Intraspecific Salt Tolerance Variation in Nicotiana tabacum Pollen Germination and Pollen Tube Growth

Abstract

Salt stress affects 20% of global cropland. Excessive salt inhibits pollen germination and pollen tube growth (PTG), two crucial aspects of angiosperm ontogenesis. Pollen tolerance to salt and how tolerances vary intraspecifically are important factors of the sexual reproduction and evolution of flowering plants. Additionally, pollen response to salt is an effective screening method for whole plant salt tolerance. While the general field of plant salt tolerance is well studied, little research has been done on intraspecific variation in salt effect on pollen germination and PTG. The objective of this study was to investigate the effect of super-optimal levels of sodium chloride (NaCl) on pollen germination and PTG in vitro in 11 diverse genotypes of Nicotiana tabacum. NaCl tolerance was evaluated in three concentrations in N. tabacum pollen tube growth medium (TPTGM), where tolerance was observed in terms of PTG and pollen germination. ‘Mpeskq’ is NaCl tolerant relative to 10 other genotypes of N. tabacum. ‘Mpsekq’ pollen germination percentage was reduced by 5.8% and PTG was reduced by 34.6% from control TPTGM to 50mM NaCl TPTGM treatments. ‘Aparecido’ was the least NaCl tolerant, with a reduction of 62.6% PTG and 93.5% pollen germination between these same treatments. A strong positive correlation between PTG NaCl tolerance and pollen germination NaCl tolerance was also discovered (r = 0.74, p-value = 7.54e^(-7)). These findings show there is genetic variation for NaCl tolerance among diverse genotypes of N. tabacum. Future research should confirm this work and identify the genes responsible for NaCl resistance among genotypes such as ‘Mpsekq’ for use in N. tabacum or other crops.