Showing papers on "Plant breeding published in 1984"

Wide hybridization experiments in cereals.

Abstract: Wide hybridization is a useful tool in plant breeding, but little is known about its possible range. For the cereals, wheat, barley and rye, this was tested with 15 different species of the Poaceae and Panicoideae. Embryo formation could be obtained with Agropyron repens, Alopecurus agrestis, Dactylis glomerata, Festuca glauca, Hordeum bulbosum, Lolium perenne, Pennisetum americanum, and Zea mays. As well, haploid as diploid embryos occurred. New embryo culture techniques should enable these embryos to grow to plants.

Applications of genetic engineering to crop improvement.

Abstract: I. Nitrogen Fixation.- 1. Breeding Legumes for Improved N2-Fixation.- 2. In vitro Systems for Studying Nitrogen Fixation.- 3. Molecular Genetics of Nitrogen Fixation.- II. Photosynthesis.- 4. Breeding for Improved CO2 Fixation.- 5. Aspects of Photosynthetic Plant Tissue Cultures.- 6. The Chloroplast Nuclear Photosynthesis Genes.- III. Seed Quality.- 7. Breeding for Grain Quality.- 8. Tissue Culture and Related Approaches for Grain Quality Improvement.- 9. Genetic Engineering of Genes Controlling Seed Quality.- IV. Stress Tolerance.- 10. Breeding Crops for Environmental Stress Tolerance.- 11. Cellular Approaches to Environmental Stress Resistance.- 12. Molecular Mechanisms of Heat Stress Tolerance.- V. Disease Resistance.- 13. Breeding for Disease Resistance.- 14. In vitro Approaches to Disease Resistance.- 15. Genetic Engineering for Improved Crop Disease Resistance.- VI. Secondary Products.- 16. Conventional Breeding for Secondary Products.- 17. Secondary Products in Tissue Culture.

Yield responses by modern wheat genotypes to phosphate fertilizer and their implications for breeding.

Abstract: The response to phosphate fertilizer by modern wheat genotypes was examined in the field under natural rainfall in three seasons. Models were developed which show that grain yield was positively correlated with biological yield and harvest index. In one of the seasons, which was relatively dry, shorter statured wheats gave higher yields at each level of applied phosphate. Higher levels of phosphate tended to offset the reduction in yield associated with late heading and the importance of biological yield on grain yield. The genotypes which produced the largest number of grains m-2 produced the highest yields. Implications for plant breeding programs are discussed.

Progress in Conventional Plant Breeding

Abstract: Grain yields of wheat, maize, sorghum and soybeans have increased continually since 1930. Variety improvement has been responsible for 50% or more of the yield increase for each crop. Genetic improvements in yield potential have increased linearly for the past 25 years and show no sign of leveling off, for any crop. Improved varieties of the cereal grains: wheat, maize and sorghum, have in part been superior because they were able to efficiently utilize increased amounts of commercial nitrogen fertilizer. Increased yield potential of new varieties of all four crops generally is due to improvements in defensive traits such as standability, heat and drought tolerance, and pest resistance. Inheritance of the improved traits is usually genetically complex and is not well understood either in genetic or physiological terms. A list of most needed genetic improvements in new varieties will include such things as improvements in yield potential, stress tolerance, and pest resistance. Until the genetics and physiology of these traits are better understood it will be difficult for biotechnology to make major direct contributions to plant breeding. However biotechnology can make many useful small contributions to plant breeding at the present time and eventually it also will provide major assistance in explaining the genetics and physiology of important traits.

Current practices for correcting iron deficiency in plants with emphasis on genetics

Abstract: There are important genetic differences in some crop species for the amount of loss in production caused by iron‐deficiency chlorosis. Progress has been made in the correction of iron deficiency by the development and use of iron‐efficient genotypes. Breeders of oat (Avena byzantina C. Koch), dry bean (Phaseolus vulgaris L.), sorghum [Sorghum bicolor (L.) Moench], and soybean [Glycine max (L.) Merrill] are engaged in the selection of cultivars with improved iron efficiency. Genotypes of soybean have been developed with iron efficiency superior to that previously identified in the species. Information on the iron chlorosis resistance of soybean cultivars is provided to farmers to facilitate their selection of appropriate seed. Seed mixtures of efficient and inefficient soybean cultivars are used to maximize production and minimize the risk of crop loss from iron deficiency under appropriate conditions.

Biotechnology touches the forest

Abstract: Both the United States and New Zealand are doing research in forest biotechnology and much of the interest is in speedy propagation from seed to mature tree. A number of propagation techniques are discussed, such as tissue culture, the culture of tissue from mature trees and somatic embryo genesis. Much of the tissue culture work has been done on radiata pine. Field testing results are considered. The aims and the advantages of forest biotechnology are discussed under the following headings. 1) Disease resistance: research is being carried out on a loblolly pine which would be resistant to fusiform rust. 2) Animal feed: some trees have been discovered to have lower lignin content and similar cellulose and hemicellulose to alfalfa. 3) Specialty chemicals: terpenes, in the tree resin, could be turned into hormones, drugs and other chemicals: the genetic system for the overall biosynthesis of terpenes has been studied. 4) Herbicide resistance. The resistance to glyphosate in poplars is being studied. In conclusion, further research into forest species, using molecular biology is considered essential.

Genetic variation for grain yield and related traits in sorghum introgression populations.

Abstract: Each of two sorghum (Sorghum bicolor (L.) Moench) cultivars were crossed with representatives of three wild sorghum races. Backcross-derived sorghum populations containing 3.125 to 50% wild germplasm were evaluated for grain yield, 100-kernel weight, days to flower, and plant height. Population means increased linearly with backcrossing for kernel weight, increased curvilinearly for grain yield, decreased curvilinearly for plant height, and changed erratically for days to flower. For all traits, the relationship between genetic variance and level of backcrossing deviated significantly from that expected based on an additive model. Genetic variance usually reached a maximum in the BC1 or BC2. The BC1 genetic variance for grain yield, averaged over matings, was twice as large as the average BC0 genetic variance. An epistatic model involving gene regulation is proposed as a plausible explanation for the results.

Mutation breeding of grain legumes

Abstract: Genetic variation among existing cultivars and in germplasm collections is the outcome of selection during evolution and plant breeding. Mutagenesis offers the plant breeder a chance to tackle unconventional objectives, particularly those that were at a selection disadvantage in the past. Effective mutagens are available, but the bottleneck is the effective selection of rare desired variants from large mutagenized populations. Selection methods must be non-destructive. Grain legume mutation breeding has already led to improved cultivars with higher yield, better grain quality, or stronger resistance to pathogens. Many mutations affecting nitrogen fixation related traits have also been reported. Some could be useful in breeding better cultivars, but the majority are being used to study the factors interacting in the complex process of symbiotic nitrogen fixation and to improve the strategy for producing cultivars with better fixation capacity.

Matromorphy in Pisum sativum L.

Abstract: The possibility of obtaining instant pure breeding lines by matromorph seed development in Pisum sativum L. has been investigated. Two types of maternal parents, namely, homozygous for the recessive marker genes and heterozygous for the dominant marker genes were pollinated with Lathyrus odoratus and the ‘P174’ variety of Pisum sativum L. carrying dominant markers. For both pollinators, induction of matromorphy by prickle pollination, irradiated pollen and IAA treatment was examined. Promising matromorphs were identified in the M1 generation which were studied in the M2 generation for assessing their genetic status with respect to homozygosis. The success of pod set varied from zero to 28% with a varying number of matromorphic seeds following different treatments. The possible mechanisms for matromorphic origin have been discussed. The evidence presented herein favours induction of matromorphy in peas for the production of homozygous stocks. In addition, the recovery of double recessive seed markers of the maternal parents along with plant markers from the paternals has prospective implications in plant breeding as an alternative tool to recurrent back crossing.

Value of Rice Characteristics in Selection for Resistance to Salinity in an Arid Environment1

Abstract: The reaction of rice (Oryza sativa L.) plants to soil salinity was studied to identify characteristics of possible value in selection and to develop rapid, reliable selection procedures for use in the development of salinity-resistant rice cultivars. Fourteen characteristics were measured on six cultivars growing in the greenhouse on a mixed hyperthermic Typic Torripsamment-Rositas very fine sand treated with three levels of salinity for 2 years. Year, cultivar, salinity, and the year ✕ cultivar interaction had highly significant effects on most characters. The significant differences for cultivars ✕ years indicate that observations should be made for 2 or more years. Few characteristics showed significant interactions for the year ✕ salinity and cultivar ✕ salinity interactions. Important exceptions were the reproductive characteristics of percent underdeveloped spikelets and chaff weight (an estimate of blanking). From this it appeared selections could be made to reduce the percentage of underdeveloped spikelets and chaff weight. Characteristics with the highest correlation with seed weight were tillers at seedling stage and panicle length. Straw weight and weight of chaff plus straw had significantly positive correlations with the other vegetative characters, plant height and days to maturity, but significantly negative correlations with the reproductive characters of panicle and seed number and weight. Significant correlations and interactions indicate selections should be made for young plants with many tillers and against vigorous adult plants failing to develop reproductively.

Plant Breeding 1910–1984

Abstract: The title of my assignment suggests that I should say something about the history of plant breeding from 1910 to 1984. Why no earlier than 1910? Perhaps it is because by 1910 we were beginning to apply Mendel’s classical genetic papers, recognizing the gene and its role in plant breeding. Certainly plant breeding did not start in 1910.