Impact of mycorrhizal fungi on P acquisition, yield and water use efficiency of onion under regulated deficit irrigation

Abstract

An experiment was conducted during 2009 for evaluation the effect of mycorrhizalcolonization and regulated irrigation at different stages of growth on yield and water useefficiency (WUE) of onion. Pre-inoculated of onion (Red Azar Shahr cv.) seedling withtwo species of Arbuscular Mycorrhizal (AM) fungi (Glomus versiforme and G. etunicatum) and non-mycorrhizal ones transplanted at density of three plants per pot.Plants were subjected to four irrigation regimes, so at different growth stages including:vegetative growth period, bulb formation and ripening, onions were received differentamount of water based on ET, I1 (100,100 and 80% of ET) I2 (75, 100 and 80 % of ET), I3 (75,75 and 60% ET) and I4 (75, 60 and 80% of ET) at three growth stages respectively. After bulb maturation, bulb yield and dry weight and P concentration were determined and WUE was calculated. The results indicated that mycorrhizal plants had high Pconcentration, and produced greater bulb than non-mycorrhizal onions in all irrigationregimes. WUE was improved by mycorrhizal symbiosis regardless of irrigation regime;however G. versiforme was more effective in comparison with G. etunicatum. Among irrigation regime treatments only sever water stress in bulb formation stage (I4) led todrastic decrease in WUE. In aspect of interaction of mycorrhizal colonization andirrigation regime result indicated that onions inoculated by G. versiforme at I2 andtreatment by G. etunicatum at I2 and I3 led to highest WUE and control plants under I4 irrigation regime showed the lowest WUE.