Effects of arbuscular mycorrhizal fungi and irrigation levels on yield and growth characteristics of lemon (Citrus aurantifolia) trees in Darab

Lemon (Citrus aurantifolia) is particularly an important tree because its fruits are freshly used and also they are used in the food industries. Lemon tree has high economical value among all other citrus trees. In order to investigate the effects of mycorrhizal inoculation on lemon tree under draught stress, an experiment was carried out in split-block design with three replications. The study area was Darab and the experimental period was two years. The main plots consisted of three levels of irrigation (60 %, 80 % and 100 % of lemon water requirements), and the subplots were three levels of mycorrhizal inoculation (0, 1 and 2 kg per tree). Mycorrhizal inoculant was prepared by mixing of three species Funneliformis mosseae, Rhizophagus irregularis and Claroideoglomus etunicatum. The results showed that moisture stress, regardless to mycorrhizal inoculation, caused significant decrease in the majority of the measured traits, except Water use efficiency (WUE) that showed the opposite trend. Main effects of mycorrhizal inoculation increased the majority of measured traits. In 2 kg per tree inoculation treatment, fruit yield, fruit weight, leaf chlorophyll, leaf phosphorous concentration, relative water content, WUE and root colonization were significantly increased (22.1, 53.3, 42.0, 19.5, 15.3, 24.0 and 508 percent, respectively). Under the conditions of mild and sever moisture stresses, the use of mycorrhizal inoculant (1 and 2 kg per tree)  improved some of the measured traits, such as fruit yield that increased 20.2% and 37.6%, respectively. As a general conclusion, using of mycorrhizal inoculation had significant effect on yield and some growth characteristics and increased tolerance to moisture stress probably due to improve P concentration and water relation in plant, such as osmotic adjustment, water hydronic conductivity and stomatal regulation