Crop Science最新文献

Drought stress poses a significant challenge to turfgrass growth, particularly in the regions like southern United States, where bermudagrass (Cynodon sp.) is widely used for lawns and sports fields. Drought stress disrupts physiological processes, leading to reduced water availability, impaired photosynthesis, and oxidative stress. To understand the bermudagrass response to drought, we investigated the physiological differences and characterized the gene expression and metabolite profiles in two bermudagrass genotypes, TifTuf and Premier. Physiological measurements showed significant variations in green cover percentage, visual quality, and relative water content between the two genotypes. RNA sequencing revealed extensive gene expression changes, with differentially expressed genes that were upregulated in both genotypes. Gene ontology (GO) analysis highlighted biological processes such as transcription regulation, lipid metabolism, and cellular structure development pathways. KEGG pathway analysis indicated that TifTuf had significant changes in galactose metabolism, carotenoid biosynthesis, and plant hormone signal transduction pathways, while Premier showed enrichment in plant hormone signaling, lipid metabolism, and secondary metabolite biosynthesis pathways. Metabolomic analysis provided insights into metabolic reprogramming due to drought stress. Principal component analysis revealed distinct metabolic patterns between control and drought-stressed samples, with both genotypes showing substantial alterations. Differential metabolite analysis identified key metabolites associated with stress adaptation, including the phytohormone ABA and various amino acids. This analysis elucidates the intricate physiological and molecular mechanisms underlying drought tolerance in bermudagrass genotypes. These findings enhance the understanding of drought stress adaptation strategies in bermudagrass and offer valuable insights for the development of drought-tolerant genotypes.

Maize (Zea mays L.) production in Argentina changed markedly during the last decade due to the widespread adoption of late sowing dates, expanding its productive area, and diversifying crop end-uses. This study was conducted to assess how the sowing date and nitrogen (N) availability affect grain yield, its physiological determinants (biomass and its partitioning), and numeric components (kernel number and kernel weight) of maize hybrids marketed for different end-uses. Field experiments were conducted in two growing seasons (2019–2020 and 2020–2021) and two sowing dates within each season (early and late) at a site in the main maize-producing region of Argentina. Within each season × sowing date combination, eight commercial maize hybrids (commercialized as grain, dual-purpose, or silage) were tested under two N levels (N0: no N applied; N250: fertilized with 250 kg N ha⁻¹). The greatest grain yield, biomass, kernel number, and harvest index corresponded to the grain hybrids. Dual-purpose hybrids showed an intermediate grain yield, the highest kernel weight, and a more “silage” than “graniferous” behavior. Silage hybrids had improved light interception up to silking + 15 days (R2) but exhibited the lowest grain yield. Differences in end-use steered crop breeding efforts toward different physiological strategies. The improved understanding of the physiological mechanisms underlying the productivity among maize hybrids with varying end-uses will assist in the selection and management of suitable cultivars to be grown under different systems and environmental variations associated with an extended sowing date period.

Continuous high ambient temperature in hot summer months leads to a sharp decline in turf quality of cool-season turfgrass. Verticillium dahliae Aspf2-like protein (VDAL) is a secretory protein of V. dahliae that can improve crop yield and resistance to disease, but its role in improving heat tolerance of cool-season turfgrass has not been reported so far. The objectives of this study were to explore the effect and mechanism of foliar application of VDAL on improving heat tolerance in cool-season creeping bentgrass (Agrostis stolonifera) and to further examine the advantage of foliar spraying with VDAL in mitigating summer bentgrass decline (SBD) in the US transition zone or other regions with similar climate. The results demonstrated that the optimal dose of VDAL for improving thermotolerance of two creeping bentgrass cultivars (heat-tolerant 13 M and heat-sensitive Seaside II) was screened as 0.2 g L⁻¹ based on analyses of chlorophyll content, photochemical efficiency of PSII, and cell membrane stability under controlled heat stress conditions. Foliar application of the optimal dose of VDAL significantly restricted chlorophyll loss under heat stress and also alleviated heat-induced declines in net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency. In addition, overaccumulations of superoxide anion radical and hydrogen peroxide could be significantly alleviated by the exogenous application of VDAL through improving the activity of antioxidant enzymes including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase in two cultivars. A further 2-year field trial showed that foliar application of VDAL improved turf quality, chlorophyll content, photochemical efficiency, and cell membrane stability of the two cultivars during hot summer months of 2022 and 2023. The results indicate that the appropriate dose of VDAL plays a positive role in photosynthetic performance and antioxidant capacity for thermotolerance of creeping bentgrass, and foliar application of VDAL could be considered an effective approach for alleviating SBD.

The goal of transgenesis in plant breeding is to make step-change improvements in traits of interest. However, improving quantitative traits, such as yield in maize (Zea mays L.), with transgenes has been difficult. Traditionally, transgene testing is done on a few isogenic lines, and results are extrapolated to entire breeding populations. Testing on limited germplasm does not provide a robust estimate of a transgene's value. Incorporating transgenes directly into breeding populations could increase genetic variance and the rate of genetic gain. Here, we used a transgene that reduces ethylene as a case study and investigated event, transgene, family, and environment effects and their interactions. We also determined whether introduction of the transgene into a breeding population would result in transgenic lines being preferentially selected over nontransgenic lines for yield. We found significant variation in transgene effects across clustered environments and families for multiple traits including yield. In environmental Cluster 2, the transgenic lines yielded 0.4 Mg ha⁻¹ more than nontransgenic lines in family KC22; yet, in family QY43, transgenic lines yielded 0.3 Mg ha⁻¹ less. Similarly, within Cluster 4, the QY43 family had preferential selection of transgenic over nontransgenic lines, whereas in families YE41 and AY91, nontransgenic lines were selected more frequently. These results show the critical importance of evaluating transgenes across broad germplasm diversity to assess their general value to a program. Integrating transgenes, or using gene editing, directly in a breeding program can expand genetic variation for quantitative traits and potentially accelerate genetic gain.

When water resources are limited, cotton (Gossypium hirsutum L.) plants adapt in part through adjustments in carbon allocation strategies, often evident in the leaves within the canopy. The dynamics of leaf carbon accumulation provide insights into how the plant partitions and uses carbon resources, a key aspect of optimizing crop productivity. In this study, we investigated the dynamics of leaf carbon accumulation in two cotton cultivars (Phytogen [PHY] 350 and Stoneville [ST] 5707) across spatial and temporal scales under two different levels of irrigation (low: 178 mm year⁻¹, high: 356 mm year⁻¹) in 2020 and 2021. For each cultivar and irrigation treatment, an increase in leaf mass occurred primarily at the bottom of the canopy early in the season, followed by additional leaf production in the middle of the plant as the season progressed. Irrigation reduction resulted in a canopy with reduced radiation interception, less leaf shading in the lower canopy, and thicker leaves. In contrast, more irrigation created canopies with a larger effective leaf area, increasing total light interception despite increased shading at the canopy base. Additionally, leaf carbon allocation is synchronized with fruit carbon demand at the onset of the first bloom stage for an early-maturing cultivar. Overall, this study provides valuable insights into the complex relationship between water availability, radiation intensity within the canopy, and leaf carbon dynamics, contributing to a more comprehensive understanding of the plant's overall performance in resource-constrained environments.

Spring dead spot (SDS) (Ophiosphaerella spp.) is the most detrimental disease to warm-season turfgrasses in areas with cold-induced dormancy. Fungicide applications do not provide consistent SDS suppression. One reason for this inconsistency is the use of solely calendar-based fungicide applications instead of considering both calendar date and soil temperature. A field study was conducted at three separate hybrid bermudagrass (Cynodon dactylon (L.) Pers. × transvaalensis Burtt Davy) locations in Virginia to determine the optimal soil temperature and timing for SDS suppression with tebuconazole and isofetamid. Tebuconazole (1.5 kg a.i. ha⁻¹) and isofetamid (4.1 kg a.i. ha⁻¹) were applied at 11 different timings throughout the year based on soil temperatures at a 0- to 10-cm depth. Plots were assessed for SDS severity in the spring and early summer of 2021 and 2022. Two in vitro studies were also conducted with Ophiosphaerella herpotricha and Ophiosphaerella korrae isolates to (1) determine the optimal temperature for growth on potato dextrose agar (PDA) placed on a thermogradient table (13–33°C) and (2) compare the daily growth rate of O. herpotricha and O. korrae isolates at 11, 19, and 27.5°C on PDA. In the field study, isofetamid suppressed SDS more than tebuconazole. Fall applications when soil temperatures were 13°C consistently provided the best SDS suppression. For the in vitro studies, both species grew optimally between 24 and 25°C, yet O. korrae and O. herpotricha growth rates differed at 11°C.

Genome editing is a powerful tool for improving the agronomic traits of polyploid crops such as wheat (Triticum aestivum) by simultaneously generating mutations in multiple homoeologs. However, improvements in cultivars that are amenable to transformation (and thus genome editing) must be tested in region-specific cultivars under field conditions. Grain dormancy helps ensure the appropriate timing of germination and strong dormancy helps prevent preharvest sprouting. We previously introduced mutations in all three homoeologs of quantitative trait locus for seed dormancy1 (Qsd1) in the wheat cultivar Fielder using genome editing and showed that this triple qsd1 mutant had strengthened grain dormancy under laboratory conditions. In this study, we introduced the triple qsd1 mutation into two Japanese cultivars, Tamaizumi and Tamaizumi R, by recurrent backcrossing. As in Fielder, the triple qsd1 mutation also altered grain dormancy in the Tamaizumi and Tamaizumi R genetic backgrounds under laboratory conditions. To evaluate the mutation's effect on grain dormancy in the field, we conducted field trials in two areas in Japan and assessed the dormancy of the harvested grains. This is the first report of field trials of genome-edited wheat in Japan. Our findings demonstrate the importance of such trials for evaluating grain dormancy, which is influenced by environmental conditions.

Rice (Oryza sativa L.) is an important food source and a primary source of high-quality protein. Polyploid breeding is an effective approach to improving the nutritional quality of crops. Several stable tetraploid rice lines with both high seed setting rates and high protein content have been bred. In the present study, the protein quality of two tetraploid rice lines GD2-4x and GD4-4x with high protein content was analyzed in detail, and mechanisms associated with the high protein quality were explored from the perspective of endosperm structure. The results showed that the total protein content of GD2-4x and GD4-4x increased significantly by 40.27% and 35.15%, respectively, when compared to that of 9311-2x (control). The content of each protein component also increased significantly, with a major increase being observed in glutelin content. The contents of 16 types of amino acids and total amino acids, as well as contents of nutrient limiting essential amino acids, such as lysine, threonine, and methionine, in tetraploid rice lines increased significantly when compared to those in the control. The thickness of the aleurone layer on the dorsal, lateral, and ventral positions of GD2-4x and GD4-4x seeds during different developmental days increased significantly when compared to that of 9311-2x seeds. Amyloplasts were more regular and loosely arranged in GD2-4x and GD4-4x seeds. The tetraploid rice lines had higher total protein and amino acid contents, with glutelin accounting for the highest proportion of the increase. The tetraploid rice lines with high protein content had higher nutritional quality and value than the diploid rice line. The high protein quality of tetraploid rice lines could be associated with an increase in aleurone layer thickness, as well as changes in amyloplast morphology and distribution. This study demonstrates that polyploidization is an effective breeding approach to improving the nutritional quality and value of rice seeds. The results provide a theoretical basis for the utilization of tetraploid high protein rice lines and a reference for improving the nutritional quality of other crops.

There are three main components of soybean (Glycine max (L.) Merr.) seeds: protein, oil, and residual. The residual fraction includes soluble and insoluble carbohydrates, lignin, and minerals. Among soluble carbohydrates, the presence of raffinose family of oligosaccharides (RFOs) has poor nutritional value (i.e., raffinose and stachyose), and the inability of monogastric animals to digest them limits the potential use of soybean meal for food and feed applications. Our objective was to understand how different environmental conditions impact soybean seed quality, particularly the concentration of the residual fraction and its components. Nine commercial genotypes from three maturity groups were sown on early and late dates. The concentration of insoluble carbohydrates + lignin was positively associated with seed weight (r = 0.67) and negatively associated with the mean temperature during the seed-filling period (R5–R7; r = −0.61). Within soluble carbohydrates, RFOs were negatively influenced by the mean temperature at the beginning of the seed-filling period (R5–R6; r = −0.37), while sucrose concentration showed the opposite effect (r = 0.43). In contrast, precipitation exhibited a positive correlation with RFOs, whereas sucrose displayed a negative correlation (r = 0.38 and r = −0.42). This study showed that the decrease in protein concentration was related to the increase in the residual fraction of the seeds, and higher temperatures during seed-filling period impacted the residual composition of the seeds, specifically by reducing RFO concentration.

Multiparent advanced generation intercross (MAGIC) populations are a new genetic resource for high-resolution mapping of quantitative traits and as a source of new germplasm or improved cultivars for breeding due to the high level of recombination events in the population. Here, we have developed an eight-founder MAGIC population for peanut (Arachis hypogaea L.) (PeanutMAGIC). Eight diverse founders were intercrossed using a simple funnel mating design to ensure that the MAGIC population would possess equal representation from each founder. This was followed by advancement using small family plot and single-seed descent, resulting in 3187 F_2:7 recombinant inbred lines (RILs). The objective of this study was to introduce this PeanutMAGIC as a new resource for genetic and genomic studies. We randomly selected a smaller subset of 310 RILs (MAGIC Core) from PeanutMAGIC and conducted genotyping using whole genome sequencing and phenotyping over two growing seasons for seed and pod traits. Whole genome characterization of the MAGIC Core demonstrated that PeanutMAGIC harbors a balanced and evenly differentiated mosaic of genomic blocks from eight founders, providing unique recombination events for high-resolution mapping of quantitative traits. Using 2-year phenotypic data, we showed that PeanutMAGIC can improve genetic mapping power of a spectrum of qualitative, like seed coat color, to quantitative traits such as pod weight, seed weight, shelling percentage, pod constriction, and pod reticulation. These findings show that the PeanutMAGIC population can be used by the peanut research community as a new resource for genetic and genomic studies and for cultivar improvement.