SCREENING A CORE COLLECTION OF CITRUS GENETIC RESOURCES FOR RESISTANCE TO FUSARIUM SOLANI

A causal agent for Dry root rot (DRR) of citrus has not been definitively identified, but the organism most consistently associated with DRR is Fusarium solani (Mart.) Sacc. To efficiently screen a citrus germplasm collection for resistance to F. solani, a core subset of the collection was evaluated. Seedlings of forty-five accessions were wounded by girdling. Treatment consisted of inoculation with F. solani, with uninoculated controls. Three parameters were evaluated: recovery from girdling (0-3); amount of DRR (0-4); and percentage of healthy feeder roots. Twenty-four accessions showed no significant difference in DRR between inoculated and uninoculated seedlings, and 12 of these accessions showed low development of DRR (<1). Thirty-three accessions showed no significant difference in recovery from girdling between inoculated and uninoculated seedlings and 10 of these accessions showed good recovery from girdling (>2.7). Twenty-four accessions showed no significant difference in % healthy feeder roots between inoculated and uninoculated seedlings and eight of these showed a high percentage (>80%) of healthy feeder roots. Five accessions were superior in all three parameters: ‘Fremont’ mandarin (PI 539507), ‘Lamas’ lemon (PI 539226), ‘Mato buntan’ pummelo (PI 529398), ‘Olivelands’ sour orange (PI 539164) and ‘South Coast Field Station’ citron (PI 539435). These accessions would probably represent the best candidates for further study of F. solani resistance.