Screening for High‐Temperature Tolerant Cotton Cultivars by Testing In Vitro Pollen Germination, Pollen Tube Growth and Boll Retention

Abstract

With radical global climate change and global warming, high temperature stress has become one of major factors exerting a major influence on crop production. In the cotton (Gossypium hirsutum L.)-growing areas of China, especially in the Yangtze River valley, unexpected periodic episodes of extreme heat stress usually occur in July and August, the peak time of cotton flowering and boll loading, resulting in lower boll set and lint yield. Breeding programs for screening high temperature-tolerant cotton germplasm and cultivars are urgent in order to stabilize yield in the current and future warmer weather conditions. In the present study, 14 cotton cultivars were quantified for in vitro pollen germination and pollen tube growth in response to temperatures ranging from 10 to 50 °C at 5 °C intervals. Different cotton genotypes varied in their in vitro pollen germination and pollen tube length responses to the different temperatures. Maximum pollen germination and pollen tube length ranged from 25.2% to 56.2% and from 414 to 682 µm, respectively. The average cardinal temperatures (T min , T opt , and T max ) also varied among the 14 cultivars and were 11.8, 27.3, and 42.7 °C for pollen germination and 11.8, 27.8, and 44.1 °C for maximum pollen tube length. Variations in boll retention and boll numbers per plant in field experiments were found for the 14 cotton cultivars and the boll retention and boll retained per plant on 20 August varied considerably in different years according to weather conditions. Boll retention on 20 August was highly correlated with maximum pollen germination (R 2 = 0.84) and pollen tube length (R 2 =0.64). A screening method based on principle component analysis of the combination of pollen characteristics in an in vitro experiment and boll retention testing in the field environment was used in the present study and, as a result, the 14 cotton cultivars could be classified as tolerant, moderately tolerant, moderately susceptible and susceptible to high temperature.

Diurnal pollen tube growth rate is slowed by high temperature in field-grown Gossypium hirsutum pistils

“…In contrast, the maximum pistil temperature observed on August 4 (34.9 • C; Fig. 3A) was above the optimal temperature range for pollen tube growth in G. hirsutum previously reported in vitro (28-32 • C; Burke et al, 2004;Kakani et al, 2005;Liu et al, 2006). A possible explanation for the differences in cooling capacity of these two tissues is that the pistil lacks sufficient stomatal development for transpirationally driven cooling observed in the subtending leaf.…”

“…Various investigators have utilized pollen germination and tube growth responses to temperature as methods of identifying heat tolerant cultivars (Rodriguez-Garay and Barrow, 1988;Kakani et al, 2005;Liu et al, 2006). However, the moderately high temperatures observed in this study were not sufficient to inhibit pollen germination (4A) or the fertilization process (Fig.…”

Assessment of morphophysiological traits for selection of heat-tolerant potato genotypes

“…In addition, PCA was used for classification of genotypes for heat tolerance in previous studies (Kakani et al, 2005;Liu et al, 2006;Demirel et al, 2016). The classification results of 17 genotypes for heat tolerance by using traits of cHDW, cLAI, cPn, cGs, cTr, cCT, and cSPAD exhibited a similarity to the yield performance of genotypes grown under higher temperature conditions (Figures 2 and 3).…”

How does timing, duration, and severity of heat stress influence pollen-pistil interactions in angiosperms?

“…have identified in vitro pollen germination and tube growth responses to a range of temperatures, 8,9,25,[27][28][29] and have used this information to identify thermotolerant genotypes of a number of important crop species, including Arachis hypogaea, 30 Gossypium hirsutum, 9,31 Glycine max 29 and Capsicum sp.…”

“…9,[28][29][30][31] However, it has been reported that in vitro pollen germination and tube growth responses to high temperature are not necessarily predictive of in vivo pollen performance under elevated temperature, 32,37,38 and high temperature can also limit pollen germination through loss of stigmatic receptivity. 39 Furthermore, under field conditions, it was recently reported that the diurnal pattern of pollen tube growth was strongly altered by moderately elevated temperature in G. hirsutum, where pollination occurred earlier in the day under higher diurnal temperatures.…”