2018 ASHS Annual Conference

Bell pepper is the second leading vegetable crop in Florida. The profitability of bell pepper has been endangered by the increasing incidence of Phytophthora capsici, an important soilborne plant-pathogen known for its destructive potential, especially in subtropical areas. While periods of high rainfall and raised water levels are considered major causes of P. capsici outbreaks, the incidence of the disease seems to be favored by salinity stress, a condition increasingly affecting the coastal areas of South Florida, where a significant amount of bell pepper production occurs. Under such conditions, vegetable grafting may represent a potential solution to manage both biotic and abiotic stress. Therefore, a greenhouse pot-study was conducted to evaluate the plant growth, nutrient accumulation, yield, and stress response of different bell-pepper grafting combinations to P. capsici in presence of 0, 30, and 60 mM of NaCl. Non-grafted and self-grafted plants of ‘Blitz’ (susceptible to P. capsici) were compared with plants grafted onto ‘Dorado’ and ‘Robusto’, both commercial rootstocks claimed to be resistant to P. capsici. Plants were grown in pots on a sandy-soil:perlite mix (50:50, v:v) and fertigated daily through drip-irrigation. Salinity treatments started 14 days after planting (DAP) and plants were inoculated with P. capsici at 28 DAP. At 64 DAP, all three factors affected plant growth and a significant interaction was observed among all three factors for leaf area and leaf dry weight. Significant three- and two-factor interactions were also observed for most measured plant nutrient accumulation parameters. Total-plant sodium accumulation increased with increasing salinity level, while a significant interaction was observed between P. capsici and rootstock. At harvest, total fruit number and fruit fresh weight per plant were affected by salinity level and grafting combination, and a significant interaction was observed between grafting combination and P. capsici. A significant interaction between the three factors was also observed for disease incidence. In infested soil, non-grafted and self-grafted plants of ‘Blitz’ showed consistently higher incidence of Phytophthora blight compared to those grafted onto ‘Dorado’ and ‘Robusto’. Moreover, plants grown under moderate salinity (30 mM of NaCl) had a higher disease incidence compared to those grown with 0 and 60 mM of NaCl. It is concluded that irrigation with moderately saline water may increase the incidence of Phytophthora blight in susceptible cultivars of bell pepper. However, commercial rootstocks resistant to P. capsici may assure the control of the disease either with no, moderate, or moderately-high salinity levels.