Manifestation of agronomically valuable traits in the progeny of a sorghum mutant carrying the genetic construct for RNA silencing of the γ-kafirin gene.

Improving the nutritional value of grain sorghum, a drought- and heat-tolerant grain crop, is an important task in the context of global warming. One of the reasons for the low nutritional value of sorghum grain is the resistance of its storage proteins (kafirins) to proteolytic digestion, which is due, among other things, to the structural organization of protein bodies, in which γ-kafirin, the most resistant to proteases, is located on the periphery, encapsulating more easily digested α-kafirins. The introduction of genetic constructs capable of inducing RNA silencing of the γ-kafirin (gKAF1) gene opens up prospects for solving this problem.

Manifestation of apomictic potentials in the line AS-3 of Sorghum bicolor (L.) Moench.

AS-3 line of Sorghum bicolor possesses functional components of apomixis-apospory, parthenogenesis and autonomous endospermogenesis. The data obtained indicate efficiency of selection for apomixis components in diploid species of cultivated crops. Apomixis (seed formation without fertilization) is one of most attractive phenomena in plant biology.

Influence of different types of sterile cytoplasms (A3, A4, 9E) on the combining ability of CMS lines of sorghum.

Investigation of the effect of the cytoplasm on the combining ability (CA) of lines with cytoplasmic male sterility (CMS) is of considerable interest in terms of understanding the genetic functions of the cytoplasm and for practical purposes to create hybrids with improved economically valuable traits. In order to investigate the effect of different types of sterile cytoplasm (A3, A4, 9E) on CA in sorghum, we studied the manifestation of a number of biological and agronomic traits in 54 F1 hybrid combinations obtained using iso-nuclear CMS lines with the nuclear genome of the line Zheltozernoye 10, differing only in the types of sterile cytoplasm (A3, A4 and 9E). Eighteen varieties and lines of grain sorghum developed at the Russian Research and Project-technological Institute of Sorghum and Maize were used as paternal parents.

[Inheritance of reversions to male fertility in male-sterile sorghum hybrids with 9E cytoplasm male sterility induced by environmental conditions].

Heritable phenotypic alterations occurring during plant ontogenesis under the influence of environmental factors are among the most intriguing genetic phenomena. It was found that male-sterile sorghum hybrids in the 9E cytoplasm from the F1 and F2 generations, which were obtained by crossing CMS lines with different fertile lines grown in field conditions, were transferred to greenhouse produce fertile tillers. Lines created by the self-pollination of revertant tillers exhibit complete male fertility upon cultivation under various environments (in the field, Tdry plot,(y) Tirrigated plot(y)).

Heritable Effect of Plant Water Availability Conditions on Restoration of Male Fertility in the "9E" CMS-Inducing Cytoplasm of Sorghum.

Heritable changes of phenotype arising in plant ontogenesis by the influence of environmental factors belong to the most intriguing genetic phenomena. An unusual inheritance pattern was detected during examination of male fertility restoration in the CMS-inducing "9E" type cytoplasm of sorghum: Rf-genes were functional in self-pollinated progeny of F(1) hybrids yet were either not expressed or poorly expressed in backcrosses of these hybrids to CMS-lines with the same cytoplasm type. In experiments on parallel growing of the same F(1) hybrid combinations in the "dry plot" and in the "irrigated plot," it was found that high level of plant water availability during panicle and pollen developmental stages significantly increased male fertility of F(1) and test-cross hybrid populations, in which fertility-restoring genes were in heterozygote state, whereas in F(2) populations the influences of water availability conditions cause less pronounce effects.

[Expression of the apomictic potential and selection for apomixis in sorghum line AS-1a].

Expression of elements of apomixis was studied for ten seasons in sorghum line AS-la and its backcross hybrids on the 9E and A3 sterile cytoplasms. Cytoembryological analysis revealed aposporous embryo sacks (apo-ESs), their initial cells, and, rare, parthenogeneic proembryos in ovules of line AS-la and its BC2 and BC3 hybrids on the 9E cytoplasm. The A3 sterile cytoplasm suppressed the development of parthenogenetic proembryos, but did not affect the apo-ES formation.

[Genetic variation in a sorghum line with multiple genetic instability induced with ethidium bromide in an in vitro culture].

Ethidium bromide treatment (15 mg/l, 26 degrees C, 18 h) of a sorghum Zheltozernoe 10 callus culture yielded line Zh10-brl displaying multiple genetic instability. The line was characterized by a broad variety of mutations, which were identified in consecutive generations obtained from one initial regenerant via self-pollination. The mutation caused male sterility (male sterility, generation R1), a low plant height (dwarfness, R2), a reduced awn length (awnless, R3), yellow leaves in seedlings (xantha, R6), leaf variegation (leaf variegation, R6), leaf bleaching (virescence, R6), etc.

[Genetic and cytological analyses of the male sterility mutation induced in a sorghum tissue culture with streptomycin].

Treatment of sorghum callus cultures with 500-1000 mg/l streptomycin led to a high regeneration frequency of plants with complete or partial male sterility (MS), up to 100% of all green regenerants. The induced MS mutation (ms-str) was preserved in the F1 and BC1 progenies and was genetically unstable: many families produced semisterile and fertile revertants, whose progenies again contained semisterile and sterile mutants. The ms-str mutation was maintained through eight generations via selection and self-pollination of semisterile plants.

Dominant male sterility in sorghum: effect of nuclear background on inheritance of tissue-culture-induced mutation.

Occurrence of genetic instability and formation of stable mutations are basic genetic processes. This study demonstrates that nuclear background may influence the formation of stable dominant nuclear gene of male sterility (MS) on the basis of unstable mutation, which was induced in tissue culture of the sorghum haploid (cv. Milo-145).

[Instability of the ploidy level in autotetraploid sorghum plants from a line with variable male fertility].

It was found that, in some of the plants in generations C1-C5 of induced tetraploids in the semisterile sorghum line AS-1-30, more than 30% of pollen grains (PGs) have sizes typical of haploid PGs. Pollen of these plants was used to pollinate different lines of sorghum with cytoplasmic male sterility (CMS). Diploid hybrids were obtained, which confirms the presence of haploid PGs in the tetraploids studied.

[Genetic control of cytoplasmic male sterility in plants: state of the problem and current approaches].

The organization and functions of genetic systems controlling cytoplasmic male sterility (CMS) in plants are reviewed. Mitochondrial genes that code for specific proteins disturbing the functions of mitochondria have been found by comparisons between CMS lines and fertile F1 hybrids and between forms originating from in vitro cultures (fertile revertants, cybrids). Nuclear fertility-restorer genes abrogate expression of these mitochondrial genes at the transcriptional or posttranslational level and thereby prevent synthesis of their protein products.