Evaluation of endophytic bacteria isolated from durum wheat on root crown rot disease under drought stress.
Emran Al-Sawalhah1, Firas Abu-El Samen1, Nehayah AlKarablieh2, Yahya Othman3, Jamal Ayad3, Ayed M. Al-Abdallat3, Kholoud M. Alananbeh2*. 1Department of Plant Sciences, School of Agriculture, Jordan University of Science and Technology, Irbid, Jordan. 2Department of Plant Protection, School of Agriculture, The University of Jordan, Amman, Jordan. 3Department of Plant Sciences, School of Agriculture, The University of Jordan, Amman, Jordan. *Corresponding author.
Fusarium crown rot (FCR) caused by Fusarium culmorum is one of the most damaging soil-borne diseases that affect wheat yield. A direct relationship was observed between FCR and drought stress, as drought affects the relationship of Fusarium to plants, and the Fusarium itself is affected by drought stress. Recently, there has been more interest in endophytes and their potential for controlling soil-borne diseases, enhancing plant growth, and increase plant tolerance and resistance in drought and salinity conditions. The objectives of this research were to: (i) test the antifungal activity of bacterial endophytes (n=60) isolated from durum wheat in Jordan against FCR aggressive isolate using the Cross-streak method and the agar well diffusion method, (ii) evaluate the ability of the selected bacterial endophytes to improve the tolerance of Hourani Jordanian durum wheat to FCR on seed and seedlings stages, and (iii) evaluate the ability of the selected bacterial endophytes to improve Hourani Jordanian durum wheat to drought stress at seeds and seedling stages. There was high antifungal effect for the 60-bacterial isolates, however, variation existed. Promising results for 12 isolates with inhibition percentage ranged from 41.17 to 446.27 for isolate #38 and #4, respectively were found. Three bacterial isolates (#52, #37 and #17) showed drought tolerance using the spectrophotometer. Based on the highest antifungal activity and the drought tolerance, five isolates were selected to test their effect on Fusarium tolerance under drought conditions on Hourani seeds and seedling stages. For seed germination assay, isolate # 50 showed the longest coleoptile (5.48 cm), followed by #52 (5.22 cm), and #32 (4.76 cm) compared to the control (3.74 cm). For radical length, isolate #52 had the longest radical (8.35 cm), followed by #50 (7.79 cm), #32 (7.23cm), and #38 (7.03 cm) compared to the control (6.22 cm). For the number of seminal roots, no significant differences were recorded with the control (1.93). For the longest seminal root, isolate #52 had the longest seminal root (7.5 cm), followed by #50 (7.4 cm), and #38 (6.7 cm) compared to the control (5.99 cm). For the seedling assay, chlorophyll content ranged from 305.3 to 332.9 in isolate #50 and #52, respectively compared to the control (248.3). Stem length ranged from 29.5 cm in isolate #38 to 33.1 cm in isolate #60 compared to the control (25.16 cm). Extended length was the highest in isolate #32 (48.2 cm), followed by #60 (48.0 cm), and #52 (47.7 cm) compared to the control (45.9 cm). Root length ranged from 52.4 cm to 55.5 cm for isolate # 32 and #38, respectively compared to the control (46.70 cm). Dry weight was the highest for isolate #52 (1.42 g) followed by #50 (1.39 g) compared to the control (1.22 g). In fresh weight, no significant differences were recorded compared to the control. Analysis of the data is still going for the remained experiments. This study presents a potential for some bacterial isolates to alleviate the effect of F. culmorum and drought stress alone or combined.