Agriculture Reference
In-Depth Information
FIGURE 3:
Example of identification and validation of a candidate gene involved in
the control of NUE and yield in maize. On the left is shown a chromosomal colocation
of QTLs for different yield traits (KW = kernel weight and GY = grain yield) and for
glutamine synthetase (GS) activity at the level of the Gln1-3 locus (encoding a cytosolic
GS involved in ammonia assimilation; see paragraph 4 and Figure 2). N+ means with high
N fertilization, N- with low N fertilization. Such a result shows that the Gln1-3 gene is a
good candidate gene for explaining variation in NUE. Validation of the candidate gene
Gln1.3 was then performed using: (1) mutants {reduction of grain yield in the mutant (m)
compared to the wild type (WT)}; (2) genetic modification by overexpressing the Gln1.3
in transgenic maize plants {increase in grain yield in the trangenics (OE) compared to
the untransformed plant (WT); see [159]; (3) association genetics linking Gln1.3 gene
nucleotide polymorphism to the increase in yield (HY = high yield, LY = low yield) to
identify the best performing Gln1.3 allele among a population covering maize genetic
diversity; (4) marker assisted selection (MAS) can be then undertaken by breeders where a
trait of interest (yield associated to the presence of the Gln1.3 locus) is selected not based
on the trait itself, but on a marker or markers linked (marker a and b)to it and introduced in
the desired elite line (L2) from the donor line (L1) containing the best performing Gln1.3
allele in terms of yield.
