Prospects for the Study and Improvement of Abiotic Stress Tolerance in Date Palms in the Post-genomics Era

Abstract

Date palm (Phoenix dactylifera L.) is a socioeconomically important crop in the Middle East and North Africa and a major contributor to food security in arid regions of the world. P. dactylifera is both drought and salt tolerant, but recent water shortages and increases in groundwater and soil salinity have threatened the continued productivity of the crop. Recent studies of date palm have begun to elucidate the physiological mechanisms of abiotic stress tolerance and the genes and biochemical pathways that control the response to these stresses. Here we review recent studies on tolerance of date palm to salinity and drought stress, the role of the soil and root microbiomes in abiotic stress tolerance, and highlight recent findings of omic-type studies. We present a perspective on future research of abiotic stress in date palm that includes improving existing genome resources, application of genetic mapping to determine the genetic basis of variation in tolerances among cultivars, and adoption of gene-editing technologies to the study of abiotic stress in date palms. Development of necessary resources and application of the proposed methods will provide a foundation for future breeders and genetic engineers aiming to develop more stress-tolerant cultivars of date palm.

Physiological responses of date palm (Phoenix dactylifera) seedlings to seawater and flooding

“…However, information on the responses of date palms to salinity and flooding combined stresses is still limited (Srikanth et al, 2016;Al Kharusi et al, 2019a;Hazzouri et al, 2020). Net CO 2…”

“…Date palm ( Phoenix dactylifera L.) is an economically important perennial plantation crop in several arid and semiarid countries in North Africa, the Middle East and Central America (Chao & Krueger, 2007; Al‐Khayri et al ., 2015; Yaish & Kumar, 2015; Yaish et al ., 2017). In their natural environment, date palms are exposed to a multitude of different stresses, for example drought, heat, air pollution and salinity (Shabani et al ., 2012; Yaish & Kumar, 2015; Du et al ., 2018; Hazzouri et al ., 2020). Although date palms are thought to be a salt‐tolerant crop able to grow in soils up to 12 dS m –1 without showing symptoms of salt stress (Ramoliya & Pandey, 2003; Yaish & Kumar, 2015; Patankar et al ., 2019; Al‐Harrasi et al ., 2020), salinity can lead to significant economic losses in date palms (Tripler et al ., 2011; Yaish & Kumar, 2015; Al‐Muaini et al ., 2019).…”

“…Although date palms are thought to be a salt‐tolerant crop able to grow in soils up to 12 dS m –1 without showing symptoms of salt stress (Ramoliya & Pandey, 2003; Yaish & Kumar, 2015; Patankar et al ., 2019; Al‐Harrasi et al ., 2020), salinity can lead to significant economic losses in date palms (Tripler et al ., 2011; Yaish & Kumar, 2015; Al‐Muaini et al ., 2019). This is particularly observed in salt susceptible cultivars (Al Kharusi et al ., 2017, 2019a; Hazzouri et al ., 2020), which showed significantly declined photosynthesis, shoot and root growth and foliar water content under salt stress (Alhammadi & Edward, 2009; Al Kharusi et al ., 2017). Salt stress affects their growth and productivity independently of drought and heat (Alhammadi & Kurup, 2012), and constitutes an increasing problem in date palm plantations due to irrigation and fertilisation.…”

“…Other salt‐tolerant species, that is mangroves, have developed specific apoplastic barriers that can function as filters against salt uptake by their roots, thereby minimising salt movement into the plant (Pannaga et al ., 2014). Although molecular pathways underlying salt‐adaptation mechanisms have been dissected and partially identified in some plant species, the mechanisms that mediate salt tolerance of date palms are still largely unknown (Yaish & Kumar, 2015; Al Kharusi et al ., 2017; Hazzouri et al ., 2020).…”

“…In addition to salt stress, both in plantations and in their natural environment, date palms are frequently exposed to water saturation of the soil, either through irrigation or flooding, and hence oxygen deficiency in the rhizosphere (Abul‐Soad, 2010; Carr, 2013; Darwesh, 2013; Kreuzwieser & Rennenberg, 2014; Hazzouri et al ., 2020). As a consequence, photosynthesis can be impaired either by stomatal or nonstomatal mechanisms, or both (Brugnoli & Björkman, 1992).…”