Selection of the Most Promising Rice Lines for Water-direct Seeding Cultivation
Jong Gun Won and Tomohiko Yoshida*
(Faculty of Agriculture, Kyushu University)
To select rice lines adapted to direct-seeding, firstly several lines were selected at the early stage based on root thickness with lodging tolerance using seed pack growth pouch seedling method (Fig.1). Among the root parameters of SPGP seedlings, only root thickness had a high positive correlation with pushing resistance, and the correlation coefficient was higher than those in the field test. Based on the root thickness in SPGP and pushing resistance in field test, 12 lines were selected from the 80 breeding lines. Strong positive correlations were observed between pushing resistance and culm thickness in field test (0.809**) or root thickness in SPGP seedlings (0.694**) from these 12 lines and 13 check cultivars (Table 1). Considering root and culm thickness, grain yield and amylose content, four promising lines (L38, L42, L53 and L76) were further selected for water-seeding cultivation or candidate parental lines for next crossing cycle.
To select good combiners for direct-seeding, the general (GCA) and specific (SCA) combining ability were estimated using the 4 x 3 factorial crossing (Design II). GCA was significant for culm length, culm thickness, panicle length, 1000-graing weight and grain yield, indicating the importance of additive gene effects for these traits (Table 2). In this study, Lemont and L42 had positive GCA for yield, culm thickness, panicle length and they could contribute to developing cultivars for direct-seeding. In the study to determine the adaptability in direct-seeding, five genotypes including 4 selected lines were grown under various environmental conditions (year, location, plant density, nitrogen). The differences in adaptability among genotypes were evaluated by a regression method and L42 showed high average yield and good adaptability at both low-yielding and high-yielding conditions (Fig. 2). Generally, L42 exhibited heavier 1OOO-grain weight and higher yield compared to the other lines across all environmental conditions (Table 3).
The palatability of L42 was similar to that of Koshihikari, implying that L42 is a very promising line for water-direct seeding or can be used as a cross parent of the breeding program.
Fig. 1. The relationship between root thickness which was scored by the degree of thickness (1 thin - 3 thick) of SPGP seedlings and pushing resistance in the field trial (←selected 12 lines). **: significant at 0.01 level.
Table 1. Relationship among several
characteristics and pushing resistance
Characteristics Pushing resistance
Root thickness 0.694**
Culm thickness 0.809**
Culm length -0.454**
Panicle number -0.563**
Plant dry weight 0.221ns
**, ns: Significant at the 0.Ol probability
level and not significant, respectively.
Table 2. Estimates of GCA* effects for several traits of direct-seeded rice.
Parents Culm Panicle No. of No. of 1000-G Grain
thickness length panicles spikelets weight yield
(mm) (cm) (g) (g plant-1)
Ansanbyeo -O.68 0.13 -0.29 -0.9 0.23 -5.7
Hinohikari -0.31 -2.31 0.46 -25.9 0.65 -15.5
Lemont 0.99 2.44 -O.17 26.9 -0.88 21.2
L 38 -0.48 1.35 -0.34 -4.5 -0.16 -9.4
L 42 0.23 0.05 0.06 -3.2 1.74 9.5
L 53 0.09 0.32 -O.01 6.8 -0.86 -7.9
L 76 0.16 -1.08 0.29 1.0 -0.72 7.8
* : General combining ability.
Fig. 2. Regression lines and population mean yield of five genotypes of rice grown under different environmental conditions (G1: Line 38, G2: Line 42, G3: Line 53, G4: Line 76 and G5: Hinohikari).
Table 3. Mean yield and yield components of five genotypes across all environmental
Genotype Panicle Spikelet 1000-grain Grain Grain Palatability2
(no. m-2) (no.m-2) Welght(g) filling(%) yield(gm-2)
Line 38 320 ab1 37047 a 20.7 c 79.1 b 605 b -2.44
Line 42 300 b 33303 ab 25.3 a 81.0 b 744 a -0.12
Line 53 267 b 30897 ab 19.7 d 82.2 ab 530 c 0.19
Line 76 259 b 29468 ab 21.0 c 85.7 a 501 c -2.38
Hinohikari 364 a 32205 ab 22.4 b 84.8 a 557 bc -
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Mean 302 32584 21.8 82.6 587 -
1) Within columns, means followed by the same letter are not significantly different
at 5 % using Duncant's multiple range test.
2) The reference cultivar for the sensory test was Koshihikari.