Potential for analytic breeding in allopolyploids: an illustration from Longiflorum × Asiatic hybrid lilies (Lilium)

Abstract

Ploidy level and intergenomic recombination was studied in interspeciWc hybrids between LongiXorum £ Asiatic lilies (LA hybrid) backcross to Asiatic parents in order to assess the possibility for analytic breeding in lily. By backcrossing the diploid (2n = 2x = 24) F1 interspeciWc hybrid between LongiXorum £ Asiatic lilies to Asiatic parents, 104 BC1 progeny plants were produced. Among these, there were 27 diploids, 73 triploids (2n = 2x = 36) and 4 aneuploids (2x ¡ 1, 2x + 2 or 2x + 3). In addition, by backcrossing triploid BC1 (LAA) plants to diploid Asiatic parents in 2x ¡ 3x and reciprocal combinations, 14 diploid BC2 progenies were produced. Genomic in situ hybridization (GISH) was performed to study the intergenomic recombination and karyotype composition. GISH indicated extensive intergenomic recombination among the chromosomes in LA hybrids. A large number of LongiXorum chromosomes were transmitted to the BC1 progenies from LA hybrids. However, very few LongiXorum chromosomes were transmitted from the BC1 triploid (LAA) plants to the BC2 progenies. The occurrence of diploid plants in the BC progenies of LA hybrids has opened the prospects of analytic breeding in lilies. In this approach, the selection of superior genotypes can be carried out at the diploid level and polyploid forms are synthesized from superior diploid parents. The advantages of analytic breeding are evident: (a) a maximum level of heterozygosity can be attained in the synthetic polyploids and (b) introgression can be achieved with a minimum of linkage drag. Based on GISH results the potential application of analytic breeding in lily allopolyploids has been discussed.

Genome constitution of Narcissus variety, ‘Tête-à-Tête’, analysed through GISH and NBS profiling

“…Similar phenomena have been recorded in Alstroemeria aurea 9 A. inodora (Kamstra et al 1999), Lilium longiflorum 9 Asiatic hybrids (Lim et al 2001) and Oriental 9 Asiatic hybrids of Lilium ( Barba-Gonzalez et al 2005). On the other hand, in some of the genotypes of Lilium species hybrids considerable amount of intergenomic recombination has been proved to occur during the origin of FDR gametes (Khan et al 2009). FDR 2n gametes have the unique property to transfer heterozygosity, epitasis and parental gene combinations intact of distant taxa in sexual polyploids.…”

Use of 2n Gametes in Plant Breeding

“…This results in a narrow selection of cultivars from mitotic polyploidization. In contrast, analytic breeding strategies allow intergenomic recombination to produce triploid Lilium varieties (Khan et al, 2009;Khan et al, 2010). Other examples of analytical breeding for crop improvement are vegetatively propagated species such as potato, sweet potato, cassava, among roots and tubers, and plantain/banana (Ortiz, 2002).…”

Relevance of unilateral and bilateral sexual polyploidization in relation to intergenomic recombination and introgression in Lilium species hybrids

“…GISH analysis proved that not only F1 OA hybrid studied here (951502-1; Table 2) resulted into intergenomic recombination but another F1 OA hybrid 952400-1 also resulted in chromosomal recombination in BC1 progenies when back crossed with some of the Asiatic cultivars (Barba-Gonzalez et al 2005). Similarly, it was found that LA hybrids produced 2n gametes and used either as male or female parents to get allotriploid progenies with certain amount of intergenomic recombination when backcrossed with various Asiatic cultivars (Zhou et al 2008;Khan et al 2009). …”

“…However, a cursory look at the literature indicates that triploid have been used successfully in crossing programs and could produce diploid or circa diploid progenies in 3x-2x or in reciprocal crosses Barba-Gonzalez et al 2006b;Proscevičius et al 2007). These diploid or circa diploid progenies are potentially useful for breeding at the diploid level (Khan et al 2009). Unlike the triploids the allotetraploids obtained after bilateral sexual polyploidization could be fertile and can produce progenies by selfing or crossing with other genotypes.…”