Document Type : Research Paper
Authors
1 Department of Agronomy and Plant Breeding Sciences, Faculty of Agricultural Technology (College of Aburaihan), University of Tehran, Tehran, Iran
2 College of Aburaihan, UT
3 Department of Agronomy and Plant Breeding, Islamic Azad University, Isfahan (Khorasgan) Branch, Isfahan, Iran,
4 university of tehran
Abstract
Abstract
Objective: Commercial maize hybrids represent not only elite cultivars for production but also valuable genetic resources for the development of new inbred lines and advanced hybrid breeding programs. This study aimed to comprehensively evaluate the phenotypic and biometric diversity present within seven commercially available maize hybrids, and to definitively determine their cytoplasmic male sterility (CMS) type utilizing CMS-specific Polymerase Chain Reaction (PCR) markers. Understanding this diversity and CMS type is critical for optimizing breeding strategies and seed production systems, particularly within specific agro-climatic regions.
Methods: The field experiment was conducted using a randomized complete block design with three replications. A widw range of traits were recorded, encompasing yied and yield-related traits, morphophysiological characteristics, agronomic attributes, and phenological observations. Different univariate and multivariate analysis were used, allowed for a thorough assessment of the genetic variation among the hybrids.
Results: Analysis of variance (ANOVA) revealed significant differences (P ≤ 0.01) among the hybrids for nearly all measured traits, providing strong evidence of substantial genetic variability within the tested population. Further analyses, including correlation and path coefficient analyses, elucidated the complex relationships between different traits. Results indicated that dry matter yield exhibited the largest positive direct effect on fresh forage (biological) yield, highlighting its importance in overall productivity. Conversely, plant height and various leaf-related traits primarily contributed to yield indirectly, suggesting their influence through complex physiological pathways. Multivariate analyses, specifically factor and cluster analyses, were employed to further dissect the genetic structure of the hybrids. These analyses successfully explained over 85% of the total phenotypic variation, effectively classifying the hybrids into three distinct genetic groups. Notably, hybrid P7 formed an independent cluster, demonstrating its unique phenological and genetic distinctiveness from the other hybrids. This isolation suggests a potentially valuable genetic background for specific breeding objectives. PCR assays were then utilized to identify the CMS cytoplasm type in each hybrid. The results revealed that five hybrids (P2, P4, P5, P6, and P7) carried CMS-C cytoplasm, a well-characterized and widely utilized CMS system. In contrast, hybrids P1 and P3 were identified as possessing normal (N) cytoplasm. Importantly, these PCR-based findings were consistently corroborated by tassel phenotyping, pollen assessment, and self-pollination tests conducted in both F₁ and F₂ generations, confirming the accuracy of the molecular marker analysis.
Conclusion: The high frequency of stable CMS-C and the observed diversity within the commercial hybrids collectively underscore their significant potential as parental materials for developing efficient CMS-based hybrid seed production and breeding programs tailored to Iranian agro-climatic conditions. This research provides valuable insights for breeders seeking to improve maize productivity and adapt to regional environmental challenges.
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