Showing papers on "Plant breeding published in 2002"

Principles and Procedures of Plant Breeding: Biotechnological and Conventional Approaches

Abstract: Preface / Introduction / Reproduction in Crop Plants / Plant Genetic Resources-Origin, Conservation and Utilization / Genetic Basis and Application of Selection in Self-pollinated Crops / Mendelian Consequences of Planned Hybridization in Self-pollinated Crops / Quantitative Inheritance / The Analysis of Genotype-Environment Interactions / Application of Biometrical Genetics in Plant Breeding / Pedigree Method / Bulk Population Breeding Method / The Single Seed Descent Method / Backcross Method / Fertility Regulating Mechanisms / Genetic Basis of Hetrosis / Breeding for Hetrosis / Genetic Structure of Cross-pollinated Crops / Population Improvement in Cross Pollinated Crops / Population Improvement Methods / Synthetic and Composite Varieties / Breeding for Asexually Propagated Crops / Breeding for Resistance to Diseases and Insect Pests / Mutation Breeding / Polyploidy in Plant Breeding / Tissue Culture in Crop Improvement / Molecular Approaches to Crop Improvement / Genetic Transformation and Production of Transgenic Plants / Biometry in Relation to Molecular Biology in Plant Breeding/ Field Plot Techniques in Plant Breeding / Plant Breeder's Rights, Release and Multiplication of Varieties/ Glossary / Index

Diversity changes in an intensively bred wheat germplasm during the 20th century

Abstract: Plant breeding may lead to narrowing genetic diversity of cultivatedcrops, thereby affecting sustained selection gains in crop improvement. A totalof 47 microsatellite primer pairs (mapped to the 21 wheat genetic linkagegroups) were assessed in 75 Nordic spring wheat cultivars bred during the20th century to determine the variation of genetic diversity in thisgermplasm throughout this period. The number of alleles ranged from one toseven, with an average of 3.6 alleles per microsatellite marker. A dendrogramresulting from analysis of the matrix of dissimilarities using the unweightedpair-group method with arithmetic average discriminated all cultivars andrevealed clusters of accessions released both from some geographical area inthe Nordic Region and the breeding era, i.e. before and after World War II. Geneticdiversity in this wheat material increased from 1900 to 1940 and again from1960 onwards. In between these two periods there was a loss of diversity, whichcould not be explained by changes in a single genome or in one or few chromosomesets. Effects of different selection within countries are revealed by cleardifferences in frequency of some microsatellite alleles. In adition somemicrosatellite alleles were lost during the first quarter of the century whileseveral new alleles were introduced in the Nordic spring wheat material duringthe second half of the century. These results suggest that genetic diversity inNordic spring wheat was enhanced by plant breeding in the first quarter of the20th century and following a decrease during the second quarter wasincreased again by plant breeding.

Genetic modification of lignin concentration affects fitness of perennial herbaceous plants.

Abstract: Populations of four perennial herbaceous species that were genetically modified for altered lignin content (or associated forage digestibility) by conventional plant breeding were evaluated for two agricultural fitness traits, plant survival and plant biomass, in three Northcentral USA environments for more than 4 years. Reduced lignin concentration or increased digestibility resulted in increased winter mortality in two of four species and reduced biomass in one species. Results from other experiment indicate that these apparent genetic correlations may be ephemeral, suggesting that selection for fitness can be successful within high-digestibility or low-lignin germplasm. Results indicate that perennial plants genetically engineered with altered lignin concentration or composition for use in livestock, pulp and paper, or bioenergy production should be evaluated for fitness in field environments prior to use in agriculture.

Screening cereals for genotypic variation in efficiency of phosphorus uptake and utilisation

Abstract: One hundred and six Australian cereal genotypes, including wheat, triticale, and rye, were screened for their ability to take up and utilise soluble phosphorus at different rates of P supply. Plants were screened in outdoor tanks irrigated at regular intervals with nutrient solution amended with 3 rates of P. Genotypes were ranked according to the following 3 criteria: shoot growth at deficient P supply, the relative shoot growth rate (dry weight at deficient P/dry weight at sufficient P), and phosphorus utilisation efficiency (amount of dry matter produced per unit of P accumulated in shoots corrected for seed P content). Considerable genotypic variation in growth and P utilisation efficiency was found in the cereal germplasm. Rye and triticale were generally more efficient in taking up and utilising P than wheat at low rates of P supply. Wheat genotypes Egret and Durati showed relatively high, and genotype Cadoux relatively low, P efficiency.

Tagging quantitative trait loci associated with grain yield and root morphological traits in rice (Oryza sativa L.) under contrasting moisture regimes

Abstract: Plant breeding for drought-prone habitats envisages a favorable combination of grain yield and drought resistance. Though several components enhancing drought resistance have been identified in rice,their association with grain yield, under low-moisture stress, has been established in very few instances. We attempt to study the associations between rice grain yield and root system parameters both at phenotypic and genotypic levels. The doubled haploid population of IR64/Azucena was evaluated for root related traits at peak vegetative stage and grain yield related traits under both low-moisture stress and non stress conditions. ‘Mean environment’ was computed for yield related traits. Correlation and QTL mapping was attempted to find out the associations. The correlation between maximum root length and grain yield was positive under stress and negative in non stress. Genotypes with thicker and deeper roots, manifested higher biomass and grain yield under stress. Only one QTL found to increase days to flowering in non stress was also found to influence root volume and dry weight negatively under stress. The study suggests that loci enhancing grain yield and related traits were not pleiotropic with loci for desirable root morphological traits studied under low-moisture stress at vegetative stage, in the genetic material used in the study. It is thus possible to combine higher grain yield and desirable root morphological traits, favorably, to enhance productivity of rice under low-moisture stress. In rainfed ecologies, where deep roots contribute to enhanced drought resistance in rice, the results indicate the possibility of combining drought resistance with higher levels of grain yield.

Scope for genetic manipulation of mineral acquisition in chickpea

Abstract: Nutrient acquisition in chickpea needs to be efficient, because it is mainly grown as a post-rainy season, rainfed crop, and generally on soils inferior in physical characteristics and poor in fertility. Nutrient deficiencies have been reported to cause yield losses of varying magnitude in chickpea, e.g., 22–50% due to iron (Fe), around 10% due to sub-optimal nodulation and hence nitrogen (N) deficiency, 29–45% due to phosphorus (P), up to 100% due to boron (B), and 16-30% due to sulphur (S). Yield losses due to salinity are equally large but are difficult to estimate because of its heterogeneous occurrence. In chickpea, genotypic differences in morpho-physiological (including root size) and functional (exudates) root traits, and in nodulation capacity for increased nitrogen fixation have been identified. Genotypic differences in response to application of Fe, B and zinc (Zn) have also been found among chickpea genotypes. A drought tolerant chickpea genotype ICC 4958, which has a relatively large root system, acquired more P than other genotypes during the vegetative period in a pot experiment at ICRISAT. The recent thrust on identifying QTLs for root size should facilitate progress in incorporating useful root traits through marker assisted selection in desirable agronomic backgrounds. Selection for nodulation capacity in released cultivars has resulted in high nodulating chickpea genotypes that produced 10% higher yield than the control varieties. Information on targeted crop improvement for higher nutrient-use efficiency for P, S, Zn, B and Fe is not readily available. Methods to screen for tolerance to salinity are available, but sufficiently high levels of tolerance have not yet been found in germplasm or wild relatives of chickpea to warrant breeding for salinity tolerance. Use of alternative approaches, such as mutation to generate genetic diversity or introgression of alien genes from other crops (transgenic) are thus required, and these remain long-term objectives.

Reduced somaclonal variation in barley is associated with culturing highly differentiated, meristematic tissues

Abstract: Modern plant breeding programs depend heavily on germplasm resources composed of closely related breeding lines and cultivars. Asexual introduction of recombinant DNA offers novel opportunities for crop improvement, but most transformation methods rely on tissue culture systems which are mutagenic. The resultant transgenic plants frequently contain undesirable genetic changes (somaclonal variation), in addition to the introduced transgene. Such plants may have reduced agronomic performance, which complicates their use as parents in a breeding program. The development of tissue culture systems that are less mutagenic should enable the production of transgenic plants with superior performance. In this study, agronomic traits were measured for plants regenerated from cultures of two barley (Hordeum vulgare L.) genotypes, using three different tissue culture systems, and compared with the performance of uncultured controls. Plants derived from all three systems were shown to have reduced performance for one or more agronomic traits, but there were clear differences attributable to the culture system. Plants derived from standard embryogenic callus tissues were shown to have the greatest reductions in agronomic performance. Two other tissue culture systems, which had been developed for increased regenerability, showed better performance. Plants derived from highly differentiated, meristematic tissues showed the least reductions in agronomic performance. Plants derived from a modification of the embryogenic callus system-which is characterized by an intermediate level of differentiation-showed intermediate levels of agronomic performance. These results demonstrate that modifications of methodology, in addition to improving plant regenerability, can reduce the level of somaclonal variation in regenerated plants.

Analysis of genetic diversity within Australian lucerne cultivars and implications for future genetic improvement

Abstract: Lucerne (Medicago sativa L.) is autotetraploid, and predominantly allogamous. This complex breeding structure maximises the genetic diversity within lucerne populations making it difficult to genetically discriminate between populations. The objective of this study was to evaluate the level of random genetic diversity within and between a selection of Australian-grown lucerne cultivars, with tetraploid M. falcata included as a possible divergent control source. This diversity was evaluated using random amplified polymorphic DNA (RAPDs). Nineteen plants from each of 10 cultivars were analysed. Using 11 RAPD primers, 96 polymorphic bands were scored as present or absent across the 190 individuals. Genetic similarity estimates (GSEs) of all pair-wise comparisons were calculated from these data. Mean GSEs within cultivars ranged from 0.43 to 0.51. Cultivar Venus (0.43) had the highest level of intra-population genetic diversity and cultivar Sequel HR (0.51) had the lowest level of intra-population genetic diversity. Mean GSEs between cultivars ranged from 0.31 to 0.49, which overlapped with values obtained for within-cultivar GSE, thus not allowing separation of the cultivars. The high level of intra- and inter-population diversity that was detected is most likely due to the breeding of synthetic cultivars using parents derived from a number of diverse sources. Cultivar-specific polymorphisms were only identified in the M. falcata source, which like M. sativa, is outcrossing and autotetraploid. From a cluster analysis and a principal components analysis, it was clear that M. falcata was distinct from the other cultivars. The results indicate that the M. falcata accession tested has not been widely used in Australian lucerne breeding programs, and offers a means of introducing new genetic diversity into the lucerne gene pool. This provides a means of maximising heterozygosity, which is essential to maximising productivity in lucerne.

Farmers' seed management practices open up new base populations for pearl millet breeding in a semi-arid zone of India

Abstract: Farmers in western Rajasthan (north-west India) produce and maintain their landrace populations of pearl millet through their own distinct seed management practices. The objective of this study was to characterize morphological and agronomic variability of different traits between and within three farmers' populations using quantitative-genetic parameters. Populations examined were a typical landrace and two modified landraces, which were generated through farmer introgression of modern varieties with different levels of subsequent selection. From these three populations, 100 random full-sib progenies were evaluated in field trials at two locations in western Rajasthan over two years. Significant genetic variation existed within the three populations. Estimates of heritability were moderate to high for all observed traits. Predicted selection response for grain yield across environments was 1.6% for the typical landrace and 2.2% for both the modified landraces. Results suggest that the introgression of modern varieties into landraces had increased the genetic diversity. Therefore, farmers' current breeding activities could open up new resources for plant breeding programmes aiming at plant improvement for the semiarid zones of India.

Relationship between genetic divergence and hybrid performance in japonica rice grown in a cold water-irrigated field

Abstract: The present study was carried out to evaluate genetic divergence among eleven japonica rice cultivars and to assess the relationship between genetic distance and hybrid performance in partial non-reciprocal crosses among them The 44 F1 hybrids along with the eleven parents were evaluated for five cold tolerance-related traits; discoloration at seedling stage, days to heading, culm length, fertility, and spikelets per panicle in a cold water screening nursery (17 °C) The eleven parents were examined for DNA polymorphism using amplified fragment length polymorphisms(AFLPs) A total of 855 polymorphic variants were generated and based on the polymorphism data, genetic distances (GDs) ranged from 0023 to0524 Very little heterosis was observed in hybrids for most of the traits,whereas heterosis was high for fertility The correlation values of GDs with F1 performance were mostly non-significant except for discoloration and fertility The correlations of GDs with mid-parent and better-parent heterosis were not significant and proved to be of no predictive value Our results indicate that GDs based on AFLP markers are not useful for predicting heterosis for cold tolerance in japonica hybrids

Genetic control of quality traits of lucerne (Medicago sativa L.)

Abstract: An important objective in lucerne breeding is the improvement of feeding value. An understanding of the inheritance of digestibility and cell wall related traits would facilitate the breeding of varieties with higher feeding value. The aim of this experiment was first to determine the genetic control of dry matter digestibility and related biochemical and morphological traits, and to assess phenotypic and genetic correlations between these traits. Quantitative genetic parameters were estimated for enzymatic solubility, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), protein content, plant height, and leaf-to-stem ratio. A 7 × 7 diallel design with reciprocals and without selfing among parents from different populations and a 7 × 7 factorial design within the 'Flamande' population were studied. In the diallel study, effects due to general combining ability (GCA) were higher than those due to specific combining ability (SCA) for all characters tested. In the factorial study, the F1 progeny effect was significant for all characters. The male effect was highly significant for all traits and higher than the female effect except for plant height. The additive variance was higher than the dominance variance for all characters except for plant height. The inheritance was predominantly additive. The highest narrow- sense heritabilities were found for NDF and ADF and leaf-to-stem ratio. As a consequence, NDF or ADF would be more efficient selection criteria than enzymatic solubility in a breeding program for improved feeding value. In both mating designs, NDF, ADF, and ADL were positively correlated with one another and negatively with enzymatic solubility and protein content. Additional keywords: combining ability, additive variance, dominance variance, heritability, within- and among- population genetic variation. A ro y t rn F

Molecular Genetics — Plant Breeder’s Perspective

Abstract: Plant breeding is the art and science of changing and improving the heredity of plants to develop desired products with new genetic properties. The science of plant breeding consists of two phases, the evolutionary phase, which aims at creating or enlarging genetic variability, and the evaluation phase, which aims at selecting desirable genotypes from the variable populations. During the last four decades, major gains have been made in increasing productivity of major food crops worldwide. As an example, world rice production has more than doubled from 257 million tones in 1966 to 596 million tones in 1999. These gains in crop productivity have been achieved mainly through the application of principles of Mendelian Genetics and conventional plant breeding methods. However, to meet the growing need of ever increasing human population, the food grain production must increase by 50% in 2025. International Food Policy Research Institute (IFPRI, 1997) has estimated that maize production must increase by 80%, wheat by 60%, and rice by 40% during the next 25 years. There are no more suitable lands available for expansion of agriculture. Also, intensive agricultural systems have raised concerns about degradation of natural resources and environment deterioration. Therefore, we have to increase the food grain production from less land, less chemicals, less water, and less labor.

Heterosis Study of Certain Important Traits in Wheat

Abstract: Heterosis studies in ten crosses of bread wheat involving three varieties viz; Chakwal-86, Pak-81 and M.H-97 and two lines viz; 9068 and 243-1 were carried out in the experimental area of the Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad. Highly significant genetic variability was present in the experimental material for the traits under study except number of tillers per plant and spike length. Most of the crosses showed significant heterosis over mid and better parents for various characters. The crosses 9068 X 243-1,Chakwal-86 X 243-1 and Pak-81 X 243-1 may be considered for selection as hybrid or pure line wheat varieties after achieving desired homozygosity.

Genetic purity analysis of hybrid broccoli (Brassica oleracea var. italica) seeds using RAPD PCR

Abstract: Determination of genetic purity of F1-hybrid seeds is aquality control requirement in the production of hybrid Brassica vegetableseeds. Hybrid varieties of these vegetable crops have arisen from a limitedgermplasm base, making discrimination of parental and hybrid lines verylaborious and troublesome. The use of RAPD PCR for evaluating seed purity in acommercial F1-hybrid broccoli a single cultivar bywithholding water. In Expt 2, plants of EP and MK were grown together in thesame container and received water daily with gradation in intensity of waterdeficit achieved by varying the daily water ration per container. All cultivars in each experiment exhibited commonly reported responses towater deficit, characterised by diminished evaporative surface area andincreased root : shoot ratio. The response of MK was primarily morphologicaland MK plants had smaller plant size, higher root : shoot ratio, and a lowergrowth rate compared with temperate cultivars. By contrast, response oftemperate cultivars was primarily physiological; stomatal conductance oftemperate cultivars was lower and these cultivars had a greater tendency forleaf lamina osmotic a

The genetic diversity of components of rye hybrids.

Abstract: The genetic variability between 5 open-pollinated varieties of rye (Secale cereale L) and between the components of rye hybrids was estimated using PCR-based marker analysis. The 22 maternal single crosses and 11 restorers were the components of hybrids investigated in the preofficial trials at the Plant Breeding and Acclimatization Institute in Radzikow (PBAI), the Danko Breeding Co. Ltd (DBC) and in the Poznan Breeding Co. Ltd (PBC) during the 2001 growing season. The PCR system using semispecific primers targeting the intron-exon junction sequences of plant genes was applied for the evaluation of the genetic diversity of rye breeding materials. The genetic distances between varieties were relatively low. The coefficients of dissimilarity did not exceed 0,15. The highest average distance between maternal hybrids and restorers (0,28) was found in materials from PBAI, whereas in materials from PBC and DBC the average distances were lower and reached 0,21 and 0,20 respectively. The cluster analysis based on PCR data indicated that hybrid components that originated from different breeding centres exhibited different genetic characters.

Genetic analysis of ear length and correlated traits in maize

Abstract: v CHAPTER 1. GENERAL INTRODUCTION

Plant Cell and Tissue Culture Techniques Used in Plant Breeding

Abstract: Plant breeding proper is applied science. It applies sciences, such as botany (taxonomy, morphology, physiology), genetics (cytology and ecological, population, quantitative, and molecular genetics), mathematics (biometry, statistics), chemistry (food, fiber, and fuel chemistry), and finally economics (agricultural, forest, and industrial economics). Plant breeding is closely related to human prosperity, producing food, feed, fiber, and fuel. It is also closely related to human socioeconomic development, from subsistence farming through stages of societal development to industrial farming and forestry. Plant breeding also has strong cultural heritage values in connection with the architecture of gardens, communities, and landscapes. Rural and urban landscapes both rely heavily on the use of cultivated plants that are the results of long-term plant domestication (man-made evolution spanning human generations) and short-term efficient plant breeding (genetic manipulations resulting in intellectual properties). Depending on its socioeconomic status in the society, plant breeding is either a state-supported social undertaking, with its values interwoven into the state infrastructure, or a private enterprise, often with international cov-

Variation and association analysis in grass pea (lathyrus sativus l.)

Abstract: The study was conducted on 50 landrace populations of grass pea at Adet Research Center, Ethiopia, using randomised complete Block design in three replications to determine morphological variability and character associations. Evaluations were made on plant and yield characters from eight plants tagged randomly from each plot. The data were subjected to Analysis of Variance (anova), heritability, correlation and cluster analyses. Higher mean and cv values were recorded for most of the agronomic traits for populations collected from Gondar region and the higher altitude group (>2500 m) indicating the presence of high genetic diversity in this region and altitude group. Phenotypic coefficient of variation (pcv) was slightly higher than genotypic coefficient of variation (gcv) for all the characters studied signifying that genotypic factors exerted reasonable effect in estimating the variation. The wide difference between pcv (22.4%) and gcv (13.0%) for seed yield per plant indicated the complexity of this trait and the important role of other factors such as environment in influencing yield potential in addition to the genetic factors. The strong positive association of pods per plant, 100 seed weight and primary branches per plant with seed yield indicated the possibility of selecting lines for yield improvement based on these characters at the very early stage of the grass pea breeding program. Key words/phrases: Correlation grass pea, heritability, Lathyrus sativus, variation SINET: Ethiopian Journal of Science Vol.25(2) 2002: 191-204

Inheritance of partial resistance to the brown spot disease in Lupinus angustifolius L

Abstract: Brown spot (BS) is a damaging disease of narrow-leafed lupins (Lupinus angustifolius L.), particularly in Western Australia. Breeding for resistance to the causal agent [Pleiochaeta setosa (Kirchn.) Hughes] has had some success. Here, earlier data on the extent and inheritance of resistance to BS are presented as a possible guide for future breeding programs. In 1980, 236 Mediterranean wild accessions from the Australian germplasm collection, and 17 cultivars and 20 breeding lines of L. angustifolius and L. albus L., were tested by natural infection in replicated short rows at 2 sites in southern New South Wales. The area of lower leaves covered by lesions was up to 70% lower on partially resistant lines than on commercial cultivars. Twelve wild accessions were consistently more resistant than 5 cultivars at Wagga Wagga in 1980 and in 2 subsequent years, in which 66 wild lines and 6 cultivars were tested. However, the rankings at Wagga Wagga differed from those in coastal Western Australia, suggesting that spatial differences occur in the pathotype composition of the fungus. The absence of sexual reproduction in the fungus suggests that its pathotype spectrum would change only slowly at each location. Unimodal distributions of BS scores for individual plants were found in the F2 of Illyarrie (susceptible) × CPI 67877 (resistant) and in the backcross to Illyarrie. The F2 mean was intermediate between the 2 parental means, and only a few plants had a score as low as the resistant parent. The regression of the mean scores for 15 F2 families from crosses among 7 wild lines, and between these and 2 susceptible cultivars, on the respective mid-parent values gave a narrow-sense heritability estimate of 0.94 ± 0.17 on a family mean basis. Thus, resistance was controlled by many loci with co-dominant alleles and should be robust. There was no linkage of resistance genes to the low alkaloid or white flower/green plant loci. Assuming the absence of dominance, the upper limit of narrow-sense heritability on a single plant basis was 0.50 ± 0.13. Several rounds of selection of partially resistant individuals in F2 families and intercrossing among F3 plants from many different wild × domesticated crosses are likely to produce cultivars with much more resistance than those now available. The applicability of the results at Wagga Wagga to the eastern wheatbelt of Western Australia, where BS is acute, and optimum field selection procedures are discussed.

Relationships between age and biomass of individual plants and seed production in two grazed tropical legumes. 1. Derivation of relationships

Abstract: The distributions of individual plant age and biomass of Chamaecrista rotundifolia cv. Wynn and a mix of Stylosanthes scabra cvv. Seca and Fitzroy in grazed grass-legume pastures were examined to determine their effect on seed production. The effects of enhanced soil water conditions and severe defoliation on seed production were assessed in ungrazed plots. These experiments were part of a larger study to develop a demographic model of perennial forage legumes. The distribution of individual plant age and biomass was highly skewed towards a large number of young/small plants, with fewer old/large plants. Lack of seed set when stem length was less than approximately 200 mm, and in most small plants ( 3000 kg/ha of grass. Using log-transformed data, plant biomass accounted for 74% of the variation in seed production (SP), but together with grass biomass accounted for 91% of the variation (ln(SP) = 6.01 + 0.91*ln(BIOMASS) - 0.28*ln(GRASS BIOMASS), P < 0.001). Total legume biomass accounted for only 44% of the variation in seed production. S. scabra herbage allowance (kg legume/head) had a major impact on seed production. Total legume biomass and individual plant biomass alone accounted for less than 40% of the variation in seed production. Using herbage allowance (HA) as well as individual plant biomass improved the prediction of seed production (SP) to account for 74% of the variation (ln(SP) = 0.11 + 1.14*ln(BIOMASS) + 0.24*ln(HA), P < 0.001). Enhanced soil water conditions increased the biomass of individual plants of both species and increased the seed production per gram of plant in S. scabra but not in C. rotundifolia. Severe defoliation in early summer or autumn can greatly reduce or even eliminate seed production by some plants by removal of flowers, reducing individual plant biomass, or allowing insufficient time for plants to reach minimum stem lengths. The different factors affecting seed production in the 2 species highlight the complexity of legume seed set in grazed pasture systems, and some implications for grazing management and modelling are discussed.