Search Results

You are looking at 101 - 110 of 463 items for :

  • "genetic variability" x
  • Refine by Access: All x
Clear All
Free access

Sandra Reed

Japanesesnowbell(Styrax japonicus Sieb. & Zucc.) is an outstanding small ornamental tree that is underutilized in the United States. Many of the cultivars of this Asian native frequently suffer spring freeze damage, especially when grown in the areas of the country that routinely experience dramatic fluctuations in late winter and early spring temperatures. The objectives of this study were to determine if there was variability within S. japonicus for time of budbreak and if this variability could be used for selecting plants with reduced susceptibility to spring freeze damage. In 1998, 224 open-pollinated seedlings were planted in the field. Percent budbreak was evaluated weekly during a 6-week period in Spring 1999 and 2000. While weather conditions varied greatly between the 2 years, there was good consistency between mean budbreak ratings in 1999 and 2000. There was a 4-week difference between the earliest and latest plants to break dormancy. Based on the 1999 and 2000 data, 28 plants were selected and propagated. A replicated trial involving these selections and three cultivars was carried out in 2002, 2003, and 2004. All of the selections broke bud later and suffered less freeze damage than `Emerald Pagoda' and `Carillon', but many performed similarly to `Pink Chimes'. Variation in height, width, caliper, and canopy shape was observed among the selections. There is an opportunity to utilize the genetic variability in S. japonicus for developing cultivars with reduced susceptibility to spring freeze damage.

Free access

Maria Susana Lopes, Duarte Mendonça, Kristina M. Sefc, Fabíola Sabino Gil, and Artur da Câmara Machado

A collection of 130 olive samples, originating from diverse areas in Europe and corresponding to 67 different cultivars denominations, was genotyped at 14 microsatellite loci. In total, 135 alleles with a mean number of 9.6 alleles per locus were detected. All but 30 accessions showed unique genotypes. Several cases of synonymy listed in the FAO database of olive germplasm could not be confirmed, as different allelic profiles were obtained from putatively synonymous cultivars. The existence of homonyms or mislabeled samples in olive germplasm collections was evidenced by allele differences of up to 60% between samples of the same denomination. An allele-sharing phenogram of the analyzed genotypes revealed several cultivars with high levels of intra-varietal polymorphism, as well as cultivar families consisting of closely related cultivars with similar denominations. Our work shows that the current designations of olive cultivars fall short of describing the genetic variability among economically important plant material. A thorough investigation of the existing variability will prove of major importance for both management and economic production of olive trees.

Free access

Michel Choairy de Moraes, Isaias Olívio Geraldi, Frederico de Pina Matta, and Maria Lucia Carneiro Vieira

The aim of this study was to estimate genetic and phenotypic parameters in a population of yellow passion fruit for determining its potential for genetic improvement, as well as to establish strategies for selection. The basic material comprises a sample of 100 F1 plants derived from a single cross between the accessions `IAPAR-06' and `IAPAR-123', which are genetically divergent. The experimental evaluation was performed in a 10 × 10 triple lattice design. At harvest, yield and number of fruit were evaluated, as well as other traits related to fruit quality. Results indicated that the population displays wide genetic variability, with coefficients of heritability on a genotype mean basis varying from 52.6% to 83.2%. High and positive genetic correlations were detected between yield and number of fruit and for combinations of the traits weight, length, and width of the fruit. Negative genetic correlations were found between the soluble solids content and the other traits. The relevance of the results from such a divergent cross to a commercial breeding program is discussed.

Free access

Jose A. Oliveira, Ana B. Monteagudo, Suleiman S. Bughrara, Jose L. Martínez, Ana Salas, Esther Novo-Uzal, and Federico Pomar

The objective of the present study was to characterize the diversity of 15 Festuca rubra accessions collected from northern Spain on the basis of amplified fragment length polymorphism (AFLP) and flow cytometry variation. Additionally, all accessions along with the cultivar Wilma (Festuca nigrescens ssp. nigrescens) were evaluated for susceptibility to one isolate of dollar spot fungus (Sclerotinia homoeocarpa F.T. Bennett) collected in Asturias. Five AFLP primer combinations of EcoRI and MseI produced 980 bands; 82.3% were polymorphic and used for analysis. The best combination of primers was EcoRI-AGC+MseI-CAG, because these displayed the highest degree of polymorphism. Jaccard's similarity coefficients between accessions varied from 0.30 to 0.63 and revealed low genetic similarity. Both the unweighted pair group method with arithmetic mean dendrogram and principal coordinate analysis distinguished two groups of accessions. Genetic variability in these accessions was not related to the geographic origin or to the agronomic data. Three accessions exhibited moderate resistance to dollar spot disease and may be valuable parent material for introducing this resistance in other susceptible cultivars.

Free access

Daniel Struve, Francesco Ferrini, Chandra Bellasio, and Alessio Fini

Quercus populations are noted for their genetic variability. However, this variability is difficult to manage through sexual propagation. The purpose of this study was to characterize the early height growth and water use of seedlings from six sources of Quercus native to Italy and to explore the rooting potential of semihardwood stem cuttings taken from young stock plants. There was great variability within a seed source for seedling height (a 1.5- to 7.8-fold difference depending on source) and water use seedling/day (a 0.7- to 16.5-fold difference). Stem cuttings rooted in high percentages (greater than 74%) for two sources of Q. petraea (Mattusch) Liebl. and Q. pubescens Willd. and one source of Q. cerris L. A second Q. cerris source had 48% rooting. Q. petraea and Q pubescens cuttings were rooted successfully in mid-June and early August with high survival percentages. Overwinter survival of cuttings from all propagation dates was 96% (303 of 314 rooted cuttings). In general, seedling stock plant height and water use were not significantly correlated with percent rooting suggesting that those characteristics could be selected independently resulting in tall or short clones with a range of water use efficiencies. Additional testing is needed to determine the relationship between the traits measured on young seedlings and those traits in older individuals.

Free access

S. Jorge, M.C. Pedroso, D.B. Neale, and G. Brown

Random amplified polymorphic DNA (RAPD) analysis was used to estimate genetic similarities between Portuguese Camelliasinensis (L.) O. Kuntze (tea plant) accessions and those obtained from the germplasm collections from the Tea Research Foundation of Kenya and from the National Research Institute of Vegetables, Ornamental Plants, and Tea of Japan. The accessions studied are taxonomically classified as C. sinensis, var. sinensis, var. assamica, or ssp. lasiocalyx. A set of 118 ten-base arbitrary primers was tested, of which 25 produced informative, reproducible, and polymorphic banding patterns. These primers were used to amplify DNA from 71 tea plant accessions and produced a total of 282 bands, of which 195 were polymorphic. The phenotypic frequencies were calculated using Shannon's Index and employed in estimating genetic diversity within tea plant populations. Our study demonstrates that tea plant populations, including the Portuguese tea plants, show considerable genetic variability. From the UPGMA cluster analysis based on a matrix using the Jaccard coefficient, it was possible to distinguish the Portuguese tea plants from the remaining accessions. The RAPD markers discriminated the three C. sinensis varieties. Moreover, within each variety cluster, subclusters formed according to geographic distribution. The RAPD analysis also separated the commercially cultivated tea plants from the Taiwanese wild tea plants. The present results show that RAPD analysis constitutes a good method to estimate genetic diversity within C. sinensis, and to differentiate C. sinensis accessions according to taxonomic variety and geographical distribution.

Free access

Sandra M. Reed

Japanese snowbell (Styrax japonicus Sieb. & Zucc.) is an outstanding small ornamental tree that is underused in the U.S. One of the reasons this Asian native is not more widely planted is that it is subject to spring freeze damage. The objectives of this study were to determine if there was variability within S. japonicus for time of budbreak and if this variability could be used for selecting plants better adapted to areas of the country that frequently experience late spring freezes. During Spring 1999 and 2000, budbreak was evaluated weekly in 224 open-pollinated seedlings. While weather conditions varied greatly between the 2 years, there was good consistency between 1999 and 2000 data. There was a 4-week difference between the earliest and latest plants to break dormancy. Based on the 1999 and 2000 data, 28 plants were selected and propagated. A replicated trial involving these selections and three cultivars was carried out in 2002, 2003 and 2004. All of the selections broke bud later and suffered less freeze damage than the cultivars `Emerald Pagoda' and `Carillon', but many performed similarly to `Pink Chimes'. Variation in height, width, caliper and canopy shape was observed among the selections. There is an opportunity to utilize the genetic variability in S. japonicus for developing cultivars with reduced susceptibility to spring freeze damage.

Free access

A. Belaj, Z. Satovic, I. Trujillo, and L. Rallo

Eighty-two Spanish olive cultivars from the World Germplasm Bank of the Centro de Investigación y Formación Agraria (CIFA) Alameda del Obispo in Cordoba (Spain) were analysed by RAPD markers to assess their genetic relatedness and to study patterns of genetic variation. The dendrogram based on unweighted pair group cluster analysis using Jaccard's index included two major groups that consisted mostly of cultivars from the southern and central part of Spain. Clustering together of cultivars from the Levante zone was also observed. The pattern of genetic variation among olive cultivars from three different Spanish zones (Levante, central and Andalusia) was analysed by means of the analysis of molecular variance (AMOVA). Although most of the genetic variability was attributable to differences of cultivars within each zone (95.88%), significant φ-values among zones (φst = 0.041; p < 0.001) suggested the existence of phenotypic differentiation. These results are consistent with the predominantly allogamous nature of Olea europaea L. species. Significant values of φst for the pair Andalusia/Levante indicate the presence of differentiation. The negative value of φst observed in the case of the Andalusia/central pair suggests that some varieties from central Spain are more similar to the Andalusian ones than to the varieties of their own geographic area, and vice versa.

Free access

Luz Marina Reyes, Orlando Martinez, and Margarita Beltran

Fifteen clones of banana and plantain of different ploidies, belonging to the Colombian Collection of Musaceas (CCM), maintained at in vitro conditions were characterized. Twenty-three isozyme systems were analyzed using young leaves of micropropagated clones. Eleven systems presented electrophoretic activity: diaphorase (DIA), esterase (EST), glutamate dehydrogenase (GDH), malate dehydrogenase (MDH), malic enzyme (ME), peroxidase (PRX), phosphoglucoisomerase (PGI), phosphogluconate dehydrogenase (PGDH), phosphoglucomutase (PGM), ribulose biphosphate carboxilase (RUB), and shikimate dehydrogenase (SKDH). DIA and RUB isozymes are reported the first time for the genus Musa, and ME, GDH, PGDH, and PGI are not reported previously in acrilamide support. A total of 24 loci were identified that encoded at least 50 alleles. The enzymes with greater genetic variability were EST and DIA, with 14 and 10 alleles, respectively—these represent 48% of the polymorphism detected in this study. The systems PGM, SKDH, PGDH, and ME allowed to differentiate clones of M. acuminata (bananas AA and AAA) from hybrid clones derived of M. acuminata × M. balbisiana (plantains AAB and ABB). Otherwise, it was found that materials maintained under in vitro conditions for more than 10 subcultures presented evidence of variation at the protein level. The isozymes that allowed us to observe these changes were: DIA, EST, ME, PGDH, PGM, and SKDH.

Free access

Fredrick A. Bliss

Fruits and vegetables are rich sources of the micro mineral elements and vitamins often lacking in diets based on cereals, grain legumes, and starchy roots and tubers, but void of animal products. When embarking on a breeding program to improve nutritional compounds, the way the fruit or vegetable is consumed in mixed diets must be considered. To alleviate nutritional problems, the nutrients must not only be present in the plant parts consumed, but also absorbed efficiently in the body. In some cases, it may be necessary to modify compounds to improve absorption as well as increase the concentration. Breeding to improve nutritionally related traits can be approached in a manner similar to that for other traits; i.e., identification of genetic variability, selection for enhanced levels using either individual phenotype or family mean values, and testing for field performance. In addition to improving amount and availability, avoidance of undesirable correlated responses due to genetic or physiological linkages between the trait of interest and other traits deleterious to either plant growth or the consumer is critically important during selection. The growing number of molecular marker-based linkage maps should prove especially useful for identifying genes of interest and employing marker-aided selection. When insufficient variability for amount or type of compound is present in the gene pool, strategies using transgenic plants may be useful.