Arbuscular mycorrhizal fungi and the plant chemistry of Sulla aculeolata spp. in Mediterranean semi-arid environments

Abstract

This study is the first to investigate the mycorrhizal associations of Sulla (Sulla aculeolata) growing wild in the semi-arid region of northeastern Morocco. The physicochemical properties of the soil and the chemical composition of the plants were analyzed at two different sampling sites (Ras El-ma and Bni Chiker). Spores were extracted from the rhizosphere, counted, and identified. The most probable number (MPN) approach was used to assess the indigenous soil mycorrhizal potential. Field surveys revealed that the plant biomass was 6512.5 kg DM/hectare at Ras El-ma and 2000 kg DM/hectare at Bni Chiker. Sulla aculeolata from Ras El-ma had a significantly higher organic matter content (86.89%) and a lower ash content (13.11%) compared to the Bni Chiker (73.15% and 26.85%, respectively). Chemical composition analysis showed no significant difference (P > 0.05) in crude protein content between the two sites. Similarly, the assessment of macronutrients revealed no differences in N, P, Mg, and S between the sites. Conversely, S. aculeolata from Ras El-ma had a higher K content (1.75%) and a lower Na concentration (0.22%), whereas plants from Bni Chiker exhibited the highest levels of Ca (4.67%) and Na (0.6%). The fungal spore density ranged between 1123 and 2300 spores per 100 g of soil, with spores predominantly belonging to the genus Glomus. The indigenous mycorrhizal potential of the soil was high, reaching 6400 propagules per kg. Root analysis revealed endomycorrhizal structures, including arbuscules, vesicles, and hyphae. The mycorrhizal frequency ranged between 88.89% and 92.22%, while mycorrhizal intensity and arbuscular intensity reached 26.2% and 39.52%, respectively. Selecting and utilizing arbuscular mycorrhizal fungi (AMF) present in the rhizosphere could enhance the production of vigorous Sulla plants, supporting their preservation and domestication in Mediterranean semi-arid pastures while improving forage productivity.