Fine mapping and distribution analysis of hybrid necrosis genes Ne1 and Ne2 in wheat in China

Abstract

Hybrid necrosis of wheat is caused by two dominant complementary genes Ne1 and Ne2 present in normal phenotype parents and is regarded as a barrier to gene ow between crop species. However, the necrosis alleles still occur at high frequency in modern wheat varieties. In this study, we constructed two high-density genetic maps of Ne1 and Ne2 in winter wheat. In these cultivars, Ne1 was found to be located in a span interval of 0.50 centimorgan (cM) on chromosome 5BL delimited by markers Nwu_5B_4137 and Nwu_5B_5114, while Ne2 co-segregated with markers Lseq102 and TC67744 on 2BS. Statistical analysis con rmed that the dosage effect of Ne alleles also existed in moderate and severe hybrid necrosis systems, and the symptoms of necrosis can also be affected by the genetic background. Furthermore, we clari ed the discrete distribution and proportion of the Ne1 and Ne2 in China's major wheat regions, and concluded that introduced modern cultivars directly affect the frequencies of necrosis genes in modern Chinese cultivars (lines), especially that of Ne2. Taking investigations in spring wheat together, we proposed that hybrid necrosis alleles could positively affect breeding owing to their linked excellent genes. Additionally, based on the pedigree, we speculated that the Ne1 and Ne2 in winter wheat may directly originate from wild emmer and introduced cultivars or hexaploid triticale, respectively. Key MessageFlanking markers useful for identifying hybrid necrosis alleles were identi ed by ne mapping Ne1 and Ne2 and the distribution of the two necrosis genes was investigated in Chinese elite wheat varieties.

Understanding and overcoming hybrid lethality in seed and seedling stages as barriers to hybridization and gene flow

“…Hybrid weakness is characterized by the weak growth of seedlings compared to both parents and is typically observed in Oryza ( Chu and Oka, 1972 ; Chen et al., 2013 ; Nadir et al., 2019 ; Shiragaki et al., 2019 ), Capsicum ( Shiragaki et al., 2020b ; Shiragaki et al., 2021 ; Shiragaki et al., 2022 ), and Phaseolus ( Koinange and Gepts, 1992 ; Reiber and Neuman, 1999a ). Hybrid necrosis may refer to both types and is mainly used for the Triticum - Aegilops complex ( Tsunewaki and Kihara, 1962 ; Toxopeus and Hermsen, 1964 ; Mizuno et al., 2010 ; Zhang et al., 2022b ) and Arabidopsis ( Bomblies et al., 2007 ; Świadek et al., 2017 ). Such hybrid seedling lethality and other similar phenomena are observed in F 1 hybrid seedlings.…”

Genetic Cause of Hybrid Lethality Observed in Reciprocal Interspecific Crosses between Nicotiana simulans and N. tabacum

“…A typical example of postmating-prezygotic barriers is the cross-incompatibility between pollen and pistils [4][5][6][7][8][9][10][11]. Postzygotic barriers include hybrid seed abortion [4,, hybrid weaknesses [37][38][39][40][41][42][43][44][45][46][47], hybrid lethality [32,[48][49][50][51][52][53][54][55][56][57][58][59][60] or necrosis [61][62][63][64][65][66][67][68][69][70][71], and hybrid sterility [72][73][74][75][76]…”

Phenotypic characterization and gene mapping of hybrid necrosis in Triticum durum–Haynaldia villosa amphiploids

“…It is favorable for reproductive isolation but harmful to gene flow among species (Chen et al 2016 ). Weak hybrid necrosis typically leads to leaf necrosis and poor growth, whereas severe hybrid necrosis can result in premature death of leaves and even the entire plant (Hermsen 1963 ; Zhang et al 2022 ). The Dobzhansky–Muller model provides a widely accepted mechanism for the evolution of reproductive isolation: incompatible substitutions disrupt interactions between genes (Bomblies and Weigel 2007 ; Morgan et al 2020 ).…”