ciatapr10, ciat, poster, "poster Exhibit",poster31, rice, arroz, CIRAD, agbio

1. Exploiting genetic resources for developing
rice germplasm with eco-efficient water use
C Grenier1,2, A Audebert1, Y Sanabria2, Y Ospina2, F Rodriguez2, M Châtel1,2
1 Cirad BIOS UPR AIVA, avenue Agropolis, F-34398 Montpellier, France, 2 CIAT/Cirad A.A. 6713, Cali, Colombia
Introduction:
For more than a decade, the Cirad/CIAT rice collaborative project has focused on the development and
enhancement of rice synthetic populations through recurrent selection (RS) with the goal to develop and diffuse
improved material, populations or lines, for various rainfed ecosystems in Latin America and the Caribbean
(LAC). The merit of the RS population breeding method is well recognized for exploiting of genetic resources
and broadening the genetic basis of improved commercial material (Guimarães and Châtel, 2007). Upland rice
represents a large fraction (46.7%) of rice cultivation in LAC. A severe constraint to upland rice production
results from the irregularity in rain distributions with dry spells occurring at the crop reproductive development
stage (da Silveira Pinheiro, 2003). For areas where drought is commonly reported and considering predictions
on climate change and orientations towards more eco-efficient agriculture, the effectiveness of water resources Synthetic population of upland rice
use is a highly desirable trait for improving upland rice production.
Materials and Methods: Figure 1 Population development
The development and improvement of rice synthetic populations is done owing PCT-4001 1/2 PCT-11001
to the male sterility recessive gene (ms) originating from the IR36 mutant
(Châtel et al., 1997). Four populations were derived from a synthetic population
PCT-11002
(PCT-4001) developed from the intermating of a large group of diverse
progenitors (geographical origins and plant types) (Figure 1). A random sample PCT-4002 PCT-4SA11
of 100 S1-plant per population was evaluated during to 2008 off-season at the
experimental station of Santa Rosa (Colombia) under drought conditions in a PCT-4003 PCT-4SA21 PCT-4SA21, Bo11 PCT-11002, Bo11
split-plot experimental design with six check genotypes. Phenotypic evaluation Pop1
for response to drought was conducted following a 15-day drought period PCT-11002, Bo21
PCT-4SA31 PCT-4SA21, Bo21
applied after panicle initiation stage. The observation consisted in thermographic
infrared imaging to relate canopy temperature to plant transpiration capacity
… … …
which translate to the ability to sustain physiological functions under drought
conditions. Genetic diversity analysis were conducted on the same set of plants,
proceeding with 10-plant bulk leaf tissues. Genotyping was done with 18 SSR PCT-4SA21, Bo41 PCT-11002, Bo41
markers following Lorieux et al. (2000). Genetic analysis consisted in calculating
Pop3 Pop4
the number of alleles per locus per population (Na), the effective number of PCT-4SA81
alleles (Ne), the Shannon diversity index (I), and a test for allelic differentiation.
Pop2
Results and Discussion: Figure 2 Canopy temperature variation among the
Response to drought was highly variable, with canopy temperature ranking from about 27 C to whole set of S1 lines in stress condition
more than 36°C (Figure 2). Within the populations, we identified plants with minimal temperature
difference (≤2ºC) between the control and the stress condition. This discrimination resulted in the 38
selection of 75 families for the four populations. The 400 S1 lines were also evaluated at the S2
Canopy temperature (°C)
36 better lines in
generation for agronomic selection (data not shown) resulting in the selection of 19 families with stress condition
good agronomic characteristics among the material with superior transpiration capacity. The first 34
cycle of recombination will be performed next year from the remnant S1 seeds of these 19 families.
32
The high diversity among the progenitors of the original population (PCT-4001) resulted in a high
allelic richness in the current populations (Table 2). Rare alleles (frequency ≤1%) were present in 30
all populations, which indicate that although they were under selective pressure, the populations
28
maintained high level of genetic variability, as well as rare alleles (Table 3). Furthermore, 11 private
alleles, i.e., alleles unique to a particular population, were found. Frequent private alleles suggest a 26
differentiation (or an admixture as in the case of PCT-11 which is a composite of PCT-4 (50%) and 0 50 100 150 200 250 300 350 400 450 500
other germplasm) and the fixation of a particular allelic variant in a population. Evaluated lines (495)
Population Na Ne I
Table 3 Allelic richness per locus per population with
Table 2 Genetic diversity estimates with the indices of frequency of observed alleles (Na) / frequency of rare
number of observed alleles (Na) Efficient number of Pop1 3.133 (0.401) 2.016 (0.292) 0.695 (0.112)
Pop2 3.200 (0.527) 1.973 (0.255) 0.704 (0.107)
alleles (≤1%) / frequency of private alleles.
alleles (Ne) and Shannon diversity index (I). Average and
standard error (SE) over loci. Pop3 3.667 (0.607) 2.203 (0.338) 0.800 (0.123) Locus Pop1 Pop2 Pop3 Pop4
Pop4 3.400 (0.559) 1.967 (0.284) 0.693 (0.118) RM8068 4/0/0 4/1/0 4/0/1* 5/1/0
RM6840 3/0/0 3/0/0 3/0/0 3/0/0
Conclusion: RM7382 2/0/0 2/0/0 2/0/0 2/0/0
Through these rice populations, we have developed important products for upland rice breeding RM5807 3/1/1 2/0/0 2/0/0 2/0/0
programs; a permanent source of genotypic diversity which evolves at each cycle of RS to generate RM85 2/0/0 2/0/0 3/1/0 3/1/0
RM5608 3/1/1 2/0/0 2/0/0 2/0/0
new allelic combinations, and a genetic material with great potential - in our case the combination of RM507 2/0/0 2/0/0 2/0/0 2/0/0
resilience to drought and good agronomic characteristics - for line development through RM5907 6/2/0 7/2/0 8/2/1* 6/2/1
conventional breeding. The RS method applied to synthetic or composite rice populations allowed RM6775 2/0/0 3/1/0 4/1/1 3/0/0
increasing the frequency of favorable alleles, while maintaining allelic diversity within the improved RM5463 6/0/0 8/0/0 9/1/1* 7/1/1
populations. We are hoping to develop a new upland rice population with effectiveness of water RM3394 6/1/0 6/1/0 7/0/0 9/2/1*
RM420 2/0/0 2/0/0 2/0/0 2/0/0
resources use and to follow its evolution during the RS process in terms of conservation of adaptive RM408 3/1/0 2/0/0 3/0/0 2/0/0
traits and genetic richness. Furthermore, we are moving towards the use molecular marker tools to RM477 2/0/0 2/0/0 2/0/0 2/0/0
refine the methods of RS; better managing of synthetic and composite populations, and to search RM23654 3/0/0 3/1/0 3/0/0 3/0/0
for genes associated with traits of interest for further use in marker assisted recurrent selection. RM7492 2/0/0 2/0/0 3/0/1* 3/0/1*
* Frequent (>1%) private alleles
References :
Châtel M. and Guimarães E.P. 1997. Recurrent selection in rice, using a male-sterile gene. CIAT/Cirad. 70p.
Guimarães E.P. and Châtel M. 2007. Exploiting rice genetic resources thought population improvement. In Guimarães E.P. (ed) Population improvement: a way of exploiting the rice genetic
resources for Latin America, Rome, pp. 3-18
Lorieux M. et al., 2000. A first interspecific Oryza sativa×Oryza glaberrima microsatellite-based genetic linkage map. Theor. Appl. Genet., 2000. 100(3): p. 593.
da Silveira Pinheiro B. 2003. Integrating selection for drought tolerance into a breeding program: the Brazilian experience. In Fisher K.S. et al. (eds) Breeding for drought-prone environments,
IRRI, Los Baños, pp 75-83.