Evaluation of Streptomyces induced resistance in different sugarcane genotypes against Sugarcane mosaic virus (SCMV)

Abstract

Sugarcane mosaic virus (SCMV) is one of the most destructive viral diseases affecting sugarcane in Egypt, causing considerable reductions in yield. In the present study, SCMV was isolated and characterized using symptomatologic observations, RT-PCR amplification of the coat protein (CP) gene and sequence analysis. The Egyptian isolate (SCMV-Eg; GenBank accession no. PX890922.1) exhibited 94.6–99.8% nucleotide identity with previously reported SCMV isolates worldwide, showing the highest sequence similarity with the Iranian isolates JGr-59 and Sr-162. This study assessed the effectiveness of a Bio-Act treatment based on Streptomyces as both a preventive and curative biocontrol strategy against SCMV in four sugarcane genotypes (GT54-9, G2003-47, EH128-2, and SP81-3250) under four different treatment applications. The four treatments comprised T1 (uninoculated control), T2 (SCMV inoculation only), T3 (Bio-Act applied before SCMV inoculation, preventive), and T4 (Bio-Act applied after SCMV inoculation, curative). Bio-Act treatment (T3) was the most effective at suppressing SCMV infection and improving sugar quality traits compared with untreated infected plants. Sucrose content, juice purity and sugar recovery were about 9.6%, 75% and 8.8%, respectively. In addition, T3 treatment significantly enhanced biochemical defense responses by increasing total phenolic content and elevating the activities of peroxidase (POD) and catalase (CAT) enzymes. RT qPCR analysis demonstrated that T3 treatment markedly reduced viral load. This effect was most pronounced in genotype EH128-2, which exhibited the lowest SCMV expression level and the strongest overall resistance response, recording the highest total phenolic content (66.9 mg GAE/g DW), POD activity (2.4 units), and CAT activity (0.109 units). Genotype SP81-3250 followed, showing substantial suppression of viral accumulation and enhanced biochemical defense responses. Principal Component Analysis (PCA) explained 56.7% of the total variation. PC1 showed sugar quality traits, while PC2 indicated enzymatic defense activity. There is promising potential for using Streptomyces based Bio-Act as an eco-friendly biocontrol strategy to suppress SCMV affection and enhance sugarcane productivity. Moreover, genotype EH128-2 has been identified as the most tolerant genotype, potentially serving as a valuable genetic resource for future breeding programs aimed at enhancing sugarcane resistance.