Grain filling in rice vis‐a‐vis ethylene production in the spikelets

Rice being a staple food worldwide necessitates that its production be enhanced to meet the demands of the continuously increasing population. However, the productivity advantages associated with breeding programs have reached their maximum. The production plateau brought on is not due to a lack of genetic potential but rather is due to the inhibition of grain filling by ethylene produced in large quantities in the heavy‐panicle‐ and compact‐panicle‐type varieties developed thus far, as evidenced by the application of ethylene synthesis inhibitors and ethylene action blockers. The inhibition could be a result of the accumulation of HCN, a byproduct of ethylene biosynthesis. In addition, inhibition of grain filling by excessive amounts of ethylene may also be the result of enhanced synthesis/expression of rice starch regulator 1, an ethylene‐responsive element binding protein that inhibits expression of the genes encoding type I starch‐biosynthesizing enzymes. In the past decade, miRNAs have also been found to inhibit grain filling by targeting starch‐biosynthesizing enzymes and the transcription factors required for their expression. Hence, biotechnological interventions should be designed to (1) decrease ethylene production and CN− accumulation and (2) downregulate/knockdown the expression of miRNAs unfavorable to grain filling in a spikelet/seed‐specific manner to enhance rice production. Core Ideas The breeding program has reached a plateau in increasing rice production. Poor grain filling in the inferior spikelets due to high ethylene production thwarts realizing the yield potential. Poor filling of the rice grains is somewhat mediated by rice starch regulator 1 (RSR1) induced by ethylene. Management of ethylene and miRNAs levels in the spikelets could enhance rice production.