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11140001 Agronomy Fellowship

Publication Date: 
30 April 2018
Author/Contact :
David Firman

Contractor :

Full Research Project Title: Agronomy fellowship - Understanding tuber formation: maintaining the capability to improve tuber quality attributes including greening
Duration: February 2015 - March 2018


Tuber greening is increasingly recognised by packers as a significant contribution to wastage but there has been limited progress in reducing its importance through variety selection or modification to agronomy.  Large differences in the variation in tuber size are found between crops and wastage of outgrades from crops with more variation in tuber size affects profitability for growers and packers. In-field greening results from exposure of tubers in the ridge to light and thus is likely to be most significant when tubers form or expand close to the soil surface. A better understanding of the key physiological and agronomic factors affecting in-field greening should help inform varietal and agronomic improvements and enable engagement with key stakeholders able to influence the impact of these to reduce wastage.


Aim: To develop new skills and knowledge of tuber formation to underpin research into greening and other aspects of tuber quality. 

This fellowship provides the opportunity for a new researcher to work alongside an experienced scientist with a background in studying tuber formation and growth to develop expertise and understanding to address tuber quality and uniformity for the potato industry. This project will investigate factors affecting in-field tuber greening, particularly the influence of the length and position of stolons on below ground stems to which tubers are attached.  Differences between varieties in the attributes of stolons and agronomic effects on stolon architecture will be characterised and compared with the extent of greening in experiments and commercial crops to establish the extent to which wastage from greening may be influenced by variety, environmental factors and agronomic practice.  The variation in attributes of tuber formation between crops will be examined and methods of characterising attributes developed to aid varietal and agronomic improvement in susceptibility to greening.  The results will also inform understanding of the effects of differences in stolon architecture on variation in other tuber quality attributes including tuber size distribution and diseases such as common scab.

Key Findings

  • Significant differences in mean stolon length were observed between the varieties each year.  The horizontal position of tubers was closely related to stolon length and tuber length indicating that it is possible to predict the cluster width of a crop for any given stolon length and tuber size.
  • Seed size did not affect stolon length or tuber greening.  Planting date affected stolon length but the effects were inconsistent and difficult to reconcile with variation in temperature. 
  • Nitrogen rate significantly affected stolon length but the extent of the effect was small for a large difference in nitrogen rate.
  • The survey of commercial crops found a similar range in stolon length as in the experiments and the average stolon depth was c. 75 % of planting depth.
  • Stolon depth differed between varieties, but the differences were small compared to the differences in stolon length between varieties.
  • Few green tubers were exposed at the soil surface with the majority still covered by soil indicating that cracking of the soil was important in allowing light to reach the tubers.
  • Varieties differed in their sensitivity to light but this did not correspond to their propensity to tuber greening in the field experiments. Planting depth varied widely, both between and within crops, and influenced the amount of yield close to the soil surface.
  • Tuber greening was most severe on sites where more tubers were close to the soil surface and tended to be more severe on soils with a higher clay content.  The planter experiment indicated that hood pressure and ridge shape could influence tuber greening.


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