Abstract
Considering its capacities, the generative system of Beta vulgaris L. is regarded as highly productive. While inbreeding, the reproductive potential of cross-pollinated beet plants with gametophytic self-incompatibility (SI) changes significantly and is determined by a joint effect of multiple factors including the level of inbred depression. In the present study, original data have been obtained revealing relationships between inbred beet seed productivity, its self-incompatibility and microgametophyte parameters, which is crucial for developing and maintaining constant fertile beet lines. It has been discovered that inbred depression increases the number of sterile microgametes and anomalous pollen grains, reduces pollen fertility and the length of pollen tubes. As a result, the seed yield in inbred beet progeny, including SI ones, reduces significantly just after the third inbreeding. At the same time, highly productive inbred beet is characterized by a lower rate of pollen tube growth in vitro. In inbred plants, there is no close relationship between pollen viability and seed productivity, because the elimination of germinated male gametes and degeneration of seed embryos may go over the entire period of fertilization starting its progamic phase. The SI plants have more degenerating embryos than self-fertile ones, but seed vessel outgrowth in the seeds with abortive embryos makes them morphologically similar to fertile seeds. For that reason, when assessing inbred beet plants based on their self-incompatibility/self-fertility, one should consider the qualitative characteristics of the seeds. Using the method of recurrent selection based on such factors as seed productivity, pollen tube length and field germination rate increase the output of plant forms with a potentially high self-compatibility in their progeny. To support such genotypes in the progeny, one has to, starting from the third inbreeding, perform sib crossing to reduce the negative effect of inbred depression and self-incompatibility.
Highlights
Table beet (Beta vulgaris L.) is one of the most common root vegetables and is cultivated all over the world
The effect of consecutive self-pollination on the variability of microgametophytic parameters was studied and the relation of these parameters with the reproductive ability of the inbred beet plants was analyzed in breed sample 274, whose population was characterized by the lowest amount of SI genotypes (7 %)
The plants selected for further inbreeding were primarily the ones prone to self-fertilization, which were typically present in all inbred progenies
Summary
Table beet (Beta vulgaris L.) is one of the most common root vegetables and is cultivated all over the world. Table beet outperforms other root vegetables in productivity due to the structure of the generative system and its crosspollination potential. Table beet is clearly identified as a crosspollinating plant with the gametophytic self-incompatibility system (Owen, 1942; Maletsky et al, 1970). A wide variety of foreign and domestic breeds of table beet is available in the market, the producers prefer F1 hybrids, which are more unified, flexible, and better suited for production. The heterosis effect reaches its peak, when the progeny hybridity is at its maximum that is effectively achieved by various genetic reproductive systems, cytoplasmic male sterility (CMS) potentially presenting in each cross-pollinated population (Maletsky, 2010)
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