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PremiseThere is considerable variation in leaf lobing and leaf size, including among grapevines, some of the most well-studied leaves. We examined the relationship between leaf lobing and leaf size across grapevine populations which varied in extent of leaf lobing.MethodsWe used homologous landmarking techniques to measure 2,632 leaves across two years in 476 unique, genetically distinct grapevines from 5 biparental crosses which vary primarily in the extent of lobing. We determined to what extent leaf area could explain variation in lobing, vein length, and vein to blade ratio.ResultsAlthough lobing was the primary source of variation in shape across the leaves we measured, leaf area varied only slightly as a function of lobing. Rather, leaf area increases as a function of total major vein length, total branching vein length, and decreases as a function of vein to blade ratio. These relationships are stronger for more highly lobed leaves, with the residuals for each model differing as a function of distal lobing.ConclusionsFor a given leaf area, more highly lobed leaves have longer veins and higher vein to blade ratios, allowing them to maintain similar leaf areas despite increased lobing. These findings show how more highly lobed leaves may compensate for what would otherwise result in a reduced leaf area, allowing for increased photosynthetic capacity through similar leaf size.

Analysis of over 100 Cannabis samples quantified for terpene and cannabinoid content and genotyped for over 100,000 single nucleotide polymorphisms indicated that Sativa- and Indica-labelled samples were genetically indistinct on a genome-wide scale. Instead, we found that Cannabis labelling was associated with variation in a small number of terpenes whose concentrations are controlled by genetic variation at tandem arrays of terpene synthase genes., By quantifying over 100 Cannabis samples for terpene and cannabinoid content and genotyping them for over 100,000 single nucleotide polymorphisms, this study finds that Cannabis labelling is associated with genetic variants in terpene synthase genes.

Premise As a leaf expands, its shape dynamically changes. Previously, we documented an allometric relationship between vein and blade area in grapevine leaves. Larger leaves have a smaller ratio of primary and secondary vein area relative to blade area compared to smaller leaves. We sought to use allometry as an indicator of leaf size and plasticity. Methods We measured the ratio of vein-to-blade area from the same 208 vines across four growing seasons (2013, 2015, 2016, and 2017). Matching leaves by vine and node, we analyzed the correlation between the size and shape of grapevine leaves as repeated measures with climate variables across years. Results The proportion of leaf area occupied by vein and blade exponentially decreased and increased, respectively, during leaf expansion making their ratio a stronger indicator of leaf size than area itself. Total precipitation and leaf wetness hours of the previous year but not the current showed strong negative correlations with vein-to-blade ratio, whereas maximum air temperature from the previous year was positively correlated. Conclusions Our results demonstrate that vein-to-blade ratio is a strong allometric indicator of leaf size and plasticity in grapevines measured across years. Grapevine leaf primordia are initiated in buds the year before they emerge, and we found that total precipitation and maximum air temperature of the previous growing season exerted the largest statistically significant effects on leaf morphology. Vein-to-blade ratio is a promising allometric indicator of relationships between leaf morphology and climate, the robustness of which should be explored further.

Indirect defenses are plant phenotypes that reduce damage by attracting natural enemies of plant pests and pathogens to leaves. Despite their economic and ecological importance, few studies have investigated the genetic underpinnings of indirect defense phenotypes. Here, we present a genome-wide association study of five phenotypes previously determined to increase populations of beneficial (fungivorous and predacious) mites on grape leaves (genus Vitis): leaf bristles, leaf hairs, and the size, density, and depth of leaf domatia. Using a common garden genetic panel of 399 V. vinifera cultivars, we tested for genetic associations of these phenotypes using previously obtained genotyping data from the Vitis9kSNP array. We found one single nucleotide polymorphism (SNP) significantly associated with domatia density. This SNP (Chr5:1160194) is near two genes of interest: Importin Alpha Isoform 1 (VIT_205s0077g01440), involved in downy mildew resistance, and GATA Transcription Factor 8 (VIT_205s0077g01450), involved in leaf shape development. Our findings are among the first to examine the genomic regions associated with ecologically important plant traits that facilitate interactions with beneficial mites, and suggest promising candidate genes for breeding and genetic editing to increase naturally occurring predator-based defenses in grapevines.

Indirect defenses are plant phenotypes that reduce damage by attracting natural enemies of plant pests and pathogens to leaves. Despite their economic and ecological importance, few studies have investigated the genetic underpinnings of indirect defense phenotypes. Here, we present a genome-wide association study of five phenotypes previously determined to increase populations of beneficial (fungivorous and predacious) mites on grape leaves (genus Vitis): leaf bristles, leaf hairs, and the size, density, and depth of leaf domatia. Using a common garden genetic panel of 399 V. vinifera cultivars, we tested for genetic associations of these phenotypes using previously obtained genotyping data from the Vitis9kSNP array. We found one single nucleotide polymorphism (SNP) significantly associated with domatia density. This SNP (Chr5:1160194) is near two genes of interest: Importin Alpha Isoform 1 (VIT_205s0077g01440), involved in downy mildew resistance, and GATA Transcription Factor 8 (VIT_205s0077g01450), involved in leaf shape development. Our findings are among the first to examine the genomic regions associated with ecologically important plant traits that facilitate interactions with beneficial mites, and suggest promising candidate genes for breeding and genetic editing to increase naturally occurring predator-based defenses in grapevines.

Understanding how root systems modulate shoot system phenotypes is a fundamental question in plant biology and will be useful in developing resilient agricultural crops. Grafting is a common horticultural practice that joins the roots (rootstock) of one plant to the shoot (scion) of another, providing an excellent method for investigating how these two organ systems affect each other. In this study, we used the French-American hybrid grapevine ‘Chambourcin’ (Vitis L.) as a model to explore the rootstock–scion relationship. We examined leaf shape, ion concentrations, and gene expression in ‘Chambourcin’ grown ungrafted as well as grafted to three different rootstocks (‘SO4’, ‘1103P’ and ‘3309C’) across 2 years and three different irrigation treatments. We found that a significant amount of the variation in leaf shape could be explained by the interaction between rootstock and irrigation. For ion concentrations, the primary source of variation identified was the position of a leaf in a shoot, although rootstock and rootstock by irrigation interaction also explained a significant amount of variation for most ions. Lastly, we found rootstock-specific patterns of gene expression in grafted plants when compared to ungrafted vines. Thus, our work reveals the subtle and complex effect of grafting on ‘Chambourcin’ leaf morphology, ionomics, and gene expression., Horticulture: dissecting the effects of grafting Researchers in the US have uncovered how rootstocks affect scions following grafting, which will help to develop more resilient crops. A team led by Allison Miller of Saint Louis University grafted the ‘Chambourcin’ grape variety onto three different rootstocks and investigated the effect on leaf shape, ion concentration, and gene expression in the scion. They discovered that the rootstock influenced how leaf shape changed in response to different irrigation conditions. A similar irrigation-dependent effect of rootstock was found for the ion composition in the shoot. The team also identified roughly 100 genes with altered expression in each of the grafted vines, including five genes which were altered by all three graft combinations. These findings are a first step toward understanding the relationship between rootstocks and scions and modulating it to produce crops better adapted to challenging environments.

Softening is a hallmark of ripening in fleshy fruits, and has both desirable and undesirable implications for texture and postharvest stability. Accordingly, the timing and extent of pre-harvest ripening and associated textural changes following harvest are key targets for improving fruit quality through breeding. Previously, we identified a large effect locus associated with harvest date and firmness in apple (Malus domestica) using genome-wide association studies (GWAS). Here, we present additional evidence that polymorphisms in or around a transcription factor gene,NAC18.1, may cause variation in these traits. First, we confirmed our previous findings with new phenotype and genotype data from ∼800 apple accessions. In this population, we compared a genetic marker withinNAC18.1to markers targeting three other firmness-related genes currently used by breeders (ACS1,ACO1, andPG1), and found that theNAC18.1marker was the strongest predictor of both firmness at harvest and firmness after 3 months of cold storage. By sequencingNAC18.1across 18 accessions, we revealed two predominant haplotypes containing the single nucleotide polymorphism (SNP) previously identified using GWAS, as well as dozens of additional SNPs and indels in both the coding and promoter sequences.NAC18.1encodes a protein that is orthogolous to the NON-RIPENING (NOR) transcription factor, a regulator of ripening in tomato (Solanum lycopersicum). We introduced bothNAC18.1transgene haplotypes into the tomatonormutant and showed that both haplotypes complement thenorripening deficiency. Taken together, these results indicate that polymorphisms inNAC18.1may underlie substantial variation in apple firmness through modulation of a conserved ripening program.

Long-term agricultural sustainability is dependent in part on our capacity to provide productive, nutritious crops that minimize the negative impacts of agriculture on the landscape. Perennial grains within an agroforestry context offers one solution: These plants produce large root systems that reduce soil erosion and simultaneously have the potential to produce nutrients to combat malnutrition. However, nutrient compositions of wild, perennial, herbaceous species, such as those related to the common bean (Phaseolus vulgaris) are not well known. In this study, seed ion and amino acid concentrations of perennial and annual Phaseolus species were quantified using ionomics and mass spectrometry. No statistical difference was observed for Zn, toxic ions (e.g., As) or essential amino acid concentrations (except threonine) between perennial and annual Phaseolus species. However, differences were observed for some nutritionally important ions. For example, Ca, Cu, Fe, Mg, Mn, and P concentrations were higher in annual species, further, ion and amino acid concentrations appear to be largely independent of each other. These results suggest variability in ion and amino acid concentrations exist in Phaseolus. As new crop candidates are considered for ecological services, nutritional quality should be optimized to maximize nutrient output of sustainable food crops.

International audience; Apples are a nutritious food source with significant amounts of polyphenols that contribute to human health and wellbeing, primarily as dietary antioxidants. Although numerous pre- and post-harvest factors can affect the composition of polyphenols in apples, genetics is presumed to play a major role because polyphenol concentration varies dramatically among apple cultivars. Here we investigated the genetic architecture of apple polyphenols by combining high performance liquid chromatography (HPLC) data with similar to 100,000 single nucleotide polymorphisms (SNPs) from two diverse apple populations. We found that polyphenols can vary in concentration by up to two orders of magnitude across cultivars, and that this dramatic variation was often predictable using genetic markers and frequently controlled by a small number of large effect genetic loci. Using GWAS, we identified candidate genes for the production of quercitrin, epicatechin, catechin, chlorogenic acid, 4-O-caffeoylquinic acid and procyanidins B1, B2, and C1. Our observation that a relatively simple genetic architecture underlies the dramatic variation of key polyphenols in apples suggests that breeders may be able to improve the nutritional value of apples through marker-assisted breeding or gene editing.

Malnutrition is a global public health concern and identifying mechanisms to elevate the nutrient output of crops may minimize nutrient deficiencies. Perennial grains within an agroforestry context offers one solution. The development and integration of perennial crops for food has critically influenced dialogue on the ecological intensification of agriculture and agroforestry. However, the nutrient compositions of wild, perennial, herbaceous species, such as those related to the common bean (Phaseolus vulgaris) are not well known. In this study, seed amino acid and ion concentrations of perennial and annualPhaseolusspecies were quantified using ionomics and mass spectrometry. No statistical difference was observed for Zn, toxic ions (e.g. As) or essential amino acid concentrations (except threonine) between perennial and annualPhaseolusspecies. However, differences were observed for some nutritionally important ions among and within lifespan groups. Ca, Cu, Fe, Mg, Mn, and P concentrations were higher in annual species. Intraspecific variability in ion concentrations and amino acids was observed within species; further, ion concentrations and amino acids differ among annual species and among perennial species. Ion and amino acid concentration appear to be largely independent of each other. These results suggest variability in ion and amino acid concentrations exist in nature. As new crop candidates are considered for ecological services, nutritional quality should be optimized to maximize nutrient output of sustainable food crops.

Exposure to stresses such as temperature fluctuations, drought and UV can cause physiological and epigenetic changes in plants. Such changes may be inherited by progeny of stressed plants and may alter their response to stress. To understand the ability of plants to inherit an epigenetic memory of exposure to cold stress and to analyze physiological manifestations of this memory, we propagated cold-stressed and control plants and compared their progeny under both normal and stress conditions. Our studies revealed that in the progeny of stressed plants, leaf number decreased and bolting occurred earlier. Transposons were also re-activated in the progeny of stressed plants. In addition to wild-type plants, we used the Dicer-like mutants dcl2 , dcl3 and dcl4 because of the role of DCL2, 3 and 4 in siRNA biogenesis and their responses to stress. DCL2 and DCL3 appeared to be more important in the transgenerational stress memory than DCL4, and the changes observed in the progeny of dcl2 and dcl3 mutants were less profound or not evident at all. Thus, this work has expanded our previous study and has shown physiological changes in the progeny of cold-stressed plants, it also has confirmed an important role of DCL2 and DCL3 in passing on the memory of stress exposure to the progeny.

Grapes are one of the most economically and culturally important crops worldwide, and they have been bred for both winemaking and fresh consumption. Here we evaluate patterns of diversity across 33 phenotypes collected over a 17-year period from 580 table and wine grape accessions that belong to one of the world's largest grape gene banks, the grape germplasm collection of the United States Department of Agriculture. We find that phenological events throughout the growing season are correlated, and quantify the marked difference in size between table and wine grapes. By pairing publicly available historical phenotype data with genome-wide polymorphism data, we identify large effect loci controlling traits that have been targeted during domestication and breeding, including hermaphroditism, lighter skin pigmentation and muscat aroma. Breeding for larger berries in table grapes was traditionally concentrated in geographic regions where Islam predominates and alcohol was prohibited, whereas wine grapes retained the ancestral smaller size that is more desirable for winemaking in predominantly Christian regions. We uncover a novel locus with a suggestive association with berry size that harbors a signature of positive selection for larger berries. Our results suggest that religious rules concerning alcohol consumption have had a marked impact on patterns of phenomic and genomic diversity in grapes.

Apple (Malus spp.) is a widely grown and valuable fruit crop. Leaf shape and size are important for flowering in apple and may also be early indicators for other agriculturally valuable traits. We examined 9,000 leaves from 869 unique apple accessions using linear measurements and comprehensive morphometric techniques. We identified allometric variation in the length-to-width aspect ratio between accessions and species of apple. The allometric variation was due to variation in the width of the leaf blade, not length. Aspect ratio was highly correlated with the primary axis of morphometric variation (PC1) quantified using elliptical Fourier descriptors (EFDs) and persistent homology (PH). While the primary source of variation was aspect ratio, subsequent PCs corresponded to complex shape variation not captured by linear measurements. After linking the morphometric information with over 122,000 genome-wide SNPs, we found high narrow-sense heritability values even at later PCs, indicating that comprehensive morphometrics can capture complex, heritable phenotypes. Thus, techniques such as EFDs and PH are capturing heritable biological variation that would be missed using linear measurements alone, and which could potentially be used to select for a hidden phenotype only detectable using comprehensive morphometrics.

Perennial crops are vital contributors to global food production and nutrition. However, the breeding of new perennial crops is an expensive and time-consuming process due to the large size and lengthy juvenile phase of many species. Genomics provides a valuable tool for improving the efficiency of breeding by allowing progeny possessing a trait of interest to be selected at the seed or seedling stage through marker-assisted selection (MAS). The benefits of MAS to a breeder are greatest when the targeted species takes a long time to reach maturity and is expensive to grow and maintain. Thus, MAS holds particular promise in perennials since they are often costly and time-consuming to grow to maturity and evaluate. Well-characterized germplasm that breeders can tap into for improving perennials is often limited in genetic diversity. Wild relatives are a largely untapped source of desirable traits including disease resistance, fruit quality, and rootstock characteristics. This review focuses on the use of genomics-assisted breeding in perennials, especially as it relates to the introgression of useful traits from wild relatives. The identification of genetic markers predictive of beneficial phenotypes derived from wild relatives is hampered by genomic tools designed for domesticated species that are often ill-suited for use in wild relatives. There is therefore an urgent need for better genomic resources from wild relatives. A further barrier to exploiting wild diversity through genomics is the phenotyping bottleneck: well-powered genetic mapping requires accurate and cost-effective characterization of large collections of diverse wild germplasm. While genomics will always be used in combination with traditional breeding methods, it is a powerful tool for accelerating the speed and reducing the costs of breeding while harvesting the potential of wild relatives for improving perennial crops.

Exposure to heat stress causes physiological and epigenetic changes in plants, which may also be altered in the progeny. We compared the progeny of stressed and control Arabidopsis thaliana wild type and Dicer-like mutant dcl2, dcl3, and dcl4 plants for variations in physiology and molecular profile, including global genome methylation, mRNA levels, and histone modifications in the subset of differentially expressed genes at normal conditions and in response to heat stress. We found that the immediate progeny of heat-stressed plants had fewer, but larger leaves, and tended to bolt earlier. Transposon expression was elevated in the progeny of heat-stressed plants, and heat stress in the same generation tended to decrease global genome methylation. Progeny of stressed plants had increased expression of HSFA2, and reduction in MSH2, ROS1, and several SUVH genes. Gene expression positively correlated with permissive histone marks and negatively correlated with repressive marks. Overall, the progeny of heat stressed plants varied in both their physiology and epigenome and dcl2 and dcl3 mutants were partially deficient for these changes.

Angiosperms do not contain a distinct germline, but rather develop gametes from gametophyte initials that undergo cell division. These gametes contain cells that give rise to an endosperm and the embryo. DNA methylation is decreased in the vegetative nucleus (VN) and central cell nucleus (CCN) resulting in expression of transposable elements (TEs). It is thought that the siRNAs produced in response to TE expression are able to travel to the sperm cells and egg cells from VN and CCN, respectively, in order to enforce silencing there. Plant gene imprinting occurs as a result of the difference in TE expression between paternal (silent) and maternal (expressed) genomes in the endosperm. Demethylation during gametogenesis helps ensure that even newly integrated TEs are expressed and therefore silenced by the resulting siRNA production. A final form of epigenetic control is modification of histones, which includes accumulation of the H3 variant HTR10 in mature sperm that is then completely replaced following fertilization. In females, the histone isoforms present in the egg cell and CCN differ, potentially helping to differentiate the two components during gametogenesis. The histone dimorphism between cells is eliminated in both males and females following fertilization, likely preventing these newly acquired epigenetic marks from being transmitted to progeny.

Exposure to abiotic and biotic stress results in changes in plant physiology and triggers genomic instability. Recent reports suggest that the progeny of stressed plants also exhibit changes in genome stability, stress tolerance, and methylation. Here we analyzed whether exposure to Ni(2+), Cd(2+), and Cu(2+) salts leads to transgenerational changes in homologous recombination frequency and stress tolerance. We found that the immediate progeny of stressed plants exhibited an increased rate of recombination. However, when the progeny of stressed plants was propagated without stress, recombination reverted to normal levels. Exposure of plants to heavy metals for five consecutive generations (S1-S5) resulted in recombination frequency being maintained at a high level. Skipping stress following two to three generations of propagation with 50 mM Ni(2+) or Cd(2+) did not decrease the recombination frequency, suggesting plant acclimation to upregulated recombination. Analysis of the progeny of plants exposed to Cu(2+) and Ni(2+) indicated higher stress tolerance to the heavy metal parental plants were exposed to. Tolerance was higher in plants propagated with stress for three to five generations, which resulted in longer roots than plants propagated on heavy metals for only one to two generations. Tolerance was also more prominent upon exposure to a higher concentration of salts. The progeny of stressed plants were also more tolerant to NaCl and methyl methane sulfonate.

Stress has a negative impact on crop yield by altering a gain in biomass and affecting seed set. Recent reports suggest that exposure to stress also influences the response of the progeny. In this paper, we analyzed seed size, leaf size, bolting time and transposon expression in 2 consecutive generations of Arabidopsis thaliana plants exposed to moderate UV-C stress. Since previous reports suggested a potential role of Dicer-like (DCL) proteins in the establishment of transgenerational response, we used dcl2, dcl3 and dcl4 mutants in parallel with wild-type plants. These studies revealed that leaf number decreased in the progeny of UV-C stressed plants, and bolting occurred later. Transposons were also re-activated in the progeny of stressed plants. Changes in the dcl mutants were less prominent than in wild-type plants. DCL2 and DCL3 appeared to be more important in the transgenerational stress memory than DCL4 because transgenerational changes were less profound in the dcl2 and dcl3 mutants.

Background Grapes are one of the world’s most valuable crops and most are made into wine. Grapes belong to the genus Vitis, which includes over 60 inter-fertile species. The most common grape cultivars derive their entire ancestry from the species Vitis vinifera, but wild relatives have also been exploited to create hybrid cultivars, often with increased disease resistance. Results We evaluate the genetic ancestry of some of the most widely grown commercial hybrids from North America and Europe. Using genotyping-by-sequencing (GBS), we generated 2482 SNPs and 56 indels from 7 wild Vitis, 7 V. vinifera, and 64 hybrid cultivars. We used a principal component analysis (PCA) based ancestry estimation procedure and verified its accuracy with both empirical and simulated data. V. vinifera ancestry ranged from 11 % to 76 % across hybrids studied. Approximately one third (22/64) of the hybrids have ancestry estimates consistent with F1 hybridization: they derive half of their ancestry from wild Vitis and half from V. vinifera. Conclusions Our results suggest that hybrid grape breeding is in its infancy. The distribution of V. vinifera ancestry across hybrids also suggests that backcrosses to wild Vitis species have been more frequent than backcrosses to V. vinifera during hybrid grape breeding. This pattern is unusual in crop breeding, as it is most common to repeatedly backcross to elite, or domesticated, germplasm. We anticipate our method can be extended to facilitate marker-assisted selection in order to introgress beneficial wild Vitis traits, while allowing for offspring with the highest V. vinifera content to be selected at the seedling stage. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2834-8) contains supplementary material, which is available to authorized users.