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Carmen de Patagones, Argentina

Torres Y.A.,National University of the South | Busso C.A.,National University of the South | Montenegro O.A.,Chacra Experimental de Patagones | Ithurrart L.,National University of the South | And 10 more authors.
Grass and Forage Science | Year: 2014

The field performance of the native Pappophorum vaginatum, the naturalized Eragrostis curvula and various cultivars of the introduced Achnatherum hymenoides and Leymus cinereus was evaluated as potential forage resources in rangelands of arid Argentina during the warm seasons of 2007/2008 and 2008/2009. Plants of these grass species, obtained from seeds, were transplanted to the field in 2006, when they were 1year old. During the study years, there were two defoliation managements: plants of all study genotypes either remained undefoliated (controls) or were defoliated twice a year during spring at 5cm stubble height. Despite tiller number being lower (P<0·05) on defoliated than on undefoliated plants, and total leaf length per unit basal area being similar (P>0·05) between defoliation managements by mid-spring, there were no differences (P>0·05) in dry weight production between defoliated and undefoliated plants in all genotypes at the end of the second growing season. Plants of one or more of the introduced genotypes showed a similar (P>0·05) or greater (P<0·05), but not lower, tiller number per plant and per square centimetre, daughter tiller production, total leaf length and dry weight production per unit basal area than the native species at the end of the first and/or second growing seasons. These morphological variables were similar (P>0·05) or greater (P<0·05) in the native than in the naturalized genotype. Plant survival, however, was lower (P<0·05, overall mean=20%) in the introduced than in the native (>70%) or naturalized (>39%) genotypes at the end of the first or second growing seasons. © 2013 John Wiley & Sons Ltd.

Baccharis ulicina is a weed widely distributed in pastures of the semiarid zone of Argentina. With the aim of evaluate potential allelopathic effects, aqueous extracts of B. ulicina (leaf, stem, root and whole plant) at two concentrations (50 and 150 g tissue/L water) were used on germination and initial growth of Avena sativa, Lolium perenne and Raphanus sativus. For each species, 100 seeds were watered and maintained at 25°C at darkness. Seed germination and length of coleoptile / hypocotyl (C/H) and radicle (R) was measured. Then, germination percentage, germination rate coefficient, germination vigor, inhibition of germination, inhibition of radicle length and coleoptile / hypocotyl length, radicle vigor index and the coleoptile / hypocotyl vigor index were calculated. High concentration extracts reduced germination an average of 65%, in addition, they produced a length inhibition of 58.8% (C/H) and 93.3% (R) to A. sativa; 71.5% (C/H) and 87.9% (R) to L. perenne, and 93.8% (C/H) and 94.5% (R) to R. sativus. There was an evident phytotoxic effect of B. ulicina on evaluated species, indicating that allelopathy would be an ecological strategy of the species.

Torres Y.A.,CONICET | Busso C.,CONICET | Montenegro O.,Chacra Experimental de Patagones | Ithurrart L.,CONICET | And 10 more authors.
Applied Soil Ecology | Year: 2011

Pappophorum vaginatum is the most abundant C4, warm-season perennial grass in rangelands of northeastern, arid Patagonia, which is often exposed to continuous grazing. Eragrostis curvula is the only naturalized, C4 warm-season genotype that has successfully established from seed during moist years in the study region, that is characterized by a scarce forage availability to livestock during the spring and summer. Successful introduction of perennial forage genotypes is then critical in that region. No studies have yet been conducted to determine the greater abundance of P. vaginatum compared to that of other native C4 grass genotypes (Aristida subulata, A. spegazzinii, Sporobolus cryptandrus) in the study area. The effect of defoliation on arbuscular mycorrhizal colonization was investigated on the four native, one naturalized and five introduced, C3 perennial grass genotypes (Leymus cinereus cvs. " Magnar" and " Trailhead" , and Achnatherum hymenoides cvs. " Paloma" , " Rimrock" and " Nezpar" ) growing at the field. We hypothesized that the magnitude of mycorrhizal colonization (1) is similar on defoliated than on undefoliated plants of the native and naturalized genotypes, (2) is greater in the native and naturalized than in the introduced genotypes, and (3) is greatest in P. vaginatum than in all remaining genotypes. Plants of all ten genotypes were either exposed or not to a severe defoliation twice in the growing seasons of 2007/2008 and 2008/2009. The results showed that all studied genotypes maintained arbuscular mycorrhizal colonization levels following defoliation similar to undefoliated controls. The greatest arbuscular mycorrhizal colonization was often found on both cultivars of L. cinereus among all genotypes. The greatest arbuscular mycorrhizal colonization in P. vaginatum than in the other native genotypes at the end of the study, parameter that contributes to defoliation tolerance, could help to explain its greater abundance in rangelands of central Argentina. The higher arbuscular mycorrhizal colonization in both cultivars of L. cinereus might contribute to their successful establishment and survival in rangelands of northeastern, arid Patagonia. Genotype introduction in these rangelands is likely to affect community dynamics because of variable effects of the mycorrhizal symbiosis on the various plant genotypes. © 2011 Elsevier B.V.

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