Genetic Erosion and In Situ Conservation of Lima Bean (Phaseolus Lunatus L.) Landraces in Mesoamerican Diversity Center

Abstract

To understand the role of a geographical region in the in situconservation of the genetic diversity of any crop, it is necessary toanalyze the current conservation status of the crop and any geneticchanges that have occurred within the last few decades in the region.Lima bean (Phaseolus lunatus L.) is an important crop in the Mayanagriculture of the Yucatan Peninsula, Mexico, its Mesoamerican center ofdiversity. In this region, 3 of the 21 landraces dominate 71.24 % ofthe cultivated area, and 12 are rare landraces grown in only 6.29 % ofthe area. This chapter analyzes the risk of the genetic erosion in Limabean landraces from the Yucatan Peninsula using molecular markers, withthe objective of generating data to develop comprehensive in situconservation programs for the crop. Molecular analyses showed that themany landraces that are planted by only a few peasants contained higherlevels of genetic diversity compared with the three most abundantlandraces. Also, they showed that the landraces planted in 1979 havehigher levels of genetic diversity than those planted in 2007 and that,over the last 30 years, the genetic make-up of this crop has shifted. Ifcurrent trends in the cultivation of the Lima bean landraces continue,many will no longer be planted within two to three generations,contributing to further genetic erosion. The establishment ofevidence-based programs for the in situ conservation of Lima beanlandraces is urgently needed in this center of genetic diversity.