**3. Genetic diversity of maize in NEH**

Singh [17] reported 10 indigenous maize varieties from the northeastern Himalayan region, namely *Nilip Mekop*, *Mikir Merakku*, *Khasi Riewhadem*, *Silken Tipang*, *Tista Mendi*, *Maidani Makka* (sub-race *Ganga*), *Cachar Gomdhan*, *Shyam Nahom*, *Asht Samsung* (sub-race *Tsungrhu*), *Mayong Sa-ah*, *Manipuri Chujak*, *Alok Sapa*, *Arun Tepi*, *Tirap NagSahypung*, and *Poorvi Botapa* (sub-race *Murli*).

As per Singh [17], *Astha Samsung*, a maize variety well adapted to high elevations above 1500 m, was commonly found in Sikkim and Nagaland. The name "Asht" refers to the presence of eight rows of kernels, a distinctive trait of this particular maize race. Samsung, on the other hand, refers to the specific location in Sikkim where this maize race was commonly cultivated. Another subrace of maize variety reported from Sikkim was *Tsungrhu*, which was also cultivated above 1500 m. The term "*Tsungrhu*" derives from the regional language of the Lotha Tribe in Nagaland, where it was extensively grown and its name signifies "maize" in their language. Similarly, *Tista Mendi* was another indigenous maize variety cultivated in the elevated regions above 1500 m along the famous River Teesta.

The races mentioned in the preceding paragraphs can be categorized into four groups for convenience: Primitive, Advanced or Derived, Recent Introductions, and Hybrid varieties. The Primitive group encompasses several races of popcorn that have differentiated at various altitudes and under diverse conditions. These races include *Poorvi Botapa*, *Murli subrace* of *Poorvi Botapa*, *Tirap NagSahypung*, *Arun Tepi*, and *Alok Sapa* [17]. The races belonging to the Primitive group display distinct traits such as popping grain morphology, prominent kernel striations, reduced kernel rows, smaller ears with higher ear numbers, tassels with fewer branches, shorter internodes, narrower leaves, and relatively higher ear placement. These races are widely distributed across the eastern Himalayan region, specifically in Assam, Nagaland, Manipur, Arunachal Pradesh, Sikkim, and Bhutan. They thrive at elevations ranging from 60 to above 2000 m, under the conditions of traditional cultivation. One fascinating aspect of the *Murli* subrace of *Poorvi Botapa* is its remarkable similarity to the reconstructed ancestral form of maize, as documented by Mangelsdorf and his collaborators [18, 19]. Notably, evidence suggests a significant differentiation in the cytoplasm between the primitive subrace of Murli and the evolved types, as evidenced by reciprocal variations in various traits observed in Sikkim and Assam [20]. The *Tirap Nagsahypung* race possesses distinctive characteristics concerning leaf size, shape, arrangement, and number. Its leaves are erect, small, numerous, and tend to cluster toward the tassel.

Singh [17] examined the second group, which included *Manipuri Chujak*, *Mayong Sa-ah*, *Asht Samsung*, *Tsungrhu* subrace of *Asht Samsung*, *Shyam Nahom*, *Cachar Gomdham*, *Mainani Makka*, and its subrace *Ganga*. These cultivars displayed distinct characteristics, such as large flinty grains exhibiting a wide array of endosperm colors, including white, cherry, red, purple, and various shades in between. They featured a smaller number of but larger ears and exhibited an earlier maturation compared to the races found in the primitive group. The leaf structure of these cultivars varied, ranging from semi-erect to flat. The collected varieties from the region exhibited limited diversity, predominantly consisting of early-flint types that closely resembled Cuban flints and northern flints. Consequently, they were classified within the *Maidani Makka* race and its subrace *Ganga*.

Singh [17] classified the third group, which includes races such as *Tista Mendi* and *Silken Tipang*. *Tista Mendi*, primarily found at higher elevations, demonstrated

#### *Exploring the Diversity of Maize (*Zea mays *L.) in the Khangchendzonga Landscapes… DOI: http://dx.doi.org/10.5772/intechopen.112566*

semi-dent grains in shades of yellow and red, accompanied by fewer but larger ears. Singh noted that *Tista Mendi* was a recent introduction that not only established itself as a distinct race but also underwent hybridization with older races, leading to the emergence of new hybrid varieties. On the other hand, *Silken Tipang* exhibited grains that exhibited popping characteristics when subjected to heat, along with a reduced number of ears. It stood out with its larger ear surfaces and more distinct grain characteristics compared to the primitive group. Singh believed that *Silken Tipang* was introduced during the early 1960s from neighboring countries like Burma and is currently confined to specific regions in Arunachal Pradesh, bordering Burma.

Singh [17] discussed the fourth group, comprising *Khasi Riewhadem*, *Mikir Merakku*, and *Nilip Mekop*. According to Singh's classification, these races were the outcome of hybridization between primitive types and advanced races. Notably, certain collections belonging to the *Tista Mendi* and *Tirap Nag-Sahypung* races exhibited remarkable resistance to the corn borer, *Chilo Zonellus*, even under natural infestation. Furthermore, varieties such as *Arun Tepi*, *Alok Sapa*, and all collections belonging to the *Tirap Nag-Sahypung* race displayed notable resistance to leaf blight caused by *Helminthosporium maydis*. Furthermore, it is worth noting that all entries from the *Manipuri Chujak* and *Mayong Sa-ah* races, along with the collections forming the *Tirap Nag-Sahypung* race, exhibited notable resistance to downy mildew, which is caused by the pathogen *Sclerospora philippinensis*. These varieties show great potential for cultivation under organic conditions, given their inherent resistance to this devastating disease.

The aforementioned discussion highlights the need for in-depth research on the genetic characterization of each variety, which remains unexplored in the region. Further investigation into the genetic traits, molecular markers, and population structure of these maize races is crucial for a comprehensive understanding of their genetic composition and diversity. Such research endeavors would contribute significantly to the conservation, utilization, and improvement of these indigenous maize varieties in the region.

### **4. Some basic characteristics of maize varieties**

In the last 30 years, Sikkim and other Northeastern region have documented several fascinating local variations of maize that possess unique traits specific to each type of landrace. Some notable examples include *Bancharey-makai*, which is a highaltitude maize variety with yellow, flint kernels. *Badam-topo* stands out as a popcorn variety, while *Chakhou chujak* is known for its aromatic, soft, and sticky properties. *Chepti-makai* is a white, dent-type maize with distinct kernels. *Chujak* is an aromatic popcorn variant, whereas *Darikincho* is characterized by its small, yellow, hard kernels. *Fingdong* is an aromatic popcorn with a distinctive *flavor*. *Gadbade-makai* displays white kernels with occasional purple flint kernels, while *Kaali-makai* is recognized for its dark purplish-black color. *Kholakitti* is a sticky variety, while *Kuchung dari* is an orange-colored popcorn with flint kernels. *Kuchung takmar* exhibits a mix of yellow, white, purple, and red kernels with a flint texture. *Kukharey-makai* is dwarf, high-altitude maize, and *Kukidolong-makai* is a flint variety. *Lachung-makai* variety displays multiple colors and possesses tolerance to cold conditions. *Nepali Sappa* is unique with three cobs per plant, *Pahenli-makai* features yellow/orange flint kernels, and *Pahenli-makai* is a light dent type. *Phensong-makai* stands out with its cob length of up to 30 cm, while *Putali-makai* is characterized by its multi-colored appearance.

*Rato-makai* is a dark red maize variant, *Sathiya-makai* is an early-maturing type, and *Seti-makai* is a white, soft variety. *Tanee-makai* is a popcorn type, and *Tista Mehdimakai* is a flint variety.

The existence of primitive maize landraces in Sikkim and other Northeastern states of India, situated in the Himalayan region, implies a possible alternative origin for this crop. The presence of a diverse collection of maize landraces in Sikkim further strengthens the notion that the Northeastern states may serve as secondary centres of origin for maize. These landraces exhibit significant morphological diversity, as documented by Sharma et al. [21]. This observation highlights the importance of studying the genetic and morphological characteristics of these landraces to unravel their evolutionary history and conservation significance.

In this region, a variety of intriguing local types and landraces with distinct traits have been documented. They include:


Apart from these, sporadic collections of early local types have also been made, such as *Ambo*, *Riewhadem* (early maturing), *Vaimin* (3 months), *Pahari makai* (adapted to mid-to-high altitudes and cold-hardy), *Nepali Sappa* (3 cobs/plant). Furthermore, modern cultivars and newly introduced landraces like *Mampokmendi, Taminlamendi, Maromendi* have been documented (**Figures 2**–**5**).

A germplasm exploration and collection program conducted in Sikkim has revealed the existence of a large number of indigenous maize cultivars suitable for different altitudes and purposes. During 2003–2004, approximately 58 local

**Figure 2.** *(a) Paheli makai and (b) Seti makai.*

*Exploring the Diversity of Maize (*Zea mays *L.) in the Khangchendzonga Landscapes… DOI: http://dx.doi.org/10.5772/intechopen.112566*

**Figure 3.** *Maize diversity grown in the Sikkim Himalaya.*

**Figure 4.** *Kali makai, Ribdi, West Sikkim.*

germplasms were collected by Indian Agricultural Research Institute at Tadong Gangtok Sikkim from four districts (now six districts) in Sikkim at different altitudes (**Figure 6**) [22].

The local germplasm collection program in Sikkim has identified a variety of indigenous maize cultivars, including white kernel maize known as *seti makai*, yellow kernel maize referred to as *pahenli makai*, orange to red kernel maize known as *rato makai*, and purple kernel maize named *baiguney makai*. There are also highaltitude maize types such as *Lachung makai*, *sehrung*, and *tempo ringing*, as well as *sano makai* which is a type of popcorn. The *seti makai* has variations and is grouped as

**Figure 5.** *Tsungrhu a sub-race of Asth Samsung (picture scanned from Singh, [17]).*

**Figure 6.** *Diversity of different traditional varieties of maize.*

*Seti Makai*-1 to 4, while *Pahenli makai* has six sub-types designated as *pahenli makai* 1–6. *Rato makai* has four sub-types named as *rato makkai* 1–4, and *sanu makai* has three sub-types referred to as Sikkim Popcorn 1–3. Finally, *baiguney makai* has two sub-types: *sano baiguney* and *thulo baiguney*. However, there are also many nondescript cultivars without specific names [22].

Over the past 30 years, the Sikkim Himalayan regions have documented a multitude of intriguing local variations of maize, each possessing distinct and specific traits, including *Badam-topo* (popcorn variety), *Baiguney Makai* (purple, soft variety), *Bancharey-makai* (high-altitude maize with yellow, flint kernels), *Chakhou*  *Exploring the Diversity of Maize (*Zea mays *L.) in the Khangchendzonga Landscapes… DOI: http://dx.doi.org/10.5772/intechopen.112566*

*chujak* (aromatic, soft, and sticky maize), *Chepti-makai* (white dent-type maize with distinct kernels), *Chujak* (aromatic popcorn variant), *Darikincho* (small, yellow, hard kernels), *Fingdong* (aromatic popcorn with a distinctive flavor), *Gadbade-makai* (white kernels with occasional purple flint kernels), *Kaali-makai* (dark purplishblack colored maize), *Kholakitti* (sticky variety), *Kuchung-dari* (orange-colored popcorn with flint kernels), *Kuchung takmar* (mix of yellow, white, purple, and red kernels with flint texture), *Kukhurey-makai* (dwarf, high-altitude maize), *Kukidolongmakai* (flint variety), *Lachung-makai* (variety with multiple colors and tolerance to cold conditions), *Nepali Sappa* (unique with three cobs per plant), *Pahenli-makai* (light dent type), *Pahenli-makai* (yellow/orange flint kernels), *Poorvi Botapa, Phensong-makai* (cob length of up to 30 cm), *Putali-makai* (multi-colored appearance), *Rato-makai* (dark red maize variant), *Sathiya-makai* (early-maturing type), *Seti-makai* (white, soft variety), *Tanee-makai* (popcorn type), *Tista Mehdi-makai* (flint variety), *Asthra Samsung*, *Tsungrhu*, *Sikkim Primitive I*, and *Sikkim Primitive II*. These maize variations exemplify the abundant diversity and unique characteristics found in the region.

The local germplasm displayed significant variation in cob orientation, cob size, kernel color, leaf orientation, silk color, height at which ear arises, cob length, number of kernels per row, and kernel yield per plant. *'Lachung makai*' exhibited para-mutation (multi-colored cob) and showed tolerance to cold weather. Some of the *seti makai* and *pahenli makai* had thick husk coverage and oblong cob orientation, which impart resistance against ear rot in the rainy season. The high-altitude maize *tempo ringing* matures in 85–90 days in mid-hills when other maize did not complete silking, indicating an extraordinary early maturity trait in mid and high-altitude maize. Local germplasm such as *murali makai*, *tempo ringing*, and *seti makai* are being utilized in the ongoing breeding programme at the Indian Council of Agriculture Research (ICAR) Sikkim Centre. In a nutshell, the maize genetic resources in Sikkim are rich, which is why the Sikkim Himalaya is considered a secondary centre of diversity for maize (**Figure 7**).

**Figure 7.** *(a) Gadbadey makai, (b) Rato makai, (c) Thulo-baiguney makai and (d) Raato makai.*

Lachung makai, characterized by its paramutation trait (multi-colored cob) and tolerance to cold weather, stands out among the local varieties. This maize variety is grown in a high temperate agroclimatic range between 2200 and 2600 m elevations. Additionally, other notable landraces such as Sikkim Primitive, *Tirap*, *Naga Sahyup* (Arunachal Pradesh), and *Tistamehdi* (Sikkim) have been previously collected and evaluated by other researchers, amounting to over 200 landraces studied (**Figure 8**) [10].

*Murali makai* is a crop that grows well in high altitudes (between 1000 and 1800 meters above sea level) and can withstand moisture-stress conditions, although it has slow vegetative growth. It has the potential to contribute adaptability and multiple cob-bearing traits to otherwise desirable varieties of maize grown in mid and high hills. Unfortunately, this rare genotype is gradually disappearing from cultivation and is considered an endangered cultivar (**Figure 9**).
