PJB-2023-524
Sumbal Naseer
Abstract
Wheat (Triticum aestivum L.) stands as the second most vital cereal crop globally. This study aimed to explore the antifungal biological control potential of endophytic bacteria from yellow rust (YR) resistant wheat cultivars. Total of nine bacterial isolates, namely B01, B04, B06y, B06b, B08, B09, B11, B35, and B37 were selected from the nine best performing wheat cultivars i.e., Pirsabak-05, Pirsabak-15, Wadan-17, Pisabak-21, Gulzar-19, Abaseen-21, Bakkar Star, Ning-8319, and Fateh Jang-16, respectively. First, the isolated bacteria were tested for antifungal potential against the Fusarium graminearum and Ustilago triticae in the in-vitro assays. Against F. graminarium, the bacterial isolate B08 demonstrated stable growth inhibition activity (58.0% ± 1), followed by B06b (54.9% ± 6.0). Against the Ustilago triticae, the bacterial isolate B06y showed highest and consistent growth inhibition activity (37.3% ± 1.44). To validate the in-vitro fungal growth inhibition activities, all the nine bacterial isolates were foliar sprayed on the YR susceptible wheat variety, Inqilab-91, followed by yellow rust inoculation at 72 hours post bacterial spray. Based on plant disease data, and morphological parameters, isolates B06b, B06y, B08, and B11 demonstrated potential biocontrol ability, with relative resistance index values of 8.2, 8.0, 7.5, and 7.9, respectively. Two bacterial isolates B04 and B35 with RRI values of 6.9 and 6.7, respectively demonstrated a moderate biocontrol of YR in wheat variety Inqilab91. Isolates B01 and B37, with RRI values of 4.8 and 3.3, respectively, demonstrated susceptible response. Clustering based on disease and morphological data resulted in clustering of bacterial isolate treatments into distinct desirable and non-desirable clusters. The biochemical characterization of the potential biocontrol isolates was performed. Isolates B06b, B06y, and B11 were gram negative, whereas B08 was gram positive. All four biocontrol isolates revealed moderate catalase activity. The highest IAA production was recorded in isolates B04 (OD600 = 0.209), whereas the lowest IAA conc was recorded for the isolate B06b (OD600 = 0.164). The inorganic phosphate solubilizations was recorded as zone of solubilization around the bacterial colonies on Pikovskaya agar medium. Highest solubilization was recorded for the bacterial isolates B06b (6.33 mm), followed by the isolate B06y (6.07mm). Using 16S rDNA sequencing, Two of the four biocontrol isolates, i.e., B06b and B08 were identified. The bacterial isolates B06b and B08 showed highest homologies with Pseudomonas moraviences (NR043314.1) and Bacillus paramycoides (NR157734.1) 99.42% and 99.08%, respectively. This study adds to the current pool of knowledge on the use of bacterial endophytes as biocontrol and biofertilizer agents. This study recommends a further evaluation of the identified bacterial biocontrol isolates in more systematic field trials to explore their potential field application.
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