Vertebrate damage to 00 and 0 varieties of oilseed rape in relation to SMCO and glucosinolate concentrations in the leaves

Abstract

‘Double-low’ (00) varieties of oilseed rape ( Brassica napus L. var. napus) have lower seed concentrations of certain astringent chemicals than have ‘single-low’ (0) varieties and as a result it has been suggested that plants of the 00 varieties may suffer higher damage by mammal and bird pests. Regular damage surveys were conducted over the winter months on 23 farms where 0 and 00 varieties of oilseed rape were being grown in close proximity. Samples of foliage were taken each month and analysed for levels of S-methylcysteine sulphoxide (SMCO) and various glucosinolates. There was no evidence that either rabbits ( Oryctolagus cuniculus) or woodpigeons ( Columba palumbus) preferred to feed on the 00 rather than the 0 varieties. The two types did not significantly differ in the foliage concentrations of SMCO or any glucosinolate. The concentrations of all the chemical constituents analysed fell significantly between February and April. There were no significant correlations between the level of damage in a field and the concentrations of SMCO or glucosinolates in the foliage of the plants grown there. There were significant correlations between the SMCO and glucosinolate concentrations in the 0 and 00 varieties grown on the same farm. This suggests that factors associated with climate, geographical location, soil type and/or cultivation may have a greater effect on the foliage concentrations of these chemicals than has the variety of the plant.