MUTAGENIC SPECIFICITY RECORDING MICRO AND MACRO MUTANTS INDUCTION

SUMMARY

Numerous tests carried out have show that by means of different mutagenic factors great genetic diversity could be obtained in cultivated plants including barley. It can be used successfully as initial material for breeding new barley varieties. Short and long-strawed forms of erectum spikes, early and late ripening ones have been induced by combined treatment with gamma rays and chemical mutagens. The mutability is connected mainly with the degree of their heterozygosis. Cultivars obtained by means of hybridization having comparatively more heterozygous genotype are more mutable than the cultivars of individual selection. The results show that each cultivar has a specific mutagenic ability.

Key words: mutagenesis, specificity, induction, frequency, gamma rays Co-60.

INTRODUCTION

Establishment of an efficient method for inducing high frequencies of agronomically profitable mutations is of great and urgent importance for mutation breeding of crop plants. Mutagenic specificity concerns all cases where mutagens differ from one another in particular effects proportions that have been induced (Kolmark, 1953; De Serres, 1971). In addition to this specificity, it has been determined that some mutagens (physical and chemical) have a different affinity to various genes, loci and chromosomal parts (Ehenberg, 1948).

MATERIALS AND METHODS

Mutagenic treatments were carried out by gamma irradiation with Co-60 at doses from 10 to 40 KR, and chemical ones - sodium azide (NaN₃), nitrozomethyl carbamid (NMC), nitrozo-dimethyl carbamid (NDMC), and ethyl methanesulfonate (EMS) in combination with NaN₃ and 15kR Co-60 + NaN₃. First group had a share of 15661 and second one 8770 spike progeenies of different two-rowed, six-rowed lines and F1 hybrids. The M1 plants were grown in the field and harvested separately. Chlorophyll, morphological mutation frequencies were calculated in M2 plant progeny.

RESULTS AND DISCUSSION

Mutagenetic specificity types most frequently reported hae proved to be chlorophyl mutation ration or mutation spectra. Table 1 summarizes results from seven different mutagenic treatements, for 1987-1993 field seed-samples.

Table 1. Mutation frequency and ratio depending on mutagens

Proportions of M2-mutations particular types have been classified as chlorophyll mutations, sterility mutations, and 4 groups of morphological and physiological changes. Chlorophyll mutations have been used as a basis for calculation of mutations particular ratios. Gustafsson and Mackey (1948) noted that chlorophyll and erectoid mutations can be found in frequencies of 5 x 10^-6 and 0-18 x 10 ^-6, i.e. in a ratio of 25:1. Ehenberg and Nylan (1954) having drawn a general conclusion from some results of Svalov, give a ratio of 15:1 for X-rays and 28:1 for chemical mutagens, with wide variations depending on variety and season of trial itself.

Different mutation types related to "erectoides" one are shown in Table 2.

Table 2. Ratio of different mutation types related to erectum

Chlorophyll mutation frequency has been 15 for gamma-rays, 22 for NaN₃, 17-18 for NMC and NDMC. In a combined treatment of both mutagens NaN₃ and EMS, frequency has been higher (25-27). Mutation frequency of eceriferum type is 1:1,2 for gamma-rays, 1:1,5 for NaN₃, 1:1 for NMC, 1:0,8 for NDMC, 1:1,6 for EMC + NaN₃ combined. The relative ratio of breviaristatum mutation type related to that of erectum is 142:102. Mutation frequency of a group "others" is above 1,5 with a variation depending on doses. It has been again higher for chemical mutagens that underlines carbamide component mutagenic activity. The most frequently reported changes have been in spikes. The relative higher proportion ratio for sterility probably depends on chromosome aberration induced during ionizing radiation. Average frequency for chlorophyll mutations from a spike progeny in different types has proved to be: breviaristatum 0,3 x 10^-6; 0,3 x 10^-6 for eceriferum; 0,4 x 10^-6 for pramaturum; 0,4 x 10^-6 for erectum and 0,5 x 10^-6 for others.

Sometimes in breeding maximum mutation frequencies are not desired since they have proved to be connected with a full or partial lethality. Out of summarized results (Table 3) on mutagen action in particular types of initial forms two-rowed, common ones and hybrid combinations it could be noticed that macromutations in hybrid combinations have got the highest part followed by six and two-rowed varieties. In two-rowed varieties early forms frequency is higher, and lower one for phenotype "breviaristatum". Type "eceriferum" has been induced in higher frequency in hybrid combinations, and "erectum" in two-rowed ones. With the exception of "erectum"type, hybrid population macromutation frequency is higher.

Table 3. Mutation frequency and ratio depending on initial variety type (1987-1993)

The weakest mutability was noticed for the variety BKH 2412/79. Short and high-strawed forms of erectum spikes, early- and late-riping ones were induced in Miraj. Mutations of short awns, wax coating and dense spike were also induced in the variety Chernomorets. A meagre spectrum but of higher frequency was characteristic for the Bernaria and Friberga varieties. A super-early-ripening mutant, heading on 20.04., was induced in Iskkra. Line # 628 gave some macromutants of short and dense spike, two-rowed ones, early-ripening and waxiess coating. Mutation frequency in Obzor and Jubilee was 8% and 7% respectively, and in Krassi 2-6,7%. Frequency of physiological changes and these ones of stem itself was the highest one in two-rowed varieties. Hybrid F2-combination average mutability including common varieties was equal to that of pure lines.

The investigations we carried out show that, by means of physical and chemical mutagens in optimal doses and concentrations as well as their combined application, a great diversity of mutant forms are obtained with useful economical characters. These can be used in combinative breeding as donors of different genes.

REFERENCES

De Serris F.J. et al., 1971, Mutation Res., 12, 129-142

Ehrenberg L. et al., 1948, The mutagenic action of ethylene in barley, Hereditas, 34, 330-336

Gustafsson A. and J. Mackey, 1948, The genetical effects of mustard gas substances and neutrons, Hereditas, 34, 371-381

Kolmark H.G., 1953, Hereditas, 34, 270-276