Breeding Citrus for salt tolerance

Poncirus trifoliata (L.) Raf. and Citrus grandis (L.) Osb. were phenotypically distinct and their selected F-1, 17-40, had features that displayed a combination of both parents. Favorable alleles at genes that condition traits for high leaf mass proportion, abundant fibrous root production, and superior tissue tolerance to high Na concentration in fibrous roots are collected in the F1, showing that these heritable traits are promising for the improvement of salt tolerance in citrus. Performance of an intergeneric BC1 population (C. grandis x 17-40), consisting of 54 individuals, relative to its parents was evaluated for different growth and mineral accumulation related traits under both saline (40 mM NaCl) and non-saline environments. The difference between the responses of the original parents and the heterotic Fi plant led to wide segregation in the BC1 progeny in response to 16 weeks of salinization. Many traits showed transgressive segregation in both directions that may yield extreme values to breed salt hardy citrus genotypes. For example, 15% of the population performed better than the best performing parent, the Fi, for growth parameters, 21% of the population displayed less leaf damage than any parent for leaf symptom responses, and some progenies accumulated less Na and/or Cl in different tissues and/or in whole plants than did any parent. Superior genotypes were identified for overall performance as well.