استجابة هجن من الذرة الصفراء لمكافحة الأدغال ببعض المبيدات الكيميائية ودراسة مقاومة دغل الدهنان

Response of maize hybrids to weed control using some chemical herbicides and study of the resistance of Echinochloa colona L. weed

Abstract
A field experiment was conducted during the fall season of 2024, with the aim of studying the response of three maize hybrids—Torro, Top, and Tawer—to weed control treatments and to detect the resistance patterns of weed herbicides. The experiment was carried out in Al-Khiraat subdistrict, Al-Hindiya district, in the province of Holy Karbala (longitude 44°13’15.3″E and latitude 32°28’26.6″N). A randomized complete block design (R.C.B.D) with a split-plot arrangement was used. The main plots, consisted of three maize hybrids (Torro, Top, and Tawer), while the sub-plots included the second factor representing weed control treatments (three chemical herbicides: Reef Sulfuran, Trinity, and Proponit, in addition to two other treatments: the weed-infested treatment—allowing weeds to compete with the crop throughout the growing season—and the weed-free treatment—manual hoeing).
The results showed that the resistant Jungle rice (Echinochloa colona) plant is characterized by clear genetic variations in the chloroplast genome and the ALS enzyme associated with resistance to Reef sulfuran herbicide. A total of 19 SNPs were recorded in the ALS enzyme and 80 SNPs in the psbA gene, with key mutations identified that were highly frequent and associated with the resistance trait. A phylogenetic tree was constructed, confirming the close relationship between the Iraqi isolate and its global counterparts, providing the first accurate molecular documentation of this local isolate. This study confirms that weed resistance to herbicides in Echinochloa colona is due to dual mechanisms involving target-site resistance (TSR) through mutations in target genome regions, and non-target-site resistance (NTSR) through changes in gene expression related to photosynthesis and defense mechanisms.
The results showed that the hybrids were similar in their competitive ability against the accompanying weeds, except for the Torro hybrid, which achieved the highest average weed control percentage 30 days after application, and the Tawer hybrid, which excelled in reducing weed density 60 days after application. The Torro hybrid outperformed others in most growth and yield traits such as plant height, leaf area and index, chlorophyll index, ear length, number of kernels per row and per ear, 500-kernel weight, grain yield, biological yield, and their respective indices. Weed control treatments showed clear and significant differences in their effects on the studied traits. The Trinity treatment excelled in plant height, leaf area, number of kernels per row, 500-kernel weight, and biological yield. The Proponit herbicide outperformed in chlorophyll and leaf area indices and the number of kernels per ear. The weed-free treatment (manual hoeing) showed superiority in all remaining traits.
The interaction between hybrids and weed control treatments was significant. The interaction between the Torro hybrid and Reef sulfuran herbicide was superior in ear length, number of rows per ear, number of kernels per ear, and 500-kernel weight. The same hybrid with Proponit herbicide excelled in leaf area, harvest index, and chlorophyll index.
We conclude from this study that the hybrids behaved similarly in their competitive ability with the associated weeds, while they varied in their response to growth and yield traits, with the Torro hybrid being superior in most growth and yield characteristics.