3.3 Growth advantages in vegetative and reproductive traits of early-season WR
The significant differences (p <0.001) in plant height were detected between the early- and late-season WR populations in the early-season common garden experiment (Figure 2), and the early-season WR populations were obviously taller than the late-season populations at different growth stages in all population pairs. In addition, significant differences were also detected in number of tillers per plant between the two-season WR populations at the early growth stages in the early season (Figure 3, p <0.001). However, no such significant differences in plant height and number of tillers per plant were detected in the late-season common garden experiment (Figure 2; Figure 3). Furthermore, differences in the leaf length and width were also detected (Figure S4; Figure S5). These results suggested significant differences in vegetative growth between the two-season WR populations in the early rice-cultivation environment, and the early-season WR populations showed advantages in vegetative growth.
Apparent differences in flowering time were observed between the WR population pairs (CDE/L and DCE/L) in the early-season common garden experiment (Figure 4). The early-season populations exhibited early flowering time compared to their corresponding late-season populations. In addition, results of flowering time at the stages of different proportions of flowered plants also supported the significant early flowering of the early-season populations in CDE/L and DCE/L population pairs (Figure 5). However, only minor differences in flowering time in CDE/L population pair were detected in the late-season common garden experiment (Figure S3), although no such differences in flowering was found in the early-season populations at different stages (Figure 5). These results indicated considerable divergences in flowering time between the two-season WR populations, and the early-season population was significant early flowering in native environment.
Also, results showed a relatively greater number of seeds per plant, higher seed setting ratios and 100-seeds weight in the early-season WR populations, in the early-season common garden experiment (Figure 6). For example, the early-season WR populations produced significant more seeds per plant than that of the late-season populations (Figure 6a), and had a significant higher ratio of seed sets than the corresponding late-season populations in CDE/L and DCE/L population pairs (Figure 6b). However, no such significant differences in reproductive traits were detected in the late-season common garden experiment (Figure 6a&b). These results suggested significant differences in reproductive traits between the two-season WR populations, and the early-season populations can produce more progenies than the late-season populations in the early rice-cultivation environment.
In addition, we found significant advantages in plant height (Figure 2), number of tillers per plant (Figure 3), and flowering time (Figure 5), reproductive traits (Figure 6) of all WR populations in the late rice-cultivation season (significance not shown), compared to that in the corresponding early season. These findings suggested that the late rice-cultivation environment may be more suitable for weedy rice growth, probably due to its high temperature and short daylength.