Reference "Evaluation of near-isogenic lines of rice introgressed with QTLs for root depth through marker-aided selection"

Reference ID

7828

Title

Evaluation of near-isogenic lines of rice introgressed with QTLs for root depth through marker-aided selection

Source

Theoretical and applied genetics, 2001, vol. 103(1), pp. 75-83

Authors (5)

Shen-L	Courtois-B
McNally-K-L	Robin-S
Li-Z

Abstract

Drought is one of the main abiotic constraints in rice. A deep root system
contributes efficiently to maintaining the water status of the crop through a
stress period. After identifying QTLs affecting root parameters in a doubled-
haploid (DH) population of rice derived from the cross IR64/Azucena, we started
a marker-assisted backcross program to transfer the Azucena allele at four QTLs
for deeper roots (on chromosomes 1, 2, 7 and 9) from selected DH lines into
IR64. We selected the backcross progenies strictly on the basis of their
genotypes at the marker loci in the target regions up to the BC3F2. We assessed
the proportion of alleles remaining from Azucena in the non-target areas of the
BC3F2 plants, which was in the range expected for the backcross stage reached.
Twenty nine selected BC3F3 near-isogenic lines (NILs) were developed and
compared to IR64 for the target root traits and three non-target traits in
replicated experiments. Of the three tested NILs carrying target 1, one had
significantly improved root traits over IR64. Three of the seven NILs carrying
target 7 alone, as well as three of the eigth NILs carrying both targets 1 and
7, showed significantly improved root mass at depth. Four of the six NILs
carrying target 9 had significantly improved maximum root length. Five NILs
carrying target 2 were phenotyped, but none had a root phenotype significantly
different from that of IR64. A re-analysis of the initial data with the
composite interval mapping technique revealed two linked QTLs with opposite
effects in this area. Some NILs were taller than IR64 and all had a decreased
tiller number because of a likely co-introgression of linked QTLs. The
usefulness of NILs, the efficiency of marker-aided selection for QTLs and the
relationship between root traits are discussed. The NILs with an improved root
system will permit testing the importance of root depth for water-limited
environments.