Relationship of Rate of Dry Matter Remobilization on Harvest Index and Yield of Medium Aged Rice Varieties

Rapid human population growth required more rice in future. Thus, it is important to increase yield potential of future rice varieties. As a physiological approach increasing rate of remobilization of assimilate as non-structural carbon to panicle, varietal variation of assimilate partitioning, quantify subsequent remobilization from leaf, sheath and stem to panicle, impact on partitioned dry matter on yield and harvest index are important to study. The field experiment was conducted in 3 consecutive seasons from 2020/21 Maha to 2021 Yala seasons in Rice Research and Development Institute (RRDI), Batalagoda.  Fifteen rice varieties were screened under irrigated condition. All cultural practices were done according to Department of Agriculture recommendations. Rate of Remobilization of Dry Matter (RRDM) of leaf, sheath and stem were calculated from flowering to maturity. All agronomic data were analyzed using STAR computer package (Statistical Tool for Agricultural Research, 2014) of IRRI, Philippines for general linear model, Duncan mean separation, Principal Component Analysis. Important yield related parameters clearly separated by stepwise regression analysis by model with strong R2, grain yield explained RRDM leaf and stem, total soluble solid in stem (brix value). Bw 367 and Bg 370 have most efficient translocation system among the tested varieties. Total soluble solid content of stem (Brix value) with harvest index are most suitable parameters that explain an efficient source sink balance as a phenotypic trait. Dry matter remobilization rate in stem and total soluble solid content of stem with greater harvest index are the most suitable phenotypic traits to break through the yield potential in rice breeding programs.