Rodríguez et al. identified and validated the qDOR-9 locus in sorghum as a key regulator of seed dormancy, linking it to ABA sensitivity and flowering time, and highlighting its unintended association with PHS susceptibility due to historical breeding for dwarfism.

Keywords: Dwarf‐1, QTL mapping, grain sorghum, pre‐harvest sprouting, seed dormancy, sorghum conversion program

This study identifies qDOR-9 as a key regulator of seed dormancy in sorghum and links its inheritance to breeding-driven susceptibility to pre-harvest sprouting. By clarifying its association with Dw1 and ABA sensitivity, the work offers a path toward breeding sprouting-resistant lines without compromising key agronomic traits. – Rodriguez

Pre-harvest sprouting (PHS) in sorghum, caused by premature grain germination, poses a significant threat to grain quality and yield. Domestication and breeding practices—particularly the U.S. Sorghum Conversion Program (SCP)—have inadvertently contributed to increased PHS susceptibility by introducing low-dormancy alleles linked to desired traits like reduced plant height and photoperiod insensitivity. In this study, conducted by researchers from CONICET, la Universidad de Buenos Aires, la Universidad de la República and Advanta Seeds, the QTL qDOR-9 was mapped using a Redlan × IS9530 RIL population, was shown to influence seed dormancy significantly. Validation with QTL-NILs carrying the IS9530 allele revealed decreased germination index (GI), implicating qDOR-9 as a key dormancy regulator. Interestingly, qDOR-9 co-localizes with the plant height locus Dw1, and historical linkage drag from the SCP donor line (DYM) appears to have propagated low-dormancy alleles in elite cultivars. This genetic linkage explains why dwarf lines are often more PHS-prone than taller ones, a problem overlooked due to the dry environments under which the SCP was conducted.

Further analysis of qDOR-9 revealed its potential role in modulating ABA sensitivity in seeds, with correlations between ABA-induced germination inhibition (EGI) and natural PHS levels supporting this hypothesis. The QTL region includes genes potentially involved in ABA signaling, including sorghum orthologues of known dormancy regulators. Synteny with the rice dormancy QTL qSD5.2 suggests possible cross-species conservation. Additionally, qDOR-9 overlaps with qDTF-9, a QTL affecting flowering time, raising the possibility of pleiotropy or tight linkage. These findings underscore the need for fine mapping to disentangle these traits and enable targeted breeding or gene editing strategies to enhance dormancy without compromising yield-related traits such as stature or flowering time.

SorghumBase examples: 

Figure 1: Several phenotypic traits associated with the QTL in this study overlap this SNP (Chromosome position 9:56182121, BTx623, Sorghum_bicolor_NCBIv3) as shown above. These include plant height, days to flowering, and sprouting (emergence rate, time to emergence).
Figure 2: Another SNP (Chromosome position 9:58523851, BTx623, Sorghum_bicolor_NCBIv3), belonging to the QTL in this study is displayed above with corresponding phenotypic traits from this study: days to flowering, germination rate, plant height.
Figure 3: A chromosome-wide breakdown of the locations of features associated with tannin content in this study based on the QTL map locations available in the Sorghum QTL Atlas.
Figure 4: A chromosome-wide breakdown of the locations of features associated with emergence rate (sprouting) in this study based on the QTL map locations available in the Sorghum QTL Atlas.
Figure 5: A chromosome-wide breakdown of the locations of features associated with time to emergence (sprouting) in this study based on the QTL map locations available in the Sorghum QTL Atlas.
Figure 6: A chromosome-wide breakdown of the locations of features associated with flowering time in this study based on the QTL map locations available in the Sorghum QTL Atlas.
Figure 7: A chromosome-wide breakdown of the locations of features associated with days to flowering in this study based on the QTL map locations available in the Sorghum QTL Atlas.

Reference:

Rodríguez MV, Sánchez DH, Glison N, Ríos CD, Demkura PV, Álvarez Correa CC, Fernández LG, Filippi CV, Heinz R, Pardo P, Rentería S, Guillaumet L, Benech-Arnold RL. Introgression of dwarfing allele dw1 reduced seed dormancy and increased pre-harvest sprouting susceptibility in grain sorghum converted lines. Plant Biotechnol J. 2025 May;23(5):1783-1797. PMID: 40089970. doi: 10.1111/pbi.70007. Read more

Related Project Websites: 

Tall (left, IS9530) and short (right, Redlan) grain sorghum lines are pre-harvest sprouting (PHS) resistant and susceptible, respectively. This association is caused by genetic linkage of a low dormancy allele with dwarfing allele dw1. Many converted lines (including Redlan and BTx623) received both dw1 and the low dormancy allele from the Yellow milo, used as donor parent.
Detail of a sprouted panicle from sprouting susceptible parent line “Redlan”, showing elongated coleoptiles and fungi proliferation.
Field trial (at the Facultad de Agronomía, UBA) for phenotyping and genotyping. Red-trained sorghum lines used in this study: IS9530 (tall, PHS-resistant, back to the left), Redlan (short,PHS-susceptible,) and NILs (same plant phenotype as Redlan, but more dormant). IS9530 panicles were covered with paper pags to avoid bird predation from the top.
Main authors of this study, Verónica Rodríguez (left) and Roberto Benech-Arnold (right), in the experimental field at the Facultad de Agronomía, Universidad de Buenos Aires. Plants are NILs carrying the dw1 allele (from Redlan) and the dormant allele (from IS9530 line, derived from ICRISAT).
Verónica Rodríguez, author of this study, in the field trial.
Pre-processing of panicles for germination trials under controlled conditions for dormancy testing.
Genetic Dissection of Seed Dormancy in Sorghum Reveals qDOR-9 as a Key Locus Linked to ABA Sensitivity, Flowering Time, and Pre-Harvest Sprouting Susceptibility

Leave a Reply

Your email address will not be published. Required fields are marked *