A comparison of phenotypic variation in Triticum durum Desf. genotypes deposited in gene banks based on the shape and color descriptors of kernels in a digital image analysis.

Durum wheat is the tenth most valuable crop on a global scale. The aim of this study was to compare the phenotypic variation of T. durum accessions of different origin with contemporary spring cultivars of this cereal species. One hundred and two accessions and 12 contemporary cultivars of Triticum durum Desf. as well as Kamut® wheat (T. turanicum), a Triticum species closely related to T. durum, were analyzed. The aim of this study was to describe the degree of variation in the phenotypic traits of grain and selected traits associated with technological quality. The examined genotypes were characterized by considerable phenotypic variation, and they can be a valuable source of material for genetic recombination in durum wheat breeding. The analyzed accessions were characterized by a higher average content of protein (16.48 vs. 14.56%) and wet gluten (38.04 vs. 32.07%), higher Zeleny sedimentation values (69.7 vs. 60.4ml), and higher flour strength (W index values of 404.64 vs. 353.47) than the reference cultivars. The kernels of the evaluated accessions and cultivars did not differ significantly in average crease depth, but significant differences were observed in the values of descriptors directly linked with kernel size, especially kernel image area and minimal Feret diameter. The traits responsible for the processing suitability of grain were more strongly correlated with color descriptors than shape descriptors, which suggests that color parameters can be used to select high-quality breeding material. The analyzed accessions have two major weaknesses, namely relatively low yields (22.6 dt ha-1 on average) and undesirable grain color, indicative of low carotenoid concentration. The accessions deposited in gene banks do not meet the relevant agronomic requirements. However, both grain yield and carotenoid concentration are polygenic traits which can be improved if desirable combinations of QTLs are assembled in breeding lines and cultivars.

Seedbank persistence of four summer grass weed species in the northeast cropping region of Australia.

Summer grass weed species are a particular problem in the northeast cropping region of Australia because they are prolific seeders and favor no-till systems. Information on weed seed persistence levels can be used for the development of effective and sustainable integrated weed management programs. A field study was conducted over 42 months to evaluate the seedbank persistence of Chloris truncata, C. virgata, Dactyloctenium radulans, and Urochloa panicoides as affected by burial depth (0, 2, and 10 cm). Regardless of species, buried seeds persisted longer than surface seeds and there was no difference in seed persistence between 2 and 10 cm depths. Surface seeds of C. truncata depleted completely in 12 months and buried seeds in 24 months. Similarly, C. virgata seeds placed on the soil surface depleted in 12 months. Buried seeds of this species took 18 months to completely deplete, suggesting that C. truncata seeds persist longer than C. virgata seeds. Surface seeds of D. radulans took 36 months to completely deplete, whereas about 7% of buried seeds were still viable at 42 months. U. panicoides took 24 and 42 months to completely exhaust the surface and buried seeds, respectively. These results suggest that leaving seeds on the soil surface will result in a more rapid depletion of the seedbank. Information on seed persistence will help to manage these weeds using strategic tillage operations.

Comprehensive genotyping of a Brazilian cassava (Manihot esculenta Crantz) germplasm bank: insights into diversification and domestication.

KEY MESSAGE: Brazilian cassava diversity was characterized through population genetics and clustering approaches, highlighting contrasted genetic groups and spatial genetic differentiation. Cassava (Manihot esculenta Crantz) is a major staple root crop of the tropics, originating from the Amazonian region. In this study, 3354 cassava landraces and modern breeding lines from the Embrapa Cassava Germplasm Bank (CGB) were characterized. All individuals were subjected to genotyping-by-sequencing (GBS), identifying 27,045 single-nucleotide polymorphisms (SNPs). Identity-by-state and population structure analyses revealed a unique set of 1536 individuals and 10 distinct genetic groups with heterogeneous linkage disequilibrium (LD). On this basis, a density of 1300-4700 SNP markers were selected for large-effect quantitative trait loci (QTL) detection. Identified genetic groups were further characterized for population genetics parameters including minor allele frequency (MAF), observed heterozygosity [Formula: see text], effective population size estimate [Formula: see text]) and polymorphism information content (PIC). Selection footprints and introgressions of M. glaziovii were detected. Spatial population structure analysis revealed five ancestral populations related to distinct Brazilian ecoregions. Estimation of historical relationships among identified populations suggests an early population split from Amazonian to Atlantic forest and Caatinga ecoregions and active gene flows. This study provides a thorough genetic characterization of ex situ germplasm resources from cassava's center of origin, South America, with results shedding light on Brazilian cassava characteristics and its biogeographical landscape. These findings support and facilitate the use of genetic resources in modern breeding programs including implementation of association mapping and genomic selection strategies.

A global overview of cassava genetic diversity.

Although numerous studies of diversity have been conducted in cassava, there is no comprehensive assessment of global genetic diversity. Here we draw on previous studies and breeders' knowledge to select diversity sets from the International Institute of Tropical Agriculture (IITA) and the International Center for Tropical Agriculture (CIAT) genebanks and breeders' germplasm, as well as elite germplasm and landraces from eastern, southern and central (ESC) Africa to make a global assessment of diversity in cassava, using a SNP based GoldenGate (Illumina Inc.) assay. A synthesis of results from genetic distance and ADMIXTURE analysis essentially revealed four populations (i) South American germplasm characterised by relatively higher genetic diversity with hypothetical ancestral founder genotypes from Brazil, (ii) a smaller group of African introduction germplasm which is more distantly related to all other germplasm, (iii) West Africa germplasm dominated by IITA breeding lines, containing sources of cassava mosaic disease resistance, and IITA genebank accessions from West Africa, both characterised by slightly lower diversity, and (iv) a less cohesive group of African germplasm, termed 'Other', with moderate levels of diversity and a majority of germplasm from ESC Africa. This study highlights opportunities for heterosis breeding, purging of duplicates in genebanks and the need for conservation of ESC Africa landraces.

Genetic diversity, phylogenetic structure and development of core collections in Melilotus accessions from a Chinese gene bank.

Melilotus is an important forage legume, with high values as feed and medicine, and widely used as green manure, honey plant, and wildlife habitat enhancer. The genetic diversity, structure and subdivision of this forage crop remain unclear, and plant genetic resources are the basis of biodiversity and ecosystem diversity and have attracted increasing attention. In this study, the whole collection of 573 accessions from the National Gene Bank of Forage Germplasm (NGBFG, China) and 48 accessions from the National Plant Germplasm System (NPGS, USA) in genus Melilotus were measured with respect to five seed characters: seed length, width, width-to-length ratio, circumference and 100-seed weight. Shannon' genetic diversity index (H') and phenotypic differentiation (Pst) were calculated to better describe the genetic diversity. The ITS and matK sequences were used to construct phylogenetic trees and study the genetic relationships within genus Melilotu. Based on seed morphology and molecular marker data, we preliminarily developed core collections and the sampling rates of M. albus and M. officinalis were determined to be 15% and 25%, respectively. The results obtained here provide preliminary sorting and supplemental information for the Melilotus collections in NGBFG, China, and establish a reference for further genetic breeding and other related projects.

Strong Heterogeneity in Advances in Cryopreservation Techniques in the Mammalian Orders.

Between 1970 and 2012, vertebrate abundance has declined by 58% with an average annual decline of 2%, calling for serious action to prevent a mass extinction and an irreversible loss of biodiversity. Cryobanks and cryopreservation have the potential to assist and improve ex situ and in situ conservation strategies by storing valuable genetic material. A great deal of studies concerning cryopreservation have been performed within the class Mammalia, although no systematic overview has previously been presented. The objective of this study is therefore to evaluate the status, pattern and future of cryopreservation within Mammalia. A strong disproportional distribution of studies in examined orders is displayed. For the majority of examined orders less than 10% of species has been examined. However, the cryopreservation of germplasm has in several cases been successful and resulted in successful applications of assisted reproductive techniques (ARTs). Various obstacles are associated with the development of cryopreservation protocols, and among them the most prominent is interspecific differences in cryotolerance. Extrapolation of protocols in closely related species is considered the most applicable procedure, and a future supplement to overcome this problem is the examination and comparison of cryobiological traits. Successful protocols have been developed for the vast majority of domesticated mammals, which gives incentive for the further extrapolation of protocols in threatened species.

What happens to the soil seed bank 17 years after clear cutting of vegetations? / ¿Qué ocurre con el banco de semillas del suelo 17 años después del corte de la vegetación?

Seed banks play an important role in the resilience of potential anthropogenic areas and are influenced by seasonal variation. The spatial and temporal heterogeneity of the forests influences the richness and density of the soil seed bank, but there is a hypothesis that such influence can be changed in anthropogenic areas, where we expect to find lower richness and seed density in relation to the seed bank of mature forests. The richness and seasonal density of seeds in the soil depth of a young caatinga forest, 17 years after an agricultural activity was abandoned, were evaluated and compared with those of a mature forest. The study was conducted at the Instituto Agronômico de Pernambuco - IPA (Estação Experimental José Nilson de Melo), located in Caruaru, Pernambuco, Brazil, in an area of tropical dry forest, known locally as “caatinga”. The local climate is seasonal, the dry season occurring from September to February and the rainy season concentrated in the remaining months. The average annual rainfall over time (time series of 30 years) is 692mm. In each climatic season (rainy and dry), the seed bank was sampled in 210 20x20cm plots (105 in the leaf litter and 105 at 5cm soil depth). The richness and seed density of the soil samples were evaluated by the method of seedling emergence. The seed bank had 47 species, with a predominance of herbaceous plants. Seasonal variation in richness and seed density in the soil (leaf litter + soil) was not significant, but 42 species of the mature forest were absent from the seed bank of the young forest, despite 17 years of natural regeneration and its proximity to the mature forest. On its own, the soil has greater richness and density of seeds than the leaf litter. The depth of seed deposition in the soil bank of the young forest significantly explained 36% of the species richness and 16% of the seed density, with a significant interaction effect with the climatic season only on species richness, explaining 4% of the variation recorded. The seed density of the young forest (1 277seeds/m²) was greater than that the mature forest indicating that the time abandoned had not yet been sufficient for complete recovery of plant diversity and there is no longer any seed limitation of pioneer species for regeneration of the young forest. Rev. Biol. Trop. 63 (2): 321-332. Epub 2015 June 01.

El banco de semillas juega un papel importante en el potencial de resiliencia de las áreas antropogénicas y sufre influencia de las variaciones estacionales. La heterogeneidad espacial y temporal de los bosques influye en la riqueza y la densidad del banco de semillas del suelo, pero hay una hipótesis de que tal influencia se puede cambiar en las zonas antropogénicas, donde esperaríamos encontrar menor riqueza y densidad de semillas en relación con el banco de semillas de los bosques maduros. La riqueza y la densidad estacional de semillas del espacio vertical del suelo de un bosque joven, con 17 años de abandono de cualquier actividad agrícola, fueron evaluadas y comparadas con las un bosque maduro. El estudio se realizó en el Instituto Agronômico de Pernambuco - IPA (Estação Experimental José Nilson de Melo), situado en Caruarú, Pernambuco, Brasil, en una zona de bosque seco tropical, conocida localmente como “caatinga”. El clima local es estacional, la estación seca ocurre de septiembre a febrero y la estación de lluvias en los meses restantes. La precipitación promedio anual (series de tiempo de 30 años) es 692mm. En cada estación climática (lluviosa y seca), el banco de semillas fue muestreado en 210 parcelas de 20x20cm (105 en la hojarasca a 5cm de profundidad del suelo). La riqueza y densidad de semillas de las muestras del suelo fueron evaluadas por el método de emergencia de plántulas. El banco de semillas presentó 47 especies, con una predominancia de las herbáceas. Las variaciones estacionales de riqueza y densidad de semillas del suelo (hojarasca+suelo) no fueron significativas, pero 42 especies del bosque maduro todavía estaban ausentes en el banco de semillas del bosque joven, apesar de los 17 años de regeneración natural y de su proximidad con el bosque maduro. Aisladamente, el suelo presentó mayor riqueza y densidad de semillas que la hojarasca. La profundidad de depósito de semillas en el banco del suelo del bosque joven explicó significativamente 36% de la riqueza de especies y 16% de la densidad de semillas, con efecto significativo de interacción con la estación climática apenas sobre la riqueza de las especies, explicando más de 4% de la variación registrada. La densidad de semillas del bosque joven (1 277semillas/m²) fue más elevada que la del bosque maduro indicando, que a pesar del poco tiempo de abandono del cultivo, fue suficiente para la recuperación completa de la densidad de semillas.