Agriculture Reference
In-Depth Information
Potential Targets for Genetic Improvement
The design of phenotypic screens for dissecting P acquisition or P utilisation
differences in crops requires an understanding of the underlying molecular mech-
anism of low-P tolerance. This section highlights mechanisms which are known in
crops and that may be potential targets for a breeding approach, integrating
physiological, molecular and genetic strategies. Genes will be listed that come
from model organisms and were subsequently investigated in crop species. A
potential candidate target would be characterised by being a key factor in the
molecular mechanism of the P starvation response, adaptation and genetic diversity
responsible for low P tolerance, keeping in mind that there is a need for different
strategies in low-input and high-input systems, focusing more on PAE or PUE
respectively. Teng et al. (
2013
) investigated the expression profiling of known P
starvation-induced genes in wheat under different levels of P fertiliser and soil
Olsen P, proving that the turning point for the genetic response was the critical P
level. This observation leads to a more general model (Fig.
4.3
) which raises the
question: which strategy would be most suitable to shift the onset of gene expres-
sion for the P starvation signalling response into lower P levels and therefore
decreasing the crop demand for equal yield performance? There were three main
scientific approaches to this problem.
The first approach comprises the majority of studies which are based on com-
parisons of low P-tolerant genotypes with more susceptible genotypes or cultivars
(Pariasca-Tanaka et al.
2009
; Li et al.
2008a
,
b
; Hammond et al.
2009
; Zhang
Fig. 4.3 Model for of the optimal yield (
red up arrow
) coinciding with the induction of
P-starvation marker genes (
green down arrow
) in field-derived wheat roots shifting towards
lower soil Olsen-P levels with improved P efficiency traits (Teng et al.
2013
)
