The use of wild halophytic species as forage resources in saline environments has gained increasing attention. Argentina ranks third in area of saline soils in the world, with a third of its territory showing various degrees of salinity, sodicity and/or alkalinity. On this type of soils, rangelands are the main forage resource for livestock production. Many wild species have forage potential and can also be used for the rehabilitation of rangelands and for intercropping. Information about these species, as well as on the physiological and genetic bases associated with salinity tolerance, provides relevant tools for efficient selection methods. This study addresses Argentine wild halophyte species with forage potential and describes selection criteria with an emphasis on the following taxa: (a) Poaceae: subfamily Chloridoideae and tribes Paniceae and Triticeae, (b) Fabaceae and (c) Amaranthaceae (formerly known as Chenopodiaceae). The review is intended to contribute to the general discussion on strategies for the improvement of wild plant genetic resources, using forage species naturally growing in saline soils in Argentina as a case study.

Vasconcellea species, often referred to as highland papayas, are wild relatives of common papaya (Carica papaya) widely distributed in tropical America, with a preference for cooler climates. The genus deserves special attention as its species show potential as raw materials in the tropical fruit industry, papain source or as genetic resources in breeding programs of C. papaya. However, studies related to breeding system and pollination biology of genus are still unexplored. We characterize the reproductive biology of dioecious Vasconcellea quercifolia, one of the southernmost Caricaceae. According to floral shape and presence of nectar, we expected that this species had a specializated pollination system, with moths as the primary pollinators. To test this, we studied floral biology, floral visitors, pollinators, and breeding system of this species. Controlled pollination experiments show that V. quercifolia is a xenogamous species that depends on its pollinators to set fruits (18 and 79 % fruit and seed set under open-pollination, respectively). Anemophily and apomixis occur very seldom. The treatments of exclusion of floral visitors and pollen load analysis showed that the main pollinators are moths belonging to Arctiidae, Noctuidae, and Pyralidae. The only reward for pollinators is the nectar produced by male flowers. Female flowers are pollinated by deceit because they do not produce floral rewards.

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Desmanthus virgatus (L.) Willd. has significant fodder potential, but its seeds have high and persistent levels of physical dormancy which interfere with its field establishment. The purpose of this study was to analyse the variability of physical dormancy in three populations of seeds from humid and arid regions of Argentina, grown and collected in different years and locations. The hardseededness and the percentage of seeds with intact lenses after a softening treatment and the seed coat thicknesses were compared. The variability observed in the obtained percentages of hardseededness, intact lenses and seed coat thicknesses was related to the origin and the environment in which these seeds had developed. Although further work is needed, arid environments seem to favour the development of thicker seminal layers, being an important factor that determines the impermeable nature of the seeds in this species. This information is required for future genetic improvement programs and for understanding the evolutionary process of the populations of this species in different environments.

Summary:Reproductive system of Trichloris (Poaceae, Chloridoideae, Chlorideae). Trichloris crinita and T. pluriflora are important native forage species with the potential to be domesticated and introduced to cultivation, but there is scarce basic information on their reproductive biology. The aim of this work was to determine the reproductive system of both plant species in populations coming from north-central Argentina. The following was proposed: 1) determine the reproductive system through the fruit/flower ratio under controlled pollination, 2) quantify the weight of the fruits produced by population under different treatments and 3) confirm or discard the presence of apomixis through embryological observations. In T. crinita, the average fruit/flower ratio was 92.4 ± 6.6%, while in T. pluriflora, it was 70.7 ± 9.9%. These results are consistent with self-compatible species, preferably self-pollinated ones. Embryo sac development indicates sexual origin of seeds in both species. Significant differences in the average weight of one hundred fruits among populations and treatments, in both species, were found. The fruits were lighter in self-pollination. The information presented is a contribution to the tasks of selection and introduction to the culture of both species as well as to the conservation and regeneration of the collected germplasm.Key words: Trichloris, Reproductive success, Self-pollination, Fruit weight.Resumen: Trichloris crinita y T. pluriflora constituyen importantes forrajeras nativas con potencialidades de ser domesticadas e introducidas al cultivo, pero es escasa la información básica sobre su biología reproductiva. El objetivo de este trabajo fue determinar el sistema reproductivo de ambas especies en poblaciones provenientes del centro-norte de Argentina. Se propuso: 1) establecer el sistema reproductivo a través de la relación fruto/flor en polinizaciones controladas, 2) cuantificar el peso de los frutos producidos, por población, bajo diferentes tratamientos y, 3) confirmar o descartar la presencia de apomixis a través de observaciones embriológicas. En T. crinita, la relación fruto/flor promedio fue de 92,4 ± 6,6%, mientras que en T. pluriflora, fue de 70,7 ± 9,9%. Estos resultados se corresponden con especies autocompatibles, preferentemente autógamas. El desarrollo del saco embrionario indica origen sexual de las semillas en ambas especies. Se hallaron diferencias significativas en el peso promedio de cien cariopsis entre poblaciones y entre tratamientos, en ambas especies. Los frutos fueron más livianos en autopolinización. La información que se presenta es un aporte a las tareas de selección e introducción al cultivo como también a la conservación y regeneración del germoplasma recolectado.Palabras clave: Trichloris, Éxito reproductivo, Autopolinización, Peso de frutos.

The genus Gleditsia (Fabaceae) comprises woody shrubs and trees that grow in temperate and subtropical regions around the world. This genus is characterised by sexual polymorphism and functionally unisexual flowers. Gleditsia amorphoides is the southernmost species of the genus, and is widely used as a source of timber and derived products for industrial applications (galactomannans are extracted from its seeds and saponins are derived from its fruits). The species is endemic to the Chaquenean Forest of South America. It is described as morphologically androdioecious, with male and perfect flowers appearing on different plants. In the current study, we characterised floral morphology, experimentally tested the breeding system and analysed flower visitors. Results indicated that G. amorphoides staminate flowers produce viable pollen grains and that perfect flowers have a functional gynoecium and empty anthers, where pollen abortion occurs early in floral development. The species relies on outcrossing, which depends mainly on pollen carried by insect pollinators, to produce seeds and fruits. We conclude that G. amorphoides is functionally dioecious, with staminate and pistillate floral morphs.

Native plant genetic resources have evolved from long processes of natural selection and adaptation to specific environments, and have developed tolerance to various stresses prevailing in their natural habitats via adaptive morphophysiological features. The associations between environmental stress conditions (aridity degree and salinity) prevailing in the original habitat of Argentine native Trichloris species (T. crinita and T. pluriflora) and various biometric and physiological traits were evaluated. Trials were carried out in hydroponics in a growth chamber. Components of initial plant growth, oxidative stress expression and antioxidant activity under drought and salt stress were measured in ecotypes of both species, as well as Na ? and K ? leaf tissue concentration and excretion rates under salinity. Ecotypes from arid and semiarid origin of both species had higher drought tolerance. Regarding salt stress, T. crinita ecotype from alkali soil showed stimulated growth under salinity and an ecotype from saline soil kept high root and shoot biomass production. Although the ecotypes of T. pluriflora were not significantly salt-sensitive, none stood out. Many active salt glands on the abaxial leaf surface, high Na/K excretion ratio and high leaf tissue concentration of sodium were found for salt-tolerant ecotypes. This study identified ecotypes with tolerance to prevailing stressful conditions of natural habitat of native forage species to be introduced to plant breeding programmes for restorations purposes. Trichloris pluriflora is an unexplored genetic resource for semiarid rangeland, thus this study is the first report of drought tolerant ecotypes.

Sporobolus phleoides Hack. is an endemic grass of Argentina that is considered an important genetic resource for saline environments. Knowledge of its germination behaviour is an indispensable requirement for the future potential use of this species. Thus, the effects of different factors on germination were evaluated in six representative populations collected from plants cultivated in a uniform environment. In addition, we investigated how the different parts of the seed contributed to dormancy and intraspecific variability. S. phleoides has non-deep physiological dormancy that appeared to be related to its testa. Thereby, dormancy was completely removed with puncturing treatments. High levels of germination were also obtained in seeds stratified at 8°C over 100 days in a solution of nitrates. After-ripening treatment did not have a significant effect in breaking dormancy. Similar germination behaviour and dormancy levels were observed in the different populations, especially when they were subjected to cold stratification. Although further work is needed, cold stratification appears to be the major factor in determining the time of seedling establishment in natural environments for this species.