Abeer S. Yassin

Sugar beet root rot disease triggered by Fusarium oxysporum f. sp. radicis-betae is a destructive disease and dramatically affects the production and quality of the sugar beet industry. Employing beneficial microorganisms as a biocontrol strategy represents an eco-friendly and sustainable approach to combat various plant diseases. The distinct aspect of this study was to assess the antifungal and plant growth-promoting capabilities of recently isolated Streptomyces to treat sugar beet plants against infection with the phytopathogen F. oxysporum. Thirty-seven actinobacterial isolates were recovered from the rhizosphere of healthy sugar beet plants and screened for their potential to antagonize F. oxysporum in vitro. Two isolates SB3-15 and SB2-23 that displayed higher antagonistic effects were morphologically and molecularly identified as Streptomyces spp. Seed treatment with the fermentation broth of the selected Streptomyces strains SB3-15 and SB2-23 significantly reduced disease severity compared to the infected control in a greenhouse experiment. Streptomyces SB2-23 exhibited the highest protective activity with high efficacy ranging from 91.06 to 94.77% compared to chemical fungicide (86.44 to 92.36%). Furthermore, strain SB2-23 significantly increased plant weight, root weight, root length, and diameter. Likewise, it improves sucrose percentage and juice purity. As a consequence, the strain SB2-23’s intriguing biocontrol capability and sugar beet root growth stimulation present promising prospects for its utilization in both plant protection and enhancement strategies.

Two field experiments were carried out in sandy soil during two consecutive growing seasons; 2021/22 and 2022/23, at West Nubaryia region in Egypt. The experimental area, which is naturally infested with Meloidogyne javanica, were prepared to evaluate the influence of three deficit irrigation (DI) rates i.e. 40, 60 and 80% from irrigation water requirements (IWR), compared to full (100% from IWR) irrigation rate on reproduction parameters, final population (Pf) and reproduction factor (Rf) of M. javanica root-knot nematode and productivity of sugarbeet. Var. Merador as well as water use efficiency (WUE). The result showed that the DI rates of 40, 60 and 80% from IWR decreased (P≤0.05) significantly Pf and Rf values of M. javanica on sugarbeet plants compared to full (100% of IWR) irrigation rate. Increasing DI from 100 to 80, 60 and 40% of IWR significantly, (P≤0.05) decreased Pf number from 26036 to 18115, 9878 and 5371, respectively and Rf from 12.70 to 8.84, 4.82 and 2.62-fold, compared to initial population, respectively. The sugarbeet yield components, roots, gross sugar and white sugar yields , and quality index then were achieved the highest (P≤.0.05) significant values with an average of 21.85, 3.75 and 3.15 tons/fed and 84.64% , respectively under DI rate of 80% from IWR, while the lowest ones (11.21, 1.8 and 1.47 tons/fed and 78.59%, respectively) were recorded at DI rate of 40% from IWR, compared to full (100% of IWR) irrigation rate, The highest ( P≤0.05) significant values of WUE for gross sugar yield (1.91 kg/m3 water) and white sugar yield (1.61 kg/m3 water) as commercial yields for sugarbeet crop , also , were recorded at DI rate of 80% from IWR, however, the lowest ones (1.27 and 1.02 kg/m3 water , respectively)were achieved by full (100% of IWR) irrigation rate. The previous results revealed that the DI rate of 80% from IWR has significant benefits in four terms of saving irrigation water, reducing damage caused by nematode, increasing yield quantity and quality, and increasing WUE. Thus, it was concluded that the application of the DI rate of 80% of IWR may led to enhance the efficiency of IPM programs to control root-knot nematodes at drip irrigated sugarbeet fields in sandy soils under semi-arid conditions.