Genotypic consistency for low temperature tolerance at the booting stage in rice grown under flooded and non-flooded conditions

Lack of irrigation water for flooded cultivation and low temperature during the reproductive phase are factors limiting rice production in the Riverina region of New South Wales, Australia. While cold tolerant genotypes are available for flooded conditions, the consistency of cold tolerance under different growing conditions including non-flooded conditions remains unknown. The objective of this paper was to determine genotypic consistency in cold tolerance under different water and soil nutrition conditions. Three experiments were conducted in which genotypes from a Kyeema//Kyeema/Norin PL8 population were exposed to low air temperature (21/15 °C day/night) for 14 days at the booting stage. Genotypic variation in spikelet sterility existed within the population and the ten most tolerant (22.8%) and susceptible (73.2%) genotypes were identified. Generally, the genotypes grown under non-flooded conditions and low temperature ranked similarly to those in the flooded and low temperature (r = 0.90**), with tolerant genotypes consistently identified as tolerant even under high nitrogen flooded (r = 0.97**) conditions. N application increased tillering and spikelet number per plant, leading to increased spikelet sterility under low temperature. Spikelet sterility negatively correlated with grain yield/plant but some genotypes with low spikelet sterility also had low grain yield, due to inherently low spikelet number per panicle. The genotypic consistency in cold tolerance under different growing conditions suggest that it may be possible for genotypes to be screened for low temperature tolerance under flooded conditions and identify genotypes appropriate for use in non-flooded conditions, thus minimising resources required to screen for low temperature tolerance and non-flooded conditions in a two-step process. However, to confirm this, testing in the field with larger population numbers from diverse genetic backgrounds is required.