Rapid Identification of Acacia Species With Potential Salt Tolerance by Using Nuclear Ribosomal DNA Markers

Abstract

Use of saline lands for agroforestry relies primarily on plant species that have the trait of salinity tolerance, and also other economic and agronomic benefits. The selection of species, however, also needs to consider other key factors such as compatibility with existing flora, and potential for environmental benefits such as improved soil fertility or lowering of the water table in the case of dryland salinity. The testing of candidate species in particular environments needs substantial investments of costs and time. In this paper, a novel approach is presented for the rapid identification of potentially salt tolerant Acacia species, based on molecular phylogenetic analysis. The approach has been applied to four species groups, Acacia pendula, A. salicina, A. victoriae and A. stenophylla. The nuclear-encoded ribosomal DNA internal and external transcribed spacer (ITS and ETS) regions were used as markers, and phylogenetic analyses undertaken to identify closely related species that may share the salt tolerance traits. Such a methodology could be used to more rapidly identify candidate native species for agroforestry in salinity-affected regions and for preventing further expansion of salinity, thus assisting in biodiversity conservation.

Salt- and alkaline-tolerance are linked in Acacia

“…Salt-tolerance appears in the victoriae clade, sister to the rest of Acacia (figure 1). Acacia adinophylla is predicted to be associated with relatively high EC soils, while A. victoriae, predicted to be associated with moderate levels of salinity, has been used to rehabilitate salt-affected land [12]. Acacia adinophylla and other highly salt-tolerant species are range restricted and broadly sympatric (figure 1a) in the Transitional Rainfall Province of Western Australia, a locus of species richness and the origin of subsequent radiations [24]; these species are unrelated (asterisk in figure 1) indicating repeated colonization of saline soil.…”

“…One uses molecular tools to identify genes involved in stresstolerance [9,10] and another uses phylogenetics to investigate the evolution of salt-tolerance [1,11,12].…”

“…Traditionally, research on salt-and/or alkaline-tolerance in plants focused on laboratory experimentation and plant breeding [5][6][7], but new paradigms have emerged. One uses molecular tools to identify genes involved in stresstolerance [9,10] and another uses phylogenetics to investigate the evolution of salt-tolerance [1,11,12].…”

Macroevolutionary patterns of salt tolerance in angiosperms

“…In this way, phylogenetic analysis may help to detect previously unrecognized halophytes, or identify lineages with an enhanced capacity to evolve salt tolerance. Phylogenetic analysis has been used to identify relatives of halophyte species as potential targets for further investigation (Joseph et al, 2013), but given the lability of salt tolerance, it cannot be assumed that all close relatives will have similar tolerance (Liu et al, 2012). However, phylogenetic analysis may identify lineages in which salt tolerance has frequently evolved, potentially because they have traits that mean that they do not have so far to go to achieve salt tolerance.…”

Diversity of gall-forming rusts (Uromycladium, Pucciniales) on Acacia in Australia

“…Acacia salicina , the originally labelled host of the holotype of U. tepperianum , belongs to the ‘ A. bivenosa group’ of closely related plant species, which also includes A. ampliceps , A. bivenosa , A. cupularis , A. didyma , A. ligulata , A. rostellifera , A. sclerosperma , A. startii , A. telmica , A. tysonii and A. xanthina ( Chapman & Maslin 1992 , Joseph et al 2013a , b ). Acacia ligulata has been historically confused with A. salicina ( Chapman & Maslin 1992 ) and at the time of the original fungal description, the two were considered conspecific.…”