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Day-neutral multiflora chrysanthemums can flower throughout the year without being influenced by daylength and have great application value in gardens. Studying heterosis and the genetic basis of important traits in day-neutral chrysanthemums can accelerate the breeding of new cultivars. In this research, a genetic population was constructed by crossing 135 F1 hybrid progeny from the day-neutral chrysanthemum '82-81-19' (female parent) and the late-flowering chrysanthemum '388Q-76' (male parent). Six traits, including abnormal (crown) bud, plant height, plant crown width, budding date, full flowering date, and number of petal layers, were selected for inheritance and heterosis analyses, and a single-generation major gene plus polygene mixed inheritance model was used to perform mixed inheritance analysis on these traits. The results indicated that the six traits were widely segregated in the F1 population, with the coefficient of variation (CV) ranging from 30% to 84%. The phenomena of heterosis and extra-parent segregation existed generally in F1 progeny, and the ratio of heterosis value of mid-parents (RHm) for the six traits was 45.5%, 2%, 2%, 6%, 6%, and −0.3%, respectively. The mixed genetic analysis showed that the abnormal (crown) bud and budding date were fitted to the B-3 model and controlled by two pairs of additive major genes. The plant height and plant crown width were fitted to the A-0 model, and no major gene was detected. The full flowering date was fitted to the A-1 model and was controlled by one pair of major genes. The number of petal layers was fitted to the B-1 model and controlled by two pairs of additive–dominant major genes. The heritabilities of major genes for abnormal bud, budding date, full flowering date, and the number of petal layers were 1.0, 0.9871, 0.7240, and 0.5612, respectively, indicating that these traits were less affected by environmental factors. Using a percentile scoring method, eight day-neutral chrysanthemum genotypes were selected from the hybrid progeny. [ABSTRACT FROM AUTHOR]

Day-neutral multiflora chrysanthemums can flower throughout the year without being influenced by daylength and have great application value in gardens. Studying heterosis and the genetic basis of important traits in day-neutral chrysanthemums can accelerate the breeding of new cultivars. In this research, a genetic population was constructed by crossing 135 F1 hybrid progeny from the day-neutral chrysanthemum ‘82-81-19’ (female parent) and the late-flowering chrysanthemum ‘388Q-76’ (male parent). Six traits, including abnormal (crown) bud, plant height, plant crown width, budding date, full flowering date, and number of petal layers, were selected for inheritance and heterosis analyses, and a single-generation major gene plus polygene mixed inheritance model was used to perform mixed inheritance analysis on these traits. The results indicated that the six traits were widely segregated in the F1 population, with the coefficient of variation (CV) ranging from 30% to 84%. The phenomena of heterosis and extra-parent segregation existed generally in F1 progeny, and the ratio of heterosis value of mid-parents (RHm) for the six traits was 45.5%, 2%, 2%, 6%, 6%, and −0.3%, respectively. The mixed genetic analysis showed that the abnormal (crown) bud and budding date were fitted to the B-3 model and controlled by two pairs of additive major genes. The plant height and plant crown width were fitted to the A-0 model, and no major gene was detected. The full flowering date was fitted to the A-1 model and was controlled by one pair of major genes. The number of petal layers was fitted to the B-1 model and controlled by two pairs of additive–dominant major genes. The heritabilities of major genes for abnormal bud, budding date, full flowering date, and the number of petal layers were 1.0, 0.9871, 0.7240, and 0.5612, respectively, indicating that these traits were less affected by environmental factors. Using a percentile scoring method, eight day-neutral chrysanthemum genotypes were selected from the hybrid progeny.

[Objectives] The present study is to investigate the genetic variability and major gene effect of the primary and secondary branch traits in spray cut chrysanthemum. [Methods] Seven branching traits, i.e., total lateral bud number, up branch number, primary branch length, primary branch angle, total secondary branch number, secondary branch length, and secondary branch angle of the segregating 'Nannongxuefeng'×'Monalisa' F1 population were measured in 2015 and 2016, and the major gene effects for each branch trait were analyzed using mixed major gene plus polygene inheritance model in F2 population. [Results] All the investigated branch traits showed continuous variations, with the coefficient of variation ranging from 12.89% to 61.55%. The phenoma of mid-paraent heterosis and extra-parent individuals existed generally for every branching trait, but transgressive heterosis was not yet to take shape in the F1population, and the mid-paraent heterosis was relatively large for total lateral bud number, up-part primary branch number, primer branch angle and total secondary branch number, with the ratio of mid-parent heterosis calculated at -9.69%, -9.10%, 12.99% and 25.51%, respectively. The mixed inheritance analysis indicated that the inheritances of total lateral bud number, secondary branch length, primary branch angle and secondary branch angle fit to the 0MG model with no major genes; the up primary branch number and total secondary branch number fit to the 2MG-AD model, governed by two pairs of major genes showing additive-dominant effect; the secondary branch length accords with the 1MG-AD model, controlled by a pair of major gene displaying additivity and part dominance or super-domimance effect. The heritability of major genes for the up-part primary branch number, primary branch length, total secondary branch number and secondary branch length were calculated at 74%, 46% and 72%, respectively. [Conclusions] The findings present an insight into the genetic variability and major gene effects of important branching traits of spray cut chrysanthemum, and provide a guide for future breeding program targeting plant architecture. [ABSTRACT FROM AUTHOR]

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