Legume Genomics and Genetics 2024, Vol.15, No.5, 232-243 http://cropscipublisher.com/index.php/lgg 234 2.3 Importance of genetic diversity for crop improvement Genetic diversity is essential for the long-term improvement and sustainability of peanut crops. It allows breeders to develop cultivars with enhanced resistance to diseases, pests, and environmental stresses. The incorporation of diverse genetic material can lead to the development of superior genotypes with improved yield, quality, and adaptability. For instance, the use of wild species and advanced breeding techniques has led to the identification of introgression lines with high levels of resistance to late leaf spot and rust, as well as significant genetic variability for agronomic traits (Sharma et al., 2017). 2.4 Current status of genetic diversity in peanut breeding programs Despite the recognized importance of genetic diversity, peanut breeding programs have historically relied on a narrow genetic base, primarily using elite breeding lines and cultivars. This has resulted in limited genetic variation within cultivated peanuts. However, recent efforts have focused on broadening the genetic base by incorporating wild relatives and developing core and mini core collections to represent the genetic variability of entire germplasm collections (Upadhyaya et al., 2002). Advances in peanut genomics, such as the development of molecular markers and genetic maps, have also accelerated the identification and utilization of beneficial alleles for crop improvement (Pandey et al., 2012). In summary, harnessing genetic diversity from wild relatives, induced mutations, and advanced breeding lines is crucial for enhancing peanut crop performance. Continued efforts to broaden the genetic base and utilize modern genomic tools will be essential for the sustainable improvement of peanut cultivars. 3 Exploration and Utilization of Genetic Resources 3.1 Germplasm collection and conservation Germplasm collection and conservation are fundamental to preserving the genetic diversity necessary for crop improvement. Large germplasm collections, such as those held in genebanks, contain a wide array of genetic material that can be used to enhance the genetic base of breeding programs. For instance, the Chinese Academy of Agricultural Sciences has developed a core collection of 576 accessions and a primary mini core collection of 298 accessions from a larger collection of 6 839 cultivated peanut lines (Jiang et al., 2012). Similarly, the U.S. has established a core collection of 831 accessions to represent its Arachis hypogaea L. germplasm collection (Holbrook and Dong, 2005). 3.2 Characterization of peanut germplasm Phenotypic characterization involves evaluating germplasm for various morphological, agronomic, and quality traits. For example, the U.S. mini-core collection has been assessed for traits such as plant height, lateral branch growth, and pod yield using both traditional and high-throughput phenotyping methods (Sarkar et al., 2022). In China, a mini-mini core collection of 99 accessions was developed and evaluated for 21 morphological traits, capturing the range of traits displayed in the larger core collection (Jiang et al., 2012). Molecular characterization uses genetic markers to assess the genetic diversity and relationships within germplasm collections. The U.S. peanut mini core collection was characterized using 73 SSR markers, revealing moderate levels of genetic variation and distinct groupings based on subspecies and botanical types (Kottapalli et al., 2007). In China, a mini-core collection was genotyped using 109 SSR markers, identifying 554 SSR alleles and demonstrating abundant genetic diversity (Jiang et al., 2014). 3.3 Core and mini-core collections Core and mini-core collections are subsets of larger germplasm collections that represent the genetic diversity of the entire collection. These collections are designed to improve the efficiency of germplasm utilization in breeding programs. For instance, a mini core subset of 184 accessions was developed from a larger peanut core collection, preserving the genetic variation available in the core collection (Upadhyaya et al., 2002). Similarly, a mini core collection of 112 accessions was established in the U.S., capturing the majority of genetic variation expressed in the core collection (Holbrook and Dong, 2005).
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