Il. Goldman et al., QUANTITATIVE TRAIT LOCI INFLUENCING PROTEIN AND STARCH CONCENTRATION IN THE ILLINOIS LONG-TERM SELECTION MAIZE STRAINS, Theoretical and Applied Genetics, 87(1-2), 1993, pp. 217-224
A study was initiated to determine the number, chromosomal location, a
nd magnitude of effect of QTL (quantitative trait loci or locus depend
ing on context) controlling protein and starch concentration in the ma
ize (Zea mays L.) kernel. Restriction fragment length polymorphism (RF
LP) analysis was performed on 100 F3 families derived from a cross of
two strains, Illinois High Protein (IHP), X Illinois Low Protein (ILP)
, which had been divergently selected for protein concentration for 76
generations as part of the Illinois Long Term Selection Experiment. T
hese families were analyzed for kernel protein and starch in replicate
d field trials during 1990 and 1991. A series of 90 genomic and cDNA c
lones distributed throughout the maize genome were chosen for their ab
ility to detect RFLP between IHP and ILP. These clones were hybridized
with DNA extracted from the 100 F3 families, revealing 100 polymorphi
c loci. Single factor analysis of variance revealed significant QTL as
sociations of many loci with both protein and starch concentration (P
< 0.05 level). Twenty-two loci distributed on 10 chromosome arms were
significantly associated with protein concentration, 19 loci on 9 chro
mosome arms were significantly associated with starch concentration. S
ixteen of these loci were significant for both protein and starch conc
entration. Clusters of 3 or more significant loci were detected on chr
omosome arms 3L, 5S, and 7L for protein concentration, suggesting the
presence of QTL with large effects at these locations. A QTL with larg
e additive effects on protein and starch concentration was detected on
chromosome arm 3L. RFLP alleles at this QTL were found to be linked w
ith RFLP alleles at the Shrunken-2 (Sh2) locus, a structural gene enco
ding the major subunit of the starch synthetic enzyme ADP-glucose pyro
phosphorylase. A multiple linear regression model consisting of 6 sign
ificant RFLP loci on different chromosomes explained over 64% of the t
otal variation for kernel protein concentration. Similar results were
detected for starch concentration. Thus, several chromosomal regions w
ith large effects may be responsible for a significant portion of the
changes in kernel protein and starch concentration in the Illinois Lon
g Term Selection Experiment.