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Rafał Mól, Dorota Weigt and Zbigniew Broda

Cytoembryological Analysis Of Causes For Poor Seed Set in Alfalfa (Medicago Sativa L.)

Poor seed set is a limiting factor in alfalfa breeding, as it slows the selection response. One strategy used to overcome this problem is to search for mutations of inflorescence morphology. Long-peduncle (lp), branched-raceme (br) and top-flowering (tf) inflorescence mutations increase the number of flowers per inflorescence, but they do not improve seed set per flower. Here we assessed pollen tube growth in styles of those inflorescence mutants and we observed embryo and endosperm development in seeds 1 to 16 days after pollination (DAP). The number of pollen tubes penetrating the style and the ovary was similar in all tested mutants and in the reference cultivar Radius. At 2 DAP, fertilized ovules were 2.7-3.9 times less numerous in certain inflorescence mutants than in the short-raceme cv. Radius. Ovule degeneration progressed at 2-4 DAP in all analyzed plants. Most ovules were not properly developed in the control cultivar (62%), nor in the forms with mutated inflorescence morphology (69-86%). The number of seeds per pod was lowest in the tf form despite its having the highest number of ovules per ovary. It appears that the number of ovules per pistil is not a crucial factor in seed set in alfalfa when fertilization efficiency is very low. Both poor fertilization and gradual ovule degeneration were factors causing poor seed set in the investigated alfalfa genotypes.

Open access

Dorota Weigt, Zbigniew Broda, Jarosław Lira and Sylwia Mikołajczyk

Morphological and cytological characteristics of inflorescence mutants in alfalfa (Medicago sativa L. Sl)

The presented study analyzed selected biometric characteristics of inflorescences, seed yield structure characters, and discussed cytological analyses concerning two spontaneous inflorescence mutants in alfalfa: top flowering (plants with the "tf" gene) and long peduncle mutants (plants with the "lp" gene). Analyses were conducted in 2005 and 2006 and the results were subjected to a one-way statistical analysis with the use of Tukey's test. It was found that mutants with gene "lp" exhibited the highest seed yielding potential, while plants with gene "tf" were characterized with the highest stability in terms of most investigated characters in the first and second year of the study; however, they set a lower number of seeds than plants of the control cultivar.

Open access

Sylwia Mikołajczyk, Zbigniew Broda, Danuta Mackiewicz, Dorota Weigt, Agnieszka Tomkowiak and Jan Bocianowski

Abstract

Breeding work using European rye populations has resulted in a considerable reduction of genetic variation in breeding materials of that species. Many taxa from the genus Secale may constitute a potential source of genetic variation in rye breeding. A source of new genetic variation can be found in such species as Secale montanum and Secale vavilovii, which are sources of resistance to fusarium ear blight and septoria leaf blotch, while Secale vavilovii may also be a source of sterilising cytoplasm. The aim of this study was to assess the efficiency of crossing the wild species Secale vavilovii and the rye subspecies Secale cereale subsp. afghanicum, Secale cereale subsp. ancestrale, Secale cereale subsp. dighoricum, Secale cereale subsp. segetale with the crop species Secale cereale ssp. cereale, and to produce F1 hybrids and describe selected morphological traits. Observations of biometric traits indicate that the F1 crosses produced may be potential sources of variation for common rye. The greatest variation in terms of all analysed phenotypic traits combined was found for the cross combinations S. c. ssp. cereale cv. Amilo × S. c. ssp. ancestrale and S. c. ssp. cereale cv. Dańkowskie Diament × S. c. ssp. dighoricum. The hybrids showed considerable variation in the analysed biometric traits within individual cross combinations.