| The evolution of light use efficiency and starch biosynthesis in grain of historical wheatcultivars released in Shandong province was investigated in order to extend the current viewand provide the theoretical basis for further wheat breeding. Eight leading wheat cultivarswidely planted in Shandong province at different time since1950s were studied. Changes ingrain yield, photosynthetic parameters, starch biosynthesis in developing endosperm and theactivities of starch biosynthetic enzymes involved in the grain filling was conducted, togetherwith the transcript levels of the corresponding genes encoding starch biosynthesis enzymes.The results showed that the grain yield, the content of amylose, amylopectin and totalstarch content in mature endosperm increased significantly with the released time of eightwheat cultivars, especially for the newest cultivars such as Jinan17and Jimai22with thehighest grain yield and starch content. During the grain filling, net photosynthesis rate (Pn),The chlorophyll content (Chl a and Chl b), respiratory rate and photochemical efficiency(ΦPSII) of flag leaves from all historical cultivars increased significantly with the releasedtime of eight cultivars; the maximum photochemical efficiency did not change significantlywith the released time of eight cultivars; and these parameters reached their maximal valuesbetween flowering date and10days after anthesis (DAA), then declined gradually. It turnedout that, the light energy use efficiency increasely with the replacement of shandong Provincecultivars, it might be have close relationship with the production increased.During the grain filling, the activities of starch biosynthetic enzymes and relativeexpressions of their encoding genes showed unimodal patterns peaking around20DAA, suchas Sucrose synthase (SuSy), UDP-glucose pyrophosphorylase (UGPase), ADP-glucosepyrophosphorylase (AGPase), granule-bound starch synthase (GBSS), and starch branchingenzyme (SBE). Whereas, the activity of soluble starch synthase (SSS) and their transcript levels declined gradually through10DAA perhaps maybe due to peaking before10DAA.The activities of SS and UGPase increased significantly with the cultivar evolution, theactivities and relative expressions of AGPase and SSS genes increased pronounced with thecultivar evolution, especially for the newest cultivars such as Jinan17and Jimai22with thehighest activities and expression levels. However, the expression levels of GBSS and SBEvaried insignificantly with the released time. The analysis showed that SuSy, AGPase, SSS,GBSS and SBE were correlated significantly with the starch content in mature period, butUGPase was not correlated pronounced with the starch content; In starch synthesis process,the activities and gene expression levels of AGPase and SSS were more related to the starchcontent in mature seeds compared to that of GBSS and SBE, suggesting their more importantroles in starch biosynthesis. The activities of starch biosynthetic enzymes correlated totranscript levels of encoding genes in developing endosperm. Therefore, grain yield can beimproved in future breeding program by modification in starch physicochemical propertiesthrough screening of key enzyme activities and expressions involved in starch biosynthesisduring developing endosperm. |
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