Processing carrots are mainly grown under rain-fed conditions in Nova Scotia, and thus become vulnerable to frequent periods of drought. Prolonged drought results in significant reductions in the yield and quality of carrot crops. Resistance to water deficit is gene controlled and it is essential to identify the genotypes that withstand water stress. It is equally important to understand the physiological mechanism(s) that contribute to drought tolerance. Physiological measurements were made on eight carrot varieties exposed to natural drought in a controlled greenhouse. Measurements were made on net photosynthesis, soil moisture, relative water content, membrane injury index, xylem pressure potential, and stem elongation. Overall, the slicer variety Bergen sustained normal plant functions under drought stress better than any of the other varieties. Bergen maintained stem elongation, photosynthetic activity, membrane function, and relative water content under droughted conditions. Another study was conducted to identify carrot varieties that are naturally resistant to drought. A mass screening of 85 slicer, dicer, and cut and peel varieties was conducted under greenhouse conditions. Two-week-old seedlings were exposed to gradual water deficit and observed for visual symptoms of wilting each day as soil moisture declined. Each variety was assigned a wilting score based upon the number of days it withstood drought (min = 1, max = 5). The dicer variety, Prodigy, was the only variety to score a 5 indicating the most drought resistance. Other varieties that withstood drought well were `Caropak', `Interceptor', `Oranza', and `Berlanda'. Varieties such as KC713126, Cello712113, and Cello711411 were more sensitive to water deficit and began to wilt 8 days after drought was imposed.
Rajasekaran Lada*, Azure Stiles and Christine Pettipas
Rowan Briscoe, Rajasekaran Lada, Claude Caldwell, Kevin Sibley, Christine Pettipas and Azure Stiles
Producing carrots with optimal root grades is the most critical aspect of carrot production for maximizing profits. Desired root grades can be optimized by maintaining optimal plant population. While precision seeding helps to seed required seeding rate, obtaining optimum seed germination and uniform emergence, especially in mineral soils and under cold and dry climates, have been great challenges to carrot producers around the world. Therefore, stand establishment is critical for optimizing yield and quality in carrots. Experiments were conducted to identify suitable germination and emergence promoters (GEPs) that will promote early and uniform emergence under temperatures of 5 °C and 20 °C and under 20% FC and 40% FC combinations. GEPs, belonging to both natural and synthetic antistress, antioxidant groups of compounds, and mineral salts were used. Carrot seeds of cv. Oranza were used in this study. Seeds were preconditioned with various GEPs, then submerged into laponite RD gel that was used as a potential “artificial exosperm” for carrot seeds. Data on emergence was collected and emergence and vigor value was calculated. Under ideal conditions, that is, at the 20 °C and 40% FC combination, there was no significant difference between treated seeds and untreated control. Germination was delayed at the 5 °C and 20% FC combination. However, seeds preconditioned with GEP-PN1.5%, GEP-LU at 1 mg·L-1, GEP-CA at 10 mg·L-1, GEP-AA at 100 mg·L-1 and GEP-SD at 10 mg·L-1 all promoted emergence resulting in the highest number of seedlings emerged at 5 °C and at 20% FC. Enhanced emergence under low temperature and low moisture may perhaps be due to synthesis of specific proteins.