Effect of rootstock on red colour of bi-coloured 'Forelle' pears
Insufficient red colour limits the profitability of bi-coloured pear cultivars in South Africa. Here we report on a trial conducted to establish whether red colour can be improved by choice of rootstock. We assessed the effect of BP1, BP3, OHxF 97, Quince A, Quince C51 and BA 29 rootstocks on the colour of 'Forelle' pears over two seasons. Light interception effects were negated by only sampling exposed fruit. Quince rootstocks showed the best red colour compared to the pear rootstocks. This does not appear to be related to differences in maturity between the rootstocks because firmness correlated poorly with background colour. Chlorophyll and carotenoid concentrations of the peel were significantly lower in fruit from quince rootstocks. Differences in anthocyanin concentrations between the treatments were non-significant, although they did follow colour measurement trends. Fruit from quince rootstocks probably appeared redder due to intrinsically lower chlorophyll concentrations in the peel. Our conclusion is that the quince rootstocks may possibly have a direct effect on red colour that is not related to differences in light interception or maturity.