Screening a core collection of citrus genetic resources for resistance to <i>Fusarium solani</i>

A causal agent for Dry Root Rot (DRR) of citrus has not been definitively identified, but the organism mostconsistently associated with DRR is Fusarium solani. To efficiently screen a citrus germplasm collection forresistance to F. solani, a core subset of the collection was evaluated. Seedlings of forty five accessions werewounded by girdling. Treatment consisted of inoculation with F. solani, with uninoculated controls. Threeparameters were evaluated: recovery from girdling (0 - 3); amount of DRR (0 - 4); and percentage of healthyfeeder roots. Thirty three accessions showed no significant difference in recovery from girdling betweeninoculated and uninoculated seedlings and 11 of these accessions showed good recovery from girdling (>2.7). Twenty four accessions showed no significant difference in DRR between inoculated and uninoculatedseedlings, and 12 of these accessions showed low development of DRR (< 1). Twenty four accessions showedno significant difference in % healthy feeder roots between inoculated and uninoculated seedlings and 8of these showed a high percentage (> 80%) of healthy feeder roots. Five accessions were superior in allthee 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). Theseaccessions would probably represent the best candidates for further study of F. solani resistance.