ABSTRACT
INTRODUCTION: Peanut is susceptible to infection of Aspergillus fungi and conducive to aflatoxin contamination, hence developing aflatoxin-resistant variety is highly meaningful. Identifying functional genes or loci conferring aflatoxin resistance and molecular diagnostic marker are crucial for peanut breeding. OBJECTIVES: This work aims to (1) identify candidate gene for aflatoxin production resistance, (2) reveal the related resistance mechanism, and (3) develop diagnostic marker for resistance breeding program. METHODS: Resistance to aflatoxin production in a recombined inbred line (RIL) population derived from a high-yielding variety Xuhua13 crossed with an aflatoxin-resistant genotype Zhonghua 6 was evaluated under artificial inoculation for three consecutive years. Both genetic linkage analysis and QTL-seq were conducted for QTL mapping. The candidate gene was further fine-mapped using a secondary segregation mapping population and validated by transgenic experiments. RNA-Seq analysis among resistant and susceptible RILs was used to reveal the resistance pathway for the candidate genes. RESULTS: The major effect QTL qAFTRA07.1 for aflatoxin production resistance was mapped to a 1.98 Mbp interval. A gene, AhAftr1 (Arachis hypogaea Aflatoxin resistance 1), was detected structure variation (SV) in leucine rich repeat (LRR) domain of its production, and involved in disease resistance response through the effector-triggered immunity (ETI) pathway. Transgenic plants with overexpression of AhAftr1(ZH6) exhibited 57.3% aflatoxin reduction compared to that of AhAftr1(XH13). A molecular diagnostic marker AFTR.Del.A07 was developed based on the SV. Thirty-six lines, with aflatoxin content decrease by over 77.67% compared to the susceptible control Zhonghua12 (ZH12), were identified from a panel of peanut germplasm accessions and breeding lines through using AFTR.Del.A07. CONCLUSION: Our findings would provide insights of aflatoxin production resistance mechanisms and laid meaningful foundation for further breeding programs.
ABSTRACT
Peanut stem rot caused by Athelia rolfsii is a serious soilborne disease worldwide and is becoming increasingly important in China. A total of 293 A. rolfsii isolates were collected from four representative peanut producing provinces in northern, central, and southern China. These isolates were assigned to 45 mycelial compatibility groups (MCGs) through pairing testing. The MCG diversity among isolates was greater in the southern sampled provinces compared with the northern provinces. A high level of genetic variability was found among the isolates from Guangdong Province in southern China. Variations were found in mycelial growth rate and sclerotial number, size, and dry weight of isolates sampled from places in different latitudes. Size and dry weight of sclerotia were positively correlated with latitude (P < 0.01), but the number of sclerotia was negatively correlated with latitude (P < 0.01). All tester isolates were pathogenic on peanut but varied in disease index. Inter-simple sequence repeat analysis and unweighted pair-group method with arithmetic average clustering resulted in three distinct clusters that were associated with the geographical location of the collection sites and sclerotial traits but were not associated with virulence of these isolates. These findings imply that genetic diversity, morphological traits, and virulence among A. rolfsii isolates varied in diverse geographical regions in China, and genetic diversity and sclerotial traits might be affected by latitude.
