Effects of drought on isolates of Bradyrhizobium elkanii cultured from Albizia adianthifolia seedlings of different provenances

Abstract

Albizia adianthifolia (Schumach) W. F. Wright, a N-fixing legume tree, has a wide distribution in Africa, in Ghana occurring in high rainfall forests and in seasonally droughted forests, and is associated in the Ghanaian forest zone with dry, infertile sites. We hypothesised that A. adianthifolia hosted different rhizobial strains in different forest types, and that these different strains would show different growth responses to moisture stress and different motility and mortality in droughted soil. Three isolates, extracted from seedlings of A. adianthifolia growing in three forest types differing in seasonal drought, were identified as Bradyrhizobium elkanii and exposed to varying levels of osmotic stress. Growth responses varied between the three strains, one of which displayed clear signs of drought tolerance. A novel approach using soil leaching columns was used to test the effects of soil pore water (in terms of neck diameter) on both the survival and movement of wet and dry forest rhizobial isolates through soil columns. The responses of the isolates were significantly different, the pore neck diameter, marginally insignificant and the drought treatment insignificant. Thus the dry forest isolate survived better in all treatments, and showed less response to the treatments, than the isolate from the wet forest. The results offer preliminary evidence that Bradyrhizobium elkanii strains from A. adianthifolia in Ghana have evolved in response to local differences in seasonal water availability. These differences could assist the selection of A. adianthifolia provenances for agroforestry or land rehabilitation.

Biological nitrogen fixation of Biserrula pelecinus L. under water deficit

“…In accordance to this, it is not surprising that SafPt12 was able to present as good performance as that of Mesorhizobium, since its origin was from the southeast part of Alentejo region, Safara (Moura) where the annual precipitation does not exceed 450 mm (Costa 2008). The same was observed by Swaine et al (2007), which described that Bradyrhizobium elkanii strains in Albizia adianthifolia in Ghana evolved in response to local differences in seasonal water availability.…”

The efficiency and competitiveness of three Mesorhizobium sp. strains nodulating Acacia senegal (L.) Willd. under water deficiency conditions in the greenhouse

“…Drought affects both partners and all stages of the establishment of the rhizobium-legume symbiosis (Serraj et al 1999;Zahran 1999). Growth and mobility of rhizobia in the soil decrease under soil dehydration conditions (Gammack et al 1992;Swaine et al 2007), and this limits symbiosis establishment (Leung and Bottomley 1994). Water deficiency reduced significantly height and shoot dry weight in A. senegal plants.…”

Hydraulic lift through transpiration suppression in shrubs from two arid ecosystems: patterns and control mechanisms

“…This phenomenon can be of great importance in sandy soils, as shrubs usually experience a higher vulnerability to xylem cavitation (Sperry and Hacke 2002). In leguminous shrub species, HL could also help maintain associated N-fixing bacteria (Athar and Jhonson 1997;Swaine et al 2007) by mitigating decreased soil water potentials during drought .…”