031 Effects on the Supercooling Capacity of Capsicum annum L. by Epiphytic Bacteria Population

The effect of epiphytic bacteria population with different ice nucleation activity (INA) on the extent of supercooling of in vitro and leaf tissue disks of greenhouse-grown Capsicum annuum L. plants was determined. Bacterial strains were isolated on PDA and King's B medium from foliar samples of weeds from commercial apple orchards in Cuauhtemoc, Chihuahua, Mexico. Bacteria were screened by colony morphology, fluorescence under UV light, while growin on King's B medium plates and screened for ice-nucleating capability at -5 °C in suspensions of 108 cfu/mL. Ice nucleating (Ice+) and non-ice-nucleating (Ice-) active strains with fluorescent capacity were isolated from symptomless leaf samples. Four bacterial strains were used with different ina as epiphytic population models. Two Pseudomonas syringae strains, Pss29A and PD, from Oregon State Univ., with high Ice+ capability; P. fluorescens A-506, in its Blight Ban™ commercial lyophilized presentation; and UC001, a native fluorescent strain from CIAD-Cuauhtemoc; both Ice-strains. Freezing tests were carried out under controlled conditions. The high Ice+ strains Pss29A and PD increased the temperature of supercooling 2 and 1 °C compared to control samples. The non-inoculated tissue showed damage over 50% at -3 °C and below. Inoculated tissue with Ice+ strains (P. syringae 29A and PD), showed damage superior to 50% at -1 and -2 °C, respectively. Conversely, at none of the temperatures assayed, Ice-strains surpassed 50% damage. These results are of interest for further development of passive strategies towards minimizing damage due to low-temperature exposure of tropical vegetable crops.