Legume Genomics and Genetics 2024, Vol.15, No.5, 232-243 http://cropscipublisher.com/index.php/lgg 235 3.4 Pre-breeding and introgression strategies Pre-breeding and introgression strategies involve the incorporation of desirable traits from wild or exotic germplasm into cultivated varieties. These strategies are essential for enhancing the genetic base and improving the performance of crop cultivars. For example, the U.S. mini-core collection has been used to identify sources of resistance to late leaf spot, improving the efficiency of identifying resistant accessions in the entire collection (Holbrook and Dong, 2005). Additionally, the Chinese mini-core collection has been evaluated for resistance to bacterial wilt, identifying accessions with high levels of resistance (Jiang et al., 2012). 3.5 Case study: utilization of wild arachis species for disease resistance Wild Arachis species are valuable sources of disease resistance genes that can be introgressed into cultivated peanut varieties. The development of core and mini-core collections facilitates the identification and utilization of these valuable genetic resources. For instance, the Chinese mini-core collection has been used to identify accessions with high oleic acid content, which is associated with improved disease resistance and agronomic traits (Yong et al., 2008). Similarly, the U.S. mini-core collection has been characterized for seed quality traits, providing information for further breeding and genetic research (Wang et al., 2011). 4 Breeding for Enhanced Crop Performance 4.1 Key traits for peanut improvement Yield potential is a critical trait for peanut improvement, as it directly impacts the economic viability of the crop. Studies have shown that plant height-related traits are closely associated with yield, and understanding the genetic basis of these traits can help in better controlling crop yield. For instance, a meta-analysis identified numerous genomic regions associated with plant height and first branch length, which are crucial for peanut development and growth (Wang et al., 2021). Additionally, introgression of wild alleles has been shown to improve photosynthetic traits and yield in peanut lines, demonstrating the potential of utilizing wild species for yield enhancement. Drought and heat tolerance are essential for peanut cultivation, especially in semi-arid regions. Research has highlighted the importance of developing peanut cultivars with enhanced drought tolerance through physiological and yield trait assessments. For example, certain peanut lines have shown improved drought tolerance and yield stability under water stress conditions, making them suitable for semi-arid environments (Pereira et al., 2016). Moreover, the introgression of wild alleles has been effective in improving water use efficiency and drought tolerance in peanut (Dutra et al., 2018). Disease and pest resistance are vital for maintaining peanut crop health and productivity. Genetic engineering techniques have been employed to introduce resistance to various fungal, viral, and insect pests in peanut. These techniques include the use of genes coding for pathogenesis-related proteins, RNA interference, and crystal proteins, among others (Krishna et al., 2015). Additionally, the development of introgression lines with high levels of resistance to late leaf spot and rust has been achieved through the use of wild species, providing valuable genetic resources for peanut improvement (Sharma et al., 2017). Improving the nutritional quality and oil content of peanut is another key breeding objective. Association mapping has been used to identify genetic markers linked to important traits such as protein and oil content, oleic acid, and linoleic acid. These markers facilitate marker-assisted selection for enhancing the nutritional quality of peanut (Zhang et al., 2018). Furthermore, genomic studies have identified significant marker-trait associations for oil and seed quality traits, which can be utilized in breeding programs to develop nutritionally superior peanut cultivars (Pandey et al., 2014). 4.2 Traditional breeding approaches Hybridization is a traditional breeding approach that involves crossing different peanut lines to combine desirable traits. This method has been used to develop peanut cultivars with improved agronomic and quality traits. For instance, the development of a mini core subset of peanut has facilitated the utilization of genetic resources in breeding programs, enhancing the diversity of cultivars (Upadhyaya et al., 2002). Backcrossing is another traditional breeding technique used to introduce specific traits from a donor parent into a recurrent parent. This approach has been employed to introgress wild alleles into cultivated peanut, resulting in improved traits such as
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