Phenological Traits Research Articles

Anatomical distribution of starch in the stemwood influences carbon dynamics and suggests storage‐growth trade‐offs in some tropical trees

Abstract Trees balance temporal asynchrony in carbon source and sink activity by accumulating and using non‐structural carbon (NSC). Previous work has demonstrated differences in the amount and distribution of NSC stored in stemwood in tropical tree species and related these patterns in NSC distribution to tree growth and mortality rates. However, we still do not know how changes in the amount and location of starch, a major component of NSC in stemwood, influence the seasonal carbon dynamics of mature trees and how this may reflect storage‐growth trade‐offs. In this work, we hypothesized that combining two life history traits, here leaf habit (evergreen/semi‐deciduous) and the anatomical distribution of starch within the stemwood (parenchyma storage and fibre storage), would allow us to explain differences in the seasonal interplay between carbon sources and sinks and the use and accumulation of starch in the tree stem. We expected semi‐deciduous/fibre‐storing species to have greater seasonal amplitudes of carbon source and sink activity, and therefore greater variation in starch content and stronger storage‐growth trade‐offs than evergreen/parenchyma‐storing species. We measured monthly increments in stem radial growth, soluble sugars and starch every 3 months during 2019 in Dacryodes microcarpa (semi‐deciduous/fibre‐storing species), Ocotea leucoxylon (evergreen/parenchyma‐storing species) and Sacoglottis guianensis (semi‐deciduous/parenchyma‐storing species). We found seasonal changes in starch but not sugars in the semi‐deciduous species, with greater amplitude in the fibre‐storing species that also had greater storage capacity and stem respiration rates. The fibre‐storing species further showed a negative relationship between starch consumption/accumulation and growth during the rainy season, suggesting a trade‐off between growth and storage, with starch accumulating in some cases when growth was low. Synthesis. Our results show the influence of seasonal starch storage on carbon dynamics in three species of tropical trees that differ in leaf phenology and starch storage traits. Semi‐deciduous/fibre‐storing species have greater temporal variation in carbon sink activities and more seasonally dynamic starch content. Since the fibre‐storing species we studied are slower‐growing and longer‐lived trees with lower mortality rates compared to the parenchyma‐storing species, these results may provide clues about how storage traits could influence their survival and life span.

Investigating of Genetic Diversity of some Coriander (Coriandrum sativum L.) Landraces in for Phenological, Morphological and Agronomic Traits

Investigating of Genetic Diversity of some Coriander (Coriandrum sativum L.) Landraces in for Phenological, Morphological and Agronomic Traits

Epibrassinolide application improves Brassica juncea L. performance by augmenting gas exchange markers, stomatal behavior, cellular viability, enzymatic activities and yield attributes

Epibrassinolide (EBL) is an emerging plant growth regulator of the brassinosteroids group that has the potential to modulate various morpho-physiological processes in plants. Therefore, due to its key role in boosting plant functioning mechanisms, it is widely used in agriculture to enhance crop growth and yield. The present research work was planned to investigate the role of exogenously applied EBL on the mustard crop by assessing morphological, physiochemical, and yield features. This randomized pot experiment contains three mustard cultivars i.e., Rohini (Roh), Chutki (Chk), and Nath Sona (Nas) and various graded levels of EBL, 0 (Control), 10−8 M, 10−7 M, 10−6 M, 10−5 M, and 10−4 M. EBL was applied twice by giving first spray at 50 days after sowing (DAS) and the second at 70 DAS. Evaluation of plants was done at 90 DAS to study phenological traits, gas exchange attributes, non-enzymatic antioxidant activities, and microscopical parameters. The yield and quality features were studied at 120 DAS. The results revealed that treatment of 10−6 M EBL proved effective and increased fresh weight by 17.76 %, 19.11 %, and 19.34 %, chlorophyll content by 26.50 %, 26.59 %, and 25.86 %, net photosynthetic rate by 45.67 %, 57.88 % and 49.76 %, protein content by 66.98 %, 68.62 % and 69.47 %, proline content by 25.70 %, 24.05 % and 21.87 %, ascorbate content by 94.91 %, 89.99 % and 87.43 %, carbonic anhydrase activity by 32.43 %, 30.84 % and 29.93 %, seed yield by 44.85 %, 51.36 %, and 57 % and oil yield by 68.75 %, 72.71 % and 74.34 % in cultivars Nas, Roh, and Chk respectively over the control plants. Moreover, 10−6 M EBL supplementation significantly improved stomatal aperture width and root cell longevity. Cultivar Nas, followed by cultivars Roh and Chk, showed better responses on nearly all characters studied. The effect of EBL treatment in terms of enhancing the performance of the crop being in the order of 10−6 M > 10−7 M > 10−8 M > 10−5 M > 10−4 M. It may be concluded that among sprayed EBL levels, two sprays of 10−6 M EBL proved efficacious in improving the phenotypic, physiochemical, and yield traits of mustard cultivars.

Challenges and Opportunities behind the Use of Herbaria in Paleogenomics Studies.

Paleogenomics focuses on the recovery, manipulation, and analysis of ancient DNA (aDNA) from historical or long-dead organisms to reconstruct and analyze their genomes. The aDNA is commonly obtained from remains found in paleontological and archaeological sites, conserved in museums, and in other archival collections. Herbarium collections represent a great source of phenotypic and genotypic information, and their exploitation has allowed for inference and clarification of previously unsolved taxonomic and systematic relationships. Moreover, herbarium specimens offered a new source for studying phenological traits in plants and for disentangling biogeography and evolutionary scenarios of species. More recently, advances in molecular technologies went in parallel with the decreasing costs of next-generation sequencing (NGS) approaches, which paved the way to the utilization of aDNA for whole-genome studies. Although many studies have been carried out combining modern analytic techniques and ancient samples, such as herbarium specimens, this research field is still relatively unexplored due to the need for improving strategies for aDNA manipulation and exploitation from ancient samples. The higher susceptibility of aDNA to degradation and contamination during herbarium conservation and manipulation and the occurrence of biochemical postmortem damage can result in a more challenging reconstruction of the original DNA sequence. Here, we review the methodological approaches that have been developed for the exploitation of historical herbarium plant materials, such as best practices for aDNA extraction, amplification, and genotyping. We also focus on some strategies to overcome the main problems related to the utilization of herbarium specimens for their exploitation in plant evolutionary studies.

Do different vegetative organs exhibit a similar temperature sensitivity in growth?

Although phenology and growth traits of leaves or woods have been the focus of research on growth-climate relationships, more is needed regarding whether there is a consistent growth response of different organs to environmental change. However, such work is crucial to accurately assess the impact of climate change on tree growth. Here, the growth timing, duration, rate, and increment of Picea meyeri needles, shoots, and stems were examined, and the corresponding environmental effects were revealed along an altitudinal gradient (2040–2740 m a.s.l.) in North-Central China during 2016 and 2017. The three organs showed a consistent altitudinal variation in growth onset timing, but a different variation in other traits; the growth duration, rate, and increment of needles changed slightly while those of shoots and stems dropped markedly with altitude. The air temperature was the key environmental factor driving the altitudinal variation. For each 1 °C increase in air temperature, the onset timing of needle and shoot elongation and xylem cell production was synchronously advanced by 3.3–3.7 ± 0.2 days; the peak timing was advanced by 3.4 ± 0.2 days, 2.2 ± 0.1 days, and 0 days; and the cessation timing was delayed by −3.8 ± 0.0 days, 2.1 ± 0.3 days, and 2.4 ± 0.1 days. Meanwhile, the duration was lengthened by 0 days, 5.6 ± 0.3 days, and 6.4 ± 0.2 days, respectively; the average rate was improved by 0%, 7.0 ± 1.2%, and 6.5 ± 0.5%, respectively; the increment was increased by 1.3 ± 0.1%, 8.2 ± 0.4%, and 11.0 ± 0.4%, respectively. These findings suggested that the aboveground vegetative growth of P. meyeri exhibits different temperature sensitivities; stem growth will benefit more from future warming than shoot and needle growth. It adds a new clue to conducting growth-climate relationship studies, and the response difference of organ growth to temperature should be considered in revealing future climate warming on tree growth.

Identification and characterization of photo-thermo insensitive cowpea (Vigna unguiculata) genotypes for hot arid environment

High green pod yield, dual purpose type, earliness and photo-thermo insensitivity are the major breeding objectives of cowpea [Vigna unguiculata (L.) Walp.]. Photo-thermo sensitivity makes this crop vulnerable to photoperiod and temperature fluctuations particularly in hot arid regions, thereby affecting its yield potential drastically. Therefore, the present study was aimed to identify such elite genotypes with photo-thermo insensitivity, which can fit well across all seasons under hot arid environment. The experiments were conducted at ICAR-Central Institute for Arid Horticulture, Bikaner during rainy and summer seasons of 2019–20 and 2020–21. A wide range of variability among genotypes was observed with respect to various phenological and yield traits over the environments. Among the evaluated genotypes, AHCP-1-4-1 and AHCP-2-3 were found photo-thermo insensitive as these were able to flower and set pods at temperatures as low as 10oC and as high as 46°C. Pollen viability studies indicated that AHCP-1-4-1 had 83.72 and 88.24% pollen viability and AHCP-2-3 had 81.58 and 85.71% viable pollen at 11°C and 46°C, respectively and normal pollen tube growth at both the extremes of temperature. The identified genetic resources will contribute for developing photo-thermo insensitive cultivars and will improve the productivity and extend the availability of cowpea with quality pod yield across all seasons and locations of hot arid regions.

Exploring agronomic traits and breeding prospects of primary tritipyrum and triticale lines to increase grain yield potential

A study was conducted to evaluate 13 non-Iranian primary tritipyrum (AABBEbEb, 2n=6x=42) as new amphiploid cereal derived from the hybridization of wild sand couch grass species, Thinopyrum bessarabicum (2n=4x=14, EbEb) and durum (Triticum durum, 2n=4x=28, AABB) wheat and five promising triticales for 31 different phenological and agronomic traits in a randomized complete block design (RCBD) with three replications under field conditions. The analysis of variance (ANOVA) showed significant differences between genotypes for most of the studied traits. The factor analysis results revealed five factors that almost explained 89% of the total variance. The stepwise regression and path coefficient analyses revealed that the number of grains per spike and harvest index were the most important traits contributing to the high-yield of the genotypes. Cluster analysis grouped 18 lines into three diverse genotypic clusters. Cluster III included 4115, 4116, and M45 triticale lines indicating the highest value for harvest index as well as grain yield and its components. The non-Iranian primary combined tritipyrum line, (Ka/b)(Cr/b)-5 and promising triticale line No. 4116, showed the highest values for grain-related traits, and therefore these lines may be used in further breeding programs to develop new commercial cereal hybrid/cultivars. Overall, the results indicated grain number per spike and harvest index could be utilized as the key selection criteria in breeding for improvement of grain yield in primary tritipyrum and triticale genotypes.

Genome-wide association studies for phenological and agronomic traits in mungbean (Vigna radiata L. Wilczek).

Mungbean (Vigna radiata L. Wilczek) is one of the important warm-season food legumes, contributing substantially to nutritional security and environmental sustainability. The genetic complexity of yield-associated agronomic traits in mungbean is not well understood. To dissect the genetic basis of phenological and agronomic traits, we evaluated 153 diverse mungbean genotypes for two phenological (days to heading and days to maturity) and eight agronomic traits (leaf nitrogen status using SPAD, plant height, number of primary branches, pod length, number of pods per plant, seeds per pod, 100-seed weight, and yield per plant) under two environmental conditions. A wide array of phenotypic variability was apparent among the studied genotypes for all the studied traits. The broad sense of heritability of traits ranged from 0.31 to 0.95 and 0.21 to 0.94 at the Delhi and Ludhiana locations, respectively. A total of 55,634 genome-wide single nucleotide polymorphisms (SNPs) were obtained by the genotyping-by-sequencing method, of which 15,926 SNPs were retained for genome-wide association studies (GWAS). GWAS with Bayesian information and linkage-disequilibrium iteratively nested keyway (BLINK) model identified 50 SNPs significantly associated with phenological and agronomic traits. In total, 12 SNPs were found to be significantly associated with phenological traits across environments, explaining 7%-18.5% of phenotypic variability, and 38 SNPs were significantly associated with agronomic traits, explaining 4.7%-27.6% of the phenotypic variability. The maximum number of SNPs (15) were located on chromosome 1, followed by seven SNPs each on chromosomes 2 and 8. The BLAST search identified 19 putative candidate genes that were involved in light signaling, nitrogen responses, phosphorus (P) transport and remobilization, photosynthesis, respiration, metabolic pathways, and regulating growth and development. Digital expression analysis of 19 genes revealed significantly higher expression of 12 genes, viz. VRADI01G08170, VRADI11G09170, VRADI02G00450, VRADI01G00700, VRADI07G14240, VRADI03G06030, VRADI02G14230, VRADI08G01540, VRADI09G02590, VRADI08G00110, VRADI02G14240, and VRADI02G00430 in the roots, cotyledons, seeds, leaves, shoot apical meristems, and flowers. The identified SNPs and putative candidate genes provide valuable genetic information for fostering genomic studies and marker-assisted breeding programs that improve yield and agronomic traits in mungbean.

Genetic and phenotypic characterization of Tinopiro (Thinopyrum intermedium) as a dual-purpose perennial crop in the Southern Cone: Doctoral thesis abstract

Agriculture based on annual crops requires intensive input management, which has been associated with significant degradation of natural resources. The development of perennial grain crops such as intermediate wheatgrass - (Thinopyrum intermedium) may greatly contribute to reduce this problem, however, previous research has been carried out in high latitude environments and there is no information on this crop for temperate regions with mild winters. The aims of this thesis were a) to determine the cold requirements of intermediate wheatgrass, b) to evaluate the agronomic performance of intermediate wheatgrass managed as a dual-purpose crop in Uruguay, c) to understand the genetic architecture of grain and forage yield components in intermediate wheatgrass under dual-purpose management. Three experiments were carried out, the first one in growth chambers and the other two in the field during two years in Paysandú, Uruguay. Flowering percentage and most grain yield components increased as the length of the cold incubation period at 5°C and 10 h photoperiod increased from 3 to 7 weeks. High intra-population phenotypic diversity was estimated. The effects of two populations produced under contrasting environments and the effects of three doses of nitrogen on grain and forage yield under dual-purpose management were evaluated in the second experiment. The first year, both populations had similar flowering percentages of about 48%, which resulted in an average grain yield of 316 kg ha -1. The average forage yield for the first year was 14695 kg ha -1 and decreased to 4037 kg ha -1 the second year. Fertilization with 160 kg ha -1 nitrogen increased grain yield by 63% and forage yield by 28%. In the third experiment, grain yield components, forage and phenological traits were evaluated in 30 half-sib families. Most of the traits evaluated showed no genotype x age interaction. Indirect selection for spikes per plant and/or yield per spike could have a greater response to selection than direct selection for yield per plant. No trade-off was detected between grain yield components and aboveground biomass production. These results suggest that expansion of this species as a dual-purpose crop to temperate regions with mild winters is feasible after some cycles of selection.

Long-term adjustment of phytoplankton structure to environmental traits at timescales during lifetime development and over generations

Long-term ecological research of deep Lake Mondsee covers over more than six decades of phytoplankton observation. According to our study, phytoplankton groups of various phenological traits are suitable to address the impact of two major environmental stressors: nutrient surplus by eutrophication from 1968 to 1998 and warming by climate change. Here, we focus on phytoplankton biovolume, phytoplankton assemblage structure, net changes rates, and phytoplankton biodiversity. Biweekly net change-dependent persistence of phytoplankton assemblages followed a dome-shaped relationship of observations. A short-term persistence of taxonomic traits along weeks is predominant and contributes to the structural stabilization of phytoplankton assemblages. This short-term persistence is interpreted by the benefit of lifetime adjustment of phytoplankton organisms. The long-term development phytoplankton structure is discussed as an alignment of organisms over generations. Single key taxa, as Planktothrix rubescens (De Candolle ex Gomont) Anagnostidis &Komárek 1988, which are omnipotent players in phytoplankton assemblages and occur during different environmental scenarios in the long-term, are most suitable for long-term ecological research. Our findings interpret that phytoplankton taxa are excellent organisms to track the impact of environmental constraints due to their short generation time (1), their lifetime adjustment (2), and the re-occurrence in the long-term over generations (3).

Exploring Prescribed Fire Severity Effects on Ground Beetle (Coleoptera: Carabidae) Taxonomic and Functional Community Composition

Prescribed fire is a management tool that is frequently used to foster biodiversity. Simultaneously, insects that provide essential ecosystem services are globally declining. Within the pyroentomology literature, there are mixed reports of positive and negative effects that prescribed fires have on insect communities. This is likely due to not accounting for fire heterogeneity created by fire severity. To better understand prescribed fire severity effects on insect communities, we used multispectral reflectance data collected by Sentinel-2 to methodically quantify prescribed fire severity and compared ground beetle (Coleoptera: Carabidae) taxonomic and functional community composition responses between an unburned site and two burned sites with contrasting fire impacts. We found 23 ground beetle species and used 30 morphological, physiological, phenological, and ecological functional traits for each species. We found that our moderate fire severity site had different taxonomic and functional community compositions from both our unburned and high-severity sites. Surprisingly, we did not find a strong difference in taxonomic or functional ground beetle composition between our unburned and high-severity sites. Our results encourage future pyroentomology studies to account for fire severity, which will help guide conservation managers to make more accurate decisions and predictions about prescribed fire effects on insect biodiversity.

Forest management drives evolution of understorey herbs

Forest management has a strong impact on the forest structure and subsequently on the biotic and abiotic forest understorey environment. Forest understorey herbs can thus be expected to exhibit an evolutionary response to management-induced environmental variation (provided sufficient time for adaptation), but this has been little tested to date.Here we use one common garden, to test for genetically based variation in phenotypic traits in populations of forest herbs sampled along a forest management intensity gradient, covering protected areas, selection forests and age-class forests. Five different herbaceous species were sampled from 70 to 100 populations in three regions in Germany and were tested for genetically based variation in flowering start, proportion of flowering ramets, and plant height. Additionally, we performed structural equation modelling to study how forest management drives trait differentiation via its effects on the microenvironment.Our results show the studied forest understorey herbs varied genetically in the measured functional and phenological traits among the sampled populations. Forest management likely affected the traits in various directions and strengths depending on the species, either directly through variation in forest structural attributes or indirectly through changes in the microclimatic environment on the forest floor.In sum, we show that forest management can have evolutionary consequences for forest understorey plants. In an applied context, diverse forest management actions within landscapes are recommended as it creates heterogeneity that selects for different plant traits and thus helps conserving genetic diversity.

Effects of intraspecific variation in a native species' phenology on its coexistence with non‐native plants

Intraspecific trait variation is ubiquitous and is likely to influence species coexistence. Despite theoretical progress, empirical work on the effects of intraspecific variation on the dynamics of competing species is rare. This is because of the formidable empirical requirements necessary to link intraspecific variation in species' functional traits with intraspecific variation in the demographic and competitive rates that mediate coexistence. Here we partially overcome these challenges to determine how intraspecific variation in reproductive phenology in a native Californian annual plant species Lasthenia californica affects its ability to coexist with two non‐native species Bromus madritensis and Lactuca serriola that display contrasting phenological patterns. Using data from a field experiment, we empirically parameterize a model of competitive population dynamics, accounting for the effects of intraspecific phenological trait variation on the native species' response to both intra‐ and interspecific competition. We find that intraspecific variation in phenology drives differences in the native species' response to competition. Moreover, simulations of the parameterized model show that this variation improves the competitive performance of the native species. This occurs because of the effects of nonlinear averaging mediated by a nonlinear, concave‐up competition function that is a general feature of competition across a wide range of taxa. While intraspecific variation improves competitive performance, we also find that the magnitude of the benefit is predicted to be insufficient to prevent competitive exclusion against the non‐native species with early phenogy Bromus. Against the second non‐native species with later phenology Lactuca, intraspecific variation is predicted to result in coexistence where competitive exclusion would otherwise occur, but we could not rule out alternative qualitative outcomes for this interaction.

Correlações canônicas em caracteres fenológicos, morfológicos, produtivos e de pendão de milho

ABSTRACT The objective of this study was to check whether there is linear dependence between phenological, morphological and production traits and tassel traits in maize genotypes. Seven experiments were conducted with 16 maize genotypes, in a randomized block design, with three replicates. Four groups of traits were evaluated: phenological (two), morphological (three), production (four) and tassel (11). Joint analysis of variance and F test at 5% significance level were performed. The matrix of phenotypic correlation coefficients between the traits was estimated and multicollinearity was diagnosed in each group of traits. Associations between the groups of traits were checked by canonical correlation analysis. There is linear dependence between phenological, morphological and production traits and tassel traits in maize genotypes. Phenological (number of days from sowing to 50% of male flowering and number of days from sowing to 50% of female flowering), morphological (plant height and spike height) and production (number of spikes and grain yield) traits are positively associated with tassel traits (tassel branch number and tassel dry matter). Tassel branch number and tassel dry matter can be used for indirect selection of maize plants.

Investigating the impact of terminal heat stress on contrasting wheat cultivars: a comprehensive analysis of phenological, physiological, and biochemical traits.

Terminal heat stress has become one of the major threats due to global climate change which is significantly affecting the production and productivity of wheat crop. Therefore, it is necessary to identify key traits and genotypes to breed heat-tolerant wheat. The present study was undertaken with the objective of comparing the effects of heat stress (HSE) and extended heat stress (EHSE) on phenological-physio-biochemical traits of contrasting heat-tolerant and heat-susceptible genotypes during the reproductive phase. Phenological traits exhibited significant reduction under EHSE compared to HSE. Heat-tolerant genotypes maintained balanced phenological-physio-biochemical traits, while heat-sensitive genotypes showed significant reductions under both stress regimes. Among phenological traits, DM (R2=0.52) and BY (R2=0.44) have shown a positive effect on seed yield, indicating that biomass and crop duration contributed to the yield advantage under stress. During the grain filling stage, both the normalized difference vegetation index (NDVI) and chlorophyll (Chl) exhibited consistently positive impacts on grain yield under both HSE and EHSE conditions. This could be attributed to the enhanced photosynthesis resulting from delayed senescence and improved assimilate remobilization under terminal heat stress. The biochemical activity of superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX) was induced in tolerant genotypes under HSE. The correlation of canopy temperature with phenological-physio-biochemical traits remained static under HSE and EHSE, suggesting CT as the best selection parameter for heat tolerance. The traits showing a positive association with yield and that are less affected under stress could be used for selecting tolerant genotypes under stress environments. These tolerant genotypes can be used to develop mapping populations to decipher the genes conferring tolerance as well as to study the molecular basis of tolerance.

Differential patterns of within- and between-population genetically based trait variation in Lupinus angustifolius.

Within-population genetic and phenotypic variation play a key role in the development of adaptive responses to environmental change. Between-population variation is also an essential element in assessing the evolutionary potential of species in response to changes in environmental conditions. In this context, common garden experiments are a useful tool to separate the genetic and environmental components of phenotypic variation. We aimed to assess within- and between-population phenotypic variation of Lupinus angustifolius L. in terms of its evolutionary potential to adapt to ongoing climate change. We evaluated populations' phenotypic variation of foliar, phenological and reproductive traits with a common garden experiment. Patterns of functional trait variation were assessed with (1) mixed model analyses and coefficients of variation (CVs) with confidence intervals, (2) principal component analyses (PCAs) and (3) correlations between pairs of traits. Analyses were performed at the population level (four populations) and at the latitude level (grouping pairs of populations located in two latitudinal ranges). Phenotypic variation had a significant genetic component associated with a latitudinal pattern. (1) Mixed models found lower specific leaf area, advanced flowering phenology and lower seed production of heavier seeds in southern populations, whereas CV analyses showed lower within-latitude variation especially in phenological and reproductive traits in southern populations. (2) PCAs showed a clearer differentiation of phenotypic variation between latitudes than between populations. (3) Correlation analyses showed a greater number of significant correlations between traits in southern populations (25 vs. 13). Between-population phenotypic variation was determined by contrasting temperature and drought at different latitude and elevation. Southern populations had differential trait values compatible with adaptations to high temperatures and drought. Moreover, they had lower within-population variation and a greater number of trait correlations probably as a result of these limiting conditions, making them more vulnerable to climate change.

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.

Single and multi‐trait genome‐wide association studies identify genomic regions associated with phenological traits in cowpea

AbstractUnderstanding the genetic control of traits linked to phenology is essential to address strategies and efforts in the development of resilient cultivars capable of adapting to climate change. In this study, we performed genome‐wide association studies on a cowpea [Vigna unguiculata (L.) Walp] mini‐core collection to dissect the genetic architecture and identify genomic regions associated with days to flowering, days from flowering to pod maturity, and days to pod maturity. Phenotypic data were collected in 2 years and used to test associations with 41,533 single‐nucleotide polymorphism markers by single and multi‐trait analysis. In addition, we searched for candidate genes putatively involved in phenological traits within genome‐associated regions. The single‐trait approach identified 28 significant marker‐trait associations for the three traits, while the multi‐trait identified 18 significant associations, both evidencing pleiotropic associations. Five of these markers were associated with phenological traits reported in previous studies. Candidate genes were identified, including genes involved in phosphorylation and encoding the maternal effect embryo arrest 60, known to be associated with pod maturity and flowering, respectively. Functional validation of these genes will further improve our understanding of the variation of phenological traits in cowpea and other related crops.

Assessing Water Relations and Carbon Dynamics of Pinus taeda Branches Undergoing Shade-Induced Mortality

Light acts as a complex signal, influencing various plant physiological, phenological and morphogenetic traits. Although previous studies have explored the effects of varying light levels on branch growth and survival, the underlying mechanisms of branch mortality under shade conditions remain poorly understood, hindering our understanding of canopy dynamics. In this study, contrasting shade conditions were imposed on Pinus taeda branches, and the changes in their water relations and carbon dynamics were evaluated. Monthly measurements of the photosynthetic light–response curve (LRC), sap flow and water potential of the branches were conducted. Furthermore, the conditions that led to the deaths of lower branches were investigated, and principal component analysis (PCA) was used to classify branches according to their mortality status. Significant shade treatment effects were observed for all photosynthetic parameters. The assimilation at light saturation (Amax), dark respiration rate (Rd), apparent quantum yield (AQY), light compensation point (LCP) and light saturation point (LSP) all decreased from full light to deepest shade, whereas the opposite was the case for the convexity term (θ). All water relations traits also decreased from full light to deepest shade; however, although significant shade effect was observed in stomatal conductance (gs) and sap flow, the differences in the pre-dawn (Ψpre-dawn) and mid-day (Ψmid-day) water potentials among treatments were not statistically significant. The PCA classification results showed that it could be used as a reliable method to screen for branch mortality as early as four months before mortality becomes evident. Our results shed more light on branch physiology and mortality under shade and have the potential to help improve the prediction of tree crown size, ultimately improving process-based forest growth models.

Effects of Nitrogen Fertilization and Plant Density on Proso Millet (Panicum miliaceum L.) Growth and Yield under Mediterranean Pedoclimatic Conditions

In recent years, the dry-land cereal proso millet has become an interesting crop for cultivation in the Mediterranean environment due to the consequences of climate change. It can be considered a resilient crop because it is particularly successful in extreme drought and high-temperature conditions. The goals of this research study were to compare different plant densities (D) and nitrogen fertilization rates (N) in millet (Panicum miliaceum), evaluating morphological, productive, and phenological traits. A 2-year field experiment was carried out in Italy, and millet (var. Sunrise) was subjected to four nitrogen fertilization rates (0, 50, 100, and 150 kg N ha−1) in interaction with three plant densities (55, 111, and 222 plants m2). Significant differences were found in all the investigated plant traits. The highest grain yield data (i.e., 3.211 kg ha−1 and 3.263 kg ha−1) and total biomass (i.e., 11.464 kg ha−1 and 11.760 kg ha−1) were obtained with the N rate of 150 kg ha−1 and density of 222 plants m2. Regarding protein content, the highest values were observed using N50, N100, and N150 (ranging from 10.03% to 10.14%) and with D55 (10.43%). Phenological parameters were affected by both plant density and nitrogen amount and decreased when higher levels of these two factors were employed.