Plant canopy architecture

A key goal of oilseed rape breeding is to create an efficient crop canopy by improving Harvest Index (HI) thus increasing seed yield.  The canopy is determined by the spatial and temporal organisation of all above-ground organs including the vegetative organs; leaves, stems and branches and the reproductive organs; the pods. 

The control of canopy architecture is very complex as it is determined by the expression of many separate traits all of which show large interactions between the plant genotype, the natural environment and agronomy. In addition, these traits are frequently quantitative characters controlled by many genes. 

 

 

These complexities, both at the physiological and genetic level, need to be understood.  To address this we have targeted a number of traits including height and branch and pod numbers and also direct components of yield: pod density, pod size and seed density within the pods.  We are also studying branch and pod angles because a more erect habit is known to improve light penetration within the canopy. 

Brassica napus and the model crop Arabidopsis thaliana are genetically related and thus share many genes and exhibit similar morphologies.  We are therefore using Arabidopsis as a model to underpin our canopy studies in B. napus. 

Brassica canopy architecture

Oilseed rape (OSR) is naturally indeterminate and has been said to behave more like a weed than a crop plant.   These ‘weedy’ characters include many late-formed flowers and branches high in the canopy which reduce light penetration and are formed too late to produce productive pods.  Within the canopy there is both intra- and inter-plant competition for resources. This gives rise to wasted growth which results in immature pods with unfilled seeds at harvest. 

Of particular importance are numbers of branches and pods and their angle to the vertical because increased ‘erectness’ improves light penetration to the first formed pods deep in the canopy and hence their productivity. 

We are investigating these traits in several Brassica napus DH populations: TNDH, QDH, CRDH and VGDH and also among B. carinata accessions. The architectural traits within a mapping population are measured and QTL determined which identify regions of the genome influencing these characters

For some traits many QTL are found on different chromosomes showing that they are controlled by many genes.  In addition, QTL for several traits may be coincident .

We are investigating how these traits impact HI and yield.

Useful Links:

• Novel Resources for Oilseed Rape Breeding  Improving Harvest Index (NOVORB-HI)  (2010) Colin Morgan, Rachel Wells, Jo Bowman, Matthew Clarke, Mark Nightingale, Richard Jennaway, Peter Werner, Jeroen Wilmer, Ian Bancroft. HGCA PROJECT REPORT 465.

• Parallel work is being carried out in the B. napus QDH population and B. carinata

 

Arabidopsis canopy architecture

Arabidopsis thaliana is closely related to Brassica napus and shares many canopy architecture features. A vast number of resources are now available for the genetically simpler Arabidopsis and we are, therefore, using this model plant for by carrying out QTL analysis on the same traits that we are studying in B. napus.

These include plant height, pod numbers, pod lengths and branch and pod angles which are recorded and analysed from digital photographs.

We are using three recombinant inbred populations (RIL): CA, SG and WC which were developed from parents with differing plant architecture. These populations show segregation for these traits some of which is transgressive.  Analysis has revealed many QTL for architectural traits and also flowering time (FT).

We are using these QTL to identify potential candidate genes from the many genes already known to control plant architecture in Arabidopsis and utilising the extensive Arabidopsis-Brassica synteny to comparatively map these QTL in Brassica.