Two species of Passiflora, P. edulis f. edulis (purple passion fruit) and P. edulis f. flavicarpa (yellow passion fruit), and P. incarnata (maypop), were evaluated for acclimation and cold hardiness, using differential thermal analysis, electrolyte leakage and the tetrazolium stain test. The two species showed the capacity to acclimate several degrees during the evaluation period and the three tests gave similar lethal temperatures for the two species; –9C to –10C for yellow passion fruit, –10C to –12C for purple passion fruit and –11C to –13C for maypop. Purple and yellow passion fruit were also assayed for survival after a freeze-thaw cycle, using a tissue culture regeneration technique called “feeder plate”. Yellow passion fruit did not show the capacity to regenerate at any of the temperatures used (0, –3, –6C). Purple passion fruit showed callus formation even at the lowest temperature (–6C).
Differential thermal analysis, electrolyte leakage, tetrazolium stain test, and the “feeder plate” tissue culture regeneration technique were used to determine cold hardiness of passion fruit and maypop. The “feeder plate” technique showed that yellow passion fruit did not regenerate at 0C, -3C, and -6C while purple passion fruit showed callus formation at all temperatures. The remaining tests gave similar lethal temperatures for the two species. Lethal temperatures were -9C to -10C, -10C to -I2C, and -11C to -13C for yellow and purple passion fruit and maypop, respectively.