The dry matter and moisture contents of the aboveground vegetative organs and kernels of four maize hybrids were studied in Martonvásár at five harvest dates, with four replications per hybrid. The dry matter yield per hectare of the kernels and other plant organs were investigated in order to obtain data on the optimum date of harvest for the purposes of biogas and silage production.It was found that the dry mass of the aboveground vegetative organs, both individually and in total, did not increase after silking. During the last third of the ripening period, however, a significant reduction in the dry matter content was sometimes observed as a function of the length of the vegetation period. The data suggest that, with the exception of extreme weather conditions or an extremely long vegetation period, the maximum dry matter yield could be expected to range from 22–42%, depending on the vegetation period of the variety. The harvest date should be chosen to give a kernel moisture content of above 35% for biogas production and below 35% for silage production. In this phenophase most varieties mature when the stalks are still green, so it is unlikely that transport costs can be reduced by waiting for the vegetative mass to dry.
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.
Several generations of maize breeders contributed to the establishment of genetic resources in Eastern Central Europe by developing open-pollinated varieties, inbred maize hybrids and parental lines successfully grown on large areas and differing from those found in the North American Corn Belt and in other regions of Europe. In some cases they used unusual methods or used known methods in an unorthodox fashion. The Caribbean Flints brought to Hungary from Spain by the Turks in the 16th century played an important role in the development of the Eastern Central Europe genetic resources and dominated Hungarian maize production for nearly four hundred years. In the early 19th century these genetic stocks of Caribbean origin were supplemented by Andean popcorn (Chutucuno Chico, Chutucuno Grande), introduced into Hungary from Italy for human consumption and export purposes and to a lesser extent by Northern Flints (Pennsylvania 8-row). Under the influence of American maize exhibitions in the 19th century, Southern Dents (especially Gourdseed, but also Shoepeg, Hickory King and Tuxpan) and Corn Belt Dents (Queen of the Prairie, Iowa Goldmine, Leaming, and to a lesser extent Funk Yellow Dent) gained ground. In Eastern Central Europe dent varieties were late maturing, so they were crossed, primarily with early-maturing hard flints, and also with early variants of the Caribbean type Old Hungarian Yellow Flint, in order to produce new varieties, which then dominated maize production in the first half of the 20th century. In the early years of hybrid maize breeding, the breeders relied greatly on local, productive, adapted sources. As the result of hybrid maize breeding in Eastern Central Europe, two distinct gene pools developed, which it is thought could contribute to a further increase in maize yield averages through an improvement in genetic variability. These two gene pools are the Ruma and Mindszentpuszta (MYD) heterosis sources. At least 30 lines of Ruma origin and 19 of MYD origin have been successfully used in the development of commercial hybrids. From the point of view of breeding early flint × dent hybrids, the European early multi-rowed hard flints, which developed locally, independently of the American Northern Flints, could also be of interest. Less significant varieties and lines that were grown successfully at one time or another could be used as genetic reserves for the development of new variations. The paper will discuss the varieties popular between 1880 and 1983, providing more detailed data on 13 open-pollinated varieties, 2 variety hybrids, 41 inbred hybrids and 40 successful lines.
If hybrids with better yield potential than that of currently grown hybrids are to be developed, new lines will be required with better genes and gene combinations. New character combinations only arise in populations. The probability of developing lines suitable for the development of commercial hybrids from heterozygotic populations is always extremely low. This is probably due to the fact that the linkage groups of the genotype carrying favourable properties are not fixed. The method by which linkage groups can be fixed has been known for several hundred years: continual selection aimed at stabilising and standardising the desired characters, and partial inbreeding. A great deal of breeding experience provides evidence of the fact that the linkage groups containing the desired characters are not necessarily confined to a single chromosome. The joint inheritance of several chromosomes over a number of generations suggests the presence of an as yet unknown mechanism which helps to preserve the favourable characters tested and accumulated by breeding or natural selection in a system offering a number of alternatives.
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.
The aboveground parts, grain yield, dry matter and water content of the silage maize varieties Bermasil (early) and Mv MSC 485 (mid-season) and the grain maize varieties Mv To 286 (early) and NKPX 9283 (mid-season) were analysed to determine how these traits should be modified to develop a variety type more suitable for the production of bioenergy, more particularly biogas.It was established that silage maize types are generally taller, with larger tassels, leaves, cobs and stalk mass below the ear, making them suitable for biogas production. It is important to note, however, that the grain yield of these varieties should not be ignored, as it makes up 40–50% of the total aboveground dry matter yield.As one of the earliest maturing varieties, the silage maize variety Bermasil could be suitable in itself for biogas production. Based on the present and earlier data, it can be concluded that varieties with later maturity dates than those generally used for silage production could also be suitable for biogas production, provided they reliably reach the “half milk line” stage of maturity and a grain moisture content of around 42% every year in the given environment.
The gene pool of Rumai 122, probably derived from Korai Arany (Early Golden, a name suggesting origin from Livingstone’s Early Golden or Early Golden Mastodon), appears to have arisen from genetic mixing between one or more Southern Dent varieties, probably of the Gourdseed type, imported from the Corn Belt in the 1890s, and the local (improved) Korai Bánáti Flint (Early Bánáti Flint) variety (Caribbean type, Old Hungarian Yellow, 8–12-row flint) grown on the Ruma estate. Ruma varieties were grown on around half the maize-growing area in Hungary for 30 years (1925–1955), and enjoyed much the same popularity in Yugoslavia. The varieties bred from the mother plant Rumai 122 in Yugoslavia were Rumai Yellow Dent, Vukovár Yellow Dent and Béllyei Yellow Dent, while those bred in Hungary were “F” Early Yellow Dent and “F” Mczőhegyes Yellow Dent. (The latter was also popular in Yugoslavia under the name Novisadski Flajsman.) As the result of Fleischmann’s breeding methods, not only were varieties with high yield potential and genetic stability developed from Ruma 122, but this strain also served as a source for the successful breeding of parental lines each used in the development of a number of commercial hybrids. A total of at least 22 first-cycle and 8 second-cycle lines of high value are known. These exhibited good combining ability with a wide range of lines, not only from the Corn Belt, but also from Europe (dent and flint alike). Due to their different origin and excellent combining ability, genetic sources that can be traced back to mother line Rumai 122 are regarded as an independent European source of heterosis.
The ancestors of the early, multi-rowed, hard-grained flint maize varieties found in Central Europe, and also of some of the dent varieties, were in all probability Chutucuno Chico and Chutucuno Grande (Timothy et al., 1961), chilling-tolerant, daylength-insensitive, small-eared, multi-rowed, prolific, hard flint popcorn varieties with reddish-brown kernels originating from the slopes of the Andes and introduced into Hungary in the early 1800s via Italy (Nagyváthy, 1822). In Italy and Hungary these varieties were given the names Cinquantino and Pignoletto. In addition to these Andean sources, a considerable contribution to the hard-grained gene pool was also made by Hungarian flints of Caribbean origin, and to a lesser extent by Southern Dents and Corn Belt Dents, while Northern Flints played little role in its development. These maize varieties were grown chiefly for human consumption (in the form of porridge) and were exported to Italy, Slovenia and Romania. The high price paid for exported maize, the low yield and undesirably long vegetation period of the initial sources, and the need to improve the colour and ear fusarium resistance of commercial maize meant that breeding was begun as early as the 1850s. The data available indicate that in around 1856, probably for the first time in Europe but independently of each other, Pál Németh and Pál Máthé crossed Cinquantino with other varieties in order to produce new varieties. These varieties, and those later selected from them, played a role in the maize production of Hungary, Romania, Yugoslavia, Slovakia and other countries for a period of 100 years. In addition, they probably exerted a significant effect on the early flint gene pools of all European countries where the vegetation period is either extremely short or extremely cool.
Between 1980 and 2000 two parallel breeding experiments were carried out to examine the effect of pedigree, backcrossing to the elite line, early testing, visual selection and late testing on the development of inbred maize lines with commercial value. In both series of experiments the standard was a hybrid between the line used as tester and the line chosen for improvement (HMv 9). Early testing was carried out using testers F 2 and HMv 23. In agreement with the literature, the frequency distribution indicated that at least half the families gave a higher yield on both testers than the original line. In the case of grain moisture and stalk strength, the derivatives of the individual populations behaved differently on each tester, suggesting the presence of a tester × donor interaction. On the F 2 tester no families were found which yielded significantly better, while also having significantly lower grain moisture and/or significantly better stalk strength. On tester HMv 23 one family was found which yielded significantly more than the standard while also having significantly lower grain moisture. The final evaluation demonstrated that 6 lines with commercial value were developed in the two breeding experiments; these were used in the breeding of 12 registered hybrids. The performance of the source populations chosen for use in line development was found to be extremely important in the development of lines with commercial value. By comparison the methods used for line development and the testing conditions were of secondary importance and were found to have no significant influence on the tested populations. It was concluded that in breeding programmes aimed at developing commercial lines, even greater attention should be paid to the performance of the source populations. In most cases, due to the small number of families/populations, the fixing of traits during inbreding takes place in a random manner, and selection has little modifying effect as the generations become increasingly homozygous. For the above reasons it is wiser and more economical to choose the simple, cheap line development method.
The grain yield was increased by 8.2% per cycle (32.8% overall) in a population of Mindszentpusztai Yellow Dent (MYD), by 8.9% per cycle (35.6% overall) in a population of Mv Syn. I and by 4.9% per cycle (19.7% overall) in a population of Westigua when tested on the closed pedigree line HMv 124-2. Averaged over the three populations the rise in grain yield was 7.5% per cycle, giving a total of around 30% after four cycles. The grain moisture at harvest showed a slight but significant decrease, while there was no change in the percentage stalk lodging. It seems probable that this increase in grain yield was achieved not at the expense of other correlated characters, but as the result of a greater frequency of gene combinations having a positive effect on grain yield, since recurrent selection was combined with selection for multiple ears at high plant density. The hybrid performance of the improved populations was extremely good, reaching 87.9% of that of commercial hybrids. Over the last 25 years around 11,500 S1 families have been tested from a total of 115 populations (including the three discussed above) and the inbreeding of the selected families was continued until the homozygous state was reached. Despite careful selection, it has not proved possible to breed inbred lines suitable for the development of hybrids with commercial value. Further research will be required to discover the reasons for this failure.