Characterising canola pollen germination across a temperature gradient
Malcolm J. Morrison A B , Allison Gutknecht A , John Chan A and S. Shea Miller AA Eastern Cereal and Oilseed Research Centre, Agriculture and AgriFood Canada, Central Experimental Farm, K.W. Neatby Bldg., 960 Carling Avenue., Ottawa, ON, K1A 0C6, Canada.
B Corresponding author. Email: malcolm.morrison@agr.gc.ca
Crop and Pasture Science 67(4) 317-322 https://doi.org/10.1071/CP15230
Submitted: 11 July 2015 Accepted: 6 November 2015 Published: 29 March 2016
Abstract
If predictions are correct, heat stress during reproduction will become a yield limiting factor in many world crops and breeding heat stress tolerance a major goal. The objective of our paper was to highlight a novel system to investigate the influence of temperature (T) on pollen germination using a thermal gradient PCR programmed to establish differential Ts across 12 wells of a PCR plate. Seven cultivars of Brassica napus L. were grown through flowering in a cool growth cabinet (20/15°C day/night) or a heat stress cabinet (HST, 27/22°C day/night). Pollen from each cultivar × cabinet combination was aspirated from 6 opened flowers, and suspended in germination media. Drops of the pollen suspension were floated on media in each well, and the PCR T was set to 30°C with a gradient of ± 10°C, creating a range from ~20 to 40°C from left to right. After an 8 h treatment, the pollen germination (pg, %) and pollen tube growth score (ptg, 1–5) were evaluated using a microscope. There were significant differences among cultivars for pg and ptg score and significant differences among well T for pg and ptg score. Pollen tubes grew best at T from 20 to 23°C. Well T exceeding 33°C reduced pg and ptg score, although 3 of the 8 cultivars had good pg even at 36°C. HST >29°C, in a growth cabinet, generally resulted in B. napus raceme sterility, although our experiment showed that pollen was still capable of germinating up to 33°C, indicating that pollen germination may not be the only reason for heat stress susceptibility.
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