Perennial rice regrowth responds to stubble characteristics, temperature and genotype

Abstract

Problem or context

The performance of perennial grain crops is highly dependent upon the successful appearance of new shoots for the next regrowth cycle.

Objective or research question

This paper examines the associations among stubble characteristics in the previous cycle, the prevailing conditions during regrowth, genotypic variation in capacity to regrow, and shoot number in the next regrowth cycle.

Methods

An experiment with perennial rice was conducted under paddy conditions at Menghai, Yunnan, China. A split-split design was used, involving 3 regrowth cycles (2020–21 dry season (DS), 2021 wet season (WS), and 2021–22 DS), 4 genotypes (PR107, PR101, PR23, PR25), 5 sampling times (14, 28, 42, 56, 70 days after stubble cut-off), and 3 replications. Crop phenology; stubble dry matter (DM), soluble sugar [Sugar] and starch concentration [Starch]; exposure to low temperature (Cold); and shoot number were recorded.

Results

Shoot number varied substantially with season (whether WS or DS), the characteristics of stubble from the previous cycle (especially stem DM, [Total sugar], [Total starch]), and exposure to Cold during shoot development in the DS (based on deviations of minimum temperature below the base temperature for rice of 13.5 °C). Genotypes also differed in their patterns of response, with PR101 showing a steady increase in shoot number, while PR25 showed a strong lag phase before a rapid increase to final shoot number.

Conclusions

Regrowth was influenced by the characteristics of stubble from the previous cycle, especially when environmental conditions were limiting, such as cold in 2020–21 DS. The contrasting patterns of increase in shoot number suggest genotypic differences in response to low temperature during the DS, and/or in apical dominance and the capacity to release axillary buds for growth of new shoots. Further study is needed on these aspects.

Implications or significance

Improved cold tolerance could allow perennial rice to be grown in more temperate areas, where annual rice is already a major crop. Axillary bud dormancy could add to this, by restricting regrowth until environmental conditions were favourable for growth, not only for cold (winter dormancy) in more temperate environments such as central China, but also for drought and heat (summer dormancy) in more tropical environments such as Sub-Saharan Africa.