, for instance, agronomic practices (planting time and geometry, nutrient management), plant growth-promoting Rhizobacteria and arbuscular mycorrhizal fungal inoculation, quantitative trait loci (QTLs), functional genomics and advanced strategies (CRISPR-Cas9) are also critically discussed. We propose that the integration of several approaches such as agronomic and biotechnological strategies as well as advanced genome editing tools is needed to develop drought-tolerant legume cultivars.