Rice panicle apical abortion (PAA) is a detrimental agronomic trait resulting in spikelet number reduction and yield loss. To understand its underlying molecular mechanism, we identified one recessive PAA mutant tutou2from the offspring of tissue cultures. The mutation locus was finely mapped to a 75-kb interval on the long arm of chromosome 10. Sequence analysis revealed a single nucleotide substitution of A to T at the 941 position of LOC_Os10g31910in tutou2, resulting in an amino acid change from isoleucine to phenylalanine. Complementation analysis showed that the degenerated panicle phenotype in tutou2was rescued in the transgenic lines. A phenotype similar to tutou2can also be obtained by LOC_Os10g31910knockout in wild-type rice. These results suggested that LOC_Os10g31910is the causative locus TUTOU2responsible for the tutou2PAA phenotype and probably also the locus of DEL1, previously documented as a leaf senescence gene. The significant phenotypic differences between del1and tutou2suggest that the locus DEL1/TUTOU2plays roles in both leaf and panicle development which were not considered fully in previous studies.