Studies on the Efficiency of Rapeseed (Brassica napus L.) Germplasm for the Acquisition and the Utilisation of Inorganic Nitrogen

Research output: ThesisDoctoral Thesis

Abstract

The utilization of rapeseed (Brassica napus L.) cultivars with improved N -
efficiency may ameliorate the negative impact of N-fertilizers in the environment. The objectives of this research were: (1) to determine whether there is genetic variation for N-efficiency amongst germplasm accessions of B. napus, (2) to determine if the genetic variation for N-efficiency is potentially useful in a breeding program and, ( 3 ) to obtain information on the genetic nature of N-uptake and N-utilization efficiency of B. napus. Response of B. napus late in the rosette stage to one N-level (static efficiency) or to increased N-levels (response-rate efficiency) were used as definitions of N -efficiency. Studies carried out to develop a screening technique for selecting N-efficient B. napus indicated that growth of 6. napus was rnaximized when some N was supplied as NH+4 and that the shoot system, and not the root system, was a major factor in determining N-efficiency components in B- napus genotypes. Furthermore, studies of the time-course responses to N supply and of the effect of N supply on B. napus growth and N-efficiency components late in the rosette stage provided information for selecting sampling time, N-treatment levels, and N efficiency parameters for screening N efficient germplasm.
A screening of 112 genotypes under deficient and sufficient N levels indicated a
large variability for both static and response-rate N efficiencies. However, the largest range of variability amongst genotypes was shown for the nitrogen use efficiency (NUE) parameter. A screening of a doubled haploid population derived frorn parents differing in N-efficiency indicated a large genetic component coupled with a strong materna1 effect for many of the N-efficiency parameters.

Nitrogen use efficiency appeared to be the N efficiency parameter with the most
potential for breeding in B. napus. However, this was accompanied by a strong
environmental effect. It can be concluded that: (1 ) genetic variation for N-efficiency parameters amongst germplasm accessions of B. napus is available; (2) the genotypic variation might be potentially useful in a breeding program; (3) there is a large genetic component for N-efficiency coupled with an strong materna! effect; (4) a static N efficiency parameter such as NUE is potentially the most promising for crop improvement and (5) breeding of N-efficient B. napus gerrnplasm might be possible, but difficult.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Alberta
Supervisors/Advisors
  • Stringam, Gary, Principal Supervisor, External person
  • Taylor, Gregory, Co-Supervisor, External person
  • King, Jane, Co-Supervisor, External person
Place of PublicationCanada
Print ISBNs0612230406, 9780612230408
Publication statusPublished - 1997

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