Selfing and selection in alfalfa breeding programmes

Abstract

Data from about 7000 alfalfa plants were analyzed, 1) to evaluate the inbreeding depression after selfing and the recovery of vigour following open pollination, 2) to estimate the correlations between sister generations and between sister and maternal generation . Results can be summarized as follows : 1) inbreeding depression, measured on a green matter basis, was very marked in all selfed generations, but most severe in 12' In 1 . there was a recovery of vigour to the I l level due to unavoidable selection for vigour and self-fertility in 12 . Among three varieties the most marked depression of vigour was observed in Lahontan, the variety with narrowest genetic background ; 2) the correlation coefficients were higher in 1963 than in 1964 but the lack of uniformity does not allow any conclusion .

Heterosis and Inbreeding Depression in Autotetraploid Rye

“…Heterogenic loci of this kind might be expected to obtain particularly frequently within young autotetraploid populations with a narrow genetic basis. But since the same tendency to an S-shaped slope of the depression curve also occurs in some materials of alfalfa (TORSSELL, 1948;PANELLA and LORENZETTI, 1966) a third interpretation should be considered. When there occur a large number of dominant genes with similar and limitedly additive effects they may interact with diminishing returns when they increase in number and, consequently, their number may be decreased to a certain extent without any great influence on performance (RASMUSSON, 1933).…”

Self-Fertilization, Inbreeding, and Yield in Alfalfa Seed Production

“…In alfalfa, inbreeding depression has been shown to impact various stages of the life cycle, including seed production and hay yield ( Aycock and Wilsie, 1968 ; Busbice, 1968 ; Melton, 1970 ; Gallais, 1984 ; Riday et al, 2017 ). In addition, selfing has also been shown to reduce the rates of flowering and winter survival ( Riday et al, 2017 ), increase the number of days to bloom ( Aycock and Wilsie, 1968 ; Posler, 1969 ), reduce plant height ( Panella and Lorenzetti, 1966 ; Gallais, 1984 ; Riday et al, 2017 ), and generally reduce disease tolerance ( Koffman and Wilsie, 1961 ). The relative impact of inbreeding depression on the different stages of the alfalfa life cycle has not yet been quantified.…”

Selection for Seed Set in Noninbred and Partly Inbred Populations of Alfalfa

“…Busbice ( 1968), pointing out that the level of inbreeding in the developingzygote had a profound effect on $eed setting, proposed that selection for improved fertility during the inbreeding process would probably remove the fertility barrier and could be a useful method for detecting the genotypes possessing the most favorable alleles for seed set. Panella and Lorenzetti (1966) found an increase in forage yield in the Ss generation over the Sz. This increase was transmitted to outcross progenies involving 53 parents.…”