201 Czech Journal of Genetics and Plant Breeding, 58, 2022 (4): 201–209 Original Paper https://doi.org/10.17221/110/2021-CJGPB Genetic variability for aluminium tolerance in sunfower (Helianthus annuus L.) Vivek Kumar Singh 1 , Subhash Chander 1 *, Ram Kumar Sheoran 1 , Anu 1 , Om Parkash Sheoran 2 , Ana Luisa Garcia-Oliveira 3,4 1 Department of Genetics and Plant Breeding, College of Agriculture, CCS Haryana Agricultural University, Hisar, Haryana, India 2 Department of Mathematics and Statistics, College of Basic Sciences and Humanities, CCS Haryana Agricultural University, Hisar, Haryana, India 3 Excellence in Breeding (EiB), CIMMYT c/o ICRAF, Nairobi, Kenya 4 Department of Molecular Biology, Biotechnology and Bioinformatics, College of Basic Sciences and Humanities, CCS Haryana Agricultural University, Hisar, Haryana, India *Corresponding author: subhash_chander@hau.ac.in Citation: Singh V.K., Chander S., Sheoran R.K., Anu, Sheoran O.P., Garcia-Oliveira A.L. (2022): Genetic variability for alumi- nium tolerance in sunfower (Helianthus annuus L.). Czech J. Genet. Plant Breed., 58: 201–209. Abstract: Breeding for aluminium (Al) tolerance is a vital approach for enhancing the productivity of feld crops in acidic soil regions where Al toxicity seems to be the most restraining factor for crop performance. Sunfower is generally considered extremely sensitive to Al toxicity; although no comprehensive information on the evaluation of sunfower genotypes for Al tolerance is available. In this study, 50 sunfower genotypes (set-I and set-II) were evalua- ted for Al tolerance at the seedling stage under hydroponic conditions. Substantial genetic variability in Al tolerance was observed among the studied genotypes. High estimates of heritability were obtained for both the total root len- gth (TRL) and root regrowth (RRG), together with high estimates of genetic advance. A cluster analysis separated the genotypes into fve diferent groups among the studied germplasm, the genotypes; NDLR-06 and EC-601861 were observed to be highly Al tolerant in terms of root regrowth under Al stress. In conclusion, the fndings lreveal the complex mechanisms of Al tolerance in sunfower and may help to fnd new genetic resource for the improvement of Al tolerance in sunfower breeding. Keywords: Al toxicity; characterization; stress; sunfower; variability Aluminium (Al) is the third most abundant element in the Earth’s crust, but very small quantities appear in soluble forms (Rengel 1992). Soil acidification enhances the Al dissolution in different ionic forms [Al(OH) 2 + , Al(OH) 2+ and Al(H 2 O) 3+ ] of which Al 3+ is considered potentially phytotoxic to plants (Kin- raide 1997). Thus, Al toxicity is a critical obstacle for crop productivity on acidic soils which cover approximately 49% of the worldwide cultivated land (Waquil & Matzenbacher 2000). At the seedlings stage, Al ions rapidly inhibit the root elongation, and the absorption of water and nutrients, resulting in an inflated root apex and in the poor development of the root system (Delhaize & Ryan 1995; Ciamp- orova 2002). In acidic soils, a significant reduction in both crop production and its quality has been observed due to Al toxicity. There is considerable evidence to indicate that different plant species adopted external and/or internal mechanisms to de- toxify the detrimental effects of Al toxicity (Garcia- Oliveira et al. 2016a). Among these mechanisms, the prominent role of organic acid exudates from the roots against Al toxicity has been well established (Ma et al . 2001; Kochian et al. 2005; Garcia-Oliveira