Maturity groups and growing seasons as key sources of variation to consider within breeding programs for high yielding rice in the tropics

Abstract

Differences in crop performance between seasons has raised concerns on whether or not contrasting rice varieties should be grown in each season in the tropics. Solving this question requires evaluation if key plant traits subtending grain yield are expressed similarly across seasons. Within each dry season (DS) and wet season (WS), one approach to address the issue was to group 32 high-yielding and contrasted cultivars with respect to crop duration, and to consider the crop cycle as two distinct phases: the first one from early vegetative to flowering (pre-flowering) and the second one from flowering to maturity (post-flowering). For each of these two phases, one key descriptive parameter was identified, the potential sink size (PSS) at flowering for the pre-flowering phase, and the grain filling rate (FR) for the post-flowering phase. Significant correlations were observed for grain yield with both PSS and FR within maturity groups in both seasons, indicating the strong effect of both phases in grain yield establishment. Finally, relevant traits in the DS were those favoring light capture along the whole crop cycle in both maturity groups. Traits for the WS differed among maturity groups. Traits for the early maturity group were also those favoring light capture, while the same traits were non desirable for the medium and late maturity groups, for which delayed leaf senescence and short plant height were identified. The difference between relevant traits highlights the need of developing distinct breeding programs respective of the growing seasons and maturity groups.