Utilizing Chromosome Segment Substitution Lines (CSSLs) for Evaluation of Root Responses to Transient Moisture Stresses in Rice

Drought and waterlogging that occur sequentially under field conditions are important abiotic stresses affection plant growth and development. The ability ot maintain the root system development during the contrasting moisture stresses may be one of the key traits for plant adaptation. This study aimed to identify the key root traits that contributed ot the above ability by comparatively examining the effects of the two moisture stresses in succession on root system development. The chromosome segment substitution lines (CSSLs) form the crosses between the japonica rice cultivar Nipponbare and indica rice cultivar Kasalath were used for precise comparison on root system development. the rice seedlings were grown by hydroponics under an continuously well-aerated condition for 14 days (non-stressed), a drought condition for 7 days followed by an oxygen (O-2)- deficient (stagnant) condition for 7 days (drought-to-stagnant, D-S), or a stagnant condition for 7 days followed by drought condition for 7 (stagnant-to-drought, S-D). CSSL43 and 47 did not show any significant differences in growth form nipponbare under the non-stressed condition, but exhibited greated lateral root production under the stresses. Lateral root production was most closely related to fatster seminal root eleongation mediated by higher aerenchyma formation in the D-S condition, and to more branching of lateral roots on reduced seminal root elongation and aerenchyma formation. These results confirmed the fact that those root traits previously identified using different cultivars greatly contribute to plant adaptation. Oxygen deficiency preceded by drought (D-S) was more stressful to roots than drought preceded by O-2 deficiency (S-D), because drought reduced root aerenchyma formation during the subsequent stagnant condition.