Effects of phosphorous fertilizer and mycorrhizal fungi on root growth characteristics and physiological traits of different cultivars of durum wheat (Triticum turgidum var. durum) under rainfed condition

Water scarcity due to limited rainfall, high temperatures, and high evapotranspiration is one of the important factors in reducing crops and reducing the efficiency of using dry areas. Iran is one of the arid regions of the world, with an average annual rainfall of 220 mm. wheat cultivation is at serious risk of drought stress. Mycorrhizal fungi, by creating a symbiotic relationship with the roots of most crops, increase the absorption of nutrients such as phosphorus, zinc, and copper, increase water absorption, reduce the negative impact of environmental stresses, and improve the growth and yield of host plants. Therefore, considering the importance of mycorrhiza inoculation in reducing the negative effects of drought stress and improving crop yield, as well as the need to optimize the use of chemical fertilizers for sustainable agriculture, the purpose of this study was to investigate the root growth characteristics and physiological traits of different durum wheat cultivars affected by the combined application of phosphorus fertilizer and mycorrhiza under dryland conditions.

In order to evaluate the effect of mycorrhizal fungi and phosphorous fertilizer on some of the root growth characteristics and physiological traits of durum wheat in rainfed conditions, an experiment was carried out as a factorial based on a randomized complete block design with three replications at Sarableh Agricultural Research station during the growing season 2018–2019. Experiment factors consisted of four cultivars of durum wheat (Dehdasht, Zahab, Saverz, and Saji) and five levels of fertilizer source (control, 25 and 50 kgha-1 P, mycorrhizal fungi, and 25 kgha-1 P). The seeds were sown in rows four meters long and at intervals of 20 cm. The dimensions of each experimental plot were eight square meters, in which eight rows were considered, and the distance between the experimental blocks was considered one meter. Also, the amount of seed used was 120 kg/ha. To measure root-related traits in the field after pollination from a metal cylinder that was manually designed and patterned Was used. To measure the amount of photosynthetic pigment, the leaves of the five-plant flag were randomly sampled. The Analysis of variance and comparison of mean data were performed by a Duncan multi-range test using SAS 9.1 software and the drawing of figures by Excel software.

The results indicated that the application of fertilizer sources significantly improved the traits. The results also showed that the interaction of cultivars and fertilizer sources on root growth characteristics and physiological traits was significant. So that, the highest root area (61.7% increased to control treatment), root special volume (91% increased to control treatment), root tissue density (47.5% increased to control treatment), root volume density (87.1% increased to control treatment), chlorophyll a and b (86.7 and 89.04% increased to control treatment, respectively), and proline (81.9% increased to control treatment) were obtained at Saji cultivar along with application of mycorrhizal fungi + 25 kgha-1 P. The relative water content of leaves also increased in different cultivars with fertilizer application. The application of treatment mycorrhizal fungi + 25 kgha-1 P in Saverz and Saji cultivars increased the relative water content by 84% and 71%, respectively, compared to the control treatment.

According to the results, it was found that the combined application of mycorrhizal fungi with 25 kgha-1 phosphorus fertilizer compared to the control treatment had the most effect on improving and increasing the studied traits. Mycorrhizal fungi seem to increase the root system of crops, and the secretion of phosphorus-soluble organic acids causes more phosphorus uptake, which together increases the surface area and root volume and consequently increases the uptake of water and elements, Which ultimately leads to improved relative leaf water content and photosynthetic pigments. The findings of this study also showed that Saji cultivars showed a better response to mycorrhizal fungi compared to other cultivars. Therefore, according to the obtained results, the Saji cultivar with Mycorrhizal fungi + 25 kgha-1 can be recommended for cultivation under dry land conditions.