Number Of Inbred Lines Research Articles

Determination of the Number of SSR Alleles Necessary for the Analysis of Genetic Relationships Between Maize Inbred Lines

The amount of molecular marker information has considerable impact on the results of studies of crop germplasm genetic relationships in crop. The number of alleles required to reveal genetic relationship in maize inbred lines is a theoretical issue that needs to be addressed. In this study, 112 pairs of SSR (simple sequence repeat) primers and 97 maize inbred lines were selected to study the relationship between the number of inbred lines and the number of SSR primers and alleles required for a stable cluster. The results showed that the number of SSR primers is not tightly associated with the stability of the cluster analysis results, while an increase in the number of alleles can significantly improve the stability of cluster analysis results. The number of inbred lines ( X) is significantly associated with the number of alleles required for stable cluster analysis ( Y), and the regression equation is Y= 600.8×e (-15.9/ x) . This equation can be used to calculate the number of SSR alleles required for a genetic relationship study of maize inbred lines. These results provide a reference for determining of SSR alleles number in genetic relationship analysis of maize inbred line and other crop germplasm.

Characteristics of Maize Inbred Lines Originating from Local Populations

Maize is the leading field crop in Yugoslavia in terms of economic importance and area sown. Over the past 400 years, which is how long maize has been grown in the country, a rich breeding material with a unique combination of agronomic traits has been developed under the influence of agroecological factors and through constant selection of desirable fenotypes. When the spread of hybrid maize began in the mid-20th century, local breeding materials were collected and assembled in gene banks in order to prevent their deterioration and enable their utilization in breeding to develop hybrid varieties. The present study includes only those lines from the first cycle of selection originating from the local populations Vukovarski Zuti Zuban, Sidski Zuti Zuban, Novosadski Zlatni Zuban, Bankut Bajsa, Socice, and Novosadski Zuti Zuban that were used for the development of commercial hybrids, which is less than 1% of the total number of inbred lines developed at the Institute of Field and Vegetable Crops in Novi Sad. The contribution of domestic inbred lines to modern maize breeding consists in the following: 1) Domestic inbred lines possess great variability for most of the agronomically important traits. In nearly every group of lines (lines of the same origin comprise one group), lines with desirable traits have been found, lines that now represent new sources of variability in breeding programs on. grain yield, resistance to lodging, early maturity, ear bareness, grain quality, and other traits. 2) The domestic inbreds differ in their heterotic potential for grain yield when crossed with the inbred testers B73 (BSSS germplasm type) and Mol7 (Lancaster germplasm type). Lines originating from the populations Vukovarski Zuti Zuban, Sidski Zuti Zuban, Novosadski Zlatni Zuban, and Novosadski Zuti Zuban combine better with the inbred tester Mol7 than with B73, so they belong to the BSSS heterotic group. Lines originating from the populations Bankut Bajsa and Socice are neutral, i.e. they respond equally to both types of germplasm (BSSS and Lancaster), so they can be said to belong to a new heterotic group.

Live gene bank of common carp strains at the Fish Culture Research Institute, Szarvas

The development of a live gene bank of domesticated carp was started in the Fish Culture Research Institute, Szarvas, in 1963, when common carp strains were collected from different regions of Hungary. The live gene bank has been enlarged by increasing the number of different groups, including common carp from different parts of Europe and Asia. At present, there are 15 Hungarian and 15 foreign strains in the gene bank with a number of inbred lines. Extensive experimental work has been carried out, including a study of the performance of the original gene pool and determination of breeding value by performance tests of their progenies, a systematic crossing programme in which each landrace was crossed with the others and the performance of their F 1 progeny evaluated, the development of new varieties produced from among races and strains, and the use of artificial gynogenesis and sex-reversal.

Inbreeding and Yield Prediction in Synthetic Cultivars of Maize: II. Alternative Methods

The first generation (Syn‐l) of synthetic cultivar is obtained by making the possible crosses among the components or parental inbred lines (Syn‐0). The second generation (Syn‐2) is the result of randomly mating Syn‐l. When the number of inbred lines is large, it is difficult to make the total number of possible crosses. Thus, in order to facilitate the hand pollination work, a smaller number of crosses among the inbred lines is desired. The yield of a synthetic cultivar depends on its inbreeding coefficient. Therefore, for an alternative method of obtaining Syn‐I to be valid, the inbreeding coefficient of its Syn‐2 has to be equal to the inbreeding coefficient of the synthetic obtained by the conventional method, in which all possible crosses are made. In this paper the inbreeding coefficient of Syn‐2 is calculated for five alternative methods of crossing to obtain Syn‐l. Results show that the inbreeding coefficient of Syn‐2 is the same for the five methods as long as each component line has the same chance of contributing to Syn‐l. In practice, choosing the method will depend on the purpose of the synthetic, the number of lines, the availability of skilled hand labor to make pollinations, and whether there is an even number of lines. It is shown that with any of the methods yield of Syn‐2 is always the same.

Genetical investigations into β-glucan content in barley

Random inbred lines produced by doubled haploidy (DH) and single seed descent (SSD) have been used to investigate the genetics of β-glucan (gum) content in barley (Hordeum vulgare). Genetical analyses indicated that gum content is controlled by a simple additive genetic system. Significant negative genetic correlations were observed between β-glucan content, thousand grain weight and height in the DH samples. These correlations were much reduced in the SSD samples and would suggest linkage of the genes controlling these characters. The presence of repulsion linkages could be exploited in a barley breeding programme by producing F1 derived DH to generate recombinants with high thousand grain weight and low β-glucan content. Genetical parameters estimated from DH and F3 samples have successfully been used to predict the number of inbred lines transgressing the parental range for β-glucan content and bivariate combinations involving β-glucan.

Cytogenetics of Lolium perenne

A number of inbred lines of Lolium perenne have been developed as far as the fifth inbred generation and are being used for basic studies on the cytogenetics of the species. An analysis on variation in the pattern of chiasma frequency and distribution, including the parent plants and all generations down to the S5, reveals that the effect of inbreeding is to reduce chiasma frequency and to increase both the cell and bivalent variances. Evidence is presented for a genetic basis of polygenic control of chiasma formation and distribution, and a model is suggested for control over the three related components of variation which involves a two-stage level of regulation.

IDENTITY OF RESISTANCE GENES TO RACE G OF BROOMRAPE IN SOME LINES OF SUNFLOWER

One of the most dangerous biotic factors that reduce the sunflower productivity is its infection by an obligate parasite of higher plants - broomrape (Orobanche cumana Wallr.). Over the past few years, a number of inbred lines of various origins that are immune to race G have been developed at V.S. Pustovoit All-Russian Research Institute of Oil Crops (VNIIMK). To combine different genes in the same sunflower genotype, it is necessary to determine their allelism. The research material was the sunflower lines – donors of resistance to race G of broomrape: RG, RGP1, RGP2, RGB, RGL1, RGL2, RGM. The identification of the race of broomrape seeds by means of lines-differentiators showed that the seeds were collected from the plants of race G. Hybrids F1 and F2 were obtained by the VNIIMK method. The mathematical processing of the segregation results was conducted by means of χ2 criterion of correspondence of the actual segregations to the theoretically expected ones in dihybrid crossings. The research results showed that, overall, the parent lines were affected by broomrape to a small degree. During the test for allelism, seven generations of F1 and F2 were obtained from pair crossing of resistant lines with each other. The tested hybrids F1 were either not affected by the parasite, or were affected to a small degree, which allowed us to classify sunflower plants as resistant. To determine the identity of resistance genes in the lines of RG with RGP1, RG with RGM, RG with RGL1, RG with RGB, RGP2 with RGL2, RGM with RGL1, RGB with RGL1, we analyzed the F2 progeny from these hybrids. The test for allelism of the resistance genes to race G of these lines showed their identity, with the possibility of some distortion of the phenotypic manifestation of the trait in various crossing combinations.

The genetical control of radiosensitivity

Examination of data from a set of diallel crosses between a number of inbred lines was used for analysing the genetic control of radiosensitivity in six tomato varieties. The six varities were crossed in all possible combinations, including reciprocals, and the parental and F1 seed were used in the experiments. Seeds were dried and exposed to 28,116 rad of Co60 gamma rays at a rate of 2000 rad/hr. The characters scored were the distance from the apex of one cotyledon to the apex of the other at the 12th day, and the lengths of the 1st and 2nd leaves at the 19th day after sowing. The results showed the response of tomato seeds to radiation to be genetically controlled. The nature of this control was polygeric, with evidence of additivity and dominance. The different varieties had various proportions of dominant and recessive alleles, and dominance and ambidirectional. Pronounced consistent and inconsistent maternal effects influenced the radiation response; these affected dominance values to produce a complex genetic situation. The genetic control of radiosensitivity was different from that of the simple growth characters, though there was some similarity in that both showed maternal effects. There was also evidence that the control ofmore » these characters varied according to whether they were measured in the cotyledon, first or second leaf. Relationships between spontaneous mutation and chromosome breakage, and induced mutation and breakage is discussed. It is concluded that radiosensitivity per se may not be a true character, and that what was measured may be some quite different character, which could control such factors as oxygen tension, metabolic rate, or production of radioprotective substances; and that different levels of expression of this character could result in different levels of radiosensitivity. (H.H.D.)« less

The ecological genetics of growth inDrosophilaV. Gene-environment interaction and inbreeding

1. The growth of a number of inbred lines from the Pacific cage population have been compared under different conditions of temperature and nutrition. Body size and duration of the larval period were taken as measures of performance. Sub-optimal diets were provided by growing larvae on chemically defined synthetic media.2. Gene-environment interaction is widespread and often very great. The phenotypic effects of inbreeding on body size, even on a live yeast medium, may be greatly influenced by temperature. In one set of comparisons, inbred lines averaged 20% smaller at 25° C. but only 3% smaller at 18° C.3. Sub-optimal diets of different chemical composition, which lead to about the same average decline in body size, may differ greatly in the level of heterogeneity of response among the same set of inbred lines. Thus much greater heterogeneity was found on diets deficient in RNA than on diets with low protein levels. Such information is a useful guide to further study of gene-environment interaction in the outbred population.4. Diets which lead to a decline in body size of flies of the foundation population do not necessarily cause greater proportional decline on the part of inbred lines. Individual lines have been encountered in which body size is quite unaffected by changes in diet which reduce the size of the outbred flies by 25% or more.5. A series of crosses between lines from the same foundation population showed a striking level of homeostasis. The average body size and development time of the F1's was close to that of the population of flies on the favourable and two alternative sub-optimal diets. Also, compared with the parent lines, there was little evidence of gene-environment interaction among the crosses.

Selective fertilization following the use of sperm mixtures in the mouse.

ARTIFICIAL insemination has been carried out in the mouse using mixtures of sperm from a number of inbred lines each containing a suitable genetic marker. The lines are REB (containing the dominant hair structure gene rex, ReRe), G (coat colour and pattern tan, atat), and C3H (coat colour agouti, AA); all possible combinations of these genes are phenotypically distinct in the offspring. The first two lines are derived from inbred lines A and CBA respectively. Sperm is obtained from the vas deferens of killed males and the density of each sample estimated by haemocytometer counts. Sperm mixtures were made with equal numbers of spermatozoa from each donor; the donor males for each mixture were of approximately the same age. Four types of sperm mixture were made, namely, a triple mixture of all three types and three double mixtures containing the three possible pairs of the types. These mixtures were used for inseminating œstrous females of the same three lines. Since fertility was rather low in the inbred lines1, the same sperm mixtures have also been used on other females taken from highly fertile non-inbred strains. These are referred to as X in the tables, which give the results obtained up to the present time.

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