title: Genetic variation in pea (Pisum sativum L.) demonstrates the importance of root but not shoot C/N ratios in the control of plant morphology and reveals a unique relationship between shoot length and nodulation intensity.
abstract: Nodule numbers are regulated through systemic auto-regulatory signals produced by shoots and roots. The relative effects of shoot and root genotype on nodule numbers together with relationships to organ biomass, carbon (C) and nitrogen (N) status, and related parameters were measured in pea (Pisum sativum) exploiting natural genetic variation in maturity and apparent nodulation intensity. Reciprocal grafting experiments between the early (Athos), intermediate (Phönix) and late (S00182) maturity phenotypes were performed and Pearson's correlation coefficients for the parameters were calculated. No significant correlations were found between shoot C/N ratios and plant morphology parameters, but the root C/N ratio showed a strong correlation with root fresh and dry weights as well as with shoot fresh weight with less significant interactions with leaf number. Hence, the root C/N ratio rather than shoot C/N had a predominant influence on plant morphology when pea plants are grown under conditions of symbiotic nitrogen supply. The only phenotypic characteristic that showed a statistically significant correlation with nodulation intensity was shoot length, which accounted for 68.5% of the variation. A strong linear relationship was demonstrated between shoot length and nodule numbers. Hence, pea nodule numbers are controlled by factors related to shoot extension, but not by shoot or root biomass accumulation, total C or total N. The relationship between shoot length and nodule numbers persisted under field conditions. These results suggest that stem height could be used as a breeding marker for the selection of pea cultivars with high nodule numbers and high seed N contents.
authors.affiliation: Crop Performance and Improvement Division, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK.
authors.forename: Ndiko N
authors.initials: NN
authors.lastname: Ludidi
authors.forename: Till K
authors.initials: TK
authors.lastname: Pellny
authors.forename: Guy
authors.initials: G
authors.lastname: Kiddle
authors.forename: Christelle
authors.initials: C
authors.lastname: Dutilleul
authors.forename: Karin
authors.initials: K
authors.lastname: Groten
authors.forename: Philippus D R
authors.initials: PD
authors.lastname: VAN Heerden
authors.forename: Som
authors.initials: S
authors.lastname: Dutt
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Powers
authors.forename: Peter
authors.initials: P
authors.lastname: Römer
authors.forename: Christine H
authors.initials: CH
authors.lastname: Foyer
mesh_terms: D002244:Carbon / Q000378:metabolism*; D035264:Flowers / Q000502:physiology; D014644:Genetic Variation; D005838:Genotype; D009584:Nitrogen / Q000378:metabolism*; D009929:Organ Size; D018532:Pisum sativum / Q000033:anatomy & histology* / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D018517:Plant Roots / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018520:Plant Shoots / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018547:Plant Stems / Q000033:anatomy & histology; D015203:Reproducibility of Results; D053204:Root Nodules, Plant / Q000378:metabolism*
chemical_list: D002244:Carbon; D009584:Nitrogen