Bacterial Seed Endophytes of the Holoparasitic Cistanche Armena and C. Phelypaea (Orobanchaceae) from Saline Habitats: Semi-Deserts vs Flooded Coasts

Abstract

The current study compares the bacterial seed endomicrobiomes of the endemic holoparasitic plant species Cistanche armena and C. phelypaea. Both species thrive in habitats that are saline but with a very different soil water status. The study aims to uncover how environmental conditions influence the diversity of the bacterial communities of seeds of these holoparasites and also highlights the physiological activities, several enzymatic and PGP traits of culturable endophytes that may support the tolerance of their hosts to abiotic stresses. A combination of culture-dependent and molecular techniques was employed for the identification of the seed endomicrobiome (culturable and unculturable). From the seeds of both parasitic plant species closely related strains were isolated. Sixteen phyla, 323 genera and 710 bacterial species were identified, mainly Gram negative, halotolerant bacteria with an environmental origin. Most of the isolates were endospore forming, halotolerant and alkaliphile Bacillus spp. which suggests that the endophytic bacteria of C. armena and C. phelypaea seeds possess traits that are correlated with the natural habitat of their hosts. The Paenibacillus strains from both plant species demonstrate similar biochemical traits. Although the seed endophytic microbiomes of C. armena and C. phelypaea contain a high number of common bacterial taxa, also remarkable differences exist. We demonstrated that the diversity of the bacterial communities is related to the environmental conditions, water status or abiotic stresses.