A reference genome for pea provides insight into legume genome evolution

Abstract

ea (Pisum sativum L., 2n = 14) is the second most important grain legume in the world after common bean and is an important green vegetable with 14.3 t of dry pea and 19.9 t of green pea produced in 2016 (http://www.fao.org/faostat/). Pea belongs to the Leguminosae (or Fabaceae), which includes cool season grain legumes from the Galegoid clade, such as pea, lentil (Lens culinaris Medik.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.) and tropical grain legumes from the Milletoid clade, such as common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.) and mungbean (Vigna radiata (L.) R. Wilczek). It provides significant ecosystem services: it is a valuable source of dietary proteins, mineral nutrients, complex starch and fibers with demonstrated health benefits 1-4 and its symbiosis with N-fixing soil bacteria reduces the need for applied N fertilizers so mitigating greenhouse gas emissions Pea was domesticated ~10,000 years ago by Neolithic farmers of the Fertile Crescent, along with cereals and other grain legumes 8 . The large reservoir of genetic diversity in Pisum has facilitated its spread throughout Asia, Europe, Africa, the Americas and Oceania where it has adapted to diverse environments and culinary practices (https://iyp2016.org/). Due to its large genome size (1 C ~ 4.45 gigabases, Gb 9 ), pea genomics has lagged behind that of legumes with smaller genomes, such as Medicago truncatula Gaertn. 10 , Lotus japonicus L. 11 or soybean (Glycine max (L.) Merr) 12 . Yet, pea has been studied as a genetic model since the eighteenth century; the analysis of the inheritance of different pea morphotypes led Gregor Mendel to uncover the laws of genetics 13 . Several pea developmental mutations have since been characterized 14 and chromosomal regions controlling agronomic traits identified 15 , but tools exploiting pea diversity for plant breeding, identifying favorable alleles underlying phenotypic variations and accelerating