Evaluation of rootstocks for March and Davis grapefruit in the Murray region of New South Wales
The influence of 5 rootstocks (Parramatta sweet orange, trifoliate orange, Troyer citrange, Appleby Smooth Seville and Somersby Smooth Seville) on the productivity and fruit quality of Marsh and Davis grapefruit was studied over 15 years in the Lower Murray region of New South Wales. Annual yields of mature trees and cumulative yield were highest on Troyer citrange; cumulative yield was lowest on trifoliate orange. Canopy volume was largest on Troyer citrange and smallest on trifoliate orange. Production efficiency (fruit yield per unit of tree size) was significantly greater on trifoliate orange than all other rootstocks. Canopy volume was 44% smaller on trifoliate orange than on Troyer citrange, but cumulative yield was only 26% lower. Because of their small size and high production efficiency, trees on trifoliate orange would be suitable for high density plantings. Trifoliate orange produced the best quality fruit. Fruit from trees on trifoliate orange had the highest total soluble solids (TSS) and TSS :acid ratio. Sweet orange and Appleby Smooth Seville produced the least acceptable fruit due to low TSS :acid ratios. Fruit size was largest on Troyer citrange and trifoliate orange. Trees on trifoliate orange accumulated excessive chloride (Cl-) during periods of high irrigation water salinity; however, no adverse effects on growth or long-term productivity were apparent. Leaf C1- concentrations for trifoliate orange varied from 0.42 to 1.10%. Leaf C1- concentrations remained below 0.30% for the other rootstocks. There were no significant effects of scion cultivar on tree size, yield or production efficiency, and differences in fruit quality were slight. Fruit size was larger with Marsh than Davis.