**3. Improvement of tropical plants using conventional approaches**

The Agricultural Revolution began when people started cultivating crops on a large scale to feed larger populations. This allowed them to grow more food per unit of land than hunting and gathering. Enhanced agricultural productivity led to population growth and an increase in urbanization. Traditional methods for the improvement of tropical plants have been developed over thousands of years. Plants were selected and bred by farmers and gardeners, who then shared their knowledge with other growers. Because of these changes, there are now many beautiful plants that can be used as decorations or as food.

#### **3.1 Domestication**

Crop domestication is the process of selecting and breeding plants or animals to produce food and other desired products. It is a human-mediated artificial selection process that gives rise to domesticated organisms with certain desirable characteristics. Plants were first domesticated around 10,000 BC when early farmers selected and bred the best edible plants they found in their fields. They later moved on to domesticating animals, cultivating grain, and storing food [17].

#### **3.2 Selective breeding**

One of the most common ways to improve plants is through selective breeding. This is a process where desirable traits are selected and passed on to offspring generation after generation. The selection of naturally occurring varieties in the wild and, subsequently, in cultivated areas was the first type of plant breeding. Plantingharvesting cycles exert selection pressure on genetic diversity. Some plant phenotypes were profoundly altered as a consequence of this process, as shown by the derivation of maize from teosinte. The result is a plant that has better survival characteristics or greater productivity than its ancestors [18]. The earliest evidence for selective breeding dates back to 7000–7500 BC in Jiahu, China; here, rice was bred from wild rice, *Oryza rufipogon,* and domesticated through artificial selection with a combination of harvesting and replanting the plant's seeds. Other early examples of selective breeding are emmer wheat, barley, flax, and cotton [19].

Selective breeding requires careful selection of individuals with desirable traits, and they must be further propagated by vegetative means (such as cuttings) so that all their descendants have these same traits. It takes time and patience but can be very rewarding if done right! Another common method is simply growing out large numbers of seedlings until one appears that has the desired trait(s). This type of selection does not require vegetative propagation or any genetic engineering—just patience! [20].

#### **3.3 Intuitive farmer selection**

One way that farmers have traditionally developed new varieties is through intuitive farmer selection (IFS). This is a form of plant breeding where farmers select plants that exhibit desirable traits and save seeds from those plants to plant the following year. This process can be repeated for several generations until the desired characteristics are fixed in the population. The first step of IFS is to observe what happens to plants over time, including which ones express certain traits and which ones do not. Farmers then select the best examples of these traits and save their seeds for planting the next season. This process can be repeated for many years before any new varieties are created [21].

#### **3.4 Pure line breeding**

Pure line selection (PLS) is a method in which a new variety is created by selecting an individual with desirable characteristics from an existing population (often consisting of many different varieties). It involves repeated cycles of crossing or self-pollination between related plants or clones that are genetically identical to each other and then selecting for one or more traits. This process can be used to produce a wide range of new varieties, including dwarfing rootstocks, disease-resistant plants, fruits with improved flavor and color, etc. PLS has been used in agriculture since ancient times, but it became more important after the nineteenth century when it helped breeders create new varieties with desirable traits such as yield, drought tolerance, frost resistance, disease resistance, and so on. PLS is also known as single gene selection or monogenic selection. It involves selecting a plant that has one desired characteristic and eliminating all other plants that do not possess that trait. So, it is possible to make a variety with only one type of flower or fruit. This makes it easier for farmers to buy seed stock of the right variety [22].

#### **3.5 Mass selection breeding**

Mass selection is the process by which farmers select the best seeds from their crops and save them for the next year. This was the main way that new varieties were developed before modern times. To select seeds, farmers would have to grow them out in their fields and observe which ones were the most productive and hardy and had good taste. Once they had chosen a few plants to grow again, they would save their seeds for the following season's crops. Over many generations, this process gradually produced new varieties of plants that were well suited to local conditions and tastes. Mass selection is a form of artificial selection that allows only those plants that exhibit the desired trait to reproduce. This method does not require any knowledge about genetics or the mechanism by which genes are inherited. The breeder just picks a desirable trait and grows out plants with that trait over and over again to choose the best ones for breeding [23].
