Authors:P. Konvalina, J. Moudrý, K. Suchý, I. Capouchová, and D. Janovská
for marginal areas by exploring geneticresources collections. In: 11th Regional Wheat Workshop for Eastern, Central and Southern Africa, 18–22. 9. 2000. CYMMIT, Addis Ababa, Ethiopia, pp. 67–77.
Conservation of maize (
L.) genetic resources has been the emphasis of national and international institutions for the benefit of mankind. However, limited resources have been devoted to their adequate exploitation, making genetic resources less useful to the public and private scientific community. As a consequence, public maize breeders have exploited a limited number of heterotic combinations for cultivar development and basic molecular studies while genetic effects are different for different hybrids. Extensive testing of maize population hybrids is a successful approach to choose and improve germplasm sources with high mean performance, useful genetic variability, and excellent combining ability. There is a need to keep applied breeding programs strong in order to link efforts in germplasm conservation with its improvement and utilization.
Maize breeding, on which the future of maize production is based, can be expected to undergo further important developments in the 21
century. Opportunities for development are latent in a more scientific approach to production methods and in the better exploitation of the available genetic resources. There is no lack of favourable gene combinations contributing to higher yield (e.g. 20–22 t/ha). However, the genes and gene combinations controlling the improvement and stabilisation of performance are unfortunately scattered over various different races, varieties and individual plants, where they occur at low frequency. Combination breeding and, more recently, cumulative source management are designed to collect these genes and concentrate them in special parental lines and heterosis sources.The pure line method has been a basic procedure in maize breeding for the last 100 years, and is likely to remain so for the next 100 years. Combination breeding and cumulative source management are an integral part of this method. The concentration of favourable genes has been facilitated to an unexpected extent by the use of this method. When breeding open-pollinated varieties all the gene combinations required had to be collected into a single population, while in the case of heterosis breeding it is sufficient if the male and female parents each contain half the required gene combinations. These are then combined automatically in the course of crossing.Over the last 20 years too little attention has been paid to the breeding of basic material, so the number of heterosis sources has declined and some have become eroded due to unsupervised mixing. There have been few reports on the development of new heterosis sources vying in quality with earlier sources. In the course of hybrid maize breeding, closely related pedigrees have been crossed to develop new elite lines in the hope of quick results. Due to the lack of substantial initial divergence this is unlikely to result in any great increase in yield. Authoritative opinions consider this to be the reason for the slower rate of yield increase, and for the very small differences now existing between the yield levels of rival hybrids.There is no lack of genetic resources, but more attention should be paid to the careful breeding of basic materials. The future of maize breeding will depend on the discovery of new gene combinations more efficient than those currently available, and on their successful concentration in different sources of heterosis.
The main characteristics of the European heterosis sources Mindszentpusztai, Rumai and Many-Rowed Early Flint probably developed in Eastern Central Europe. Little time and few funds are currently spent on their improvement, so they are constantly being eroded in number and their relative breeding value has declined. The elaboration of methods for the utilisation of European sources could be of great assistance in achieving improvements in maize yield potential and crop safety on a global scale. The first step in this work will be the clarification of the possible origin of the heterosis sources.
In every time, the genetic basis of maize production is represented by the varieties and hybrids grown on the greatest area. It is interesting to note that, compared with the number of races and varieties available, there has always been only a small number of varieties that dominated the given maize production era.Chronologically, the Old Hungarian Yellow Flint group of varieties was popular from 1610–1914, American dent varieties (Iowa Goldmine, Queen of the Prairie, etc.) from 1900–1920, Bánkúti (Late) Dent from 1910–1935 and the varieties developed by Fleischmann from 1935–1960. Hybrid maize production was based on Mindszentpusztai Yellow Dent up till 1983 and on Iodent from 1983 onwards. Among the varieties previously popular for human consumption (porridge) in Eastern Central Europe, varieties related to Cinquantino and Pignoletto dominated variety use for a long period, and varieties in the Lapusnyaki group for a shorter time.The group of popular varieties, which were originally improved varieties, and others related to them, make up the “useful” part, or “heart core” of the genetic variability of maize in Eastern Central Europe. Due to the special methods employed for variety development and variety maintenance in this region, it is not difficult to identify variants of these previously popular varieties on the basis of morphological traits. These are of potential value. In many cases variety collections also include varieties developed by breeders or farmers, which differ genetically and morphologically from the popular varieties, but only increase the number of items in the collection. Experience shows that the adapted varieties that remained popular for a long period were used in maize breeding as sources of heterosis, while these latter were used as simple gene sources.The pure line method has been used widely and still holds the promise of success. As yet there does not appear to be any fundamentally new method that could replace it to make breeding more efficient.In each era, creative breeders developed competitive new varieties by exploiting the useful genetic variability available, so from the evolutionary point of view, new varieties should be regarded as foundation populations. Banning or restricting the re-utilisation of these populations could block the human regulation of evolution and limit increases in food production.The key question in maize breeding is always the active possession, practical preservation and systematic improvement of the type of biodiversity that is useful from the economic point of view in breeding.
High-molecular-weight glutenin subunits (HMW-GSs) are important seed storage proteins associated with bread-making quality in common wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD). Variation in the Glu-A1x locus in common wheat is scare. Diploid Triticum monococcum ssp. monococcum (2n = 2x = 14, AmAm) is the first cultivated wheat. In the present study, allelic variations at the Glu-A1mx locus were systematically investigated in 197 T. monococcum ssp. monococcum accessions. Out of the 8 detected Glu-A1mx alleles, 5 were novel, including Glu-A1m-b, Glu-A1m-c, Glu-A1m-d, Glu-A1m-g, and Glu-A1m-h. This diversity is higher than that of common wheat. Compared with 1Ax1 and 1Ax2*, which are present in common wheat, these alleles contained three deletions/insertions as well as some single nucleotide polymorphism variations that might affect the elastic properties of wheat flour. New variations in T. monococcum probably occurred after the divergence between A and Am and are excluded in common wheat populations. These allelic variations could be used as novel resources to further improve wheat quality.
Wheat is an important source of staple food and has a major role at human nutrition and it is essential to know the relationships between yield and its components in wheat breeding programs. In the examined characteristics, positive and the expression significant correlation were found statistically between the flag leaf area, germination in mannitol, survival after desiccation and number of tillers per plant with grain yield. Negative and significant relationships were determined statistically between the plant height, water loss of excised leaves, root length and root depth with grain yield. Path coefficient revealed that number of tillers per plant (9.166) and root depth (0.2675) had the highest positive direct effects on grain yield. In addition water loss of excised leaves (−9.057) and survival after desiccation (−0.449) have highest negative direct effect on grain yield. The improvement in grain yield will be efficient if the selection is based on the number of tillers per plant, root depth and flag leaf area under drought conditions. Comparatively high genetic variability was found in grain yield, flag leaf area and tillers per plant. Number of tillers per plant had direct and marked effect and majority of the traits affected grain yield through it.
The sweet cherry (Prunus avium L.) gene-bank collection in Hungary comprises mainly local cultivars. The incompatibility (S) genotypes of 48 accessions from the central region of Hungary were investigated by PCR amplification of the intron regions of the SRNase and SFB genes responsible for compatibility relationships in sweet cherry. The Sgenotypes of 38 accessions were completely determined; they showed various pairs of nine alleles and could be assigned to 15 of the existing incompatibility groups or, in the case of three accessions having the novel genotype S6S13, to the new incompatibility group XLII. For 10 accessions only one S-allele could be identified, as a single S-RNase product was generated and the intron region of the SFB gene of the second allele could not be amplified.
Since a variety registration system was introduced in Hungary in 1914, all the necessary information about varieties improved by professional breeders is made public. However, little is known about the origin of varieties bred by local farmers for their own purposes in Eastern Central Europe. The catalogue of the First National Maize Exhibition, held in Budapest in 1914, provides a unique opportunity to investigate the genetic background of the maize varieties of the time. It seems likely that the diversity of this genetic background was preserved until the beginning of hybrid maize breeding. The flint varieties of the time proved to be the most variable (Caribbean, Andean, Paduan and Northern flints). Among the Corn Belt Dents, Leaming, Queen of the Prairie, Reid Yellow Dent, Iowa Goldmine and Northwestern Dent were the most frequent varieties, while Tuxpan, Gourdseed, Shoepeg, Hickory King and Southern Prolific were the most frequent of the Southern Dent varieties. In many cases the varieties introduced into Eastern Central Europe mixed and crossed spontaneously. In addition to professional breeders, many farmers also used the available varieties as components in crosses, in order to develop new varieties. The most popular were dent × flint crosses, using roughly equal proportions of Old Hungarian Yellow Flints of the Caribbean type and early hard-grained flints of the Andean type. Flint × flint crosses were also popular, partly due to the use of maize for human consumption, and partly to the great genetic variability exhibited by flint varieties. Locally developed maize varieties, which have a background quite different from those developed in the North American Corn Belt, could, after suitable breeding, enrich the available sources of heterosis. Further research will be required to determine which of them are the most valuable.