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Toward Genomics-Based Breeding in C3 Cool-Season Perennial Grasses.

ABSTRACT: Most important food and feed crops in the world belong to the C3 grass family. The future of food security is highly reliant on achieving genetic gains of those grasses. Conventional breeding methods have already reached a plateau for improving major crops. Genomics tools and resources have opened an avenue to explore genome-wide variability and make use of the variation for enhancing genetic gains in breeding programs. Major C3 annual cereal breeding programs are well equipped with genomic tools; however, genomic research of C3 cool-season perennial grasses is lagging behind. In this review, we discuss the currently available genomics tools and approaches useful for C3 cool-season perennial grass breeding. Along with a general review, we emphasize the discussion focusing on forage grasses that were considered orphan and have little or no genetic information available. Transcriptome sequencing and genotype-by-sequencing technology for genome-wide marker detection using next-generation sequencing (NGS) are very promising as genomics tools. Most C3 cool-season perennial grass members have no prior genetic information; thus NGS technology will enhance collinear study with other C3 model grasses like Brachypodium and rice. Transcriptomics data can be used for identification of functional genes and molecular markers, i.e., polymorphism markers and simple sequence repeats (SSRs). Genome-wide association study with NGS-based markers will facilitate marker identification for marker-assisted selection. With limited genetic information, genomic selection holds great promise to breeders for attaining maximum genetic gain of the cool-season C3 perennial grasses. Application of all these tools can ensure better genetic gains, reduce length of selection cycles, and facilitate cultivar development to meet the future demand for food and fodder.

SUBMITTER: Talukder SK

PROVIDER: S-EPMC5526908 | biostudies-other | 2017

REPOSITORIES: biostudies-other

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Project description:In semi-arid and arid regions, the selection of suitable grass species with high-yield production, tolerance to drought stress, and potential for recovery from drought is of special importance. Despite extensive research in cool-season grasses, inter-species differences in post-drought recovery, persistence, survival, and summer dormancy and their relationship with drought tolerance need more investigation. In the present study, 28 diverse genotypes belonged to seven cool-season grass species, including Festuca arundinacea (tall fescue), Festuca pratensis (meadow fescue), Festuca ovina (sheep fescue), Festuca rubra (red fescue), Lolium perenne (perennial ryegrass), Lolium multiflorum (Italian ryegrass) and Lolium × hybridum were evaluated during 2016-2019 under three irrigation regimes (normal, mild, and intense drought stress). Then in the fourth year (on August 2019), irrigation was withheld at all previous irrigation regimes for two months during summer, and then species were re-irrigated to study the effect of prolonged drought conditions. A wide range of genetic diversity was detected in all the measured traits among and within species in response to different irrigation levels. Recurrent drought stress decreased forage productivity, post-drought recovery, and survival in all grass species. Among the studied species, tall fescue had higher forage production, drought tolerance, survival, recovery rate, and persistence. Sheep fescue had low forage production and recovery after drought. Drought tolerance (based on stress tolerance score, STS) was highly associated with forage yield and post-drought recovery and partially with summer dormancy under both mild and intense drought stress conditions. This indicated that selection based on higher STS would lead to choosing genotypes with better recovery after prolonged drought. Superior species and preferable genotypes for forage use from species Festuca arundinacea and for turf application from species Festuca arundinacea, Lolium perenne and Lolium × hybridum were identified across different water environments for future programs.

Project description:Abiotic stress is an important factor affecting turf establishment and limiting the sustainability of the turf industry. To alleviate the effects of combined cold and drought stress in cold- and drought-prone regions, it is essential to select and introduce turfgrass germplasms that are suitable for these conditions for successful turf establishment. Thus, we evaluated the effects of combined extreme cold and drought stress on the morphological, plant leaf functional, photosynthetic, and physiological and biochemical traits of 16 wild annual bluegrass (Poa annua) germplasms. We found that there were significant differences (P < 0.05) among different provenances, combined cold and drought stress, and the main interaction factors. Combined cold and drought stress altered the morphological characteristics of the 16 germplasms to varying degrees. Furthermore, combined cold and drought stress significantly reduced the net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), instantaneous water use efficiency (WUE), chlorophyll content, chlorophyll fluorescence parameters, accumulated intercellular CO2 concentration (Ci), and relative electrical conductivity (REC) and malondialdehyde (MDA), proline (Pro), soluble protein (SP), soluble sugar (SS), superoxide anion (O2.-), hydrogen peroxide (H2O2), and hydroxyl radical (·OH) and other active oxygen, and increased the superoxide dismutase activity (SOD), peroxidase activity (POD), catalase activity (CAT), ascorbate peroxidase activity (APX) and glutathione reductase (GR) activities. Comprehensive evaluation using principal component analysis (PCA), membership function analysis, and clustered heatmaps indicated that the 'HZ' germplasm had stronger combined cold and drought tolerance, whereas the 'ZQ' germplasm was more sensitive to combined cold and drought, which was roughly consistent with the order of morphological damage symptoms. Therefore, it is recommended to use the 'HZ' germplasm for planting projects in cold- and drought-prone areas, while the 'ZQ' germplasm is more suitable for use under warmer and non-water-deficient conditions.

Project description:Symptomless fungal endophytes in the genus Epichloë are repeatedly mentioned to increase tolerance of cool-season grasses to a wide range of environmental stress factors, mainly drought. However, the generality of this idea is challenged because (i) most studies have been conducted on two economically important forage grasses {tall fescue [Festuca arundinacea (Schreb.) Dumort] and perennial ryegrass (Lolium perenne L.)}, (ii) endophyte-mediated mechanisms and effects on plant responses to drought have shown to be highly variable across species, and that (iii) symbiosis incidence in plant populations occurring in extremely arid environments is usually low. We question this idea by reviewing the existing information about Epichloë fungal endophyte effects on drought tolerance in cool-season grasses. We combined standard review, vote counting, and calculation of effect sizes to synthesize the literature, identify information gaps, and guide future research. The total number of studies was higher for domesticated than for wild species, a ratio that was balanced when papers with data quality for effect size calculus were considered. After the drought, endophyte-infected plants accumulated more aboveground and belowground biomass than non-infected counterparts, while no effect on tillering was observed. However, these effects remained significant for wild (even on tillering) but not for domesticated species. Interestingly, despite the continuous effort in determining physiological mechanisms behind the endophyte effects, no studies evaluated plant fecundity as a measure of ecological fitness nor vital rates (such as survival) as to escalate individual-level variables to population. Together with the high variability in results, our work shows that generalizing a positive effect of fungal endophytes in plant tolerance to drought may be misleading. Future studies combining field surveys with manipulative experiments would allow us to unravel the role of fungal endophytes in plant adaptation by considering the evolutionary history of species and populations to the different ecological contexts.

Project description:Background:Incorporation of legume species into native North American pastures is considered an effective method to increase native pasture productivity and improve the nutritive value of forage. This study evaluated the effects of inclusion of purple prairie clover (PPC, Dalea purpurea Vent.), a native legume forage, with native cool-season grasses on the in vitro fermentation and in situ digestibility of mixed forages. Methods:Whole plant PPC and mixtures of cool-season grasses were harvested when the PPC reached the vegetative (VEG), full flower (FL) and seedpod (SP) stages, and were combined in ratios (DM basis) of 0:100, 25:75, 50:50, 75:25 and 100:0 at each maturity. In vitro ruminal incubations using these mixtures were conducted for 48?h to determine gas production (GP), in vitro DM disappearance (IVDMD), total volatile fatty acids (VFA) and ammonia-N production. Mixtures of forages harvested when the PPC reached the FL stage and 50:50 mixture of forages harvested at VEG, FL and SP stages were incubated in the rumen of three heifers for 0, 2, 6, 12, 24, 48, 72 and 96?h to determine in situ degradabilities of DM, neutral detergent fibre (aNDF) and crude protein (CP). Results:Contents of aNDF and ADF increased (P?<?0.01), while CP decreased (P?<?0.001) as PPC matured. Concentrations of extractable condensed tannins in PPC ranked as FL?>?VEG?>?SP (P <?0.05). Regardless of PPC proportions in the mixture, GP decreased (P <?0.05) with increasing PPC maturity. Increasing PPC proportions linearly increased (P?<?0.001) GP, IVDMD and total VFA at VEG, but linearly decreased (P?<?0.001) them at SP. Irrespective of PPC maturity, ammonia-N production linearly increased (P?<?0.01) with increasing proportions of PPC and the concentration was higher (P?<?0.05) at VEG than at FL and SP stages. Increasing proportion of PPC at either maturity linearly increased (P?<?0.001) molar percentage of acetate (A) and branched-chain VFA, but linearly decreased (P?<?0.001) molar percentage of propionate (P), resulting in a linearly increase (P?<?0.001) in the A:P ratio. Increasing FL PPC in the mixture linearly and quadratically (P?<?0.01) increased a (soluble fraction), but linearly and quadratically decreased (P?<?0.01) b (potentially degradable fraction) for DM and aNDF, resulting in linear (P?<?0.05) and quadratic (P?<?0.01) increases in DM and aNDF maximum potential degradabilities (a + b). Effective degradabilities of DM and aNDF were also linearly and quadratically increased (P?<?0.05), and CP was quadratically increased (P?<?0.05) with increasing FL PPC, with the greatest effective degradability being observed with ratios between 50:50 and 75:25. Ruminal maximum potential degradabilities of DM and aNDF decreased (P?<?0.001) as the forage matured. Effective degradability of DM ranked as VEG?>?FL?>?SP (P?<?0.001), whereas the effective degradability of aNDF was similar between VEG and FL and both were greater (P?<?0.01) than SP. Conclusions:Inclusion of vegetative PPC in a mixed forage diet resulted in the greatest digestibility and incorporation of PPC before seedpod stage with native grasses had a positive effect on ruminal fermentation. Effects of PPC on ruminal digestion depend on both the stage of maturity and its proportion in mixed legume-grass pastures. Pastures containing 50% of PPC in full flower stage would likely provide the greatest quality diet to grazing ruminants subject to potential animal selectivity.

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Toward Genomics-Based Breeding in C3 Cool-Season Perennial Grasses.

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