Nitrogen Use Efficiency in Potatoes
Commercial production of potatoes requires high levels of N fertilizer. This is due to the high nutrient demand of the crop and to the very shallow root system of potato plants. In addition, the fact that potatoes are often grown in light sandy soils, results in the production of potato crops causing high levels of environmental pollution by nitrogen losses.
In order to improve nitrogen use efficiency (Nit-UE) in potato, it is essential to get a basic understanding of the genetic factors affecting physiological and/or morphological characteristics that are associated with Nit-UE under limiting nitrogen input. In addition, basic information about the performance of modern varieties/genotypes under limited nitrogen supply is desirable to encourage further breeding progress for Nit-UE
Consequently work under SP4, with the participation of partners at Newcastle University (UK), Wageningen University (Netherlands), and Agrico (Netherlands; Fig. 1), was focused on the development of markers for Nit-UE in potato through an integrated agronomic, physiological and genetic analysis.
Fig. 1. Agrico field trial site, 2010
Activities in WP4.1 involved three main approaches :
Identify QTLs for rate of crop development and nitrogen accumulation in the SH X RH population (100 genotypes).
Phenotyping an extensive set of potato germplasm (200 varieties/genotypes) to identify genetic variation by association mapping
Quantify plasticity of Nit UE in selected genotypes under 2 N input types and 2 levels (not reported here).
In 2009 and 2010, a series of 186 potato varieties were grown in 16 plant yield plots at two levels of N-fertiliser input in Bant, The Netherlands. Fig. 2, relates the yield performance of potato varieties under Low N-input (70 kg/ha) to the variation in the efficiency of using the N-fertilizer when changing the input from low to high (180 kg/ha). The scatter points were divided into four quadrants (Qs) by using as a crossing point of the axes the mean values of both variables. Q1 contains varieties with a high response but low yield performance under low input. Q2-varieties combine a high response with good performance. Q3 contains varieties with both a poor response and performance. Q4 varieties show a high response but low yield performance. Thus, quadrant 2 shows the best varieties from an agronomic point of view. These had yield values above the average for both axes, under low condition and they showed a high and positive response to the change in N input as well. The majority of the varieties in this quadrant belonged to the late and intermediate maturity groups. In general, most of the early varieties had a lower performance under poor N condition whereas the response to extra nitrogen did not seem to be maturity dependent. This approach to identifying NitUE varieties could be transferred to other crops and is an alternative to conducting trials at a broad range of N rates at the varietal selection stage.
Fig. 2. Yield performance of potato varieties (E=early maturing, M=mid-season maturing, L=late maturing) on the x-axis versus efficiency of N-fertilizer when changing input from low to high (AEN). Quadrants are: Q1=top left; Q2=top right; Q3=bottom right; Q4=bottom left
Fig. 3. SHXRH population, soil coverage assessments (left) and plant height assessments (right) Agrico 2011
It is clear that the efficiency in using nitrogen decreases with an increase of N input. The magnitude of this decrease would be equivalent to the change in response to nitrogen. Therefore a variety that combines a good yield at low N input rates and that shows good response to extra fertilizer will probably have better nitrogen use efficiency. Additionally, when selecting potato varieties, the maturity group a variety belongs to, needs to be taken into account since it is a fixed characteristic for each variety that influences the overall performance of the plant
The key conclusions from the workpackage on NitUE in potatoes were:
- Canopy development traits are related with yield
- Maturity type affects most of the traits
- NUE decreases with more N input
- Low N conditions show better expression of discriminative traits
- Selection should combine performance under low input and response to N fertilizer
- Preliminary association shows QTL for maturity associated with all traits
- Some associations are N dependent
Publications resulting from this workpackage included:
Khan MS, Van Eck HJ, Struik PC (2013) Model-based evaluation of maturity type of potato using a diverse set of standard cultivars and a segregating diploid population. Potato Research 56 (2):127-146
Khan MS, Yin X, Van Der Putten PEL, Struik PC (2013) An ecophysiological model analysis of yield differences within a set of contrasting cultivars and and F1 segregating population of potato (Solanum tuberosum L.) grown under diverse conditions. Ecol Model in pressOpsina Nieto C, Lammerts Van Bueren E, Allefs S, Vand Der Putten PEL, Van Der Linden G, Struik PC (2014) Diversity of crop development traits and nitrogen use efficiency among potato cultivars grown under contrasting nitrogen regimes. Euphytica 199:13-29