Molecular Microbiology Research 2024, Vol.14, No.4, 181-187 http://microbescipublisher.com/index.php/mmr 185 Breeding programs should focus on incorporating these resistant traits into new cotton varieties. The identification of resistant sources and their utilization in breeding programs can accelerate the development of ALS-resistant cotton cultivars. Continuous screening and evaluation of breeding lines under field conditions are essential to ensure the effectiveness of these resistant varieties (Jindo et al., 2021; Rajesha et al., 2021). 6 Case Studies and Field Applications 6.1 Successful control in major cotton-growing regions In New Mexico, Alternaria leaf spot (ALS) caused by Alternaria alternata has become increasingly prevalent due to favorable weather conditions in the late cropping season. A comprehensive study evaluated 125 Upland cotton genotypes and 8 Pima cotton cultivars for resistance to ALS under natural infection field conditions. Despite high disease incidence and severity, certain genotypes exhibited consistent resistance. Notably, glandless lines such as NuMex COT 15 GLS, NM 13P1117, and NM 12Y1002, along with glanded commercial transgenic varieties like FM 2484 B2F, PHY 444 WRF, and NG 4545 B2XF, showed lower disease severity indices (DSI) in multiple tests, providing valuable insights for breeding resistant cotton varieties (Razavi, 2021). In southern New Mexico, field surveys in 2016 revealed a 100% disease incidence in 13 out of 14 evaluated fields, with an average disease severity index ranging from 21.5 to 87.0. The causal agent, identified as A. alternata, was confirmed through morphological and molecular characterization. This study underscores the importance of monitoring and identifying disease-causing agents to implement effective control measures (Zhu et al., 2019). 6.2 Comparative effectiveness of different control methods Comparative studies in New Mexico have highlighted the effectiveness of breeding for resistance as a control method. The significant genotypic variations observed among Upland cotton lines, with some glandless lines showing lower DSI compared to glanded lines, suggest that genetic resistance can be a viable strategy for managing ALS. The broad-sense heritability estimates for DSI ranged from 0.489 to 0.702, indicating a moderate to high potential for breeding resistant varieties (Zhu et al., 2018; Pranaya et al., 2020). In Türkiye, the first report of A. alternata causing leaf spot diseases in cotton emphasized the pathogen's potential to cause significant yield losses, up to 30% under severe infection conditions. The study involved isolating and characterizing the pathogen from infected fields and conducting pathogenicity tests to confirm its identity. This research highlights the need for integrated disease management strategies, including the use of resistant cultivars and monitoring secondary hosts like Prosopis farcta that can harbor the pathogen (Olmez et al., 2023). These case studies demonstrate the importance of regional monitoring, identification of resistant genotypes, and the implementation of integrated disease management practices to control ALS in cotton effectively. 7 Concluding Remarks Control strategies for Alternaria leaf spot in cotton have been diverse, ranging from chemical treatments to the use of resistant cultivars. Chemical fungicides such as mancozeb and propiconazole have shown effectiveness in reducing disease severity. For instance, mancozeb demonstrated a significant zone of inhibition at various concentrations, making it a reliable chemical control option. Additionally, botanical treatments like Allium sativum have also been effective, providing an eco-friendly alternative to chemical fungicides. Field evaluations have identified several Bt. cotton hybrids with resistance to Alternaria leaf spot. Hybrids such as Tulasi-144 BG-II and U5-SS-33 BG-II have shown resistant reactions, while others like Jadoo and Brahma have demonstrated moderate resistance. These resistant hybrids can significantly reduce the cost of plant protection and enhance net returns for farmers. Integrated Disease Management (IDM) is crucial for controlling Alternaria leaf spot in cotton. IDM combines multiple strategies, including the use of resistant cultivars, chemical treatments, and cultural practices, to manage the disease effectively. The importance of IDM is underscored by the varying effectiveness of individual control measures under different environmental conditions. For example, the prevalence and severity of Alternaria leaf
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