Molecular Plant Breeding 2024, Vol.15, No.5, 269-281 http://genbreedpublisher.com/index.php/mpb 270 examine their impact on sugarcane improvement within the context of global agricultural and industrial needs, assess the challenges and future prospects of sugarcane farming. 2 Sugarcane Diversity: Origins and Global Distribution 2.1 Historical origins and domestication of sugarcane Sugarcane (Saccharumspp.) has a rich history of domestication that dates back to prehistoric times. The initial domestication involved the selection of desirable clones and interspecific hybrids, which brought many agronomically useful traits into the cultivated species. The primary species involved in the domestication process were Saccharum officinarum and S. spontaneum, with S. officinarum being the main contributor to the high sucrose content in modern cultivars (Budeguer et al., 2021). The domestication process was complex and involved multiple stages of selection and hybridization, leading to the development of the noble cane varieties that are widely cultivated today (Mirajkar et al., 2019). 2.2 Genetic diversity in sugarcane species The genetic diversity within sugarcane species is crucial for the crop’s adaptability and yield improvements. Modern sugarcane cultivars are highly polyploid and aneuploid hybrids with extremely large genomes, originating from artificial crosses between S. officinarum and S. spontaneum (Budeguer et al., 2021). Despite the genetic complexity, the genetic diversity in modern cultivars is relatively narrow due to intensive breeding practices (Aitken et al., 2018; Liu et al., 2018). Studies have shown that the genetic diversity in sugarcane cultivars from the USA and China is low, with Chinese cultivars exhibiting particularly low diversity (Liu et al., 2018). However, wild species like S. spontaneumstill harbor a significant amount of genetic diversity, which can be utilized for breeding programs to introduce traits such as stress tolerance and disease resistance (Lu et al., 2004; Aitken et al., 2018). 2.3 Global distribution and cultivation regions Sugarcane is cultivated in tropical and subtropical regions around the world, with major production areas in Brazil, India, China, and the USA (Yang et al., 2018). The crop is a major source of sugar and biofuel, contributing to approximately 80% of the world’s sugar and 40% of biofuel production (Budeguer et al., 2021). The global distribution of sugarcane is influenced by climatic conditions, with the majority of cultivation occurring in regions with warm temperatures and adequate rainfall (Yang et al., 2018). The genetic diversity of sugarcane cultivars varies by region, with some areas like Indonesia and China showing higher diversity in wild species compared to cultivated varieties (Aitken et al., 2018). 2.4 Importance of genetic diversity for adaptation and yield improvements Genetic diversity is essential for the adaptation of sugarcane to various environmental conditions and for improving yield. The narrow genetic base of modern cultivars poses a risk to the crop’s resilience against pests, diseases, and changing climatic conditions (Liu et al., 2018). Utilizing the genetic diversity present in wild species like S. spontaneumcan help introduce beneficial traits into modern cultivars, enhancing their stress tolerance and overall performance (Lu et al., 2004; Aitken et al., 2018). Molecular markers and genomic selection techniques are being employed to identify and incorporate these valuable traits into breeding programs, aiming to broaden the genetic base and improve the adaptability and yield of sugarcane (Singh et al., 2020; Yadav et al., 2020; Mahadevaiah et al., 2021). 3 Traditional Cultivation Practices 3.1 Overview of early sugarcane cultivation methods Early sugarcane cultivation methods were primarily based on natural selection and conventional breeding techniques. These methods were labor-intensive and relied heavily on the manual selection of superior plants for propagation. The process was slow and required extensive field trials to identify desirable traits such as high sugar content and disease resistance. Traditional breeding programs often took over a decade to develop new varieties due to the complex polyploid nature of sugarcane and its low fertility under natural conditions (Budeguer et al., 2021; Ram et al., 2021).
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