Journal of Experimental Botany最新文献

Pigeonpea (Cajanus cajan L. Millsp.) is a grain legume crop that is crucial for food and nutrition security in the sub-tropical regions of Asia and Africa. However, its production is constrained by undesirable varietal features and susceptibility to biotic and abiotic stresses. There is an urgent need to develop pigeonpea varieties with ideotype combining traits needed by the stakeholders. Landraces and wild relatives of pigeonpea are rich source of genes for genetic advance towards the desired ideotype. Pigeonpea genome and extensive transcriptome data required for gene discovery are available. Simple sequence repeat and single nucleotide polymorphism marker assays have been designed and used in mapping of genes and quantitative trait loci for key traits, but these need to be validated and utilized in breeding. Pigeonpea genetically modified for pod borer resistance is awaiting regulatory approval, and the power of genome editing is poised to be harnessed. Marker-assisted selection is still not a practical reality in pigeonpea, but mapping studies position the crop for future breakthroughs. Marker-assisted selection is expected to play a greater role in accelerating pigeonpea ideotype breeding. This review provides a comprehensive account of stakeholder preferences of varietal traits and genetic and genomic resources to help devise molecular breeding strategies for pigeonpea.

Wheat production is continually threatened by stripe and leaf rust because virulent races rapidly overcome single race-specific genes. Durable, broad-spectrum resistance is needed. Adult plant resistance (APR) provides partial, stable resistance from multiple minor-effect loci acting additively; pleiotropic loci like Lr34/Yr18 and Lr46/Yr29 add durability. We used an elite Australian panel (OzWheat=589) and a diverse landrace panel (Vavilov=295), genotyped with ∼30K SNPs and phenotyped across environments. Linkage disequilibrium partitioning defined 7,659 genome-wide haploblocks. To prioritise robust signals, we ranked haploblocks by haplotype effect variance and examined the top 100 per trait. For stripe rust, 52/100 were significant, with 32 shared across panels; for leaf rust, 50 were significant, 29 also detected in Vavilov. Several intervals co-localised with APR regions (Lr46/Yr29), and one 7BL interval intersected seedling gene Lr14a. To translate mapping into breeding decisions, we developed an introgression fitness index to quantify the value of resistant haplotypes in elite backgrounds. Using elite cultivar Scepter, we applied a genetic algorithm to select 50 donor parents carrying desirable haplotypes. Simulations showed that pyramiding these haplotypes can enhance resistance while maintaining elite genomic background. This study provides practical breeding tools, including haplotype catalogue and a novel selection index to accelerate rust-resistant wheat development.

The flag leaf is a major contributor of photosynthetic assimilates to developing grains. We investigated the genetic architecture and cellular basis of flag leaf length (FLL) and width (FLW) in a multiparent population of 45 recombinant inbred line (RIL) populations (HvDRR) in barley. Fine-mapping of a major quantitative trait locus (QTL) was performed to prepare the isolation of the causal gene. Natural variation of FLL and FLW across environments was highly heritable, and genotypes from warm climates produced longer and wider flag leaves than those from cooler regions. Variation in flag leaf size was quantitatively inherited and influenced by 24 consensus QTLs, of which 17 have not previously been reported. Validation of QTLs qHvDRR-FLS-8 and qHvDRR-FLS-17 in nearly isogenic RILs showed that these QTLs also controlled length and width of leaves older than the flag leaf. The number of epidermal cells primarily determined FLL, whereas the number and size of epidermal cells collectively determined FLW differences. In addition, we identified the previously unknown effect of genic alleles and epialleles at Vrn-H1 on flag leaf size variation in spring barley. Furthermore, we fine-mapped qHvDRR-FLS-8, narrowing the interval from 8.7 Mb to 3.5 Mb. In conclusion, our study identified the genomic regions associated with morphological and anatomical variation for leaf size and set the stage to uncover causal genes.

Growing plants are remarkable at negotiating obstacles in their unstructured and changing environments. Measuring the mechanical interactions of growing plants with surrounding objects is a critical step towards deciphering thigmotropic responses underpinning complex growth strategies. Yet, available force measurement systems have limited capacity to capture weak forces in freely moving plant organs-such as the forces applied by a growing shoot pushing at an obstacle. We developed a measurement system based on the deflection of a pendulum by a freely moving shoot. Unlike many force measurement systems, the organ is not tethered to the device. Moreover, force is measured along two axes, as opposed to one axis in commonly used methods. Orthogonal cameras track the 3D position of the rod and shoot, yielding the rod deflection angle and, using a mechanical torque equilibrium equation, allowing extraction of the force applied by the plant over time. This system is relevant for measuring weak forces in macro-sized systems (e.g. growth or turgor pressures), and the force detection range can be tuned by altering rod mass and length. We demonstrate the system with Phaseolus vulgaris shoots, measuring the forces they apply on a candidate support during inherent circumnutation movements, prior to twining. Such measurements lay the foundations for deciphering how climbing plants assess whether to twine or not- an open question since Darwin's first observations.

Crassulacean acid metabolism (CAM) plants primarily fix atmospheric CO2 at night and store it as malic acid in their vacuoles. During daytime, the vacuolar malate is remobilised and decarboxylated to supply CO2 for Rubisco assimilation. Light intensity and photoperiod play crucial roles in regulating this process, but their influences on the underlying molecular and biochemical mechanisms remain unclear. In this study, physiological, biochemical, and molecular approaches were integrated to uncover the temporal patterns and light responsiveness of gene transcript and protein abundances, and the activities of enzymes involved in diurnal malate remobilisation in the obligate CAM plant Kalanchoë fedtschenkoi. Vacuolar malate transport was primarily influenced by the endogenous clock and photoperiod, with the ALUMINIUM-ACTIVATED MALATE TRANSPORTER 4 (ALMT4) being a more plausible transporter candidate than the TONOPLAST DICARBOXYLATE TRANSPORTER (tDT). Malate decarboxylation was mainly dictated by photoperiod, with light intensity playing a supplementary role. Both photoperiod and light intensity greatly affected CO2 refixation and pyruvate recycling, with PYRUVATE ORTHOPHOSPHATE DIKINASE (PPDK) being the most strictly light-regulated player at the mRNA, protein abundance and activity levels, closely matching malate dynamics. Overall, PPDK seems to be a key regulator of light-dependent diurnal deacidification in CAM leaves, rather than the vacuolar malate transport or decarboxylation processes.

Tree height varies across environments, with taller individuals found in cool, moist habitats and shorter trees in drier regions. Within species, trees can exhibit height variation due to environmental factors such as drought-induced dieback. A key question is what drives changes in leaf structure with increasing height-whether some trait values cannot be produced under the developmental conditions at treetops or whether differences arise because natural selection favors particular trait values at different canopy positions. Some hypotheses suggest that increasing height imposes 'limits' on mature leaf traits, making some structural changes developmentally inevitable. However, selection could also favor structural changes within wide fields of developmentally possible trait configurations. We examined leaf epidermal cell size distributions in Bursera simaruba and Eucalyptus camaldulensis from seedlings to maximum tree heights in situations in which seedlings to adults were all exposed to full sun and thus had all 'sun' leaves. We found that in general cell sizes increased, variance remained high, and distributions did not systematically shift with height. These results indicate that, rather than reflecting a developmental inability to produce certain leaf epidermal cell sizes at greater heights, the patterns we observed are better explained by selection simply favoring some cell sizes from among the many that development can produce.

Tea gray blight disease represents a major fungal threat to tea plants, leading to substantial reductions in yield and declines in quality. It is prevalent in tea plantations globally. Given the considerable genetic diversity of pathogen populations across various tea-growing regions, understanding the population structure and pathogenic variation of dominant pathogens is essential for the development of sustainable ecological and economic management strategies. In this study, seven isolates of Pseudopestalotiopsis camelliae-sinensis, one of Pestalotiopsis camelliae, and one of Neopestalotiopsis sp. were identified from diseased leaves of Camellia sinensis 'Fudingdabai' in Shaanxi, China. Strain '10' demonstrated the highest pathogenicity and was identified as the primary pathogen responsible for gray blight. By assessing lesion area, leaf architecture, and biochemical constituents, the resistance levels of 20 tea cultivars were classified as highly resistant (one), resistant (four), intermediate resistant (eight), susceptible (five), and highly susceptible (two). Dynamic enzyme activity assays demonstrated a positive correlation between disease resistance in tea cultivars and the activities of peroxidase and phenylalanine ammonia-lyase, establishing a resistance hierarchy as follows: 'Longjingchangye'>'Zhongcha 108'>'Longjing 43'. Notably, cultivars exhibiting resistance showed significantly stabilized superoxide dismutase activity in comparison with susceptible genotypes. Cytological analyses of tea gray blight disease infection in highly resistant ('Longjingchangye'), highly susceptible ('Longjing 43'), and intermediate resistant ('Zhongcha 108') cultivars revealed a significantly reduced presence of appressoria and infection pegs in resistant genotypes relative to the susceptible cultivar. These findings provide a scientific foundation for the breeding of disease-resistant tea varieties and contribute to the understanding of plant-fungal pathogen interaction mechanisms.

The species Alternanthera philoxeroides is a flood-tolerant plant that has to cope with the hypoxic stress under submergence. However, the pith cavity in stems of this species is interrupted and partitioned by low-porosity diaphragms at the nodes. To date little knowledge is available about whether discontinuous pith cavities are functional for internal gas transport in plants. To disclose the role of stem discontinuous pith cavities in internal gas transport, the diffusive transport capacity of O2, the tissue O2 status of intact plants, and the influence of restricting longitudinal O2 supply on whole-plant growth during partial submergence were assessed. We found that stem pith cavities were the main pathway for diffusional supply of molecular O2; blocking only one internode significantly decreased the O2 flux to lower internodes, and the reduced O2 flux translated into reduced growth in partially submerged plants. A major output component of the study is a model that uses normalized tissue dimensions and concentration gradients to establish a fair foundation for comparison of contrasting species under different experimental conditions. We therefore predict that future studies will use this approach to further broaden the scope and value of resistance and flux measurement in target species.

Root system architecture affects water and mineral uptake and is important for plant adaptation to fluctuating nutrient availability. Small signaling peptides and their receptors influence root traits associated with macronutrient uptake. In this study, genome-wide association analyses were performed using 2D images of agar plate-grown Medicago truncatula accessions to understand the impact of GOLVEN10 peptide (GLV10) treatment on three root traits: root tortuosity, lateral root (LR) branch angle, and the gravity setpoint angle (GSA). Upon GLV10 treatment, roots of wild-type M. truncatula Jemalong A17 and R108 accessions showed increased primary root coiling (or tortuosity), increased LR branch angle, and reduced GSA. We identified 88 significant single nucleotide polymorphisms (SNPs) associated with these traits in GLV10-treated plants, distinct from the 163 SNPs in untreated plants. Importantly, the ethylene regulatory pathway was implicated in root tortuosity and LR emergence relative to the primary root. Application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid reduced root sensitivity to GLV10, while the ethylene signaling mutant sickle was hypersensitive, indicating that GLV10 and ethylene pathways act antagonistically to control root tortuosity. These findings have implications for root gravitropic responses, and the ability of roots to penetrate deeper soil layers for nutrients and water.