**1. Introduction**

Maize (*Zea mays* L.) is a significant cereal crop worldwide, widely cultivated and highly valued for its diverse uses. In high-income countries, it serves as a primary source of feed and industrial products, while in sub-Saharan Africa (SSA), Asia, and Latin America, it plays a crucial role in providing food, feed, and nutritional security for some of the

world's poorest regions [1]. Originating from Mexico, maize has extended its presence to critical agroecologies in tropical, subtropical, and temperate regions across the globe.

The center of origin for maize has been established as the Mesoamerican region, encompassing present-day Mexico and Central America [2]. Maize cultivation was introduced to the rest of the world during the sixteenth century [3, 4], and in India, it was brought by the Portuguese in the seventeenth century [5–7]. In India, there is speculation that maize was initially introduced in the North-West Himalayas by traders, from where it subsequently spread to the Himalayan region [8]. This includes the introduction of primitive forms of maize in the old world, including the Himalayas during the pre-Columbian period [9].

The exceptional genetic diversity of maize is evident from well-defined landraces found in various countries. Landraces, which serve as a valuable reservoir of useful genes and alleles, are the germplasm preserved by farmers over extended periods. These landraces were developed and selected to thrive under specific environmental conditions and fulfill local food preferences.

India is a significant centre of diversity for maize landraces, with extensive variations observed in plant, ear, and tassel characteristics in the northeastern and northwestern highlands. However, relatively less varietal diversity is found in the plains of India [10]. Anderson [11] was particularly impressed with the diversity of maize in the north-eastern Himalayan region and believed that maize had an ancient Asiatic origin. Dhawan [12] renamed a productive popcorn variety from Sikkim as 'Sikkim Primitive' due to its distinctive characteristics. This landrace exhibits unique physiological features, such as the absence of apical dominance, prolificacy (5–9 ears), uniformity in ear size, erect leaves, a top-bearing habit, and drooping tassels for efficient fertilization [13]. The Sikkim Primitive maize is commonly used as fodder for livestock by local farmers. The primitive maize strain, also known as the SP strain, comprises 13 different strains distributed throughout the NEH region, excluding Sikkim [14].

A significant portion of the genetic diversity in maize remains unexplored, partly due to the challenge of identifying valuable genetic variations within local varieties [15]. This limited utilization of diverse genetic resources can be attributed to the lack of understanding of the agronomic performance and genetic makeup of these landraces. Prasanna and Sharma [10] addressed this bottleneck by conducting the first comprehensive molecular characterization and population genetic analysis of 17 Indian maize landraces sourced from diverse agroecologies. The study utilized 27 microsatellite or simple sequence repeat (SSR) markers to reveal a higher level of genetic divergence among the Northeastern Hill (NEH) landraces when compared to those from other regions.

Maize is a crucial crop in Sikkim, although its current productivity is quite low, with an average of 1750 kg/ha [16]. Given this, it is important to develop varieties that are well-suited to the region's unique conditions. To accomplish this, breeders require an understanding of character associations and path analysis.

Landraces are a type of germplasm that has been preserved by farmers over the course of decades or even centuries. They have been carefully selected to adapt to specific environmental conditions and meet local food preferences. While maize originally came from Mexico, it is now widely grown across the world, and India has a particularly rich array of maize landraces, particularly in the North-Eastern Himalayan region [10]. These landraces contain many valuable genes that could be used for allele mining and population improvement. In recent years, molecular analysis of maize landraces from the Americas and Europe has led to significant insights into their diversity, genetic structure, and global migration routes. It is essential to have a comprehensive understanding of the genetic and agronomic characteristics of

landraces for effective management and use in breeding programs. In this review, we discuss the extensive diversity of maize landraces globally and in India in Sikkim and NEH, and explore the potential for harnessing this vast genetic resource.
