Variation for seedling root architecture in the core collection of pea germplasm

Root growth is an important component of plant growth but has received little attention by plant breeders because of difficulties associated with root observation. Improved root architecture and production are likely to improve pea (Pisum sativum L.) production because they are often grown on marginal land and suffer from increased disease pressure and poor fertility. The objective of this study was to quantify the phenotypic variation in seedling root production among Pisum germplasm and to classify the root architecture observed. Seed of 330 accessions from the core collection of Pisum germplasm were germinated and grown under artificial conditions for 14 d and their root characters analyzed. Root systems were scanned and digitized by the WinRHIZO program. Data collected included taproot length, shoot length, and root and shoot dry weight. Data generated by WinRHIZO included total root length, surface area, average root diameter, and root volume. Taproot length ranged from 181 to 433 mm, while root and shoot dry weight ranged from 6 to 57 mg and 13 to 1.04 mg, respectively. Total root length ranged from 54 to 399 cm, root surface area ranged from 9 to 75 cm(2), and root volume ranged from 0.11 to 1.12 cm(3). Seed weight was significantly correlated with all root characters with the exception of taproot length. Shoot and root dry weight were positively correlated with total root length, average root diameter, and root volume. PI 261631, an accession from Spain, produced the greatest total root length, had a root:shoot weight ratio of 0.79, and the largest root volume (1.12 cm(3)). Plant breeders will be able to use the wide variation for root characters in their crossing and selection programs to modify root traits during cultivar development.