Morphological Comparison of Progeny Derived from 4x‐2x and 4x‐4x Hybridizations of Lotus glaber Mill. and L. corniculatus L

Abstract

ble the chromosome number of 2x diploid Lotus species (2n ϭ 2x ϭ 12 or 14) for germplasm transfer to L.Unreduced gametes (2n gametes) from Lotus glaber Mill. (2n ϭ corniculatus: (i) autotetraploid production by colchi-2x ϭ 12) may aid intercrossing with L. corniculatus L. (2n ϭ 4x ϭ 24) to produce progeny with a greater heterotic advantage than progeny cine-induced chromosome doubling of 2x species, and derived from colchicine-induced {7-acetamido-6,7-dihydro-1,2,3,10-(ii) 2n gametes to create 4x interspecific hybrids between tetramethoxybenzo[a]heptalen-9(5H)-one} tetraploid (4x ) L. glaber. 2x and 4x species. Polyploidization can be achieved by The objective of this research was to compare progeny produced from somatic doubling of the chromosomes (asexual poly-4x with 2x (4x-2x ) and 4x with 4x (4x-4x ) crosses and determine if ploidization) or functional production of 2n gametes by 2n gametes had a heterotic advantage over normal gametes derived aberrations in the meiotic process by sexual polyploidifrom colchicine-induced tetraploids. Vegetative cuttings of the 2nzation (Camadro and Peloquin, 1980). Although both gamete-producing L. glaber genotype 204882-1 (2x 204882-1) were modes can double chromosome number, their relative treated with colchicine and successfully yielded an autotetraploid efficacy becomes evident when genetic variability, in-(2n ϭ 4x ϭ 24) of 204882-1 (4x 204882-1). Three randomly chosen breeding, heterozygosity, and epistasis are considered genotypes from the L. corniculatus germplasm MU-81 were used as maternal parents in crosses to 2x 204882-1 and 4x 204882-1. Progeny (Camadro and Peloquin, 1980; Iwanaga and Peloquin, produced from 4x-2x crosses were intermediate to or larger than their 1982). Almost all polyploid angiosperms arose primarily parents in their leaf and flower morphology. Progeny from 4x-4x through sexual reproduction from 2n gametes rather crosses were intermediate to or smaller than their parents in leaf and than through spontaneous doubling of somatic chromoflower size. Size of leaves and flowers of progeny from 4x-2x crosses somes (Harlan and de Wet, 1975). were similar to or larger than 4x-4x progeny. Morphological compari-Amphidiploid development from the interspecific hysons demonstrated that heterotic expression of progeny from 4x-2xbridization of 2x Lotus species followed by colchicinecrosses was greater than progeny from 4x-4x crosses. The results induced autotetraploidy has been successful (Somaroo indicate that the generation of interspecific L. corniculatus ϫ L.

Use of 2n Gametes in Plant Breeding

“…report that sexual polyploids have been much more useful for crop improvement than mitotic polyploids. Beuselinck et al (2003) has shown that 2n gametes from Lotus glaber may aid intercrossing with Lotus corniculatus to produce progeny with a greater heterotic advantage than progeny obtained from the colchicine induced tetraploid (4x) Lotus glaber. In alfalfa, McCoy & Rowe (1986) showed better breeding value of 2n gametes from the diploids than n gametes from chromosome doubled tetraploids.…”

Induction of Tetraploid Lotus japonicus and Interspecific Hybridization with Super‐Root‐Derived Lotus corniculatus Regenerants

“…On the other hand, tetraploid L. japonicus produced in our study had significantly shorter pods and fewer seeds per pod than the diploid L. japonicus . Beuselinck et al (2003) reported that pollen tube growth of the tetraploid was reduced to 32%, whereas pollen tube germination of the diploid was 90% in L. tenuis . In general, plants with doubled genomes have low fertility (Beuselinck et al, 2003).…”

“…Chromosome doubling through the application of spindle‐toxins, such as colchicine or oryzalin, is an established technique to create new autopolyploid varieties and overcome ploidy‐based hybridization barriers. Colchicine or oryzalin have been applied to various plant parts including roots (Sebastiampillai and Jones, 1976), apical meristems (Iyer and Randhawa, 1965; Beuselinck et al, 2003), and seedlings (Swenne et al, 1981; Schifino and Moraes Fernandes, 1987) to create novel tetraploid germplasm in various species. Artificial tetraploids produced by chromosome doubling facilitated gene transfer between species and genera (Simioni and Valle, 2009) and the creation of fertile interspecific hybrids between L. corniculatus and L. tenuis Waldst.…”

“…ex Willd. (Beuselinck et al, 2003). Interspecific hybridization has important applications for the improvement of Lotus pasture species (Bent, 1962; Somaroo and Grant, 1971, 1972; O'Donoughue and Grant, 1988; Castillo et al, 2012; Escaray et al, 2014), but there have been no reports of crosses between tetraploid L. corniculatus and chromosome‐doubled L. japonicus .…”

Seed pod shattering in the genus Lotus and its overcoming

“…Attempts to transfer the indehiscent pod trait from distantly related species via interspecific hybridization (Beuselinck et al 2003), diploid bridge species, amphidiploidy, backcrossing to birdsfoot trefoil or somatic hybridization have been promising. Genetic transformation by Agrobacterium tumefaciens has been carried out in Lotus, starting with the diploid L. japonicus (Handberg & Stougaard 1992).…”