Morphological Variation and Ecological Adaptation of Weedy Rice Populations in Sri Lanka

Abstract

Introgression is an important biological process which occurs naturally between closely related plant species. This process is essential for genetic divergence and adaptive evolution of feral species, originated either by endoferality or exoferality. Weedy rice [Oryza sativa f. spontanea) is a well-known example of ferality. As gene introgression can be influenced by various agronomic and ecological impacts, weedy rice come from different locations may have distinguished adaptive origins. Therefore, a common garden experiment was carried out to observe the morphological diversity and variation patterns of 12 weedy rice populations collected from different locations representing dry zone (Akkareipattu-P9, Ampara-PIO, Lahugala-Pll, and Damana-P12) and wet zone (Pasgoda-Pl, Pitabeddara-P2, Akuressa-P3, Thihagoda-P4, Kirinda-P5, Mulatiyana-P6, Kamburupitiya-P7, Hakmana-P8) of Sri Lanka. All the populations were transplanted in a common field with 4 replicates under completely randomized design and thirteen quantitative and four qualitative characteristics at various growth stages were assessed for phenotypic diversity. The mean comparison of morphological traits among populations revealed that weedy rice coming from different locations of the country has great diversity in morphology, except plant vigor, leaf angle and flag leaf angle. But there was no significant correlation of morphological variation with wet and dry geographic distances. PCA analysis indicated that 07 morphological traits; plant height, no of tillers, no of days to flowering, leaf length at vegetative stage and panicle length, shattering/panicle, no of filled seeds/panicle at ripening stage were the major determinants of the diversity which accounted for 75.8% of total variation. The cluster analysis placed all the accessions into two groups. Clustering was not associated with the geographical distribution. Accessions were mainly grouped due to their morphological differences. All the analysis based on plant morphology suggested that weedy rice in dry and wet zone in Sri Lanka has great variability showing their adaptive co-existence in heterogeneous ecological systems.