Assessment of haplotypes of Pi21 in 325 rice accessions and blast inoculation of the pi21-2428-containing varieties. (A) A total of 11 haplotypes were identified among 325 rice accessions. The haplotypes were named based on insertion/deletion patterns. Pi21-NPB, Pi21(-9), and Pi21(-24/-15) were identical to the previously identified haplotypes B, C, and H, respectively [16]. Open boxes represent exons, lines represent introns, and dotted lines represent deletions. Numbers above the diagrams indicate positions of deletions corresponding to the Pi21-NPB allele, and numbers below the diagrams represent the start and end nucleotide positions of exons of each allele. (B) Phenotypes of the pi21-2428-containing varieties 02428, ShuHui881 (SH881), Yong4 (Y4), and ZhengDa4Hao (ZD4) inoculated with M. oryzae isolates 2Y838-1, 501-3, CHNOS, IR16-1, KJ201, RB6, and RB22, respectively. Rice varieties LXG and MengGuDao (MGD) were used as highly susceptible controls.