Phenotypic Analyses of Multi-Environment Data for Two Diverse Tetraploid Potato Collections: Comparing an Academic Panel with an Industrial Panel

Phenotypic analyses of two different association panels of tetraploid potato cultivars are presented. Association panels are sets of variously related genotypes assembled for association analysis purposes. The aims of this research were to inspect, analyse and compare two phenotypic data sets, a first step in association mapping analysis. A first panel of 205 contemporary and historical cultivars, selected to represent the commercial potato germplasm pool, was evaluated in two trials in 2006, one on sandy soil and the other on clay soil, both with two replications. It was called the academic panel. Data for the second panel with 299 genotypes were compiled from contributions from five breeding companies and included 66 locations and 18 years. Each of the participating breeding companies contributed data from their clonal selection programmes for 38 advanced breeding clones and a series of standard cultivars. It was called the industrial panel. Variance components for genotypic main effects and genotype-by-environment interactions were calculated, and estimates for the random genotypic main effects were produced. The genotypic main effects for 19 agro-morphological and quality traits were used to study trait by trait correlations within each panel. In addition, for the genotypes shared by both panels, the correlation of genetic main effects between the panels was investigated. The heritability of all traits was high and no large differences were observed between panels. Coefficients of trait variation were highly correlated (r = 0.9) for both panels and trait by trait correlations in both panels showed highly similar patterns. These results demonstrate that a single-year balanced field trial as well as using breeders’ records yields robust phenotypic information that can be used in a genome-wide association study. Issues related to data management and definition of traits are discussed.     

The prospects of reduced tillage in tef (Eragrostis tef Zucca) in Gare Arera, West Shawa Zone of Oromiya, Ethiopia

Soils in Ethiopia are traditionally ploughed repeatedly with an oxen-drawn plough before sowing. The oxen ploughing system exposes the soil to erosion and is expensive for farmers without oxen. This study was undertaken to assess agronomic and economic impacts of alternative, reduced tillage methods. Field experiments were carried out on a Vertisol and a Nitisol for 2 years to study the effect of zero tillage, minimum tillage, conventional tillage, and broad bed furrows (BBF) on the yield of tef (Eragrostis tef Zucca). No significant differences in tef biomass and grain yields were observed between the treatments on both soils in the first year. In Nitisol in the second year, yield was lower in the zero tillage treatment as compared to the other treatments. No difference in yield was observed between single plough, conventional, and BBF. On Vertisol, the yields were higher in BBF as compared to the other treatments. The yields on Vertisol were 1368, 1520, 1560 and 1768 kg ha⁻¹ for the zero tillage, minimum tillage, conventional tillage and BBF treatments respectively. More than twice as much grass weed was observed on zero tillage treatment as compared to the BBF treatment on both soils. Zero tillage gave the lowest gross margin on both soils whereas BBF gave the highest gross margin. The gross margin on Nitisols for the zero tillage and BBF treatments were −108 and 1504 Birr/ha respectively and corresponding numbers for the Vertisol were 520 and 1924 Birr ha⁻¹. On Vertisol there were no significant difference in gross margin between minimum tillage and conventional tillage. Minimum tillage is an interesting option on Vertisols, particularly for female-headed households as it reduces the tillage cost. It may also improve overall productivity of the farming system because it allows partial replacement of oxen with cows and reduces soil erosion.     

The probability of the spread of Amblyomma variegatum in the Caribbean

The risk of a disease occuring is often more difficult to estimate than estimating a monetary value of the losses sustained when the disease occurs. The probability of a non-infested island in the Lesser Antilles becoming infested with Amblyomma variegatum was integrated into the formula for calculating the present value of the benefit of avoiding the costs of infestation by the tick. Based on the history of the spread of A. variegatum in the Caribbean, the probability of becoming infested was estimated to be one island or island group per year and the tick needed 5 years to spread over a 15-km area from an initial point of infestation. This rate of spread is slow compared with that of Boophilus microplus, which spread over the 160-km long island of Puerto Rico in <4 years.     

Soft tissue application of lasers.

Despite increasing numbers of veterinarians incorporating lasers into their clinical practices, little information has been published about laser clinical applications in soft tissue surgery. This article reviews soft tissue interaction, describes laser equipment and accessories commonly marketed to veterinarians, and discusses clinical applications of the carbon dioxide laser in a systems-based approach. A table of recommended laser tips and settings based on the authors' experiences using a carbon dioxide laser (AccuVet Novapulse LX-20SP, Bothell, WA) is provided.     

Mixed function oxidase and glutathione transferase activity in last instar Heliothis virescens larvae

Methyl parathion-resistant and -susceptible strains of Heliothis virescens were assayed for mixed function oxidase and glutathione transferase activity at four time periods within the last instar. No significant differences were found between the mixed function oxidase or glutathione transferase activities of the resistant and susceptible strains. However, significant differences did appear among time periods within the last instar. Larvae assayed during the postfeeding time period (60–80 hr) had the highest mixed function oxidase activity, which was 28 times that of last instar larvae assayed during the first time period (0–19 hr). Glutathione transferase activity appeared to be highest during the 20- to 39-hr and 40- to 59-hr time periods, but the differences among time periods were small. The importance of these findings to studies of insecticide resistance and plant herbivore interactions is discussed.