Melilotus albus
Desr. is recognized as one of the species with greatest potential as a forage source for ruminants in saline rangelands. The objectives of the current research were threefold: (1) to ...estimate heritability and genetic correlation of traits associated with winter forage production and regrowth capacity in
M. albus
prebreeding material, as measured in spaced plants grown in a nonsaline environment; (2) to evaluate winter forage production of a selected population grown in plots at sites with contrasting soil salinities; and (3) to evaluate the agronomic performance of blended (mixed) populations and monocultures of
M. albus
grown in plots. Results indicated presence of genetic variability associated with winter production and regrowth capacity in a prebreeding population selected for one trait, viz. late flowering. Results also showed that selection in a nonsaline environment did not modify the relative salinity tolerance of
M. albus
populations. Finally, varietal mixtures (blends) of two selected populations showed a slight increase in and more seasonally balanced dry matter (DM) yield than monocultures. Mixtures combined favorable characteristics from the two selected populations (i.e., highest winter forage production, as expressed in the SP1 population, and highest regrowth capacity, as expressed in the SP2 population). Furthermore, results indicated that
M. albus
genotypes naturalized in Argentina could be used as genetic resources for sweet clover breeding for saline environments and that alternative breeding approaches could improve forage productivity in saline environments.
(common name dallisgrass), a productive C4 grass native to South America, is an important pasture grass found throughout the temperate warm regions of the world. It is characterized by its tolerance ...to frost and water stress and a higher forage quality than other C4 forage grasses.
includes tetraploid (2
= 40), sexual, and pentaploid (2
= 50) apomictic forms, but is predominantly cultivated in an apomictic monoculture, which implies a high risk that biotic and abiotic stresses could seriously affect the grass productivity. The obtention of reproducible and efficient protocols of regeneration and transformation are valuable tools to obtain genetic modified grasses with improved agronomics traits. In this review, we present the current regeneration and transformation methods of both apomictic and sexual cultivars of
, discuss their strengths and limitations, and focus on the perspectives of genetic modification for producing new generation of forages. The advances in this area of research lead us to consider
as a model species for the molecular improvement of C4 perennial forage species.
Paspalum dilatatum Poir. (common name dallisgrass) is a native grass species of South America, with special relevance to dairy and red meat production. P. dilatatum exhibits higher forage quality ...than other C4 forage grasses and is tolerant to frost and water stress. This species is predominantly cultivated in an apomictic monoculture, with an inherent high risk that biotic and abiotic stresses could potentially devastate productivity. Therefore, advanced breeding strategies that characterise and use available genetic diversity, or assess germplasm collections effectively are required to deliver advanced cultivars for production systems. However, there are limited genomic resources available for this forage grass species.
Transcriptome sequencing using second-generation sequencing platforms has been employed using pooled RNA from different tissues (stems, roots, leaves and inflorescences) at the final reproductive stage of P. dilatatum cultivar Primo. A total of 324,695 sequence reads were obtained, corresponding to c. 102 Mbp. The sequences were assembled, generating 20,169 contigs of a combined length of 9,336,138 nucleotides. The contigs were BLAST analysed against the fully sequenced grass species of Oryza sativa subsp. japonica, Brachypodium distachyon, the closely related Sorghum bicolor and foxtail millet (Setaria italica) genomes as well as against the UniRef 90 protein database allowing a comprehensive gene ontology analysis to be performed. The contigs generated from the transcript sequencing were also analysed for the presence of simple sequence repeats (SSRs). A total of 2,339 SSR motifs were identified within 1,989 contigs and corresponding primer pairs were designed. Empirical validation of a cohort of 96 SSRs was performed, with 34% being polymorphic between sexual and apomictic biotypes.
The development of genetic and genomic resources for P. dilatatum will contribute to gene discovery and expression studies. Association of gene function with agronomic traits will significantly enable molecular breeding and advance germplasm enhancement.
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Antarctic hair grass (Deschampsia antarctica E. Desv.), the only grass indigenous to Antarctica, has well-developed freezing tolerance, strongly induced by cold acclimation. Here, we show that in ...response to low temperatures, D. antarctica expresses potent recrystallization inhibition (RI) activity that, inhibits the growth of small ice crystals into potentially damaging large ones, is proteinaceous and localized to the apoplasm. A gene family from D. antarctica encoding putative homologs of an ice recrystallization inhibition protein (IRIP) has been isolated and characterized. IRIPs are apoplastically targeted proteins with two potential ice-binding motifs: 1-9 leucine-rich repeats (LRRs) and c. 16 'IRIP' repeats. IRIP genes appear to be confined to the grass subfamily Pooideae and their products, exhibit sequence similarity to phytosulphokine receptors and are predicted to adopt conformations with two ice-binding surfaces. D. antarctica IRIP (DaIRIP) transcript levels are greatly enhanced in leaf tissue following cold acclimation. Transgenic Arabidopsis thaliana expressing a DaIRIP has novel RI activity, and purified DaIRIP, when added back to extracts of leaves from non-acclimated D. antarctica, can reconstitute the activity found in acclimated plants. We propose that IRIP-mediated RI activity may contribute to the cryotolerance of D. antarctica, and thus to its unique ability to have colonized Antarctica.
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Elymus scabrifolius es una gramínea perenne nativa de Sudamérica con gran potencial como recurso forrajero para ambientes con limitantes edáficas. En el presente trabajo se analizó la utilización de ...caracteres morfológicos y marcadores moleculares AFLP para la identificación genotípica de seis accesiones, un cultivar comercial y siete híbridos artificiales de esta especie. Ambos tipos de marcadores permitieron diferenciar a los materiales analizados en los respectivos dendrogramas, aunque las relaciones entre materiales variaron según el tipo de marcador. El Análisis de Componentes Principales permitió identificar las variables más relevantes para la diferenciación morfológica. Los híbridos se diferenciaron morfológicamente de ambos parentales, excepto un híbrido que se agrupó con su material paterno. Aunque en el análisis de los marcadores AFLP los híbridos se agruparon con uno de sus parentales, se pudo corroborar su origen híbrido mediante el registro de bandas paternas y polimórficas entre parentales. Se concluye que las metodologías empleadas para caracterizar los materiales analizados de E. scabrifolius serían de gran utilidad para el manejo eficiente de colecciones de germoplasma como así también para su utilización en programas de mejoramiento genético.
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This is the first report about Na and K fluxes and heritability of Na exclusion in the Elymus genus. Argentine wheatgrass Elymus scabrifolius (Döll) J.H. Hunz. is an important forage genetic resource ...for saline environments. A previous study showed that salt‐sensitive lines accumulated toxic levels of Na in shoots. The aim of this study was to increase the understanding of Na exclusion in Argentine wheatgrass. Growth and Na and K accumulation rates were analyzed in two homozygous salt‐tolerant genotypes (T1 and T2) and a salt‐sensitive genotype (S1), under different salt stress levels. The Na accumulation rate in shoots was 1.5 times higher in the sensitive line than in the tolerant ones at 100 mM NaCl, and five times higher at 200 mM NaCl. A negative association was found between Na concentration and leaf weight in parent genotypes, F1, and segregating F2 populations generated by crossing homozygous S1 and T2, suggesting that growth in the third leaf was more affected in Na‐including genotypes. The inheritance of Na exclusion was estimated under salt stress conditions in a segregating F2 population and in F2:3 families obtained by crossing two homozygous genotypes with contrasting values of shoot Na exclusion. In the F2 population and F2:3 families, Na concentration segregation was compatible with intermediate inheritance (with very low partial dominance). High heritability values estimated for Na exclusion suggest that this trait might be used as a priority selection criterion for salt tolerance. Results will be useful to design breeding strategies for salt tolerance in this and related species of the Elymus genus.
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Seed germination and seedling emergence are key processes for population recruitment. Flooding and grazing are disturbances forming gaps that may strongly influence recruitment patterns in space and ...time, but their combined effects and action mechanisms have rarely been addressed. In this study we analysed the effects of microhabitat conditions associated with winter flooding and spring-summer defoliation on seed germination and seedling establishment of Paspalum dilatatum, a dominant perennial C₄ grass in native grasslands of the Flooding Pampa, Argentina. The dynamics of seedling emergence from natural seed banks and buried seeds was studied in a factorial experiment with flooding and defoliation treatments applied to soil monoliths (mesocosms) collected from natural grassland. Additional laboratory experiments were applied to investigate seed germination under different combinations of temperature, light quality and simulated flooding. Seed germination and seedling emergence of P. dilatatum were promoted by flooding and high intensity defoliation. Gaps generated by flooding were maintained by high intensity defoliation exercising a synergistic effect on survival seedlings. Flooding resulted in the breaking of seed dormancy and higher germination rates associated with alternating temperature and the activation of the phytochrome system. Our results indicate that microhabitat conditions associated with the disturbances forming gaps, such as flooding and heavy grazing, synergistically promote the recruitment process of this dominant grass species.
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Bromus setifolius var. pictus (Hook) Skottsb., B. setifolius var. setifolius Presl. and B.setifolius var. brevifolius Ness are three native Patagonian taxa in the section Pnigma Dumort of the genus ...Bromus L. AFLP and RAPD analysis, in conjunction with genetic distance measurements and statistical techniques, revealed variation within this group and indicated that B. setifolius var. brevifolius was closely related to B. setifolius var. pictus, with both taxa being more distantly related to B. setifolius var. setifolius. Cytogenetic analysis confirmed the chromosomal number of B. setifolius var. pictus (2n = 70) and B. setifolius var. setifolius (2n = 28) and showed for the first time that B. setifolius var. brevifolius had 2n = 70. The combination of molecular genetic and cytogenetic evidence supported a species status for two of the three taxa and suggested hypotheses for the evolutionary origin of these complex taxa. Species status was also indicated for B. setifolius var. setifolius. Based on these findings, we suggest that B. setifolius var. pictus be referred to as B. pictus Hook var. pictus, and B. setifolius var brevifolius as B. pictus Hook var brevifolius. The correlation between AFLP diversity and variation in ecological parameters suggested that this marker system could be used to assess breeding progress and to monitor the domestication of Patagonian Bromus species for agronomic use.
Water supply affects seed germination and seedling establishment of shallow-rooted warm-season grasses. This may explain the difficulty of incorporating Dallisgrass (Paspalum dilatatum Poir.) into ...humid temperate grasslands through interseeding. We studied the effects of water availability on seed germination and seedling growth under controlled conditions to determine which step of the establishment process was most affected. In a laboratory experiment, seeds were germinated at 0, –0.25, –0.5, –0.75, and –1MPa water availability generated with solutions of polyethylene glycol. Although both maximum rate and total germination (P < 0.05) significantly decreased with increased water stress, the speed of germination was even more sensitive. In a greenhouse experiment, variations in seedling emergence and morphological characteristics were measured in relation to water availability. Pregerminated and dry seeds were sown in pots that were irrigated at 1-, 2-, 4-, or 7-day intervals. This species showed high sensitivity to water stress during germination and early emergence. High emergence was obtained from the daily irrigation treatment. In all other treatments, where watering frequency was extended, emergence was decreased. Results suggest that rapid germination and early adventitious root growth can be obtained only with reliable availability of water. These conditions, combined with the high temperatures required for breaking seed dormancy, occur infrequently, explaining the difficulty of achieving successful establishment of Dallisgrass. Water availability during seed germination and seedling emergence is a critical factor for survival of this species.
El suministro de agua afecta la germinación y el establecimiento de las gramíneas megatérmicas de raíces superficiales. Esto puede explicar la dificultad para incorporar Pasto miel en pastizales templado húmedos por medio de la intersiembra. Se evaluaron los efectos de la disponibilidad hídrica sobre la germinación y el crecimiento de plántulas bajo condiciones controladas para determinar cuál es el paso del proceso de establecimiento que es más afectado. En un experimento de laboratorio se incubaron semillas variando la disponibilidad de agua mediante el uso de soluciones acuosas de Polietilenglicol (PEG 8000) (0, -0.25, -0.5, -0.75, y –1 MPa). La velocidad de germinación fue más sensible que la germinación total al aumento del estrés hídrico, aunque ambas disminuyeron significativamente (P < 0.05). En un experimento, realizado en invernáculo, se caracterizó morfológicamente el crecimiento aéreo y radical de plántulas con diferente disponibilidad hídrica. Se sembraron semillas pre-germinadas y secas en macetas sometidas a diferentes frecuencias de riego (cada 1, 2, 4, y 7 días). Esta especie mostró una sensibilidad elevada al estrés hídrico durante la germinación y la emergencia temprana. La mayor emergencia se obtuvo bajo el tratamiento de riego diario. En los otros tratamientos, la emergencia de plántulas disminuyó con la menor frecuencia de riegos. Los resultados sugieren que la germinación rápida y el desarrollo temprano de las raíces adventicias sólo pueden lograrse con una disponibilidad de agua segura. Estas condiciones, combinadas con las temperaturas elevadas requeridas para romper la dormición de las semillas ocurren con baja frecuencia, y explicarían la dificultad para lograr el establecimiento exitoso de Pasto miel. La disponibilidad de humedad durante la germinación de las semillas y la emergencia de las plántulas es un factor crítico para la sobrevivencia de esta especie.
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Water supply affects seed germination and seedling establishment of shallow-rooted warm-season grasses. This may explain the difficulty of incorporating Dallisgrass (Paspalum dilatatum Poir.) into ...humid temperate grasslands through interseeding. We studied the effects of water availability on seed germination and seedling growth under controlled conditions to determine which step of the establishment process was most affected. In a laboratory experiment, seeds were germinated at 0, –0.25, –0.5, –0.75, and –1 MPa water availability generated with solutions of polyethylene glycol. Although both maximum rate and total germination (P < 0.05) significantly decreased with increased water stress, the speed of germination was even more sensitive. In a greenhouse experiment, variations in seedling emergence and morphological characteristics were measured in relation to water availability. Pregerminated and dry seeds were sown in pots that were irrigated at 1-, 2- , 4-, or 7-day intervals. This species showed high sensitivity to water stress during germination and early emergence. High emergence was obtained from the daily irrigation treatment. In all other treatments, where watering frequency was extended, emergence was decreased. Results suggest that rapid germination and early adventitious root growth can be obtained only with reliable availability of water. These conditions, combined with the high temperatures required for breaking seed dormancy, occur infrequently, explaining the difficulty of achieving successful establishment of Dallisgrass. Water availability during seed germination and seedling emergence is a critical factor for survival of this species.
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