Abstract
Several studies, performed mainly in pots, have shown that arbuscular mycorrhizal symbiosis can mitigate the negative effects of water stress on plant growth. No information was available about the effects of arbuscular mycorrhizal symbiosis on berseem clover growth and nitrogen (N) fixation under conditions of water shortage.
A field experiment was conducted in a hilly area of inner Sicily, Italy, to determine whether symbiosis with AM fungi can mitigate the detrimental effects of drought stress on forage yield and symbiotic N2 fixation of berseem clover. Soil was either left under water stress (rain-fed conditions) or the crop was well-watered. Mycorrhization treatments consisted of inoculation of berseem clover seeds with arbuscular mycorrhizal spores or suppression of arbuscular mycorrhizal symbiosis by means of fungicide treatments. Nitrogen biological fixation was assessed using the 15N-isotope dilution technique.
Arbuscular mycorrhizal symbiosis was able to mitigate the negative effect of water stress on berseem clover grown in a typical semiarid Mediterranean environment. Under water stress conditions, arbuscular mycorrhizal symbiosis resulted in increases in total biomass, N content, and N fixation, whereas no effect of crop mycorrhization was observed in the well-watered treatment.
Honggang W, Guanyi W, Huiquan L (1989) Effects of vesicular-arbuscular mycorrhiza on the growth of mungbean and its water use. Acta Pedol Sinica 26:393-400.
Why This Research Matters
This field study -- conducted under real-world conditions in a semi-arid Mediterranean environment -- confirms that arbuscular mycorrhizal symbiosis provides meaningful drought protection. The results are especially noteworthy because the benefit was observed for both biomass production and nitrogen fixation, two critical drivers of forage crop productivity. The absence of effect under well-watered conditions is also consistent with other research showing that mycorrhizal benefits are greatest under stress conditions.