INSTITUTE OF PLANT THYSIOLOGY, GENETICS AND BIOENGINEERING
Laboratory of Physiological Genetics of Plants, Timiryazav str. 45, Almaty, 480090, Kazakhstan.
Anna Kokhmetova.
Variability in the environment has long been recognized as an important factor influencing the performance of genotypes. The genotype-environment interaction reflects fluctuations of the environment, which in most cases are unpredictable. Therefore, ensuring the stability of high yields in unfavorable conditions is an important objective. This problem is of special importance for Kazakhstan, where the main areas of agricultural production are characterized by a lack of moisture and heat. The value of agricultural varieties depends not only on the absolute level yield capacity, but significantly on stability, i.e., the ability of variety to attain a definite yield in a fluctuating environment.
Yield stability is one of the most important agronomic traits. Therefore, analyzing 'GxE' can be an effective in a breeding program. To this end, we can utilize the genetic potential in the wheat gene pool and after studying their ecological niches.
Creating genotypic variability in populations for selection is an important stage of the breeding process. Intravariety variation provides great possibilities for selecting agronomically useful material, because varieties are good initial material for further breeding. There are many examples of improved cultivars bred from wheat varieties. A complicated population structure of wheat varieties, coupled with changes over the long course of reproduction, is true for many varieties. The varieties become a population with a definite structure. The lines, which become the basis of the biotype of the population, have productivity and adaptability potential, which is frequently not realized. These facts prompted us to study the lines of the standard variety Progress, which has a population structure, to assess the effect of environment on performance of the individual lines making up the variety in order to identify stable genotypes.
Gliadins are useful as markers for identifying and screening of initial breeding material. In wheat, the gliadin loci are on short arms of chromosomes 1A, 1B, 1D, 6A, 6B, and 6D. An analysis of the allelic state of the gliadin-coding loci was conducted by A-PAGE (pH 3.1). Protein percentage and sedimentation tests also were made.
The lines were grown at three location, KazNIIZ (an irrigated, foothill zone), Taldyrkorgan (an irrigated, hill-steppe zone), and Karaoi (nonirrigated, desert-steppe zone). These locations differ widely in altitude, rainfall, and temperature. The major traits of productivity (plant height, number of tillers/plants, number of spikelets/spike, number grain/spike, weight of grain/spike, and weight of grain/plant) were evaluated. Stability parameters were measured according to Tai (1971).
An analysis of variance was done for each test and for all characters of productivity. The adaptability of the Progress lines is a genetically determined trait. Differences between all sources of variation were highly significant (P = 0.01) for all traits except tillers/plant. The contribution of variability to the productivity of each genotype is not equal. For example, the influence of genotypes P7 and P4a was the greatest, 13 and 11 %, respectively. The lowest level of variability was observed in P11.
Grain weight/plant, like all traits of productivity, are considered polygenic and the genotype of each plant cannot be determined accurately from the phenotype. This trait is controlled by a complicated genetic system with definite gene action and interaction and is able to be modified. All lines of Progress are distinct with respect to content (13-17 %). The lines P17, P10, P9a, and P4 have the highest protein content. According to sedimentation data, lines P9a, P10a, P13, and P17 belong to the high technological quality group. These lines are similar in genetics to the chromosome homoeologous group 1. Perhaps this circumstance determines good grain quality. The other lines in the population are in a group with good technological quality. One exception is line P1, which is of satisfactory quality. The dependence between the genetic formulae of gliadin-coding loci and quality should be noted. Thus, line P7 and population P11, which are characterized by the same gliadin composition, have adequate grain quality (Table 1).
| Genotype | Gliadin component blocks in chromosome | Protein content (%) | Sedimentation index (ml) | |||||
|---|---|---|---|---|---|---|---|---|
| 1A | 1B | 1D | 6A | 6B | 6D | |||
| P1 | 1 | 1 | 1 | 1 | 1 | 1 | 13.7 | 36.5 |
| P7 | 1 | 1 | 1 | 3 | 1 | 1 | 13.8 | 40.1 |
| P14 | 1 | 1 | 5 | 1 | 1 | 1 | 13.8 | 42.0 |
| P3A | 1 | 1 | 5 | 3 | 1 | 6 | 15.1 | 48.0 |
| P9 | 1 | 1 | 5 | 3 | 1 | 1 | 16.1 | 66.0 |
| P4 | 1 | 1 | 5 | 1 | 1 | 6 | 15.4 | 48.5 |
| P10 | 1 | 1 | 5 | 3 | 1 | 1 | 16.7 | 62.0 |
| P17 | 1 | 1 | 5 | 3 | 1 | 6 | 17.0 | 55.0 |
| P13 | 4 | 1 | 5 | 3 | 1 | 1 | 14.4 | 56.0 |
| P4 | 1 | 1 | 5 | 1 | 1 | 1 | 15.9 | 48.0 |
| P11 population | 1 | 1 | 1 | 3 | 1 | 1 | 13.2 | 40.1 |
Self-fertilizing, heterozygous plants manifest a greater buffer than homozygous plants. In favorable years, high yields are obtained from both homozygous and heterozygous lines, whereas heterozygous plants yield more in unfavorable years. We compared the yields of lines and population P11 of the Progress variety and confirmed this hypothesis. The mean value of productivity/plant in optimal (KazNIIZ) versus limited (Karoi) environments and in favorable conditions was not of advantage for the population P11 over the individual lines for weight of grain/plant. The lines P 17, P 4, and P 3a were more productive. In these conditions, the variety exhibits an intermediate productivity. Under unfavorable conditions, the productivity of population P 11 was significantly higher than that of the individual lines.
The variability coefficient, which was calculated after several years of testing, was 30.8 % for the population and 4051 % for the individual lines. The adaptability of the individual lines and population P 11 has been estimated by means of the parameters of stability a and l, according to Tai (1971).
The data are evidence that the stability of a population is higher than that of individual lines (Table 2). Plants of a population develop normally despite unfavorable environmental conditions because of their stability. Stability is manifested by a decrease in variability under different conditions. Our results show that populations are less sensitive to changes or deteriorating environmental factors and continue to develop in wider ranges of temperature, moisture, and other environment factors. Perhaps the different level of plasticity of the lines that make up the population P 11 determines its maximal adaptability.
| Genotype | Height of plant | Length of spike | No. of spikelet | No. of grainspike | Weight of grainspike | Weight of grain/plant | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| a | l | a | l | a | l | a | l | a | l | a | l | |
| P1 | 0.4 | 19.7 | -0.2 | 7.6 | 0.1 | 5.1 | -0.1 | 3.8 | -0.3 | 2.6 | -0.1 | 9.8 |
| P7 | 0.4 | 3.4 | 0.3 | 2.3 | 0.0 | 0.1 | 0.1 | 1.8 | 0.1 | 1.9 | 0.2 | 5.5 |
| P14a | 0.3 | 6.2 | -0.1 | 4.8 | -0.2 | 2.3 | -0.3 | 8.7 | 0.0 | 2.7 | -0.1 | 5.3 |
| P3a | 0.8 | 2.2 | 0.1 | 2.1 | 0.1 | 2.3 | -0.4 | 1.2 | 0.0 | 1.8 | 0.0 | 1.9 |
| P9a | 0.1 | 6.7 | -0.4 | 1.6 | -0.2 | 3.6 | -0.2 | 0.8 | -0.1 | 1.7 | 0.1 | 1.9 |
| P4a | -0.8 | 15.4 | 0.2 | 5.2 | 0.0 | 1.3 | 0.1 | 1.8 | 0.1 | 1.0 | 0.1 | 6.8 |
| P10a | -0.4 | 23.9 | 0.4 | 0.6 | -0.2 | 1.2 | 0.2 | 1.0 | 0.2 | 0.6 | -0.1 | 9.7 |
| P17 | 0.4 | 4.5 | 0.3 | 3.6 | 0.4 | 4.3 | 0.6 | 7.5 | 0.4 | 5.1 | -0.1 | 6.1 |
| P13 | -0.7 | 20.7 | -0.4 | 4.1 | -0.1 | 1.3 | 0.0 | 2.5 | -0.2 | 1.2 | 0.1 | 3.3 |
| P4 | -0.8 | 8.7 | 0.0 | 3.6 | 0.0 | 2.9 | 0.1 | 1.0 | 0.1 | 1.3 | 0.1 | 4.4 |
| P11 population | 0.1 | 19.4 | -0.1 | 1.9 | -0.1 | 0.7 | -0.3 | 1.5 | -0.2 | 0.1 | -0.2 | 2.4 |
Our study has shown the complicated population structure of the variety Progress. Lines of this variety differ not only by allelic state of gliadin-coding loci but also in their level of productivity, quality of grain, and stability parameters. Some of these lines are promising genetic material and are in the last stages of a breeding program.
Reference.