Miguel Dall’Agnol

Genetic diversity in red clover (Trifolium pratense L.) revealed by morphological and microsatellite (SSR) markers

The NPGS-USDA core collection with 85 accessions of red clover, an important forage species, is little described. The goal of the present study was to evaluate the diversity of a set of accessions from the core collection at the morphological and molecular level in order to extract some valuable accessions for Brazilian red clover breeding programs. Twenty-one morphological traits, collected in field and greenhouse in South Brazil, and seven SSR markers were used to describe 57 accessions from the U.S. core collection and one population cultivated in Southern Brazil. Variation between accessions was large for most of the 21 morphological traits. A cluster analysis based on the morphological traits revealed five distinct clusters that separated the populations according to flowering earliness, as already described, but also according to persistency, growth habit and dry matter productivity. Over seven SSR loci, the number of alleles averaged 11.1 alleles per locus. Genetic diversity measured with SSR markers was high, with a mean expected heterozygosity of 0.86. An analysis of molecular variance revealed that the largest proportion of variation (83.6%) resided at the within population level. Although the molecular markers also separated accessions into five clusters, there was no coincidence between the composition of groups found with morphological and molecular data. Use of genetic diversity in breeding programs requires to use the most promising populations, to combine positive traits such as persistency and forage yield, and probably to use within population variation to detect valuable genotypes that could be used as parents of synthetic varieties.

Genetic variation in polyploid forage grass: Assessing the molecular genetic variability in the Paspalum genus

BackgroundPaspalum (Poaceae) is an important genus of the tribe Paniceae, which includes several species of economic importance for foraging, turf and ornamental purposes, and has a complex taxonomical classification. Because of the widespread interest in several species of this genus, many accessions have been conserved in germplasm banks and distributed throughout various countries around the world, mainly for the purposes of cultivar development and cytogenetic studies. Correct identification of germplasms and quantification of their variability are necessary for the proper development of conservation and breeding programs. Evaluation of microsatellite markers in different species of Paspalum conserved in a germplasm bank allowed assessment of the genetic differences among them and assisted in their proper botanical classification.ResultsSeventeen new polymorphic microsatellites were developed for Paspalum atratum Swallen and Paspalum notatum Flüggé, twelve of which were transferred to 35 Paspalum species and used to evaluate their variability. Variable degrees of polymorphism were observed within the species. Based on distance-based methods and a Bayesian clustering approach, the accessions were divided into three main species groups, two of which corresponded to the previously described Plicatula and Notata Paspalum groups. In more accurate analyses of P. notatum accessions, the genetic variation that was evaluated used thirty simple sequence repeat (SSR) loci and revealed seven distinct genetic groups and a correspondence of these groups to the three botanical varieties of the species (P. notatum var. notatum, P. notatum var. saurae and P. notatum var. latiflorum).ConclusionsThe molecular genetic approach employed in this study was able to distinguish many of the different taxa examined, except for species that belong to the Plicatula group, which has historically been recognized as a highly complex group. Our molecular genetic approach represents a valuable tool for species identification in the initial assessment of germplasm as well as for characterization, conservation and successful species hybridization.

Genetic diversity of the complex Paspalum notatum Flügge (Paniceae: Panicoideae)

The genus Paspalum L. comprises approximately 400 species worldwide and about 220 in Brazil. Paspalum is ecologically and economically important, and has been very useful as pasture and P. notatum Flügge (bahiagrass) is a valuable forage grass in the subtropics. This species consists of several sexual (diploid) and apomictic (tetraploid, ocasionally tri and pentaploids) biotypes. In this work, inter simple sequence repeats (ISSR) markers were used to assess the genetic variability of a bahiagrass (P. notatum) collection. Vegetative tissues of 95 bahiagrass accessions were obtained from various locations in South America (Brazil, Argentina and Uruguay). A total of 91 reproducible ISSR fragments were observed and 89 fragments (97.5% of the total observed) were polymorphic. Cluster analyses (UPGMA) were performed from the ISSR data set and the results illustrate the genetic relationships among the 95 accessions of P. notatum. A comparison among molecular, morphological and ploidy levels data were done. ISSR markers were effective in distinguishing the genotypes analyzed, and a wide variability was observed for this species. These results add new information regarding the genetic diversity in P. notatum, thus contributing toward the biological knowledge of this species, and providing with subsides for future plant breeding and conservation programs.

Alocação da biomassa e correlações morfofisiológicas em leguminosas forrageiras com hábitos de crescimento contrastantes

The biomass allocation analysis and the correlation among morphophysiological variables allow greater understanding of the establishment, yield and persistence of perennial species in plant breeding projects, management and ecology of forage plants. To analyze the biomass allocation of forage legumes (Adesmia latifolia, A. punctata, A. tristis, Lotus corniculatus, L. uliginosus), an experiment was carried out under greenhouse conditions for 210 days (4000 degree-days); the plants were cultivated in 1 m2 wooden boxes. Plants were harvested to evaluate the morphological components and to describe their growth habit. The root, stem and leaf biomass allocations were expressed as dry mass percentages. The greatest allocation on leaves occurred for stoloniferous species, A. latifolia (63.5%) and A. punctata (61.4%), which presented the smallest allocation for roots, 10.9 and 14.7%, respectively. Largest stem biomass allocation (39.4%) and roots (24.4%) were found for L. uliginosus, a species with rhizomes. The leaf area index (LAI) was positively correlated with the number of leaves, secondary stems and aerial biomass. A. latifolia and Lotus spp. are extreme examples of the relative importance of morphological components in the formation of LAI and biomass. The accumulation pattern and forage allocation of stoloniferous legumes are mainly characterized by leaf production, pointing out the importance of stolon elongation and rooting, while for A. tristis and Lotus spp., the stem and root fractions had the same importance.

Análise da diversidade genética de cornichão com o uso de marcadores microssatélites

The aim of this work was to analyze the genetic diversity of 14 Lotus corniculatus L. materials through microsatellite markers. Four cultivars and one population of L. corniculatus and their respective genotypes selected were analyzed aiming aluminium tolerance and sensibility. The 17 markers used detected a total of 36 alleles, with an average of 2.25 alleles per locus. The result of the similarity analyses showed the formation of three groups: one enclosing germplasm and selected genotypes for aluminium sensibility, while the other two groups were formed by selected genotypes for aluminium tolerance. The molecular analysis was efficient in detecting and quantifying the variability among the genotypes, adding useful information to the breeding program. The utilization of microsatellite markers permitted the distinction of genotypes originated from a selection program aiming aluminium tolerance. The performed selections originate polymorphic genotypes in relation to the original populations.

Crescimento de plântulas de Adesmia spp. submetidas a doses de alumínio em solução nutritiva

Among the several native legume species found in the Southern part of Brazil, one of the most important is the genus Adesmia DC., which has several species with a great potential as forage plants. Among the several factors to be studied in these species, the aluminum tolerance is one particularly important because the soils from this region are acid with high levels of aluminum. In this paper it is reported the response of A. latifolia and A. tristis to five aluminum doses in nutritive solution (0; 0,15; 0,45; 0,75 and 0,75mg l) containing only calcium (25mg l). The aluminum tolerance was assessed by measuring the roots weight and length after 13 days of growth in the solution. At the end of this time, it was observed that both species showed an inhibition in secondary roots development, with A. tristis having symptoms of aluminum toxicity, showing roots stubbier than A. latifolia. There was a significant effect for the species factor over root length and dry matter and also a significant effect upon the species-aluminum interaction to the relative root growth (RRG), pointing out the differential response presented by both species. A. latifolia did not show a significant decrease in the RRG, pointing out to the tolerance to the aluminum levels used. A. tristis was more sensitive, with a significant decrease in the root elongation.

Genetic diversity assessed by microsatellite markers in the amphicarpic species Trifolium polymorphum Poir.

Trifolium polymorphum Poir. is an amphicarpic forage legume from southern Brazil, Uruguay, Argentina, Paraguay and Chile. Information on the genetic diversity of natural populations in natural grasslands in southern Brazil is limited. In order to increase the knowledge about this species, an analysis of the genetic diversity was carried out in 10 natural populations of T. polymorphum with the use of 20 microsatellite markers. The expected heterozygosity in T. polymorphum populations ranged from 0.40 to 0.43, with a mean of 0.42. A total of 193 alleles were detected with a mean of 9.3 alleles per locus and polymorphic information content (PIC) for these markers of 0.62 to 0.89 with a mean of 0.84.The grouping based on the Jaccards coefficient of similarity classified populations, regardless of their regions of origin, into two groups with a mean similarity coefficient of 0.32, reflecting the high genetic variability of the populations, especially those located in the Campanha phytogeographic region. This information on diversity can be used to plan future germplasm collection strategies for conservation purposes and also for the breeding of the species.

Growth of Adesmia spp. seedlings submitted to aluminum doses in nutritive solution

Among the several native legume species found in the Southern part of Brazil, one of the most important is the genus Adesmia DC., which has several species with a great potential as forage plants. Among the several factors to be studied in these species, the aluminum tolerance is one particularly important because the soils from this region are acid with high levels of aluminum. In this paper it is reported the response of A. latifolia and A. tristis to five aluminum doses in nutritive solution (0; 0,15; 0,45; 0,75 and 0,75mg l) containing only calcium (25mg l). The aluminum tolerance was assessed by measuring the roots weight and length after 13 days of growth in the solution. At the end of this time, it was observed that both species showed an inhibition in secondary roots development, with A. tristis having symptoms of aluminum toxicity, showing roots stubbier than A. latifolia. There was a significant effect for the species factor over root length and dry matter and also a significant effect upon the species-aluminum interaction to the relative root growth (RRG), pointing out the differential response presented by both species. A. latifolia did not show a significant decrease in the RRG, pointing out to the tolerance to the aluminum levels used. A. tristis was more sensitive, with a significant decrease in the root elongation.