Patterns of phenotypic diversity for phenologic and qualitative traits in Ethiopian tetraploid wheat germplasm

A total of 4,840 entries of tetraploid wheat germplasm collections representing 121 accessions from Ethiopia were evaluated for phenologic and qualitative trait diversity. The objectives were to assess the diversity patterns of the germplasm with respect to regions, species and altitudinal class. High values of Shannon–Weaver Diversity Index (H′) were recorded for most traits in each region, altitudinal classes, and species. Monomorphism was also high at accession levels. Both H′ and Nei’s gene diversity value for the entire data set (total gene diversity H _T = 0.572; the within accessions gene diversity H _S = 0.112; and gene diversity among accessions D _ST = 0.460) showed the variation for the trait is mainly among accessions/populations rather than within accessions/population. The least mean H′ value over all the traits used for the study was obtained from released varieties (among the origin groups) and Triticum dicoccon (among species). Triticum durum exhibit the highest H′ for a number of traits. Accessions collected from altitudinal class III (2401–2800 m a.s.l.) and class II (2001–2400 m a.s.l.) showed the highest H′ values for a valuable number of traits. Thus classifications using various phenology and qualitative traits enable to identify adaptation of a genotype and would improve the evaluation of genotype for potential adaptation.     

Cytogenetic analysis of a spontaneous 5B/6B translocation in tetraploid wheat landraces from Ethiopia, and implications for breeding

Three tetraploid (2n= 4x= 28) wheat Triticum turgidum L. landrace morphotypes (= genotypes) from Ethiopia were found to carry a variant karyotype directly discernible under the microscope. This was possible because the rearrangement involved one of the satellited chromosomes. Giemsa C-banding revealed that the rearrangement resulted from a 5BS.6BS(5BL.6BL) centric reciprocal translation. The banding pattern on 5BL was polymorphic, suggesting that this translocation might have occurred more than once. There was little C-band polymorphism for the remaining chromosomes, except for 2A. As pure lines, all three morphotypes showed normal chromosome pairing at metaphase I (MI) in pollen mother cells (PMCs). indicating that they are genomically stable. Meiotic analyses of F₁ hybrids and F₂ segregates derived from crosses with tester varieties clearly indicated that one of them (B-l–9) carried another translocation. However, we were not successful in delecting the chromosomes involved, presumably the interchanged segments did nol include C-banding regions. By using T5BS.6BS, direct evidence for segregation distortion against translocation homozygotes in intervarietal hybrids was obtained. The distorted segregation was attributed lo zygotic selection. No aneuploid plants were obtained from the F₂ segregates. However, translocation heterozygotes resulting in unstable meiosis were abundant in the F₂ generation. The implications of the results in using the indigenous landraces in hybridization breeding are discussed.     

Real-time RT-PCR detection of Citrus bark cracking viroid (CBCVd) in hops including an mRNA-based internal positive control

Journal of Plant Diseases and Protection - Citrus bark cracking viroid (CBCVd), formerly known as pathogen in the genus Citrus and first detected in Slovenian hops in 2014, threatens hop production...     

Variation and interrelationships of agronomic traits in Ethiopian tetraploid wheat landraces

Summary Sixty tetraploid wheat (Triticum turgidum L.) landrace agrotypes collected from the central highlands of Ethiopia and one commercial check cultivar (Boohai) were evaluated at Akaki experimental station for grain yield and 11 other component traits. The objectives were to estimate phenotypic (PCV) and genetic (GCV) coefficients of variation, broad-sense heritability (H) and genetic advance (GA), and to determine the interrelationships among the various traits. Genotypic differences among the agrotypes were highly significant for all the traits considered. Compared to Boohai, the landrace agrotypes were later in days-to-heading (DTH) and maturity (DTM), and had shorter grain filling period (GFP), lower fertility (KS) and lower 1000-kernel weight (TKW). By contrast, they were superior to Boohai in tiller number (TN), biological yield (BY) and grain yield plant^-1 (GYP). Intermediate to high order estimate combinations of GCV, H and GA (as % of the mean) were observed for TN, GYP, number of kernels spike^-1 (NKS), harvest index (HI) and TKW. GYP showed a moderate heritability which was higher than GFP, BY and Plant height (PHt). DTH and DTM were strongly correlated, but both were negatively associated with the rest of the traits except PHt. The negative correlation of DTM with GYP was largely indirect via other characters. PHt had either a weak or negative association with the other traits. TN and TKW were positively correlated with GYP, and had high and intermediate direct effects, respectively. These two traits, however, were negatively correlated and showed a substantial counter-balance effect via one another. It appears that, for the short-term, improvement of the Ethiopian wheat landraces may be possible through indirect selection for TN and TKW or direct selection for grain yield per se. In the long-run, crossing programmes between indigenous and introduced germplasm may be necessary.     

Genetic diversity and gene flow in six accessions of Meso-America teosintes

The genus Zea (teosinte) has a native distribution from Mexico to Nicaragua (Meso-America region) and studies on teosinte species may help improve our understanding of maize genetics, population genetics, genome evolution and crop evolution. Moreover, since F1 hybrids between teosinte and maize are fertile, all teosinte species can potentially contribute to maize breeding in the form of traits such as resistance or tolerance to heavy metals in the soil and other adverse environmental conditions. Gene flow between maize and teosinte occurs in Mexico and Central America. This study analysed the genetic diversity of teosintes by using the microsatellite technique on a total of 120 individuals from six different species and 21 Simple Sequence Repeats (SSR). A total of 109 alleles were found and the number of alleles per locus ranged from 2 to 7. The genetic diversity varied between all species from 0.514 to 0.572, with a mean value of 0.548 (Nei index). Rare and unique alleles were detected in all species, with the highest frequencies found in Zea diploperennis Iltis, Doebley et Guzman, Zea perennis (Hitchc.) Reeves et Mangelsdorf and Zea nicaraguensis Iltis et Benz, which had more than seven rare alleles each. Analysis of molecular variance revealed that 19.87% of the variation between species was statistically significant (P < 0.001). When the different species were compared with the Wright (Fst) value, genetic variation between species was confirmed. The data also revealed a moderate rate gene flow between the species. Genetic diversity was found to be somewhat higher in Central America than in Mexico.     

Land use history and historical soil erosion at Albersdorf (northern Germany) — Ceased agricultural land use after the pre-historical period

The Holocene landscape history and historical soil erosion were reconstructed at Albersdorf (Schleswig-Holstein, Germany) from soils and colluvial layers. In contrast to many landscapes in central Europe, agricultural land use and soil erosion were more frequent during pre-historical times, whereas it has almost ceased after the advent of history. Pre-historical soil erosion rates from about 0.1 to 6.9 t ha^− 1 a^− 1 were reconstructed with no significant differences between the prehistoric cultural phases. The study of buried soils within the soil/soil-sediment-sequences provided evidence for an acceleration of soil formation processes probably as a consequence of excessive prehistoric woodland pasture on poor sandy soils.     

A study of genetic diversity of sesame (<Emphasis Type="Italic">Sesamum indicum</Emphasis> L.) in Vietnam and Cambodia estimated by RAPD markers

Sesame (Sesamum indicum L.) is a traditional oil crop cultivated throughout South East Asia. To estimate the genetic diversity of this crop in parts at the region, 22 sesame accessions collected in Vietnam and Cambodia were analyzed using 10 RAPD markers. The 10 primers generated 107 amplification products of which 88 were polymorphic fragments (83%). Genetic diversity of all populations was H_t = 0.34 when estimated by Nei’s genetic diversity and species diversity was H′_sp = 0.513 when estimated by Shannon diversity index. Genetic distance ranged from 0.03 to 0.43, with a mean genetic distance of 0.23. The unweighted pair group method with arithmetic averages (UPGMA) cluster analysis for the 22 accessions divided the material in four groups. The dendrogram revealed a clear division among the sesame accessions based on their geographical region. Interestingly, some geographically distant accessions clustered in the same group, which might indicate the human factor involved in the spreading of sesame varieties. The high level of polymorphism shown suggests that RAPD techniques can also be useful for the selection of parents in sesame (Sesamum indicum L.) breeding program and for cultivar differentiation.