Assessment of Cold and Heat Tolerance of Winter‐grown Canola (Brassica napus L.) Cultivars by Pollen‐based Parameters

Abstract

Winter‐grown canola (Brassica napus L.) production is limited mostly by frost and winter kill in the southern canola‐growing regions of the United States. Tolerance to cold and heat were assessed by studying percentage of pollen viability (PV), in vitro pollen germination (PG) and pollen tube length (PTL) for 12 field‐grown cultivars. Freshly collected pollen from all cultivars were incubated on artificial solid growth media at a constant temperature ranging from 10 to 35 °C at 5 °C interval for 30 h to determine PG and PTL. A modified bilinear model best described the temperature response functions of PG and PTL. Canola cultivars showed significant variability (P < 0.001) for PV (61.3 % to 89.7 %), PG (29.0 % to 48.2 %) and PTL (463 to 931 μm). The average cardinal temperatures, Tmin, Topt and Tmax, for PG and PTL were 6.4, 24.3 and 33.7 °C, respectively. Principal component analysis revealed that maximum PG, PTL, Tmin and Topt of both PG and PTL were the most important factors in determining cold tolerance, whereas Tmax of PG and PTL, and maximum PG and PTL were more responsible in separating the cultivars for heat tolerance. The canola cultivar, KS3077, was the most cold tolerant with the lowest Tmin and the widest temperature adaptability range, and the cultivar Kadore was the most heat tolerant with the highest Tmax for the PG. The identified cold‐ and heat‐tolerant cultivars may be useful in canola‐breeding programmes to develop cultivars suitable for a niche environment.

Breeding Methods for Winter Sorghum Improvement

“…The severity or extent of such effects depended on the degree of cold tolerance of the cultivars. In vitro pollen growth assays have been considered as a possible screen to identify germplasm, with the potential for improved reproductive stress tolerance (Kakani et al, 2002(Kakani et al, , 2005Salem et al, 2007;Singh et al, 2008). It was concluded that in susceptible types, low temperatures reduced the number of pollen mother cells and their ability to produce pollen, and that difference in tolerance between genotypes suggested that the character was polygenic (Gonalez et al, 1986).…”

Maize growth and developmental responses to temperature and ultraviolet-B radiation interaction

“…The growth and development processes, such as stem elongation, leaf initiation and expansion, leaf area development, photosynthesis, flowering and fruiting of many crops including maize, are highly dependent on growth temperature (Tollenaar 1989a, b;Kim et al 2007, Singh et al 2008a, Li et al 2010. Yield and seed quality of many crops including maize are sensitive to frequently observed temperature extremes, and both to ambient and elevated UV-B radiation levels (Teramura et al 1990, Kim et al 2007, Ballare et al 2011, Yin and Wang 2012.…”

High Temperature Effects on in vitro Pollen Germination and Seed Set in Field Pea

“…Indeed, with 64-72% of genes in vegetative tissues of Tradescantia and maize also being expressed in pollen (reviewed by Hamilton and Mascarenhas, 1997), in vitro pollen germination has been investigated as a rapid screening criterion for tolerance to a variety of agronomically-important characteristics including soil acidity and salinity, metal and herbicide toxicity, as well as for heat tolerance (Sari-Gorla and Frova, 1997). Exposure to high temperatures reduces in vitro pollen germination percentage and pollen-tube length in many crops including canola (Singh et al 2008;Morrison et al 2016), cotton (Kakani et al 2005Song et al 2015), and sorghum (Nguyen et al 2013;Djanaguiraman et al 2014;Singh et al 2015Singh et al , 2016, as well as legumes like chickpea (Cicer arietinum; Devasirvatham et al 2012), field pea (Pisum sativum; Petkova et al 2009;Lahlali et al 2014;Jiang et al 2015), groundnut (Arachis hypogaea; Kakani et al 2002), and soybean (Glycine max; Koti et al 2005;Salem et al 2007). In sorghum, seed-set percentage (the number of seeds filled at physiological maturity divided by the total number of florets) was strongly and positively associated with in vitro pollen germination across genotypes and temperature regimes (Nguyen et al 2013;Singh et al 2015Singh et al , 2016.…”