ValSten: a new wild species derived allotetraploid for increasing genetic diversity of the peanut crop (Arachis hypogaea L.)

Abstract

Introgression of desirable traits from wild relatives plays an important role in crop improvement, as wild species have important characters such as high resistance to pests and pathogens. However, use of wild peanut relatives is challenging because almost all wild species are diploid and sexually incompatible with cultivated peanut, which is tetraploid (AABB genome type; 2n = 4x = 40). To overcome the ploidy barrier, we used 2 wild species to make a tetraploid with the same allotetraploid genome composition as cultivated peanut. Crosses were made between 2 diploid wild species, Arachis valida Krapov. and W.C. Greg. (BB genome; 2n = 2x = 20) and Arachis stenosperma Krapov. and W.C. Greg. (AA genome; 2n = 2x = 20). Cuttings from the diploid F1 AB hybrid were treated with colchicine to induce chromosome doubling thus generating an induced allotetraploid. Chromosome counts confirmed polyploidy (AABB genome; 2n = 4x = 40). We named the new allotetraploid ValSten. Plants had well-developed fertile pollen, produced abundant seed and were sexually compatible with cultivated peanut. ValSten exhibits the same high resistance to early and late leaf spot and rust as its diploid parents. Notably, we observed morphological variations, including flower width and branch angles in the earliest generation (S0) of allotetraploids. A SNP array was used to genotype 47 S0 allotetraploids. The great majority of markers showed the additive allelic state from both parents (AABB). However, some loci were AAAA or BBBB, indicating homeologous recombination. ValSten provides a new, vigorous, highly fertile, disease resistant germplasm for peanut research and improvement.

Marker-assisted introgression of wild chromosome segments conferring resistance to fungal foliar diseases into peanut (Arachis hypogaea L.)

“…Since most Arachis wild species are diploid and A. hypogaea is an allotetraploid, the introgression of useful wild genes into peanut is not a trivial task. To overcome this, interspecific induced allotetraploid plants have been developed ( Burow et al., 2001 ; Fávero et al., 2006 ; Kumari et al., 2014 ; Leal-Bertioli et al., 2015b ; Leal-Bertioli et al., 2017 ; Gao et al., 2021 ; Bertioli et al., 2021b ). In this so-called tetraploid route ( Simpson, 1991 ), species with A and B genomes are intercrossed and the resulting sterile hybrid (AB) is treated with colchicine to duplicate the chromosomes and restore fertility (AABB).…”

Spontaneous generation of diversity inArachisneopolyploids (Arachis ipaënsis×Arachis duranensis)4x replays the early stages of peanut evolution

“…This recurring inconsistency in the number of 45S rDNA sites detected indicates high genome instability in these distinct lineages distributed to both groups. One possibility is that 45S rDNA tandem repeats were lost or reduced in size in cyt-B3 and cyt-B7 in both IpaDur1 and IpaDur2; another is the remodeling of chromatin ( Liu and Wendel 2003 ; Neves et al 2005 ; Chiavegatto et al 2019 ) that altered probe hybridization or fluorescence detection (also see Gao et al 2021 ). These chromosomal changes are consistent with those observed in other recently formed allotetraploids ( Xiong et al 2011 ; Chester et al 2015 ) but contrasts very strongly to the higher cytogenetic stability generally observed in polyploid crops, including the natural allotetraploids, A. hypogaea and A. monticola ( Nascimento et al 2018 ; Bertioli et al 2019 ).…”