In the verdant orchards of the northwestern Himalayas, a silent battle is unfolding between apple farmers and a tenacious fungal foe. Venturia inaequalis, the culprit behind apple scab disease, has been wreaking havoc on apple crops, and the indiscriminate use of triazole fungicides has led to the emergence of resistant strains. A recent study published in ‘Scientific Reports’ sheds light on the mechanisms behind this resistance, offering insights that could reshape pest management strategies in the agricultural sector.
Syed Shoaib Mubashir, a researcher from the Division of Plant Pathology at Sher-e-Kashmir University of Agricultural Sciences and Technology, led a team that investigated the resistance profiles of V. inaequalis populations from North, South, and Central Kashmir. The study revealed a significant shift in sensitivity to two commonly used fungicides, difenoconazole and flusilazole, among the fungal isolates.
“Our findings indicate a major shift in sensitivity against both fungicides,” Mubashir explained. “This suggests that the indiscriminate use of these fungicides has led to the development of resistant strains, posing a significant threat to apple production in the region.”
The research team conducted baseline sensitivity assays on 30 V. inaequalis isolates unexposed to any fungicides. The mean ED50 value and discriminatory dose of difenoconazole and flusilazole were determined to be 0.584, 0.15 µg ml−1 and 0.018, 0.02 µg ml−1 respectively. The assessment at these discriminatory doses revealed a major shift in sensitivity against both fungicides. The sequencing of conserved region-2 of CYP51A1 revealed that the resistant isolates have TTT (Phenylalanine) instead of TAT (Tyrosine) codon at position 133. Moreover, the same mutation was observed in some shifted isolates which confirmed that this mutation is not solely responsible for the development of resistance.
The study also assessed the fitness parameters of resistant isolates, revealing that except for oxidative stress at 1 mm H2O2 (wherein a decreased micro colony growth linearly increases with resistance), there is no fitness cost associated with the development of resistance against difenoconazole and flusilazole. Meanwhile, the resistance against both fungicides is phenotypically stable. Consequently, it is speculated that these populations are unlikely to regain their sensitivity even in the absence of these frequently used fungicides.
“Our results suggest that the resistance against difenoconazole and flusilazole is phenotypically stable,” Mubashir noted. “This means that even if we stop using these fungicides, the resistant strains are likely to persist, posing a long-term challenge for apple farmers.”
The implications of this research are far-reaching. For the agricultural sector, understanding the mechanisms behind fungicide resistance is crucial for developing effective pest management strategies. The findings could lead to the development of new fungicides or integrated pest management approaches that can combat resistant strains. This could have a significant impact on the energy sector, as apple production is a vital component of the agricultural industry, which in turn contributes to the overall energy demand and supply chain.
As the battle against apple scab continues, the insights gained from this study offer a glimmer of hope. By understanding the resistance mechanisms and fitness penalties associated with V. inaequalis, researchers and farmers can work together to develop more sustainable and effective pest management strategies. The future of apple production in the northwestern Himalayas may hinge on these efforts, as the fight against resistant strains of V. inaequalis intensifies.