Pollen-based screening of coconut (Cocos nucifera L.) varieties for tolerance to high temperature and drought stress

Cocos nucifera L. is a vital crop in South Asia, particularly in coastal areas vulnerable to climate change, with heat and drought stress significantly impacting its production. The reproductive stage of coconut is more sensitive to these stresses. Recent studies have employed in vitro pollen screening to assess heat tolerance. Osmotic adjustment (OA) has been recognized as a key factor in drought tolerance by maintaining turgor pressure. This study examined the effects of temperature on pollen germination (PG) and tube growth across eight coconut hybrids, with temperatures ranging from 15 to 50 ºC. The hybrids showed significant differences in cardinal temperatures (Tmin, Topt, Tmax) for PG and tube growth. This work also assessed osmotic stress responses using polyethylene glycol (PEG) solutions in the presence or absence of an osmolyte potassium chloride (KCl), revealing differences in intrinsic OA and osmolyte-induced OA. The Chowghat Orange Dwarf (COD) x Andaman Ordinary Tall (ADOT) hybrid was found to be the most heat tolerant. These findings provide valuable insights into coconut hybrid tolerance to climate change, highlighting the potential for combining intrinsic and osmolyte-induced OA to enhance drought resistance.