Principles of Plant Genetics and Breeding

506 CHAPTER 29
References
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polymorphism differentiate apparent amylose classes in an extended pedigree of U.S. rice germplasm. Theor. Appl. Genet.
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Bollich, C.N., B.D. Webb, M.A. Marchetti, and J.E. Scott. 1990. Registration of Gulfmont rice. Crop Sci. 30:1159.
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suitable for marker assisted selection of three Pi genes conferring resistance to multiple Pyricularia grisea pathotypes. Crop
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edn (Champagne, E.T., ed.), pp. 25–48. American Association of Cereal Chemists, St Paul, MN.
McClung, A.M., R.G. Fjellstrom, C.J. Bergman, C.A. Bormans, W.D. Park, and M.A. Marchetti. 2004. Registration of “Saber” rice.
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about 25–50 mm in a good seedbed. Ground equipment
may be used to apply fertilizer at the time of seeding.
The rate of nitrogen application may vary between
30 and 100 lb/acre. High levels may cause lodging in
some varieties. Where soils are deficient, application of
moderate amounts of phosphorus and potassium may
be beneficial.
A photoperiod of 10–12 hours is preferred for rice
growth. The optimum temperature for growing rice is
about 27°C, but the optimum temperature for flowering
is dependent on photoperiod.
Greenhouse nursery and growth chamber
Crossing indoors under controlled environments in a
greenhouse or growth chamber is especially convenient
for breeders working in the monsoon tropics or flooded
paddies. Under these conditions, the parents may be
grown in the field and dug up and placed in pots for
crossing in the greenhouse. Working indoors allows
the breeder to optimize photoperiod, temperature, and
light level for optimal growth and flowering.
Artificial pollination
Materials and equipment
Various methods are used by rice breeders for emasculations
and pollination. The equipment and materials
differ for the method used, the common ones being
scissors, fine forceps, glassine bags, pot labels, paper
clips, wax pencil, tags, hot water bath, and vacuum
emasculator.
Emasculation
The plant is ready for the preparation of the female for
pollination when 50–60% of the panicle has emerged
from the boot. Emasculation of individual flowers is
done before anthesis and after they emerge from the
boot. Emasculation in the tropics is best done after
mid-afternoon, when anthesis has ceased for the day. In
the temperate regions, preparation of the female can be
done in the morning or late afternoon. Hot water emasculation
is done by soaking the panicle for 5 minutes
in water maintained at 43°C. This treatment must be
followed by pollination within 30–60 minutes after
emasculation. The hot water may be carried in a vacuum
flask. A simpler and more efficient emasculation technique
is to clip the spikelets and remove the anthers with
a pair of forceps or using a vacuum unit.
Where plants have to be transplanted from the field
into pots, the relocation must be completed at least
6 hours before emasculation, to allow plants to recover
from any transplanting shock. Once a panicle has been
identified for emasculation, it is separated from the
others nearby to facilitate the emasculation process.
The flag leaf is carefully removed. Florets at the top
of the panicle that may have already self-pollinated and
the young flowers at the bottom are cut with a pair of
scissors. Next, about one-third to one-half of each floret
is cut off at a slant to expose the anthers. If cut too low,
the stigma may be damaged. If the anthers are to be