Patrones de reclutamiento en cuatro especies de Physaria (Brassicaceae): implicancias para el mantenimiento de la densidad en poblaciones silvestres y en cultivo

En zonas áridas, el reclutamiento de nuevos individuos es un proceso crítico que determina la viabilidad poblacional, el potencial de invasión de plantas alóctonas y el éxito en el establecimiento de cultivos. Se evaluaron las principales etapas del reclutamiento (lluvia de semillas, fecha de emergencia y supervivencia de las plántulas) en cuatro especies de Physaria (P. gracilis, P. angustifolia, P. pinetorum, y P. mendocina) en un experimento a campo en la Patagonia argentina, con el objetivo evaluar el potencial de este proceso para entender la dinámica poblacional y su utilidad como una alternativa sustentable de restablecimiento del cultivo. Se estudió el efecto de la disponibilidad de agua y de la densidad inicial de plántulas sobre la densidad final del cultivo. La cantidad total de semillas dispersadas fue mayor en P. gracilis y P. pinetorum que en las otras especies. No hubo germinación en P. mendocina. Las semillas de P. pinetorum germinaron a fines del verano, mientras que el resto de las especies germinó en primavera. La supervivencia estuvo modulada por un mecanismo denso-dependiente. En P. pinetorum, la densidad de plántulas fue estable en el tiempo en las parcelas de baja densidad inicial, mientras que decreció en las parcelas de densidades media y alta. A pesar de esto, la densidad final fue mayor en las parcelas de alta densidad inicial. La densidad final de P. gracilis respondió a la frecuencia de riego. Concluimos que la cantidad de semillas es adecuada para el restablecimiento de la población en las cuatro especies, aunque los procesos que resultan en la densidad final fueron dependientes de la especie. El control apropiado de la densidad inicial de plántulas jugaría un rol relevante para que el restablecimiento se produzca a densidades apropiadas para el cultivo en P. pinetorum.Seedling recruitment is a critical stage of a plant's cycle which determines population viability, the potential for invasiveness of a plant species and the success of establishment of a crop, among other processes. We evaluated the most relevant stages leading to recruitment (seed-rain, the time of seedling emergence, and seedling survival) in four species of Physaria (P. gracilis, P. angustifolia, Physaria pinetorum and P. mendocina) in a field experiment in Patagonia, Argentina, to assess the possibility of using spontaneous recruitment to understand population dynamics and to evaluate the potential of this process as a tool for crop reestablishment. We determined the effect of water availability and initial seedling density on final stand density. The total amount of dispersed seed was higher in P. gracilis and P. pinetorum than in the other two species. Physariapinetorum germinated in late summer, while P. angustifolia and P. gracilis germinatedin spring. No germination was registered for P. mendocina. In the three species whose seeds germinated, seedling survival was modulated by a density-dependent mechanism. For P. pinetorum seedling density was stable over time in low-density plots, while it decreased in high- and medium-density plots. Still, the highest final density was found in those plots with high initial density. Final density of P. gracilis also responded to irrigation treatment. The amount of dispersed seeds was adequate for the re-establishment of the crop in all four species, although the following stages were species-dependent. An appropriate control of seedling density at the initial stage of crop establishment may play a relevant role in the proper regeneration of the crop.Fil: González Paleo, Luciana. Museo Paleontológico Egidio Feruglio; Argentina. Universidad Nacional de la Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pastor Pastor, Alejandro. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Bar Lamas, Marlene Ivonne. Universidad Nacional de la Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vilela, Alejandra Elena. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ravetta, Damián Andrés. Museo Paleontológico Egidio Feruglio; Argentina. Universidad Nacional de la Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Progress and bottlenecks in the early domestication of the perennial oilseed Silphium integrifolium, a sunflower substitute

Silflower (Silphium integrifolium Michx.) is in the early stages of domestication as a perennial version of oilseed sunflower, its close relative. Grain crops with deep perennial root systems will provide farmers with new alternatives for managing soil moisture and limiting or remediating soil erosion, fertilizer leaching, and loss of soil biota. Several cycles of selection for increased seed production potential following initial germplasm evaluation in 2002 have provided opportunities to document the botany and ecology of this relatively obscure species, to compare agronomic practices for improving its propagation and management, and to evaluate the differences between semi-domesticated and wild accessions that have accrued over this time through intentional and unintentional genetic processes. Key findings include: domestication has increased aboveground biomass at seedling and adult stages; seed yield has increased more, achieving modest improvement in harvest index. Harvest index decreases with nitrogen fertilization. Silflower acquires nitrogen and water from greater depth than typical crops. In agricultural silflower stands within its native range, we found that Puccinia silphii (rust) and Eucosma giganteana (moth) populations build up to unacceptable levels, but we also found genetic variation for traits contributing to resistance or tolerance. Breeding or management for reduced height and vegetative plasticity should be top priorities for future silflower research outside its native range.Fil: Vilela, Alejandra Elena. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: González Paleo, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Turner, Kathryn. The Land Institute; Estados UnidosFil: Peterson, Kelsey. The Land Institute; Estados UnidosFil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Crews, Timothy E.. The Land Institute; Estados UnidosFil: Van Tassel, David. The Land Institute; Estados Unido

Long-term plasticity in growth, storage and defense allocation produces drought-tolerant juvenile shrubs of Prosopis alpataco R.A. Philippi (Fabaceae)

Evaluation of phenotypic plasticity of plants is important to predict the long-term fate of populations exposed to environmental change. Climate scenarios predict a decrease in rainfall and increase in temperature for Northern Patagonia (Argentina). The long-term assessment of the effect of water shortage on allocation patterns of . Prosopis alpataco provides insights into how climate change could affect this dominant shrub of the Monte Desert. A single-factor (water supply) field experiment was conducted. Phenotypic plasticity in biomass partitioning and allocation to storage and defense was assessed over the course of pre-reproductive growth during five years. Water-effect and size-dependent effects were sorted out. Our results indicate that as plants grow larger, root:shoot ratio increases, as well as total non-structural carbohydrates pool, irrespective of water treatment. Increasing belowground allocation through partitioning to reserves instead of allocation to non-storage mass, favors carbohydrate forms that later can be mobilized. Spine mass ratio increased 3-fold in response to drought. These conservative strategies might facilitate the persistence of . Prosopis alpataco in a novel and drier environment, through the production of drought-tolerant juvenile individuals.Fil: Vilela, Alejandra Elena. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Agüero, Paola R.. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Ravetta, Damián Andrés. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: González Paleo, Luciana. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Balancing forage production, seed yield, and pest management in the perennial sunflower silphium integrifolium (Asteraceae)

The perennial sunflower Silphium integrifolium Michx. (Asteraceae), also known as silflower, is a prospective dual-purpose forage plus grain crop. Pre-flowering biomass harvest for animal feed and the subsequent delay in plant growth and anthesis has the potential to benefit seed yield and/or offset yield loss from native pests, such as the native North American Eucosma giganteana (Lepidopera: Tortricidae). The aim of this study was to develop a cropping technology for silflower to (A) balance forage and grain production and (B) minimize seed loss. Silflower produced high-quality forage, but biomass harvest in early spring reduced same-season seed production by 45%. Despite significantly delaying flowering, forage harvest alone did not effectively reduce Eucosma colonization, although treating plants with the insecticide permethrin did reduce colonization. Our results do not support the proposal that S. integrifolium could be profitably harvested for both high quality forage and as an oilseed grain within the same season. Nevertheless, our findings suggest the possibility of developing a strategy of alternating between forage or seed production, depending on their differential economic values. The choice between harvesting biomass vs. seed could be made much later in the season for this perennial crop than the choice of planting an annual forage vs. annual grain crop.Fil: Vilela, Alejandra Elena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: González Paleo, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Murrell, Ebony G.. The Land Institute.; Estados UnidosFil: Van Tassel, David. The Land Institute.; Estados Unido

Indirect changes associated with a selection program for increased seed-yield in wild species of Lesquerella (Brassicaceae): Are we developing a phenotype opposite to the expected ideotype?

Seed-yield stability, frequently associated with drought-tolerance strategies, is one of the main breeding objectives for the development of crops for semi-arid mediterranean-type environments. Since breeding of new industrial crops targeted for arid lands is not appreciably different from that of traditional crops, higher yield is achieved by increased harvest-index, at the cost of losing traits associated with drought-tolerance and reduced seed-yield stability. Using Lesquerella as a model we compared selected and unselected accessions of annual (L. gracilis and L. angustifolia) and perennial (L. pinetorum and L. mendocina) genotypes grown in field experiments in Patagonia, Argentina. Our objective was to assess the effects of breeding for increased seed-yield on traits related to the main characteristics that define the most common ideotype for mediterranean-type environments: early vigor, conservative growth strategy post-anthesis and reserves storage. Our specific question was: Have any of the attributes associated with seed-yield stability been indirectly selected during the domestication process? Our results show that these characteristics were reduced or lost, in selected lines compared to their wild relatives. Early vigor was lower in selected accessions and was associated mainly with reduced relative growth rate and CO2 assimilation. During the reproductive period the growth strategy was changed by selection towards a non-conservative and more acquisitive resource use strategy. Traits associated with this strategy were linked to higher water use efficiency and growth capacity (higher CO2 assimilation rate, specific leaf area, and leaf allocation), but also with loss of structural adaptation to low resource environments (i.e. low specific leaf area), an increase in nutrient and water demands, and reduced nutrient use efficiency. Carbohydrates accumulation pre-anthesis was lower in selected accessions of all four species, and also, just in perennials we found lower reserves storage post-anthesis. These changes in the pattern of carbohydrates accumulation could be associated to lower seed-yield stability due to the loss of buffer capacity linked with the use of pre-anthesis reserves for seed filling. On the other hand, in perennial species lower reserves storage after seed harvest could reduce plant longevity and survival. We conclude that indirect changes occurred during the preliminary domestication of both annual and perennial species of Lesquerella used in our experiment. These changes were against those required if these species were to be developed as crops for semi-arid, mediterranean environments and should result in low seed-yield stability.Fil: González Paleo, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentin

Seed oil content and phenology of Physaria species (Brassicaceae) differing in their life-cycle

Phenology of reproduction influences the concentration of the oil in the seeds, through changes in grain filling dynamics and biosynthetic activity. The objective was to evaluate differences in seed quality and phenology among species of Physaria differing in life-cycle: annuals-P. gracilis and P. angustifolia; and perennials- P. pinetorum and P. mendocina. The effect of the timing of the seed filling on seed weight and oil content in a common garden experiment in Patagonia, Argentina, was evaluated. Both annual species bloomed earlier and had a shorter and compressed growth-cycle, than the perennials. P. mendocina showed longer phenological phases and bloomed and started the fruit ripening stage later, while P. pinetorum had an intermediate duration of the flowering-fruiting stages. Seed yield was 25 % higher in annuals, but oil concentration and oil-yield were not related to life-cycle. P. gracilis and P. mendocina produced seeds with higher oil content that those reported for the commercial species Physaria fendleri. Higher temperature during seed-filling influenced oil accumulation in the seed. The seed oil content of P. mendocina, remained stable throughout the season while in the other three species it tended to decrease over time as temperature increased, in an inverse relationship between temperature and oil content. Indirect effects of temperature on growth components such as premature senescence or low photosynthetic capacity could also explain these trends. Seed weight was stable in time in all species. Selection of early maturing plants should improve oil-content only in those species in which oil-content is temperature-dependent (i.e. annuals and P. pinetorum) or is affected by a reduction in the capacity of the source to produce carbohydrates. The source-sink ratio and the plant´s internal balance of carbohydrates, including reserves could play an important role in the regulation of grain quality.Fil: González Paleo, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentin

Changes in resource-use strategy and phenotypic plasticity associated with selection for yield in wild species native to arid environments

Along history, wild plants have been introduced into cultivation and domestic derivatives radically altered by this move due to changes in selection pressure: wild species are exposed to natural selection that operates to continue survival and domesticated species to artificial selection that emphasized yield. Here we assess whether selection for yield triggered a shift in resource-use strategy and changes in phenotypic plasticity. We compared co-generic wild and domesticated species grown in a common garden under two levels of water availabilities. Our results indicate that resource-use strategy shifted from conservative to acquisitive. The change in selection force from survival to reproduction provoked an increase in mean values of reproduction-related traits and a decrease in survival-related traits. Trade-offs between reproduction and storage were found in both groups. This occurred concurrently with an increase in phenotypic plasticity of most traits. Wild species showed higher homeostasis than domesticated species. Despite the lesser homeostasis of the latter, improvements in reproductive traits were not completely reversible under low resource availability: across environments domesticated species always showed higher reproductive biomass and reproductive effort than their wild relatives. The combination of higher mean values of advantageous traits and greater plasticity might contribute to the success of domesticated species in plentiful environments.Fil: Vilela, Alejandra Elena. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: González Paleo, Luciana. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Carbon acquisition strategies uncoupled from predictions derivedfrom species life-cycle

We compare carbon use strategies of congeneric annual (P. gracilis and P. angustifolia) and perennial (P. mendocina and P. pinetorum) Physaria (Brassicaceae), to evaluate the relevance of eco-physiological traits as determinants of differences in growth and to add information on the current debate on the agro-ecological suitability of perennial species for grain production in low resource ecosystems. Because of differences in growth and in seed-output previously found within this genus, we hypothesized that C acquisition strategies would not be fully coupled with predictions derived from a species life-cycle. Further, we expected to find different suites of traits related to C-acquisition among perennial species of Physaria. We found species with high (P. gracilis and P. pinetorum) and low (P. mendocina and P. angustifolia) relative growth rate (RGR) and biomass. The variation in RGR was linked to differences in specific leaf area (SLA) and allocation to leaves (leaf mass ratio, LMR) and roots (root mass ratio, RMR), but not to the species life-cycle. Physaria gracilis had high allocation to leaf area (leaf area ratio, LAR), LMR, high SLA, and low RMR and carbohydrates reserves. The slow-growth strategy found in P. mendocina was linked to low LAR, low SLA and large below-ground allocation. The other species showed intermediate strategies between these two. The sets of traits present in P. gracilis and in P. mendocina are extremes in the C acquisition–conservation trade-off, and may allow them to cope with low resource environments in different ways. SLA, LMR and RMR were the main determinants of RGR, while total non-structural carbohydrates (TNC) and leaf longevity were linked to the life-cycle. Taken together these characters define the intermediate growth strategies of P. angustifolia and P. pinetorum. These intermediate strategies were not dependent on the species life cycle and support the hypothesis of uncoupled relationships between growth, C acquisition strategies and life-cycle.Fil: González Paleo, Luciana. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ravetta, Damián Andrés. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Allocation patterns and phenology in wild and selected accessions of annual and perennial Physaria (Lesquerella, Brassicaceae)

Two processes that determine a good performance of plants in arid environments are phenology and resource allocation patterns. With a longer growing season and larger allocation to root, perennials achieve better access to resources and are more resilient to stresses than annuals. In traditional agricultural systems selection for optimal soil nutrient uptake has been a secondary breeding objective, because crops receive subsidies of water and fertilizers. However in arid lands, caution is required during domestication, to avoid changes in structural traits which may be the basis for sustainable production. Due to inherent differences in hierarchy among annual and perennial species, we propose that the changes in phenology and allocation brought about by selection will depend on the life cycle. We performed field studies comparing wild and selected accessions of annual and perennial species of Physaria. Life cycle determined the functional basis of seed yield. In annuals, selection resulted in early anthesis (1 week earlier), a lower allocation to roots and leaves (twofold lower), and an increase in harvest index (an increase of 62%). Selected perennials had higher biomass at maturity (45% higher), linked to a longer reproductive period (3 weeks longer) than their wild relatives. The vegetative allocation found in wild perennials remained unchanged after selection. While annuals selected for seed yield could compromise the capacity for acquisition of resources, selection in perennials did not modify the allocation strategy responsible for their positive adjustment to low resource environments. We found a trade off between seed yield potential and yield stability that resulted in lower performance of selected accessions in low quality environments in relation to their wild relatives.Fil: González Paleo, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Ravetta, Damián Andrés. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Age-related changes in root traits are linked to internal nitrogen cycling in the perennial forb Physaria (Brassicaceae)

Age-related changes in root morphology and physiology, and the relationship with N dynamics between species that differ in resource use (i.e., conservative or acquisitive) and lifespan strategies are largely unexplored and experimental evidence very scarce. Objective: to compare age-related changes in root traits and their relationship with internal N recycling in two co-generic perennial species differing in their resource-use strategy and plant lifespan. We hypothesized that the root system of both species will become more conservative with age, but the root system of the acquisitive short-lived Physaria pinetorum (Brassicaceae) will decrease its acquisition capacity while the conservative long-lived P. mendocina will increase its storage capacity. Results and conclusion: we confirmed that the root system of both species shifts from acquisitive to conservative with age, reducing N acquisition and relying either on N translocation from leaves or root stores to sustain growth and grain filling. As hypothesized, the species responded differentially according to their longevity and resource-use strategy: P. pinetorum showed a great loss of acquisition and storage capacities with absolute age, and turned to N stores when acquisition was deficient while P. mendocina increased storage capacity with age and obtained N from resorption to sustain allocation to grain, decreasing the quality of its litter. Species differing in their plant lifespan and resource use strategies have different patterns of N dynamics with age, that could affect yield stability and the provision of ecosystem services.Fil: Pastor Pastor, Alejandro. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Vilela, Alejandra Elena. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: González Paleo, Luciana. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin