**3.3 Garlic**

Garlic research in Nigeria has been initiated with the breeding strategy focusing on collection, introduction, adaptation and selection of superior lines. However, there is a considerable morphological and physiological variation within and among cultivars [36]. Analysis of genetic diversity and relatedness between individuals is important for breeding purpose. Although garlic displays wide morphological differences [36], clonal propagation narrows garlic variation, given rise to a genetic bottleneck. This situation complicates garlic breeding programs geared towards improving preferred agronomic traits. In view of this, assessing the morphological and molecular polymorphisms in garlic genotypes originating from Nigeria is important for breeding programmes. Molecular characterization of 115 garlic accessions has been done in Ethiopia using 11 SSR markers [37]. There is paucity of information on genetic diversity studies of garlic germplasm in Nigeria using molecular markers.

*Nigeria Root Vegetables: Production, Utilization, Breeding, Biotechnology and Constraints DOI: http://dx.doi.org/10.5772/intechopen.106861*

Garlic is cultivated vegetatively due to its sexual sterility [38]. Vegetative propagation is achieved via division of the ground and aerial bulbs which results in lower multiplication rate. Many of the elite garlic cultivars succumb to diseases incited by viruses, nematodes and fungi, as well as insect pests [39]. Virus infection has been reported to reduce the bulb yield by 20–60%, and up to 80% with mixed infection, depending on cultivar and stage of infection [40]. The low propagation rate coupled with continuous accumulation of serious diseases such as viruses observed in the field warrants the development of in vitro propagation of garlic [41, 42]. There is a great influence of genotype on garlic in vitro cultures [43]. A combination of 1 mg/l 2,4-D + 5 mg/l BAP + 5 mg/l NAA resulted in 100% callus induction from root apices of garlic. The shoot has been reported to have higher callus induction frequency and higher callus fresh weight relative to root apices in some cultivars of garlic [44]. The use of root tips as explant greatly increases the regeneration potential than shoot tips as the number of regenerated shoots per explant was higher than that obtained from callus induced from shoot apices [42, 44].

#### **3.4 Turmeric**

Turmeric (*C. longa* L.), a cross-pollinated and triploid species (2*n* = 3*x* = 63), is propagated vegetatively through its yellow-fleshed rhizomes. Due to its numerous beneficial uses, the National Root Crops Research Institute (NRCRI) Umudike, Nigeria commenced research on turmeric in 1998 by pioneering collection of genetic resources and indigenous knowledge pertaining to its production and use. An active gene bank consisting of strong genetic base is a basic requirement for a sound crop improvement programme. Minor root and tuber crops nearly lacked a gene bank at the onset to enable take-off of meaningful crop breeding efforts. However, several germplasm exploration trips within the last decade resulted in the collection of a total of 76 accessions of Turmeric [45]. Ekiti State topped the list of collections (12) while Abia and Kwara were the least with one collection each. The passport data of the colections including the number collected and the local utilization at the source of collection are well documented to guide future breeding work. Following multi-locational evaluation at different locations in Nigeria—Jos, Otobi, Umudike and Igbariam, 10 genotypes were identified as promising and need to be further evaluated before their official registration and release to farmers.

Scarcity of planting materials resulting from low multiplication rate of turmeric (*C. longa*) limit their massive production. Micropropagation would help solve the challenge of limited planting materials. The phytohormone, 2,4-D, has been reported as the most effective auxin for callus induction in ginger and turmeric [46, 47]. MS media containing cytokinin (BAP or kinetin) either alone or in combination with auxin (NAA or IAA or IBA) are commonly utilized to induce multiple shoots and subsequent plantlet formation in turmeric (**Table 2**) [48, 49]. MS media containing 3.0 mg/l BAP yielded the best average vigor survival rating of [35]. This can be compared with results of other researchers as shown in **Table 2** [29, 50]. This finding is in conformity with [51] who reported that the higher BAP concentration decreased shoot multiplication rate in turmeric among the different BAP levels (1–6 mg/l) tested. In turmeric, maximum rooting to multiple shoots was notable on half strength MS medium supplemented with 0.5 mg/l NAA [52]. Rooting on MS + 0.5 mg/l IBA of microrhizomes produced multiple roots/explants [53].


#### **Table 2.**

*Studies on in vitro micropropagation of turmeric (Curcuma sp.) plants.*
