The possibility of selecting spring rape for cold tolerance at the mature pollen grain stage was studied by investigating the effects of pollen storage at low temperatures on the quality of pollen grains and on the cold tolerance of the plants generated from them. Pollen treatments of F, hybrids affected fertilization ability much more than viability and even after 10 days storage at 3 or 10°C the pollen germination percentage was reasonably high. Pollen storage for 7 or 10 days at 3 or 10°C significantly increased the cold tolerance of F2 seed germination, with 3°C being more effective. Pollen storage for a shorter time had no effect upon the number of resulting genotypes tolerant to low temperature. This approach may be successfully apphed in plant breeding to enrich segregating plant populations with cold-tolerant genotypes.
During two growing seasons there were studied 11 sunflower breeding lines and their 30 analogues obtained via backcrossing, chemical mutagenesis and selected as natural mutants. The variability of such agronomic traits as crop yield, seed oil content, 1,000 seed weight, plant height, leaf and petiole size, number of leaves and branches, and head diameter was investigated. The traits of crop yield, leaf size, number of branches were the most variable, whereas the most stable were 1,000 seed weight, seed oil content, plant height, and the number of leaves. The influence of mutant genes which control ray flower color and shape, leaf color and shape, dwarfness, number of leaves and ray flowers, and shape of bracts on the manifestation of important agronomic traits was estimated. No negative impact of the genes of ray flower color and shape and leaf color was noticed. The gene of fringed leaf margin reduced plant height while the gene of erect petiole increased development of that trait. The genes of dwarfness can negatively influence seed oil content and 1,000 seed weight.
The frequency and spectrum of morphological and physiological mutations obtained in M 2 and M 3 generations after sunflower immature embryos treatment with ethyl methanesulphonate (EMS) have been studied. Immature 9 -10 and 14 -15-day-old embryos of two genotypes were treated with EMS at the concentration of 0.02% for 16 hours. Thirty-three types of mutation were found, described, and classified into the following groups: chlorophyll deficiency (3 types), cotyledon mutation (1), leaf mutations (6), stem mutations (9), inflorescence mutations (11), seed mutation (1) and physiological mutations (2). Differences were observed between genotypes for the spectrum and frequency of mutation. Mutation frequency after immature embryo treatment in the M 2 generation did not exceed the amount of mutations in M 3. At the same time, some mutations such as sterility, leaf venation, and different shapes of leaf lamina were unique for the M 3 generation. Morphological mutations were rarest after mutagen treatment of immature 9 -10-day-old embryos.Key words: sunflower, ethyl methanesulphonate, immature embryos of different age, morphological and physiological mutations, mutation spectrum and frequency
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