The Influence of Potato Cultivar on Lipid Content and Fecundity of Bolivian and British Populations of Globodera rostochiensis

The influence of host cultivar on the lipid levels provided by a female to her progeny was investigated with Oil Red O stain and a quantitative image analyzer. A population of Globodera rostochiensis was multiplied at Toralapa Field Station in Bolivia on 25 different potato cultivars grown in that country. The mean neutral lipid content of newly formed second-stage juveniles varied significantly with cultivar over a 200% range. The corresponding range was only 18% and 28% for the same Bolivian and a UK population of G. rostochiensis, respectively, when both completed reproduction concurrently on 10 pot-grown European cultivars in the United Kingdom. Egg numbers per female varied with host for Bolivian cultivars that lack known partial resistance to Globodera spp. There was a 15-fold range between the most and least fecund nematode-host combinations (Kosi and Gendarme). The Bolivian G. rostochiensis population showed only a 2-fold range in mean eggs per cyst when grown on European cultivars in the UK. The fatty acid profiles of lipids from Bolivian G. rostochiensis cysts reared on Bolivian potato cultivars were dominated by C₂₀ (37-64%) and C₁₈ (28-46%) fatty acids and ranged from C₁₄ to C₂₂. The three major fatty acids detected were C_20:4:, C_20:1, and C_18:1. Few differences between cultivars were observed. For a UK population of G. rostochiensis reared on ssp. tuberosum, higher relative percentages of C₁₈ and monounsaturated fatty acids and lower relative percentages of C₂₀ and polyunsaturated fatty acids were found.     

Effective transgenic resistance to Globodera pallida in potato field trials

A cysteine proteinase inhibitor expressed in potato plants provides the first demonstration that transgenic resistance to nematodes such as the potato cyst nematode Globodera pallida can be effective under field conditions. The highest level of resistance obtained in the field for one of the four transformed lines of the normally fully susceptible Solanum tuberosum tuberosum cv. Désirée was 70±9%. The partially resistant cv. Sante that is currently of commercial use in the UK showed a resistance of 85±3%. In containment experiments a change in G. pallida population to one known to be virulent against cv. Sante caused a significant loss of its resistance from 80±4% to only 51±6%. In contrast, the resistance of transgenic Désirée was similar for challenge by the avirulent and virulent populations with values of 68±6% and 71±4%, respectively. Constitutive expression of the cystatin had no detrimental effect on either number or weight of tubers and the weight of the haulm for 3 of the 4 lines in the field. The results establish that transgenic field resistance against G. pallida can be achieved. Clearly food and environmental safety must be assured before commercialisation can be contemplated. However, a prima facie case can be made that the technology is benign and can reduce the use of environmentally hazardous nematicides.     

Metabolism of 1,1,1,2,2-pentafluorohexane and 1,1-difluorocyclohexane by rat liver microsomes in vitro

Metabolism of 1,1,1,2,2-pentafluorohexane with liver microsomes from phenobarbital-treated rats gave only one metabolite, namely, the 5-hydroxy derivative. Under similar conditions 1,1-difluorocyclohexane was metabolized to give mainly the 3- and 4-hydroxy derivatives in the ratio 1: approximately 5.5. The structures of these metabolites were established by chemical ionization (CI) and/or electron impact (EI) mass spectrometry and confirmed by synthesis in the case of 1,1-difluorocyclohexan-4-ol. Oxidation of 1,1-difluorocyclohexane with lead tetrakis(trifluoroacetate) also gave, inter alia, the 3- and 4-hydroxy derivatives. In saturated hydrocarbons complete replacement of hydrogen by fluorine at one particular carbon will not only block microsomal hydroxylation thereat but will also inhibit hydroxylation at neighbouring hydrogen-bearing carbons, (alpha almost completely, beta markedly, gamma slightly).