LOCAL ADAPTATION, PHENOTYPIC DIFFERENTIATION AND DIVERGENCE OF LIFE-HISTORY TRAITS OF Oryza nivara AND  Oryza rufipogon IN SRI LANKA 

Reciprocal transplant experiments are great approaches to studying phenotypic plasticity, life history trait divergence, and speciation and adaptation of plants. Wild species of rice, Oryza nivara and O. rufipogon are the progenitors of Asian cultivated rice and have been recognized as a valuable genetic resource for rice genetic improvement. The phenotypic plasticity and fitness of wild relatives of rice in Sri Lanka have not been well documented. A reciprocal transplant experiment was conducted for a one year in Hambantota (DL5) and Matara (WL1a) district in Sri Lanka. By considering species factor and locations factor, experimental units (plots) were replicated by using the two-factor factorial Randomized Complete Block Design (RCBD).  The aim of the study was to investigate the phenotypic plasticity, life history trait divergence and survivability of two wild rice species, Oryza nivara and Oryza rufipogon, in response to varying environmental conditions driven by their adaptation to the specific environment. Fifteen morphological parameters were observed to estimate the phenotypic variations while three reproductive traits were measured to find the life history divergence of wild rice species. The plant survival rate was measured in the wet and dry zones to determine plant fitness. The advantage of the fitness of the local population at each site in reciprocal transplant studies provides evidence of the contribution of several differentiated phenotypic traits to local adaptation. These two species demonstrated greater adaptability and fitness in their native environment since they are already adapted to the biotic and abiotic stressors. However, O. nivara in the wet zone showed stronger growth performance with a longer reproductive period for altering their phenotypic, life history, and high survivability in line with divergent environmental circumstances, which may indicate superior growth performances in contrasting environments referred to as foreign advantage. In response to changing environments, O. rufipogon also changes its phenotypic and life history traits, both in native and foreign environments, while exhibiting poorer fitness in stressed circumstances. Conversely, based on seed performances and survival rates, O. rufipogon is less fitted than O. nivara. These studies provide important insights into the initial data for understanding the adaptation, speciation and evolution in ex-situ and in-situ wild rice populations in Sri Lanka, which is of great significance in conserving these wild genetic resources and facilitating their utilization in rice genetic improvement for climate smart crop.