Studies on the varietal difference of harvest index in rice - Relationshipbetween harvest index and morphological characteristics and leaf color

To find useful indexes for the selection of new rice varieties having a hig h harvest index, the correlation of harvest index (HI) with morphological c haracteristics and leaf color was examined using 60 Japanese varieties (J g roup) and 20 high -yielding varieties bred in Asian countries (H group). In the J group, HI showed a positive correlation with leaf color (SPAD value, SV) and a negative correlation with plant length (PL) at the heading time. In the HI goup, HI showed a positive correlation with SV, but the correlat ion coefficient between HI and PL was not significant. The correlation betw een HI and culmlength (CL) was similar to that between HI and FL. HI showed a negative correlation with ear length (EL) in the J group, but significan tly positive correlation in the H group. There was a significantly positive correlation between EL/CL and HI in the H group. A multiple regression ana lysis was conducted to clarify the relationship between morphological chara cteristics and HI. A significant multiple correlation coefficient was obtai ned between HI and SV (X-1), PL (X-2) or EL/CL (X-3). The ratio of standard partial regression coefficient of X-1, X-2 and X-3 to HI was 54:15:31. Con sequently, it is considered that these morphological characteristics are us eful indexes to select varieties with a high harvest index.