Abstract:
Rice (Oryza sativa L.) is one of the largest staple food crops worldwide, particularly in
Asia. Abiotic factors such as drought stress are a key factor that has reduced the yield
of rice, especially at the initial stages, and the root system architecture is also
significant in adaptation of plants to water – stress conditions to increase its ability to
gain water and nutrients. In this study, the drought tolerance of plants at the vegetative
stage was assessed in ten rice varieties, such as IR116713D, Bg 374, IRRI 264, Bg 22 –
3434, IR21C1106, IR21C1071, IR21C1100, Bg 377, IR93980S and IR21C1061. Among
the chosen rice lines, Bg 374 and Bg 377 are released as cultivars in Sri Lanka, but other
rice lines are still not released but have a possibility of later evaluation under local
agronomic conditions. Drought stress caused notable impact on root length and root
volume with stress conditions generally facilitating the promotion of root development
although the responses of the varieties differed depending on the genetic variation in
the drought tolerance. Root length and root volume were measured at 45 days after
using root scanner (WinRHIZO model). Drought stress significantly (p<0.05, ANOVA)
affected root traits, with genotypic variation. IR21C1071 exhibited the greatest root
elongation (12.3 cm), while IR116713D showed the highest root volume increase (11.4
cm³), reflecting superior adaptive capacity under stress. IR21C1071 and IR116713D
are promising donors for breeding programs targeting drought-prone environments.
Variation in root architecture, particularly elongation vs. volume expansion, provides
a basis for selecting resilient rice genotypes at the vegetative stage.
