Molecular and physiological analysis of flag leaf senescence and remobilization of assimilates in bread wheat under terminal drought stress

Abstract

In the physiological study of stem remobilization of assimilates during grain filling, mutant genetic materials are a valuable tool. Two advanced mutant lines of bread wheat (T-67-60 and T-65-7-1) along with their wild type (Tabasi Cv.) were planted at two moisture conditions (normal and 30-40% of field capacity) as a factorial experiment based on a completely randomized design with three replications. Drought treatment initiated at full heading stage (Zadoks 60) and sampling done at 5 steps (0, 7, 14, 21 and 28 days after anthesis). Based on the results remobilization of stem and its efficiency in the mutant lines was significantly more than wild type, under terminal drought stress. The reasons for this were higher capability of the sink and early senescence in the mutant lines compared to the wild type. In consequence of changes in chlorophyll content and relative gene expression of key photosynthetic Rubisco (Rubisco large and small subunits and Rubisco activase), in the genotypes during grain filling seems degradation of chloroplasts and photosynthetic system occurred caused by senescence drought stress-induced in the mutant lines more strongly than in the wild type, and because of senescence is stimulating remobilization of assimilates from stem to grain, remobilization of stem and its efficiency in mutant lines were more than wild type. Also, wild type further with continuation of current photosynthesis in the leaves has acted for the grain filling.

Keywords

• gene expression
• senescence
• mutant
• rubisco
• chlorophyll