A mandarin-like Tahiti lime hybrid, resistant to fruit fly

Abstract

Tahiti lime is the most HLB-tolerant of all commercial citrus cultivars and is tolerant/resistant to other important diseases and pests, including Citrus black spot, Alternaria, and Queensland fruit fly. However, it has seldom been used by plant breeders because of extreme infertility; being completely male-sterile and mostly seedless. These challenges did not deter the pioneering work of the South African breeders DeLange and Vincent in the 1970s who used Tahiti lime as their main parent for HLB resistance, considering it 'highly tolerant to greening'. They performed 2,600 hand pollinations to obtain 5 seeds, none of which germinated, but subsequently obtain a population of 86 seedlings from 20,000 open pollinated fruit, via tissue culture. Within 20 years, all of this material had been lost through a combination of natural causes and neglect of the breeding program. We re-visited the use of Tahiti lime as a breeding parent in 2013, with a modest effort in which seed from 289 open pollinated fruit were collected from two isolated trees surrounded by mandarin cultivars. A surprisingly large number of seed (115) were obtained and 51% of these germinated. However, many died after germination and only 11 trees were suitable for field planting 18 months later. After four years only four trees remained and molecular analysis showed that two of them were nucellar and the other two were hybrids. One of the hybrids has large (180 g) red fruit, similar to a mandarin. It produces fertile pollen and abundant monoembryonic seed and has already been used in the Australian breeding program to backcross for HLB screening. Tests indicate that this hybrid, like its parent, is resistant to fruit fly. Larger populations of open-pollinated Tahiti lime seedlings need to be produced, to properly test a HLB strategy envisaged by conventional breeders more than 50 years ago. © 2026 International Society for Horticultural Science.