P1 (Juvenile Phase)

Time period or basic vegetative phase of the plant (expressed as growing degree days [GDD] in ˚C from seedling emergence during which the rice plant is not responsive to changes in photoperiod.

P2O (Critical Photoperiod)

Critical photoperiod or the longest day length (in hours) at which the development occurs at a maximum rate.

P2R (Photoperiodism Coefficients)

Extent to which phasic development leading to panicle initiation is delayed (expressed as GDD) for each hour increase in photoperiod above P2O.

P5 (Grain filling duration coefficient)

Time period in GDD) from beginning of grain filling (3 to 4 days after flowering) to physiological maturity with a base temperature of 9˚C.

G1 (Spikelet number coefficient)

Potential spikelet number coefficient as estimated from the number of spikelets per gm of main culm dry weight (less lead blades and sheaths plus spikes) at anthesis.

G2 (Single grain weight)

Under ideal growing conditions, i.e., non limiting light, water, nutrients, and absence of pests and diseases.

G3 (Tillering coefficient)

A higher tillering cultivar would have coefficient greater than 1.0 G4 (Temperature tolerance coefficient) = Usually 1.0 for genotypes grown in normal environments.

G4 (Temperature tolerance coefficient)

Usually, 1.0 for genotypes grown in normal environments. G4 for japonica type rice growing in a warmer environment would be 1.0 or greater. Likewise, the G4 value for Indica type rice in very cool environments or season would be less than 1.0.