Selection of cultivars for direct seeding in rice based on the developmentof root system analysis

This study was carried out to develop a useful method for selection of prom ising cultivars for direct seeding cultivation based on the development of root system analysis. To select cultivars at the early stage for root syste m with lodging resistance, transparent polyethylene seed pack growth pouch (SPGP) was used. Among the root parameters of SPGP seedlings, only root thi ckness of F4 lines was positively correlated with pushing resistance of fie ld test (r=0.46**). The root thickness of SPGP also had a positive correlat ion with root thickness of field test (18 Days After Seeding : r=0.348*, 30 DAS : r=0.512**, respectively). Root thickness of SPGP, 18 DAS and 30 DAS seedlings in field were positively correlated with panicle weight (r=0.336* *, r=0.298*, r=0.341**, respectively). Therefore, we can also select panicl e weight type by root thickness of SPGP. In path analysis, the direct effec t of root thickness of SPGP on pushing resistance occupied 63% (0.289) of t otal coefficient of correlation (0.458). However, that of 18 DAS seedlings of field test on pushing resistance occupied only 39 % (0.1255) of total co rrelation coefficient (0.3189), and the direct effect of 30 DAS seedlings w as negative. From these results we concluded that the root thickness of SPG P could be a very useful selection index for lodging resistance in direct s eeding cultivation.