Submitted to: Annals Of Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/25/2005
Publication Date: 4/25/2005
Citation: Kakani, V.G., Reddy, K.R., Koti, S., Wallace, P.V., Prasad, P.V., Reddy, V., Zhao, D. 2005. Differences in in vitro pollen germination and pollen tube growth of cotton cultivars in response to high temperature. Annals Of Botany. 96:59-67. Interpretive Summary: High temperature environments with temperatures higher than 30 degrees C during flowering reduces boll retention and yield in cotton. Global surface air temperature is projected to increase by 1.4 to 5.8 degrees C by the end of the 21st Century. In the projected global climate change conditions, episodes of high temperatures are expected to occur more frequently. A study was conducted to evaluate the effects of high temperature on pollen germination of cotton cultivars and identify screening techniques for cotton cultivar evaluation. It was concluded from this study that variability in optimum temperature for pollen germination can be used for screening cotton cultivars for high temperature tolerance. These results are extremely useful to cotton breeders for developing cotton cultivars tolerant to high temperature extremes.
Technical Abstract: High temperature environments with >30ºC during flowering reduce boll retention and yield in cotton. Episodes of projected high temperatures in future climates are expected to occur more frequently. Therefore, identification of cotton cultivars with high temperature tolerance would be beneficial. To understand differences in temperature tolerance among cotton cultivars, response of pollen germination and pollen tube growth to temperature was quantified, and their relation to leaf cell membrane thermostability and photosynthetic parameters were studied in 13 cultivars. At anther dehiscence, pollen was collected from flowers of field-grown cotton cultivars and germinated at temperatures from 10 to 45 degrees C at 5 degree C intervals. Cultivar variation existed for cardinal temperatures of pollen germination percentage and pollen tube growth. Pollen germination and pollen tube length of the cultivars ranged from 20-60% and 411-903 um, respectively. Results showed that a modified bilinear model best described the response to temperature of pollen germination and pollen tube length. Mean cardinal temperatures calculated from the bilinear model for the 13 cultivars were 15.0, 31.8 and 43.3 degree C for pollen germination and 11.9, 28.6 and 42.9 degree C for pollen tube length. No significant correlations were found between leaf physiological parameters (leaf membrane thermostability, leaf photosynthesis, stomatal conductance and fluorescence and pollen germination or pollen tube length). We conclude that variability in optimum temperature for pollen germination and pollen tube growth can be used for screening cotton cultivars and cultivars with optimum temperatures >32ºC for pollen germination and tube growth would be more tolerant to high temperature.