Dry matter production and allocation in Eucalyptus cloeziana and Eucalyptus argophloia seedlings in response to soil water deficits

Effects of soil water availability on seedling growth, dry matter production and allocation were determined for Gympie (humid coastal) and Hungry Hills (dry inland) provenances of Eucalyptus cloeziana F. Muell. and for E. argophloia Blakely (dry inland) species. Seven-month-old seedlings were subjected to well-watered (100% field capacity, FC), moderate (70% FC) and severe (50% FC) soil water regimes in a glasshouse environment for 14 wk. There were significant differences in seedling growth, biomass production and allocation patterns between species. E. argophloia produced twice as much biomass at 100% FC, and more than three times as much at 70% and 50% FC than did either E. cloeziana provenance. Although the humid provenance of E. cloeziana had a greater leaf area at 100% FC conditions than did the dry provenance, total biomass production did not differ significantly. Both E. cloeziana provenances were highly sensitive to water deficits. E. argophloia allocated 10% more biomass to roots than did E. cloeziana. Allometric analyses indicated that relative biomass allocation patterns were significantly affected by genotype but not by soil water availability. These results have implications for taxon selection for cultivation in humid and subhumid regions.     

Changes in plant species composition within a planted forest in a deciduous agroecosystem in Ghana

Plantations provide a micro-climate that can facilitate the regeneration of other forest species. Often exotic species have been tested for these kinds of functions. To determine the potential for indigenous trees as plantation species for their ability to foster forest species regeneration, this study was undertaken in a mixed indigenous plantation stand. Understories of the stand at 8?years of age were surveyed for plant diversity. The species richness increased by 24% per 1,000?m² between 2001 and 2008 and the number of families represented increased by 48%. The Shannon Diversity and Simpson Index values confirm a greater diversity 8?years after the plantation was established. The most abundant species in study plots were Chromolaena odorata and Cedrela odorata, which collectively represent about 54% of all species identified in the plots. The most species-rich families were Fabaceae and Euphorbiaceae representing 31% of the total species recorded. Asteraceae and Meliaceae were the two most dominant families, which collectively represent about 55% of all species identified in the plots. 47 forest tree species were found per 1,000?m² but those classified as ??saplings?? occurred in low densities. The 47 tree species included pioneer species such as Entandrophragma angolensis, Milicia excelsa, and Ceiba pentandra. Growth rates of planted species were differed, with half of the tested species having similar growth capacity to the exotic species. Generally, planted indigenous species enhanced habitats for other forest tree species in degraded sites. The observed growth of indigenous species, if planted and protected, shows that they may help in biodiversity recovery within agricultural landscapes.     

Intraspecific hybridization in Pinus caribaea var. hondurensis I. Performance for growth and form traits

Inter-provenance hybrids of Pinuscaribaea var. hondurensis wereprogeny tested in Queensland, Australia inorder to assess the feasibility ofincorporating some desirable traits intothe local breeding population, consistinglargely of a single upland provenanceMountain Pine Ridge (MPR). Data onphenotypic traits up to seven years fromplanting revealed that an inter-provenancehybrid, MPR × coastal had greater diameter,straightness and wind-firmness, and fewerramicorns than the MPR control provenance.The data were mostly consistent for twowidely separated sites, and also whenpooled across those sites (p <0.05). In addition, hybrid vigor for treevolume was apparent (p < 0.05).Trees of coastal × Guanaja Island, and purecoastal provenances were as large as thoseof the MPR provenance but had fewerramicorns. Even though the coastal ×Guanaja provenance seemed to produce treesthat were more crooked than the MPRprovenance, there was evidence at leastwithin one site to suggest that the hybridtrees were superior in terms ofwind-firmness (p < 0.01). Breedingfor hybrid vigor and pedigree selection ofthe priority hybrid, MPR × coastal aresuggested as future measures. Pureprovenance populations of coastal andGuanaja island are to be bred as sublinesto the MPR breeding population for futureuse in inter-provenance hybridization andfor gene conservation.     

Inheritance of the virgata pattern of partly colored seed coats in ‘Early Giant’ common bean

The inheritance of the virgata pattern of partly colored seed coats found in common bean (Phaseolus vulgaris L.) Early Giant (EG) was studied by a series of test crosses with line 5-593 and genetic stocks developed by backcrossing selected genes into the recurrent parent 5-593, a Florida dry bean breeding line with a self-colored, black seed coat with genotype T Z Bip P [C r] J G B V Rk. Analysis of the F₂ from the cross EG × 5-593 led to the hypothesis that the virgata pattern of EG has genotype t z bip^vgt, where vgt stands for virgata. The test cross EG × t z virgarcus BC₃ 5-593 confirmed the hypothesis that EG carries t z from data recorded in F₁, F₂, and 27 F₃ progenies from randomly selected F₂ plants. The F₃ segregation was also consistent with the hypothesis that a single recessive gene converts virgarcus into virgata. The test cross EG × t z bip bipunctata BC₃ 5-593 failed to show genetic complementation in F₁ progeny, and the F₂ segregated 3:1 for the parental phenotypes virgata and bipunctata, respectively. Including previously published data, all possible crosses were made among bipunctata, virgata, and virgarcus parents, supporting a multiple allelic series at Bip. We propose the gene symbol bip^vgt for the new allele at Bip, where the allelic series has the order of gene dominance Bip > bip^vgt > bip. Based on test crosses, the complete seed-coat color and pattern genotype of EG is tz bip^vgt P [C r] J G B v^lae rk^d.     

Molecular epidemiology of white pine blister rust: recombination and spatial distribution

ABSTRACT Multilocus haplotypes (MLHs) were derived for the spermogonial (monokaryotic haploid) stage of Cronartium ribicola, the causal agent of white pine blister rust. Six random amplified polymorphic DNA loci and three single-strand conformational polymorphism markers were analyzed for 246 rust samples collected from two heavily infected white pine plantations. All cankers sampled were spatially located within the plantations. The hypothesis that spores are not locally disseminated was supported by the absence of any spatial clustering in the distribution of the MLHs. A large number of MLHs was found at both sites and the haplotypic diversity was close to the maximum (one) in both populations. All measures of recombination were not different from expectations under a scenario of sexual recombination. Genetic differentiation between the two sites was very low (theta = 0.023), yet it was significantly different from zero (P < 0.01). This analysis is in agreement with a scenario of extensive sexual recombination followed by some long-distance dispersal.     

Commercial Seed Lots Exhibit Reduced Seed Dormancy in Comparison to Wild Seed Lots of Echinacea purpurea

Seed germination patterns were studied in E. purpurea (L.) Moench grouped by seed source, one group of seven lots from commercially cultivated populations and a second group of nine lots regenerated from ex situ conserved wild populations. Germination tests were conducted in a growth chamber in light (40 μmol·m(-2)·s(-1)) or darkness at 25 °C for 20 days after soaking the seeds in water for 10 minutes. Except for two seed lots from wild populations, better germination was observed for commercially cultivated populations in light (90% mean among seed lots, ranging from 82% to 95%) and in darkness (88% mean among seed lots, ranging from 82% to 97%) than for wild populations in light (56% mean among seed lots, ranging from 9% to 92%) or in darkness (37% mean among seed lots, ranging from 4% to 78%). No germination difference was measured between treatments in light and darkness in the commercially cultivated populations, but significant differences were noted for treatments among wild populations. These results suggest that repeated cycles of sowing seeds during cultivation without treatments for dormancy release resulted in reduced seed dormancy in E. purpurea.     

Secondary spread of Zygophiala wisconsinensis on the surface of apple fruit

Although the fungus Zygophiala wisconsinensis is a prominent component of the sooty blotch and flyspeck (SBFS) disease complex of apple, few studies have characterized in situ morphological adaptations of this or other SBFS species that accompany colonization of the epicuticular wax layer of fruit. Scanning electron microscope was used to monitor stages in the formation of sclerotium-like bodies on the wax surface, as well as ramifications from these structures to form secondary sclerotium-like bodies. At a mature stage in the formation of sclerotium-like bodies, the matrix of hyphae, conidiophores, and conidia between these bodies collapsed, resulting in formation of the independent clusters of typical colonies of species in the flyspeck mycelial type. Formation of conidiophores and secondary conidia in situ were also described for the first time for any flyspeck species. Observation of conidiophores on naturally and artificially inoculated apple peels with light microscope raises the possibility that formation of secondary conidia may be an important means of spatial dispersion of Z. wisconsinensis in apple orchards and the conidia might function in secondary spread.