Short answers, pulled from the story.
Nikolai Vavilov first identified centers of origin in 1924. He proposed that the geographic area with the highest genetic diversity in a species is also the region where that species was first domesticated.
Vavilov himself revised the count repeatedly: three in 1924, five in 1926, six in 1929, seven in 1931, eight in 1935, and then back to seven in 1940. Later researchers such as Purugganan and Fuller (2009) identified more than a dozen distinct centers using archaeological and genetic dating.
The Chinese Center is the largest independent Vavilov center, with a total of 136 endemic plants. It is the origin of rice, soybean, peach, apricot, orange, and many other crops.
Vavilov centers identify where wild relatives and related species of crop plants can be found. These wild relatives carry new genes, including dominant genes that may provide disease resistance, making them essential resources for improving modern crops.
Genetic erosion is the loss of germplasm caused by the disappearance of ecotypes and landraces, habitat loss such as deforestation, and urbanization. Preserving natural habitats within Vavilov centers of origin, alongside gene banks and seed collections, is one of the main strategies used to prevent it.
The South Mexican and Central American Center is the origin of maize, common bean, lima bean, sweet potato, pepper, papaya, cacao, cashew, upland cotton, and bourbon cotton, among other crops. It covers southern Mexico, Guatemala, El Salvador, Honduras, and Costa Rica.