Branching Traits Research Articles

Comparative shoot morphology between cultivated Utricularia bremii plants and those growing in natural habitats in the Czech Republic

In summer 2023, the morphometry of large adult plants of Utricularia bremii was studied in an outdoor culture and at three shallow pools in two oligotrophic sand-pits in South Bohemia, Czech Republic, with a focus on shoot length and biomass, shoot branching traits and ecological conditions. Overall, the mean length of main shoots was 34-43 cm (range 23-73 cm) and the shoots bore on average 11-18 branches of three orders. On main shoots, branches were initiated on average every 7.7-9.2 internodes, which indicates a very fast propagation and growth. A new branch is theoretically initiated every ca. 3.3-3.8 days. This study confirms that shallow, well-lit, oligomesotrophic, soft-water sand-pit pools may represent an ecological optimum for this species.

Identification of Genomic Regions for Traits Associated with Flowering in Cassava (Manihot esculenta Crantz).

Flowering in cassava (Manihot esculenta Crantz) is crucial for the generation of botanical seed for breeding. However, genotypes preferred by most farmers are erect and poor at flowering or never flower. To elucidate the genetic basis of flowering, 293 diverse cassava accessions were evaluated for flowering-associated traits at two locations and seasons in Uganda. Genotyping using the Diversity Array Technology Pty Ltd. (DArTseq) platform identified 24,040 single-nucleotide polymorphisms (SNPs) distributed on the 18 cassava chromosomes. Population structure analysis using principal components (PCs) and kinships showed three clusters; the first five PCs accounted for 49.2% of the observed genetic variation. Linkage disequilibrium (LD) estimation averaged 0.32 at a distance of ~2850 kb (kilo base pairs). Polymorphism information content (PIC) and minor allele frequency (MAF) were 0.25 and 0.23, respectively. A genome-wide association study (GWAS) analysis uncovered 53 significant marker-trait associations (MTAs) with flowering-associated traits involving 27 loci. Two loci, SNPs S5_29309724 and S15_11747301, were associated with all the traits. Using five of the 27 SNPs with a Phenotype_Variance_Explained (PVE) ≥ 5%, 44 candidate genes were identified in the peak SNP sites located within 50 kb upstream or downstream, with most associated with branching traits. Eight of the genes, orthologous to Arabidopsis and other plant species, had known functional annotations related to flowering, e.g., eukaryotic translation initiation factor and myb family transcription factor. This study identified genomic regions associated with flowering-associated traits in cassava, and the identified SNPs can be useful in marker-assisted selection to overcome hybridization challenges, like unsynchronized flowering, and candidate gene validation.

Genetic analysis of grapevine root system architecture and loci associated gene networks.

Own-rooted grapevines and grapevine rootstocks are vegetatively propagated from cuttings and have an adventitious root system. Unraveling the genetic underpinnings of the adventitious root system architecture (RSA) is important for improving own-rooted and grafted grapevine sustainability for a changing climate. Grapevine RSA genetic analysis was conducted in an Vitis sp. 'VRS-F2' population. Nine root morphology, three total root system morphology, and two biomass traits that contribute to root anchorage and water and nutrient uptake were phenotyped. Quantitative trait loci (QTL) analysis was performed using a high density integrated GBS and rhAmpSeq genetic map. Thirty-one QTL were detected for eleven of the RSA traits (surface area, root volume, total root length, fresh weight, number of tips, forks or links, longest root and average root diameter, link length, and link surface area) revealing many small effects. Several QTL were colocated on chromosomes 1, 9, 13, 18, and 19. QTL with identical peak positions on chromosomes 1 or 13 were enriched for AP2-EREBP, AS2, C2C2-CO, HMG, and MYB transcription factors, and QTL on chromosomes 9 or 13 were enriched for the ALFIN-LIKE transcription factor and regulation of autophagy pathways. QTL modeling for individual root traits identified eight models explaining 13.2 to 31.8% of the phenotypic variation. 'Seyval blanc' was the grandparent contributing to the allele models that included a greater surface area, total root length, and branching (number of forks and links) traits promoting a greater root density. In contrast, V. riparia 'Manitoba 37' contributed the allele for greater average branch length (link length) and diameter, promoting a less dense elongated root system with thicker roots. LATERAL ORGAN BOUNDARY DOMAIN (LBD or AS2/LOB) and the PROTODERMAL FACTOR (PFD2 and ANL2) were identified as important candidate genes in the enriched pathways underlying the hotspots for grapevine adventitious RSA. The combined QTL hotspot and trait modeling identified transcription factors, cell cycle and circadian rhythm genes with a known role in root cell and epidermal layer differentiation, lateral root development and cortex thickness. These genes are candidates for tailoring grapevine root system texture, density and length in breeding programs.

Identification of Newer Stable Genetic Sources for High Grain Number per Panicle and Understanding the Gene Action for Important Panicle Traits in Rice

Rice is an important food crop extensively cultivated worldwide, and rice's grain yield should be improved to meet future food demand. Grain number per panicle is the main trait that determines the grain yield in rice, and other panicle-related traits influence the grain number. To study the genetic diversity, 50 diverse Indian-origin germplasm were evaluated for grain number per panicle and other panicle traits for two consecutive seasons (Rabi 2019 and Kharif 2020). The maximum genotypic and phenotypic coefficient of variation was obtained for the number of spikelets and filled grains per panicle. The genotypes were grouped into eight clusters with Mahalanobis' D2 analysis and six groups using Principal component analysis. Based on, per se, performance for grain number per panicle and genetic distances, six parents were selected and subjected to full diallel mating. The genotypes CB12132, IET 28749, and BPT 5204 were the best general combiners for the number of filled grains per panicle and other panicle branching traits, viz., the number of primary and secondary branches per panicle. The hybrid BPT 5204 × CB 12132 identified as the best specific combination for most of the studied panicle traits. The additive gene effects were high for the number of filled grains per panicle, the number of primary branches, and secondary branches, whereas non-additive gene action was high for the number of productive tillers and grain yield per plant. The information obtained from this study will be useful in rice breeding programs to improve panicle traits, especially the grain number, which would result in higher grain yield.

Studies on genetic variability, heritability, correlation and path coefficient analysis in curry leaf (Murraya koenigii Spreng.) genotypes

A study was conducted on thirty curry leaf genotypes to analyse the variability and correlation among different qualitative traits viz., plant height, number of secondary branches, secondary branch length, secondary branch weight, length at branching, compound leaves, leaflet length, number of leaflets and inter nodal length that influences the fresh leaf yield. Analysis of variance revealed that the genotypes significantly differed for all the traits studied. The results showed that PCV was higher than the GCV for all the characters and high genotypic and phenotypic coefficient of variation was recorded for the traits viz., plant height, number of secondary branches, secondary branch length, compound leaves and fresh leaf yield per plant. High heritability was observed for plant height, secondary branches, secondary branch length, length at branching, number of leaflets and inter nodal length. Correlation studies showed that fresh leaf yield per plant was significantly and positively correlated with almost all the traits studied. The highest and direct effect on fresh leaf yield per plant was observed for compound leaves (1.195) followed by leaflet length (0.093), number of leaflets (0.306), secondary branch length (0.300) and length at branching (0.142). Hence, compound leaves, leaflet length, number of leaflet, secondary branch length and length at branching traits will be useful for selection of superior genotypes in curry leaf . Keywords: Genotypes, variability, correlation, fresh leaf yield

Evaluation of interspecific hybrid clones of Casuarina for adaptability and growth in arid and semi-arid regions of North-West India

Aim: The present study aimed at introducing high yielding clones of commercially important short rotation tree species such as Casuarina junghuhniana under arid and semi-arid conditions of North India and investigating their adaptability, growth and productivity potential for identification of superior clones for cultivation. Methodology: Nine clones of Casuarina, four of Casuarina junghuhniana and five of inter-specific hybrid of C. equisetifolia x C. junghuhniana, were introduced from the Institute of Forest, Genetics and Tree Breeding, Coimbatore, Tamil Nadu and were planted at two distinct agro-climatic conditions representing the arid and semi-arid conditions of Punjab, India. Results: The clones were studied for morphological traits (quantitative, qualitative, and fruiting) and showed significant variation in terms of adaptability, growth and branching traits under both environmental conditions. The clones IFGTB CH 2, CH 5 and CJ 108 were found superior for growth, stem quality characters and adaptability for which the data were recorded at the age of 2 ¼ and 3 ¼ yrs. Interpretation: Findings of the current study will contribute in the adoption of selected clones in agroforestry situations. Further, field testing is required to estimate the yield potential of shortlisted clones and to broaden the genetic diversity of planting material through introduction of more number of clones.

Transcriptome and metabolite analysis related to branch development in two genotypes of Eucalyptus urophylla.

Branching in long-lived plants can cause scarring at the base and affect wood density, which greatly inhibits wood yield and quality. Eucalyptus urophylla is one of the most important commercial forest tree species in South China, with diverse branch number and branch angles under different genetic backgrounds. However, the main elements and regulatory mechanisms associated with different branching traits in E. urophylla remain unclear. To identify the factors that may influence branching, the transcriptome and metabolome were performed on the shoot apex (SA), lateral shoot apex (LSA), and stem segment at the 5th axillary bud from the shoot apex (S1) in lines ZQUC14 (A) and LDUD26 (B), with A exhibiting a smaller Ba than B. A total of 307.3 million high-quality clean reads and nine hormones were identified from six libraries. Several differentially expressed regulatory factors were identified between the two genotypes of E. urophylla. The Kyoto Encyclopedia of Genes and Genomes pathways were enriched in plant hormone signal transduction, plant hormone biosynthesis and their transport pathways. Furthermore, gene expression pattern analysis identified genes that were significantly downregulated or upregulated in S1 relative to the SA and LSA segments, and the plant hormone signal transduction pathway was constructed to explain branching development. This study clarified the main plant hormones and genes underlying branch numbers and angles of E. urophylla, confirmed that ABA and SA could promote a larger branch angle and smaller branch number, while IAA has an opposite function. Numbers of key candidate genes involved in plant hormone signal transduction were found in the positive regulation of branch formation. These novel findings should aid molecular breeding of branching in Eucalyptus.

Various distances and orientations influenced the branching traits of Dendrocalamus minor var. amoenus in Dongshan Island, China

Branch patterns play a key role in assessing plant architecture and are adapted to forest ecosystems. The study aimed to reveal the pattern of branch traits at various distances and orientations from the seashore. For that reason, four sites with various distances from the seashore (SP1: 50–60 m, SP2: 60–100 m, SP3: 100–200 m, and SP4: 200–800 m) were selected and branch traits of Dendrocalamus minor var. amoenus were determined in Dongshan Island, China. The results showed that there were differences in the branch traits between both the 1st-order and 2nd-order branches, and distance from seashore had a significant impact on branch angle, length, diameter, and the number of leaves of 1st-order branches, whereas branch diameter, length, and the number of leaves of 2nd-order branches. In different orientations, the branch angle, length, number, and diameters of the 1st-order and 2nd-order branches showed no significant differences. Nonetheless, the number of leaves of the 1st-order branches were significantly influenced by different orientations. D. minor var. amoenus exhibited strong phenotypic plasticity with longer branches and formed a sparse crown shape. It adjusted the fractal dimension of the crown and branches by modulating the allometric growth relationships among branching traits to adapt to harsh coastal pressure. This study would provide valuable recommendations for D. minor var. amoenus as windbreaks in the coastal climate.

Genetic evaluation on growth and branching traits of 4-year-old half-sib families of loblolly pine

Genetic evaluation on growth and branching traits of 4-year-old half-sib families of loblolly pine

Short Communication: Correlation and regression among rice panicle branches traits

Abstract. Hastini T, Suwarno WB, Ghulamahdi M, Aswidinnoor H. 2019. Short Communication: Correlation and regression among rice panicle branches traits. Biodiversitas 20: 1140-1146. Panicle was a very important organ in rice since the grains are developed from the panicle branches. This study aimed to find out the information about the relationship among rice panicle branching traits using correlation and regression analysis. The trial was conducted at the IPB Research Station, Babakan, Bogor, Indonesia from December 2015 until April 2016. Twenty genotypes of lowland rice were used as treatments with three replications and arranged in a completely randomized design. The panicle branches traits were observed. The result showed that there was positively and a highly significant relationship among the panicle branches traits in general. Analysis using linear regression revealed that, in general, the total grains number per panicle showed the linear relationships with other traits, and only total grains number per panicle vs tertiary branches number, total grains number per panicle vs grains number of tertiary panicle branch, and total grains number per panicle vs the number of secondary branches per panicle branch showed the quadratic relationship. Among all rice panicle branching traits, the secondary panicle branches number had the highest contribution to the total grains number per panicle.

Root Branching and Nutrient Efficiency: Status and Way Forward in Root and Tuber Crops.

Plants are immobile organisms that require roots to efficiently and cost-effectively exploit their habitat for water and nutrients. Plant root systems are dynamic structures capable of altering root branching, root angle, and root growth rates determining overall architecture. This plasticity involves belowground plant-root mediated synergies coupled through a continuum of environmental interactions and endogenous developmental processes facilitating plants to adapt to favorable or adverse soil conditions. Plant root branching is paramount to ensure adequate access to soil water and nutrients. Although substantial resources have been devoted toward this goal, significant knowledge gaps exist. In well-studied systems such as rice and maize, it has become evident that root branching plays a significant role in the acquisition of nutrients and other soil-based resources. In these crop species, specific root branching traits that confer enhanced nutrient acquisition are well-characterized and are already being incorporated into breeding populations. In contrast, the understanding of root branching in root and tuber crop productivity has lagged behind. In this review article, we highlight what is known about root branching in root and tuber crops (RTCs) and mark new research directions, such as the use novel phenotyping methods, examining the changes in root morphology and anatomy under nutrient stress, and germplasm screening with enhanced root architecture for more efficient nutrient capture. These directions will permit a better understanding of the interaction between root branching and nutrient acquisition in these globally important crop species.

Repetibilidad de parámetros genéticos de las características de ramificación en progenies de Pinus patula

La ramificación de los árboles tiene un impacto económico importante en las plantaciones forestales, ya que afecta la calidad de la madera. La posibilidad de incorporar estas características en un programa de mejora genética depende de su heredabilidad y estructura genética con la productividad de los árboles. El objetivo del estudio fue estimar la repetibilidad de los parámetros genéticos de las características de ramificación en progenies de Pinus patula a 7 años y 10 años de edad, así como su relación genética con la tasa de crecimiento de los árboles. Las características de ramificación (número de verticilos, número, diámetro y ángulo de ramas, y presencia de defectos en la ramificación) y crecimiento (altura, diámetro y volumen del tronco) se evaluaron en 84 familias de polinización libre. Con estos datos se estimó la heredabilidad y las correlaciones genéticas, fenotípicas y edad-edad de las características. El control genético de las características de ramificación varío de nulo a moderado (0.00 ≤ h2i ≤ 0.23; 0.00 ≤ h2f ≤ 0.42), pero fue estable en las dos edades. Las características de ramificación con variación genética mostraron una estructura genética favorable con las de crecimiento. El número de verticilos y el diámetro de ramas ajustado tuvieron una correlación negativa (-0.60 ≤ rg ≤ -0.01), y el ángulo de ramas una correlación positiva (0.14 ≤ rg ≤ 0.47), con el crecimiento de los árboles. La repetibilidad de la estructura genética de las características de ramificación y crecimiento de los árboles fue alta, en términos de las correlaciones edad-edad (0.58 ≤ rg ≤ 0.94; 0.83 ≤ rpf ≤ 1.00) y del coeficiente de correlación entre las matrices de correlaciones genéticas y fenotípicas en las dos edades (r ≥ 0.86). La selección individual o familial para aumentar la productividad en esta población causaría mejoras en la ramificación (menor número de verticilos y ramas más delgadas, con ángulo mayor) y, por lo tanto, en la calidad de la madera.

In-field lucerne root morphology traits over time in relation to forage yield, plant density, and root disease under two cutting managements

Changes in lucerne (Medicago sativa L.) root morphology concurrent with forage growth have been little studied in multi-year field experiments with lucerne stands though they could provide explanations for differences in performance among tested treatments. Our objectives were: (i) to compare lucerne root trait development under three- and four-cut managements over a 4-year period, and (ii) to investigate relationships among root traits, and between root traits and lucerne varieties, cutting frequencies, root sampling periods, lucerne dry matter yield and evidence of root disease incidence and plant density, using multivariate methods. Treatments were a factorial combination of 15 lucerne cultivars with managements of three and four cuts per year. Each spring and autumn, plants were evaluated for root morphology traits and scored for root disease. Root morphology traits were strongly modified by sampling period and plant density, which together explained over 40% of total variability. The development over time was positively associated with an increase in tap-root diameter (TD) and root mass accumulation, whereas root density determined changes in root branching traits. The four-cut management reduced TD and root branching in association with lower forage yield. Variety effect was significant but contributed only 2.8% of total variability. Root branching showed a positive correlation with forage yield through a large increase of TD for branch-rooted plants, but more intensive root branching was associated with a significantly higher disease score than in tap-rooted plants. For optimization of evaluation of root traits, we proposed a root potential index (RPI) integrating TD and plant density. This RPI showed a closer relation to yield than TD, plant density or root biomass alone, in the arable cultivation layer. Our results reveal that monitoring of root morphology is an effective tool to characterize the production potential of lucerne as a sown field crop, and may explain yield differences among the various experimental treatments. Understanding these relationships between root morphology and lucerne stand performance can help in breeding selection as well as effective lucerne stand evaluation.

X-ray computed tomography to decipher the genetic architecture of tree branching traits: oak as a case study

A new method for obtaining internal views of tree trunks was recently developed using X-ray computed tomography (CT). This technology makes it possible to observe and measure rameal traces that are left by latent buds, sequential branches, and epicormic branches in the wood. Epicormic branches are undesirable for producing high-value solid wood, especially in Quercus robur, an important hardwood forest tree species in Europe, which is prone to epicormic branches that develop from abundant latent buds. For the very first time, branching-related traits deduced from X-ray CT observation make it possible to analyze the genetic architecture of oak branching through a quantitative trait locus (QTL) analysis. Highly significant QTLs were detected for traits related to latent buds and epicormic branches. The number and effect of these QTLs suggest a moderate genetic determinism for the formation of latent buds and the development of epicormic branches. Three hotspots were found, grouping QTLs for different branching traits. An analysis of the common physiological denominators of these coincident traits suggests that their genetic controls are related to either the regulation of the axillary meristem initiation or to bud dormancy. Conversely, the position of only the separate QTL related to the number of sequential branches suggests an independent genetic control.

Legume shovelomics: High—Throughput phenotyping of common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata subsp, unguiculata) root architecture in the field

Low phosphorus (P) availability and drought are primary constraints to common bean and cowpea production in developing countries. Genetic variation of particular root architectural phenes of common bean is associated with improved acquisition of water and phosphorus. Quantitative evaluation of root architectural phenotypes of mature plants in the field is challenging Nonetheless, in situ phenotyping captures responses to environmental variation and is critical to improving crop performance in the target environment. The objective of this study was to develop flexible high-throughput root architectural phenotyping platforms for bean and cowpea, which have distinct but comparable root architectures. The bean phenotyping platform was specifically designed to scale from the lab to the field. Initial laboratory studies revealed cowpea does not have basal root whorls so the cowpea phenotypic platform was taken directly to field evaluation. Protocol development passed through several stages including comparisons of lab to field quantification systems and comparing manual and image-based phenotyping tools of field grown roots. Comparing lab-grown bean seedlings and field measurements at pod elongation stage resulted in a R2 of 0.66 for basal root whorl number (BRWN) and 0.92 for basal root number (BRN) between lab and field observations. Visual ratings were found to agree well with manual measurements for 12 root parameters of common bean. Heritability for 51 traits ranged from zero to eighty-three, with greatest heritability for BRWN and least for disease and secondary branching traits. Heritability for cowpea traits ranged from 0.01 to 0.80 to with number of large hypocotyl roots (1.5A) being most heritable, nodule score (NS) and tap root diameter at 5cm (TD5) being moderately heritable and tap root diameter 15cm below the soil level (TD15) being least heritable. Two minutes per root crown were required to evaluate 12 root phene descriptors manually and image analysis required 1h to analyze 5000 images for 39 phenes. Manual and image-based platforms can differentiate field-grown genotypes on the basis of these traits. We suggest an integrated protocol combining visual scoring, manual measurements, and image analysis. The integrated phenotyping platform presented here has utility for identifying and selecting useful root architectural phenotypes for bean and cowpea and potentially extends to other annual legume or dicotyledonous crops.

Heterosis and genetic analysis of branching in cut-flower chrysanthemums

The single-head cut-flower chrysanthemum is one of the most important and popular varieties of Chinese export cut flowers, but the less collateral varieties are very rare in the market. To produce new, high-quality varieties, we generated two hybrid combinations from the varieties Fukashi (SZ), Jinba (SM), and FengWofen (FW; “SM × SZ” and “SZ × FW”, respectively). A detailed analysis of morphological tests revealed the heredity and variation in the F1 populations. Hybrid plant height showed significant negative heterosis. Flower diameter and the number of small flowers were both diminished, but the ornamental traits of the population overall showed wide variation. The results provided a basis of genetic differences for subsequent analysis. In both crosses, Fukashi played an important regulatory role in determining branching traits in the middle zone and basal zone of the progeny plants: it reduced hybrid branching traits in the middle zone to a certain extent, however, it increased those in the basal zone and there were some transgressive progeny. These results indicate that hybridization is an effective way to contribute to the phenotypic variation of cut-flower chrysanthemums. The inheritance of branching traits identified in this study will be important in improving the plant architecture of chrysanthemum cultivars.

Identification of quantitative trait loci for branching traits of spray cut chrysanthemum

Branching is an important horticultural trait that influences plant architecture and production of cut chrysanthemum; however, its genetic determinism is poorly understood. In this study, an F1 mapping population derived from a cross between two spray cut chrysanthemum cultivars was used to determine QTL underlying branching. The branching traits in the F1 mapping population exhibited over-parent segregation and relatively high heritability (0.68–0.92). Based on the branching traits across two consecutive years, 16 additive QTL, including five QTL for primary branch number, each four QTL for branch height, and branch angle, and three QTL for primary branch length, were identified, with each accounting for 6.9–24.4 % of the phenotypic variation. Of these, four QTL expressed stable, located in the same genomic regions across two consecutive years. Results from this study add new understanding of the genetic basis of branching in spray cut chrysanthemum, and the putative major QTL detected here are valuable for future breeding cut chrysanthemum that exhibits desirable branching type.

Leading dimensions in absorptive root trait variation across 96 subtropical forest species.

Absorptive root traits show remarkable cross-species variation, but major root trait dimensions across species have not been defined. We sampled first-order roots and measured 14 root traits for 96 angiosperm woody species from subtropical China, including root diameter, specific root length, stele diameter, cortex thickness, root vessel size and density, mycorrhizal colonization rate, root branching intensity, tissue density, and concentrations of carbon and nitrogen ([N]). Root traits differed in the degree of variation and phylogenetic conservatism, but showed predictable patterns of cross-trait coordination. Root diameter, cortex thickness and stele diameter displayed high variation across species (coefficient of variation (CV)=0.51-0.69), whereas the stele:root diameter ratio and [N] showed low variation (CV<0.32). Root diameter, cortex thickness and stele diameter showed a strong phylogenetic signal across species, whereas root branching traits did not, and these two sets of traits were segregated onto two nearly orthogonal (independent) principal component analysis (PCA) axes. Two major dimensions of root trait variation were found: a diameter-related dimension potentially integrating root construction, maintenance, and persistence with mycorrhizal colonization, and a branching architecture dimension expressing root plastic responses to the environment. These two dimensions may offer a promising path for better understanding root trait economics and root ecological strategies world-wide.

The potential to improve growth rate and quality traits of stem straightness and branching habit when breeding Picea sitchensis (Bong.) Carr

Tree breeders continue to use visual assessments of stem shape and branching habit as part of their selection criteria because these are key features used by timber merchants in assessing stand value. However, it is not known how effective these assessments are in introducing real improvements in stem and branching traits to breeding and production populations of Sitka spruce. This study determined the genetic characteristics of several traits associated with stem straightness and branching, and examined whether these traits are suitable as future selection criteria. Trees were sampled from 33 families selected from a 20-year-old half-sibling progeny trial growing in northern Scotland and a control of directly imported material from Queen Charlotte Islands, Canada. Stem straightness and branching habit were ‘scored’ for quality in addition to direct measurements made on growth and branching characteristics. Results indicate that heritability values for most external stem and branching properties evaluated visually are sufficiently strong to enable effective selection in tree improvement programmes. Estimated genetic correlations suggest that substantial improvements in branch and stem quality could be achieved without a reduction in growth rate. Visual scoring systems appear to successfully target families of good growth and small branch size relative to the control population.

Adaptive introgression of abiotic tolerance traits in the sunflowerHelianthus annuus

*Adaptive trait introgression is increasingly recognized as common. However, it is unclear whether adaptive genetic exchanges typically affect only a single trait, or instead affect multiple aspects of the phenotype. Here, we examine introgression of abiotic tolerance traits between two hybridizing North American sunflower species, Helianthus annuus and Helianthus debilis. *In two common gardens in the hybrid range, we measured 10 ecophysiological, phenological, and architectural traits for parents and their natural and artificial hybrids, and examined how fitness covaried with trait values. *Eight of the 10 traits showed patterns consistent with introgression from H. debilis into H. annuus, and suggested that H. debilis-like traits allowing rapid growth and reproduction before summer heat and drought have been favored in the hybrid range. Natural selection currently favors BC(1) hybrids with H. debilis-like branching traits. *We demonstrate that introgression has altered multiple aspects of the H. annuus phenotype in an adaptive manner, has affected traits relevant to both biotic and abiotic environments, and may have aided expansion of the H. annuus range into central Texas, USA.