Horticultural evaluation of new Citrus latipes hybrids as rootstocks for Citrus

In 1968, the CRA-Research Center for Citriculture and Mediterranean Crops (CRA-ACM) started a research program aimed at breeding citrus rootstocks. Thespecies C. latipes (Swing.) Tan. was used as the female parent; trifoliate [Poncirus trifoliata (L.) Raf.], sour orange, and volkamer lemon (C. volkameriana .) were used as male parents. The behavior of some of these hybrids tested with other rootstocks in Sicily and Sardinia was evaluated. The cultivars under comparison 'Washington' navel orange and 'SRA 92' clementine in Sardinia and 'Tarocco' orange in Sicily. Our results showed the dramatic influence of rootstock ongrowth and yield; only minor effects on fruit quality were observed. Among therootstocks tested, Swingle citrumelo provided the highest yield. Some of the hybrids (F5 P12, F6 P12, and F6 P13) may improve plant yield, thus maintainingfruit quality. Encouraging data obtained with these hybrids may justify the use of monoembryonic species of the Papeda subgenus for breeding citrus rootstocks.