THERMAL HARDENING FOR SEED VIGOUR AND SALT TOLERANCE IN CABBAGE

A healthy crop is desirable in direct seeded vegetables to ensure good quality of the produce and is affected by a number of environmental and cultural factors. A number of seed treatments had been used to enhance the performance of seeds in several crops. Alternate cycles of dry heat and chilling (thermal hardening) is one of these seed treatments, used in cereals to invigorate the seeds, but reports about such treatments in vegetable crops are scarce. Therefore, seeds of cabbage varieties Golden Acre (GA) and Green Ball (GB), varying in their germination (%) and vigour, were exposed to different temperature (-20 and 40°C) and duration (24, 36 and 48 hrs) regimes and the effect of these treatments on seed vigour was evaluated. Different thermal hardening treatments, especially H-C 24 hrs, C-H 36 hrs, C-H-C 24 hrs and C-H-C 48 hrs, increased final germination percentage (FGP), power of germination and seedling vigour. These treatments decreased the germination spread over time in cabbage variety GB. However, such response was not observed in GA that already had high seed vigour. The impact of these better performing treatments was evaluated on germination and vigour of GA seeds under saline conditions. Interestingly, mean germination time and time taken for 50% germination was less for C-H 36 hrs and C-H-C 24 hrs treated seeds at all salinity levels. These seed treatments (H-C 24 hrs, C-H 36 hrs, C-H-C 24 hrs and C-H-C 48 hrs) improved vigour index at all salinity levels except at 200 mM NaCl concentration. Overall results depicted that C-H 36 hrs and C-H-C 24 hrs were more effective than other treatments to impart salinity tolerance and can be used as a safe tool for direct seeding of cabbage crop under normal and saline conditions.