Variation in chloroplast behaviour of tomato genotypes exposed to dark treatment under ex vivo condition

Chloroplasts play a crucial role in photosynthesis because their chlorophyll content has a positive relationship with the photosynthetic rate. The chlorophyll content is an important assessment parameter for crop improvement research and is affected by dark-induced stress. The present investigation was undertaken to study variation in the chlorophyll content of 45 tomato genotypes exposed to dark treatment under ex vivo conditions and its association with fruit yield. Forty days after transplanting, healthy and well-expanded leaves were excised from the mother plant and exposed to dark treatment for 7 days. Chlorophyll content was indirectly measured by using a Minolta SPAD-502 chlorophyll meter on 0, 3rd, 5th and 7th day of dark treatment. Results revealed wide variation in the SPAD value at different durations of dark treatment. On 3rd day of dark treatment, the SPAD value ranged from 4.17 to 21.33 SPAD unit with a mean of 12.06. On 5th day of dark treatment, the SPAD value ranged from 4.07 to 20.56 SPAD unit with a mean of 10.43 and at 7th day of dark treatment the SPAD value ranged from 3.32 to 14.33 SPAD unit with a mean of 8.03. Some genotypes, such as BT 3, BT 17 and BT 207-2, were susceptible to the dark. The genotypes such as BT 2, Utkal Raja, BT 101, BT 218, BT 17-2, BT 442-2, BT 12-3-2, BT 413-1-2, BT 429-2-2, & BT 433-1-2 were identified as tolerant to dark. A positive association was observed between SPAD values and fruit yield.