Molecular Breeding for Phosphorus-efficient Rice - Translational Genomics for Crop Breeding: Abiotic Stress, Yield and Quality - page 71

identified as P-deficiency tolerant, based on its
superior P uptake from a highly P-fixing soil
(Figure 5.2a). Although Dular, likewise an aus -
type variety, was more tolerant, Kasalath was
chosen since bacterial artificial chromosome
(BAC) libraries were available, which later facil-
itated sequencing of the Pup1 locus (see below).
The japonica -type variety Nipponbare was used
as the intolerant parent for the development of a
mapping population, and the Pup1 region on Chr.
12 was shown to significantly enhance P uptake
and plant performance under the applied screen-
ing conditions (Figure 5.2b, c; Wissuwa and Ae
2001b; Wissuwa et al. 2002). An intermediate-

effect QTL at the tip of Chr. 6 was additionally
identified, and it was shown that this region con-
tains a cluster of P-response genes (Heuer et al.
2009), including OsPTF1 , a transcription factor
gene that was shown to enhance plant perfor-
mance under P deficiency (Yi et al. 2005). In
contrast, none of the currently known P-response
genes was located within or near the Pup1 region,
based on an analysis of the Nipponbare refer-
ence genome (Heuer et al. 2009). In agreement
with this, physiological studies of Nipponbare-
Pup1 near-isogenic lines (NILs) failed to reveal
commonly known P-starvation responses, such
as exudation of organic acids or elongation of

(b)

Intermediate QTL

(a) 14

12

Kasalath

10

8

6

Nipponbare

4

2

Major QTL
Pup1

0

(c)

Nipponbare

Nipponbare- Pup 1

Fig. 5.2. Mapping of the Pup1 major QTL. A screening of 30 diverse rice accessions under P-deficient field
conditions was conducted to identify genotypes with high P-uptake ability ( a ). The data were derived from Wissuwa
and Ae (2001a). QTL mapping was conducted using a Kasalath x Nipponbare mapping population and Pup1 was
identified as a large-effect QTL on Chr. 12 ( b ). An intermediate-effect QTL is located on Chr. 6 (Wissuwa et al. 1998;
see text for details). Nipponbare and a tolerant near-isogenic line with the Pup1 QTL were grown in a P-deficient
field in Tsukuba, Japan ( c ). For a color version of this figure, please refer to the color plate.