Gulden: Developing a Rapid Method to Evaluate Pod-Drop in Canola
Date: April 2016
Term: 3 years
Status: Completed
Researcher(s): Rob Gulden, University of Manitoba; Steven Shirtliffe, University of Saskatchewan
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
Canola is a crop associated with large seed losses before and at harvest, including from pod shatter and pod drop. Researchers conducted a three-year study to develop and refine a method for measuring pod-retention resistance. This project resulted in significant improvement in the understanding of yield losses due to pod drop in canola and showed a clear relationship between specific pod-retention resistance and absolute pod drop. This is encouraging in that it suggests a significant component to pod drop appears to be heritable and could be exploited by canola breeders to reduce canola harvest losses due to pod drop.
Canola is a crop associated with large seed losses before and at harvest. Two phenomena contribute to these seed losses, i) pod shatter where siliques open and lose their seeds while still attached to the plant and ii) pod drop, where entire siliques break at the petiole and drop to the ground. Pod drop is less well understood than pod shatter and also is more difficult to measure. Researchers have started using force gauges as a way to measure pod-retention resistance and to assist with understanding pod drop.
Researchers at the University of Manitoba and University of Saskatchewan conducted a three-year study from 2013 to 2015 to develop and refine a method that can be used to measure pod-retention resistance in Brassica napus canola. The objectives of the study were to: 1) Refine the number of measurements and rachis type and position from where to obtain meaningful pod-retention resistance measurements; and, 2) Use this method to determine and validate a relationship between pod-retention resistance and pod-drop across a number of genotypes and environments.
Field experiments were established at two locations for Objective 1, Carman, MB and Saskatoon, SK. In 2013 and 2014, two seeding dates were used in Carmen (mid-May and early June), while only one seeding date was used in Saskatoon (mid-May). Six hybrid varieties (three considered susceptible to pod shatter and three more resistant) were seeded at two different target densities (120 and 30 plant m2). At BBCH stage 84-85 (40 to 50% pod ripening, seeds dark and hard) before any pod drop or pod shatter had occurred, 2 meters row crop sample were collected to determine plant biomass and seed yield samples that were used to determine proportional (%) seed harvest losses. The early-planted experiment at Carman was lost in 2013 due to untimely hail on the 30th of August. The early-planted experiment at Carman in 2014 was only used for the pod retention resistance measurement; the high frequency in precipitation during the first months of the field season caused a sclerotinia outbreak, which compromised the final harvest and pod drop collection.
Canola Performance Trials (CPT experiments) from the ‘Co-operative Tests’ were used to take measurements with the pod-retention-resistance method for Objective 2. In 2014, two locations were selected at Carman, MB and Outlook, SK, while in 2015 a larger number of locations were used either in Manitoba (trials located in Thornhill (DL Seeds) and Elm Creek (Cargill)), or in Saskatchewan (trials located in Saskatoon (DL Seeds), Wakaw (ICMS), and Melfort (Bayer)). Seed loss samples were collected with catch trays only in 2015. A total of 19 varieties were included, with pod-retention resistance measurements obtained using a force gauge device for all varieties at the BBCH 78 developmental stage.
Overall, the results from the project highlighted the contribution of key factors and their relative importance to pod-retention resistance (rachis position, cultivar and location) and pod drop (location, rachis position and genotype). Canola stand density was not significant and a minor component across the study. The results also showed a clear relationship between specific pod-retention resistance and absolute pod drop, which is new and provides important insights into this environmentally sensitive mechanism for harvest losses in canola.
Researchers found that specific pedicel attachment strength appears to play an important role in pod drop and requires further investigation. Dropped pods from canola genotypes where low pod drop was observed required on average a higher force per gram pod to dislodge from the plant than dropped pods from plants with higher yield losses from pod drop. It is still not known how environmental factors during seed maturation contribute to this relationship or how plasticity in pod size and pod-retention resistance interact. The results from the study are encouraging in that it suggests a significant component to pod drop appears to be heritable and could be exploited by canola breeders to reduce canola harvest losses due to pod drop.
Full Report PDF: Developing a Rapid Method to Evaluate Pod-Drop in Canola