ICRISAT Archival Report 2006 - The seedlings of success in the ...

Milestone 5B.4.1.1: An effective P-acquisition protocol applicable for large-scale screening developed (VV/HDU,
2007)
Large efforts have been dedicated in 2005 and 2006 to develop an efficient and reproducible protocol to test the
response of pearl millet genotypes to low P availability under controlled conditions. This protocol has been
developed based on the fact that pearl millet seeds are small and that plant establishment is a key factor to a
successful performance under low P conditions. To get uniform sowing depth, a template making holes of a standard
depth is used, in which seeds are placed. Several seeds were usually sown per hill, and then thinned to one seedling
per hill. It was observed that thinning was affecting the development of the remaining seedling (probably by
disturbing roots of the remaining seedling). Therefore, 9 seeds are now planted per pot, one each into an individual
hole made with the template, and most uniform 3 seedlings are retained. The protocol is also based on observations
that growing 3 plants per replicate pot helps in decreasing the replicate-to-replicate variation. We are also aware of a
genotype by nitrogen interaction effect under low P soil, which has to be taken into account at the time of screening
for low-P tolerance (choice has to be made and repeat experiment should use the same N source). Finally, we have
found out that small differences in soil Olsen P value could bring about large differences in the response of pearl
millet plants. Therefore, the same soil lot is used for each experiment, and this lot is first homogenized with a
concrete mixer prior to preparing the soil:sand mix (1:1 v/v).
Vincent Vadez
Milestone 5B.4.1.2: Pearl millet germplasm with superior P-acquisition from low-P sources identified (VV, 2009)
We have initiated the assessment of two pearl millet open-pollinated varieties (OPVs) (ICMV IS 92222 and ICMV
IS 89305) for their ability to acquire P from low-P soils. In a controlled pot experiment using the protocol described
above, we have found a 2-fold variation for biomass under low-P in 184 S 1 progenies. The top and bottom 25 S 1 s for
shoot biomass under low-P conditions have been planted to generate full-sibs of the top and bottom ranked. These
will be selfed for one generation and S 1 s will be evaluated in 2007.
Vincent Vadez and KV Padmaja
Milestone 5B.4.1.3: QTL for P acquisition from low-P sources identified in pearl millet (VV/CTH, 2011)
The parents of existing mapping populations of pearl millet have been tested for their ability to acquire P from low-P
sources. Consistent contrast has been found between 2−3 pairs of parents. We have found that the shoot biomass
under low-P conditions was well correlated to the shoot biomass under controlled conditions, meaning that low-P
tolerance may be better assessed by the ratio biomass under low-P / biomass under control. However, differences
found with in mapping population parents were relatively small. Larger number of inbred parents will be tested to
identify the most contrasting pairs for developing new RIL populations.
Vincent Vadez
Output target 5B.5: At least five pearl millet breeding lines with tolerance to high air temperatures (>45°C)
during reproductive stage developed (2009)
Activity 5B 5.1: Evaluate a diverse range of parental lines, advanced breeding lines and populations for high
temperature tolerance during flowering and grain- filling period; and identify major QTL associated with
this trait
Milestone 5B.5.1.1: Breeding lines with >70% seedset under field conditions at high temperatures identified/
developed and their tolerance under glasshouse conditions validated (KNR/RB/VV, 2009)
Heat-tolerant hybrid parents: Most of the hybrids bred for rainy-season adaptation have been found to become
male-sterile, or set very poor seed during the summer season if flowering takes place at a time when the air
temperatures could be as high as 46-48°C. A few of the hybrids, however, set excellent seeds, indicating genetic
variability for thermo-tolerance during the reproductive stage. With the assistance of MAHYCO, 92 maintainer
lines (B-lines) and 7 restorer lines (R-lines) were evaluated for seed set under open pollination in a summer planting
at Jodhpur. Most of the lines either did not set, or had