THE INHERITANCE OF2nPOLLEN FORMATION IN DIPLOID ALFALFAMEDICAGO SATIVA

Abstract

The inheritance of 2n pollen formation was studied in two diploid clones of alfalfa, Medic-ago suriva L. The two clones consistently produced a high frequency of 2n pollen, and they also porduced good seed set when used as males in 4.r-2x crosses due to the functioning of 2 n ( 2 x ) pollen. For the inheritance study the two clones were crossed with diploid clones of cultivated alfalfa at the diploid level (CADL), and with several clones of diploid M. fulcura. In segregating families, plants that produced a high frequency of 2n pollen were identified by good seed set when used as males in 4.r-2.r crosses, andlor by bimodal pollen sizes. Plants that produced 4% or more 2n pollen generally produced greater than one seed per pollination in 4x -2x crosses, and these plants were considered 2n pollen producers. Analysis of self, F,, F, and backcross (BC) families indicated 2n pollen formation was controlled by a single recessive gene, designated rp (restitution pollen). An allelism test indicated 2n pollen formation was controlled by the same recessive gene in both clones. Although there was considerable variation in the frequency of 2n pollen in rplrp plants grown in different environments, all rplrp plants consistently produced a significant frequency of 2n pollen (greater than 4%). Simple genetic control of 2n pollen formation has important implications in the evolution of the genus Medicago. In addition, 2n pollen formation controlled by a single gene may have potential application in the breeding of highly heterozygous tetraploids and in the efficient transfer of germplasm across ploidy levels.On a etudie la transmission genetique de la capacite de formation de pollen 2n chez deux clones diploi'des de luzerne Mcdic.clgo sutiva L.. Les deux clones ont constamment fourni un haut taux de pollen 2n ainsi qu'une bonne production de semences lorsqu'utilises comme miles dans des croisements 4x-2x ceci etant attribuable a I'action du pollen 2n(2.r). Pour cette etude on a croise les deux clones avec des clones diploldes de luzerne cultivee au niveau diploide (CADL) et avec plusieurs clones du diploi'de M. fillc,clro. Lors de la separation des familles, les plants qui ont fourni un haut taux de pollen 2t1 ont ete identifies par une bonne production de semences lorsque utilises comme miles dans les croisements 4.r-2.r, ou encore par les dimensions bimodales du pollen. Les plants qui fournirent 4% ou plus de pollen 2n ont generalement fourni plus d'une graine par pollinisation dans les croisements 4 x -2 x , et ces plants ont ete retenus comme fournisseurs de pollen 2 n . L'analyse des familles des autopollinises, des F,, des F, et des retrocroisements (BC) a indique que la formation du pollen 2n etait imputable e un seul gene recessif, nomme rp (restitution pollen). Un test d'allelisme a revele que la formation de pollen 2n etait imputable au m6me gene recessif chez les deux clones. Quoiqu'on air note une variation importante du taux de formation de pollen 2n chez les plants rplrp cultives dans des environnements differents,...

Use of 2n Gametes in Plant Breeding

“…Moreover, frequencies may vary in different populations, within a certain genotype and during time (season) due to environmental fluctuations (Bani-Aameur et al, 1992;Crespel et al, 2006;McCoy, 1982;Ortiz et al, 1998;Ortiz & Vulsteke, 1995;Parrott & Smith, 1984;Pécrix et al, 2011;Veilleux et al, 1982). In Table 2, some recently published data on 2n gamete frequency in different (hybrid and non hybrid) populations are given.…”

Meiosis-Driven Genome Variation in Plants

“…For example, the wheat msg gene [165], barley tri gene [171], and maize el gene [172] were found to condition the formation of unreduced eggs, but not to affect the formation of normal haploid male gametes (sperm). In diploid alfalfa (Medicago sativa), two single recessive genes, rp (restitution pollen) and jp (jumbo pollen), condition 2n pollen formation by disorientation of spindles at metaphase II and failure of cytokinesis at the second division [173,174]. In the cultivated potato (Solanum tuberosum) and related diploid Solanum species, meiotic restitution appears to be associated with asynapsis and desynapsis [129,175], abnormal spindle orientation at the second division [175][176][177], and abnormal cytokinesis [177].…”

Sexual polyploidization in red clover

“…In the work of Parrott & Smith (1984) for instance, 3% of the diploid red clover plants analyzed produced more than 1% GP (reaching up to 84% GP). Other authors also reported variable GP production, ranging from 4 to 37% in alfalfa (McCoy, 1982), and from 1 to 11% in Lotus tenuis (Negri, 1992). In this study, the range of variation in GP production in the initial population (0 to 9.07%) was lower than those values cited above, but the percentage of individuals producing more than 1% GP (19.91%) was remarkably higher in comparison to the red clover population studied by Parrott & Smith (1984).…”