Field phenomics for response of a rice diversity panel to ten environments in Senegal and Madagascar. 1. Plant phenological traits

The GRiSP Global Rice Phenotyping Network seeks to assemble a multi-environment, multi-trait phenomics resource for rice (Oryza sativa L.) diversity panels in order to understand existing genetic diversity and identify genes/alleles conveying adaptation and yield potential. Phenology is central to plant adaptation and productivity in different agro-ecologies. We studied a panel of 209 accessions, including 189 indica types and 20 acc. representing other genetic groups. The panel was field-phenotyped under flooded conditions for duration to flowering (F) for 6 sowing dates in Senegal (capturing different thermal and day length regimes) and during two years at two altitudes (mid, 857 m asl; high, 1497 m asl; with similar latitude) in Madagascar. The experiments had an augmented design in Senegal (6 blocks × 6 dates as subplots and 209 acc. as sub-subplot) with 4 replicated check varieties; and a complete block design with 3 replications at 2 sites × 2 years in Madagascar. To dissociate different traits contributing to variation of F, five genotypic Index Variables were calculated. Among them, PCA identified three as describing 98% of diversity: Estimated basic vegetative phase (BVP), photoperiod (PP) sensitivity, and altitude response. Three clusters were identified within the indica group and related to genotype origin, agronomic type and ecosystem of adaptation. Cluster C1 was PP-sensitive, C2 had short BVP and C3 had long BVP. Within C1, a sub-cluster was highly altitude sensitive, and within C3 two sub-clusters were comparatively altitude insensitive. Harvest index (HI), aboveground dw and stem height observed in the most favorable environment (Senegal wet season) showed distinct patterns among clusters, with C2 having high HI and C1 being tall. The phenomics resources will be further analyzed using a crop model and genome-wide association (GWA) studies.