Aleza Pablo, Garavello Miguel Fernando, Rouiss Houssem, Benedict Ana Cristina, Garcia-Lor Andres, Hernández Maria, Navarro Luis, Ollitrault Patrick
Departamento de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Valencia, Spain.
Concordia Agricultural Experimental Station, National Agricultural Technology Institute, Concordia, Entre Ríos, Argentina.
Front Plant Sci. 2023 Dec 8;14:1327872. doi: 10.3389/fpls.2023.1327872. eCollection 2023.
Citrus polyploidy is associated with a wide range of morphological, genetic, and physiological changes that are often advantageous for breeding. Citrus triploid hybrids are very interesting as new seedless varieties. However, tetraploid rootstocks promote adaptation to different abiotic stresses and promote resilience. Triploid and tetraploid hybrids can be obtained through sexual hybridizations using tetraploid parents (2x × 4x, 4x × 2x, or 4x × 4x), but more knowledge is needed about the inheritance pattern of tetraploid parents to optimize the efficiency of triploid varieties and tetraploid rootstock breeding strategies. In this work, we have analyzed the inheritance pattern of three tetraploid genotypes: 'Chandler' pummelo () and 'Cleopatra' mandarin (), which represent two clear examples of autotetraploid plants constituted by the genome of a single species, and the 'Sevillano' sour orange, which is an allotetraploid interspecific hybrid between and . Polymorphic simple sequence repeat (SSR) and single-nucleotide polymorphism (SNP) markers were used to estimate parental heterozygosity restitution, and allele frequencies for centromeric loci were used to calculate the preferential pairing rate related to the proportion of disomic and tetrasomic segregation. The tetraploid pummelo and mandarin displayed tetrasomic segregation. Sour orange evidenced a clear intermediate inheritance for five of the nine chromosomes (1, 2, 5, 7, and 8), a slight tendency toward tetrasomic inheritance on chromosome 3, and intermediate inheritance with a tendency toward disomy for chromosomes 4, 6, and 9. These results indicate that the interspecific versus intraspecific phylogenomic origin affects preferential pairing and, therefore, the inheritance patterns. Despite its high level of heterozygosity, the important preferential chromosome pairing observed in sour orange results in a limited diversity of the genotypic variability of its diploid gametes, and consequently, a large part of the genetic value of the original diploid sour orange is transferred to the tetraploid progenies.
柑橘多倍体与一系列形态、遗传和生理变化相关，这些变化通常对育种有利。柑橘三倍体杂种作为新的无核品种非常有趣。然而，四倍体砧木能促进对不同非生物胁迫的适应并提高恢复力。三倍体和四倍体杂种可通过使用四倍体亲本进行有性杂交获得（2x × 4x、4x × 2x或4x × 4x），但需要更多关于四倍体亲本遗传模式的知识，以优化三倍体品种和四倍体砧木育种策略的效率。在这项工作中，我们分析了三种四倍体基因型的遗传模式：“钱德勒”柚（）和“埃及艳后”橘（），它们代表了由单一物种基因组构成的同源四倍体植物的两个明显例子，以及“塞维利亚诺”酸橙，它是 和 之间的异源四倍体种间杂种。使用多态性简单序列重复（SSR）和单核苷酸多态性（SNP）标记来估计亲本杂合性恢复情况，并使用着丝粒位点的等位基因频率来计算与二体和四体分离比例相关的优先配对率。四倍体柚和橘表现出四体分离。酸橙在九条染色体中的五条（1、2、5、7和8）上表现出明显的中间遗传，在染色体3上有轻微的四体遗传倾向，而在染色体4、6和9上表现出中间遗传且有二体倾向。这些结果表明，种间与种内系统发育基因组起源会影响优先配对，进而影响遗传模式。尽管酸橙杂合性水平较高，但在酸橙中观察到的重要优先染色体配对导致其二倍体配子的基因型变异性有限，因此，原始二倍体酸橙的很大一部分遗传价值转移到了四倍体后代中。
