Kole - Wild crop relatives genomic and breeding resources <9> Industrial crops

J. Mitchell McGrath 1

Abstract

Sugarbeet is the primary crop in the genus Beta. Beta vulgaris spp. vulgaris also includes crop types used for root and leafy vegetables used since antiquity as well as for fodder. All are ultimately derived from the wild form B. vulgaris spp. maritima , an often annual form predominantly found in coastal areas around and adjacent to the Mediterranean Sea. Accessing other Beta species as a source of traits, especially disease resistance, has a rich history; however, it has achieved limited success via traditional breeding due to progressively less viability and fecundity of hybrids as the more distant of the four Beta sections are hybridized. Recent breeding has been successful in accessing novel genes and alleles from the maritima types. All Beta species are based on a common haploid chromosome number of nine, with the majority of crop types being true diploids, except in the case of induced tetraploids for creating triploid and anisoploid sugarbeet varieties. All species are conserved in active ex situ germplasm collections as well as some preserved in situ. Genome organization in Beta species likely is conserved, with divergence in highly repetitive DNA fractions; however, recent efforts have focused on cultivated types for which genome and transcriptome sequencing is a priority activity. The cultivated types contain the greatest potential for novel uses, and the wild species will undoubtedly contribute to the further evolution of crop beets for economic benefit, perhaps by contributing novel genes or by facilitating accumulation of high-value industrial compounds. Data on Beta species are relatively difficult to access, with databases scattered throughout the world, and assuming novel genes are accessed and transferred to the crops via transgenesis, pollen flow between wild and cultivated populations presents a challenge for deployment of such varieties, especially where weed and crop beets are sympatric. A genome sequence will allow integration of Beta species into a genoplasm pool, and facilitate understanding the modes and tempos of evolution within Beta .