**12. Rice**

monocropping with genetically uniform hybrids and improved cultivars. Modern agriculture has contributed to decreasing agricultural biodiversity as most of humankind lives now on only crops, with wheat (*Triticum aestivum*) L.), rice (*Oryza sativa* L.), maize (*Zea mays* L.) and potato (*Solanum tuberosum* L.) accounting for 60% of diets [2]. For example, 74% of rice cultivars in Indonesia are derived from the same stock, while 50% of wheat, 75% of potato and 50% of soybeans in the USA. The genetic erosion was estimated at 72.4 and 72.8%, respectively [53]. Furthermore, the number of rice cultivars declined in India farms from about 400,000 before colonialism to 30,000 in the mid-nineteenth century with unknown thousands more being lost after the Green Revolution. Greece also lost 95% of its wheat landraces after being

The concepts of the local variety have already existed in the guidelines for the proper in situ, on-farm and ex situ conservation of plant varieties. A local variety is a variety or local crop that reproduces by seed or by vegetative process. It is a variable population, which is identifiable and usually has a local name. It lacks 'formal' genetic improvement and is characterized by specific adaptation to the environmental conditions of the area of cultivation (tolerant to the biotic and the abiotic stresses of that area) and is closely associated with the traditional use, knowledge, habits, dialects and celebrations of the people who developed and continue to grow it [54].

In Nigeria, in spite of the event of the formal certified seed sector, many rural farmers continue to use traditional seeds or other planting materials to meet their seed need [55]. They have their own method of selection and conservation of seeds. This method varies slightly from one crop to another. Indeed, seeds are collected at maturity on apparent healthy plants and saved from season to season by individual farmers. As with selection, storage and conservation methods varied with crops. As such, seeds were stored either in packages and suspended at kitchen roofs (in the case of maize and cowpea, for example, in Yorubaland in Nigeria) or in grain and bottled (case of peppers, tomatoes, etc.). Yet, there can also be significant amounts of exchange between neighbors and relatives. They are also purchased when necessary. On-farm management of local seed diversity is predominant in the Nigeria seed sector since conversely to the cotton culture; no organized provision system exists for food crops.

Durum wheat (*Triticum turgidum* var. L. *durum*) is grown on over 1 million ha. Forty-five percentage of which are sown in the arid and semiarid regions, 11% in high altitudes and 44% in more favorable areas [56]. The complexity of the population structure of wheat landraces

encouraged to replace them with modern cultivars.

**10. On-farm management of local seed diversity**

**9. The concept of local variety**

12 Rediscovery of Landraces as a Resource for the Future

**11. Durum wheat**

Rice is among the most important crops worldwide. While much of the world's rice harvest is based on modern high-yield varieties, traditional varieties of rice grown by indigenous groups have a great importance as a resource for future crop improvement. These local landraces represent an intermediate stage of domestication between a wild ancestor and modern varieties, and they serve as reservoirs of genetic variation. Such genetic variation is influenced both by natural processes such as selection and drift and by the agricultural practices of local farmers. How these processes interact to shape and change the population genetics of landrace rice is unknown [58]. Compared to new rice cultivars, rice landraces have more complex genetic backgrounds and more abundant genetic diversity and heterogeneity, as well as strong adaptability to the environment, excellent resistance to diseases and pests, high yields and good quality [59]. The Southwest China, Guizhou, Yunnan and Guangxi provinces, is one of the largest centers of rice genetic diversity and high-quality germplasm in the world [21, 60].

**9.** There is an increasing consumer concern worldwide about food safety and nutrition. Landraces or old crop cultivars may prove solutions as sources of healthy and nutritious food.

Landraces and Crop Genetic Improvement http://dx.doi.org/10.5772/intechopen.75944 15

**1.** 1. Landraces are generally less productive than commercial cultivars.

**15. Implication of replacement of landraces by commercial cultivars**

**1.** It increases and causes genetic erosion by the replacement of diverse landraces with comparatively few, homozygous modern cultivars, which caused considerable concern among

**2.** Landrace replacement by modern cultivars demonstrated a marked reduction in overall

**3.** People's concerns over this rapid extinction or erosion of landrace diversity resulted in

Conservation of all gene pools is a high priority for sustaining food security and coping with current and future climate change effects. Not only must landraces be conserved, but so should local varieties that have been replaced by new and more productive ones. Older varieties, due to the emphasis on landraces and more exotic materials, must not be forgotten, and older varieties, as well as other breeding materials, need to be conserved as a source of genetic diversity. Despite the enormous efforts made by national and international programs to conserve landrace diversities, eventually the conservation of germplasm and characterization of key traits will provide specific information to breeders that will promote the use of

The discovery of abiotic stress at tolerant alleles in landraces of maize, rice and wheat clearly shows the importance of conserving and exploring landrace germplasm as a means to identify gnomonically beneficial alleles for enhancing adaptation and productivity in stress-prone

**i.** Dealing with duplication where tracking is lost when moving germplasm from one place

**ii.** Genetic diversity of collections widely determined by DNA markers available in gene

**14. Disadvantages**

genetic diversity.

environments [2].

bank facilities

**16. Landrace conservation**

conservationists and breeders alike.

widespread action to promote their conservation.

genetic resources by the scientific community.

**16.1. Specifically, several challenges need attention:**

to other, particularly if a unique notation is not used

The genetic variability found within landraces affords the possibility of genetic flexibility; landraces have the potential to adapt to local field conditions, and they can adapt to changing environments, farming practices and specific uses such as animal vs. human consumption [61]. Moreover, the genetic diversity of traditional landrace varieties is the most immediately useful and economically valuable component of rice biodiversity [19]. To efficiently conserve, manage and use such germplasm resources, an understanding of structure, apportionment and dynamics of local landrace variation is required. Several studies have examined genetic variation and differentiation among rice landrace varieties [62, 63]. However, little to no information is available on how genetic diversity is structured within a given landrace.

Local adaptation plays an important role in maintaining yields in traditional agricultural systems. Selection for adaptation to each village environment by the farmer's seed selection enhances overall crop diversity and maintains evolutionary flexibility [64]. Almekinders [21] explained that farmers' selection in combination with natural selection results in landraces with high levels of adaptation to biotic and abiotic stresses and for agricultural traits. For example, the genetic diversity of *Phaseolus vulgaris* landraces in Italy has been shaped by local adaptation to microenvironments [65], and in wheat, selection by farmers has strongly influenced the evolution of neutral loci [66].
