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Sesame is a labor intensive crop with limited mechanized harvesting mainly due to the seed shattering (SS) trait. In this study, we performed a genetic analysis of the seed-shattering resistance (SR) trait with a SR sesame mutant 12M07. Unlike the SS type, the parenchyma cells in the abscission zone of the 12M07mutant are arranged loosely but adhere to the seed coat. Inheritance analysis of six generations derived from 12M07(SR)×Xiangcheng Dazibai (SS) showed that the SR trait is recessive and controlled by a single gene pair. Association mapping of the F2population with 888,619 variants (single-nucleotide polymorphisms (SNPs) and insertion-deletion (InDels)) and 31,884 structural variations (SVs) determined that only SV12002 in the 5´ upstream region of gene Sindi0765000(named SiHEC3) in Chr.3 was significantly associated with the SR trait. SiHEC3encodes the bHLH transcription factor. A 1,049 bp deletion occurred in the 5´ UTR of Sihec3in 12M07. SiHEC3is mainly expressed in developing placental tissues, with the expression peaking in capsules at 45 days after pollination. A dual-luciferase reporter assay in tobacco confirmed that the promoter activity of Sihec3was reduced because of the deletion of the 1,049 bp promoter sequence. Protein–protein interaction network analysis showed that HEC3 is co-expressed with nine key proteins, such as SHATTERPROOF1 (SHP1) and SEEDSTICK (STK) which participate in the secondary wall biosynthesis of the abscission layer in plants. The findings of this study show the important function of Sihec3corresponding with the SR trait and supply the genetic information for breeding new varieties that are amenable to mechanized harvesting in sesame and other crops.

Sesame Fusarium wilt (SFW), caused by Fusarium oxysporumf. sp. sesami(Fos), is one of the most devastating diseases affecting sesame cultivation. Deciphering the genetic control of SFW resistance is pivotal for effective disease management in sesame. An inheritance study on a cross between the highly resistant variety Yuzhi 11 and the highly susceptible accession Sp1 using a Fospathogenicity group 1 isolate indicated that resistance was conferred by a single dominant allele. The target locus was located in a 1.24 Mb interval on chromosome 3 using a combination of cross-population association mapping and bulked segregant analysis. Fine genetic mapping further narrowed the interval between 21,350 and 21,401 kb. The locus Sindi_0812400was identified as the SFW resistance gene and officially designated SiRLK1. This gene encodes a specific malectin/receptor-like protein kinase with three putative tandem kinase domains and is considered a kinase fusion protein. Sequence analysis revealed that a high proportion (49.44%) of variants within the locus was located within the kinase domain III, and several of which were evidently associated with the diversity in SFW response, indicating the critical role of kinase domain III in expression of disease resistance. These findings provide valuable information for further functional analysis of SFW resistance genes and marker-assisted resistance breeding in sesame.

Fusariumwilt is a common fungal disease in sesame caused by Fusarium oxysporumf. sp. sesami(FOS). To determine the toxin production profiles of the FOSisolates with different pathogenicity levels under various culture conditions, we assessed the content variation of fusaric acid (FA) and 9, 10-dehydrofusaric acid (9, 10-DFA) produced by the four representative FOSisolates. Results indicated that the concentration of FA reached to a maximum of 2848.66 ​μg/mL in Czapek medium, while 9, 10-DFA was mainly produced in Richard and Low-carbon Richard medium. The concentration of 9, 10-DFA on Richard culture medium varied from 0 ​μg/mL to 716.89 ​μg/mL. Of the five culture media used in this study, Czapek culture medium was the most conductive to produce FA. FA production was significantly affected by culture medium, culture time, and their interactions. Results suggest that there is no correlation between toxin production and pathogenicity level of FOSisolates. These findings provide key information for the mechanism analysis of FOS- sesame interaction and pathogen control.