Dissertations / Theses on the topic 'Alfalfa – Breeding'

This investigation examined the efficiency of various screening procedures which could be used in breeding for increased production of root-proliferating (RP) genotypes of alfalfa (Medicago sativa L. s. l.). Also investigated were relationships between RP and winter growth characteristics in populations derived from crosses between dormant, RP clones and nondormant, non-RP clones. In addition, this investigation also considered the inheritance of the RP habit. Plants from an 11-month F₁ progeny test containing 3508 offspring were qualitatively analyzed for RP expression using three pairs of screening procedures. Procedures compared included: (1) direct-seeding vs. transplanting; (2) use of characterized parental clones (known RP-expressing genotypes selected from field nursery) vs. uncharacterized parental clones (genotypes derived from RP seed lots with no prior knowledge of their ability to express the RP habit) in RP x nondormant crosses; and (3) low vs. high harvest frequencies. A low frequency (3.3%) of F₁ plants exhibited adventitious shoot formation. No differences were observed in the frequency of RP-expressing genotypes between the direct-seeded and transplanted treatments or between the low and high harvest frequency treatments. Characterized RP parents produced a hybrid population with a significantly higher frequency of RP-expressing genotypes than did the F₁ population derived from uncharacterized RP parents. Average winter forage production of the F₁ hybrids were similar in magnitude to the midparent value. Plant height was significantly and positively correlated with forage yield and could be used as an accurate indicator of winter forage yield in analyses of RP segregants. Estimates of components of genetic variance for RP expressivity indicated a predominance of additive effects and narrow sense heritability of 8.4%. Family selection and progeny testing are suggested for maximum breeding progress.

Regrowth and yield of 23 Middle Eastern (ME) cultivars and the elite cultivar Lew were evaluated for twelve regrowth harvests in pure stands and 50:50 mixtures with Lew in 1988 at Tucson, Arizona. Stem elongation rate and crown shoot development were measured on selected ME cultivars and Lew in the spring of 1988. No significant differences in yield were observed between mixtures and monocultures. Few significant differences were observed over all yields among ME cultivars and Lew. Cultivars from Saudi Arabia and Egypt produced more forage than Lew in spring harvests. These cultivars developed crown shoots precociously and had high stem elongation rates during the first week of regrowth. Most ME cultivars had higher leaf area and leaf:stem ratio than did Lew. These findings suggest that ME cultivars may be useful in improving forage yield during the winter and spring and forage quality in elite nondormant cultivars.

Thesis (MTech (Agriculture))--Cape Technikon, 1998.
The drymatter - and animal production of nine lucerne cultivars were evaluated under dryland conditions with SA Mutton Merino sheep at Outeniqua Experimental Farm (George). The nine lucerne cultivars that were chosen for this experiment, were already evaluated in cutting trials for their drymatter production. They consist of one winterdormant cultivar (Alfagraze), two semi-winterdormant cultivars (WL 320 and Meteor), five intermediate-winterdormant cultivars (SA Standard, Standard Tygerhoek, Aurora, Diamond and WL Southern Special) and one winteractive cultivar (Cuf 101). The mild climate of this area resulted mainly in a difference in drymatter production between the most winterdormant cultivar (Alfagraze) and winteractive cultivar (Cuf 101). The only difference in the rate of production of winterdormant types appear in winter and spring. The production rate of the winterdormant and semi-winterdormant cultivars was lower in the winter than that of the intermediate winterdormant (WL Southern Special) and the winteractive cultivar (Cuf 101). The drymatter production of the semi-winterdormant cultivar (WL 320) was higher than that of the winteractive cultivar (Cuf 101) in spring. There is a seasonal difference in the drymatter production of lucerne cultivars from the same winterdormancy class. Some of the more winterdormant cultivars also achieve a comparable and even higher dry matter production than that of the more winteractive cultivars. This tendancy is prominant between the semi-winterdormant cultivars (WL 320 and Meteor). WL 320 has a higher dry matter production than Meteor. It also has a higher or equal production rate, dependant on the seasons, than the winteractive cultivar (Cuf 101). A similar tendancy appears in the intermediatewinterdormant cultivar (WL Southern Special). The seasonal drymatter production and production rate of this cultivar are the same as that of Cuf 101. The appearance of annual grasses and weeds had a seasonal influence on the availability of dry matter and animal production. The grass production increases over the years resulting in up to 20% increase of the green matter during winter and spring. The grazing capacity of the winterdormant cultivar (Alfagraze) has increased during this seasonal grass production. The lucerne cultivar with the highest drymatter production rate and the highest seasonal dry matter production, also had the highest grazing capacity. The yearly and seasonal grazing capacity of WL 320, Aurora, WL Southern Special and Cuf 101 was generally higher than most of the other cultivars. This was also the most important reason for the high live mass increase with these cultivars.

There has been limited research on the rooting patterns of alfalfa. This information would be important in developing new germplasm sources that are more water efficient, salt tolerant and drought tolerant. Ten alfalfa varieties were evaluated for possible genetic control of rooting traits. Seedlings were grown hydroponically in a growth chamber. The cultivars evaluated showed a significant statistical difference for width of lateral root system and number of lateral roots. The variation in seedling rooting patterns is sufficient to warrant a selection program for improved lateral rooting patterns.

The performance of an alfalfa (Medicago sativa L.) population has been improved by recurrent selection for germination salt tolerance. However, recurrent selection may lead to increased inbreeding. Since alfalfa is subject to severe inbreeding depression, accumulation of inbreeding during the selection process may negatively affect performance. This experiment was designed to determine the effects of inbreeding on germination performance in alfalfa under saline and non-saline conditions. The germination performance of seed having three different levels of inbreeding as examined. No adverse effects of inbreeding were observed in non-saline conditions. Consistent (but nonsignificant) declining trends were observed in germination percentage in saline conditions as the level of inbreeding increased. Proportionately larger declines were observed between generations in germination speed and early seedling vigor. These results suggest heterozygosity in alfalfa may be maintained simultaneously while recurrent selection for germination salt tolerance is conducted. Moreover, reducing inbreeding during recurrent selection for germination salt tolerance may be more successful if germination speed index or early seeding vigor are used for the measurement.

Deposition of salts from irrigation water is an increasing concern for Arizona farmers and agronomists. Selection for salt tolerance during the seedling stage has been undertaken over the past three years. Yield tests were conducted in greenhouses and a significant increase in dry matter production was shown in the selected material.

Increasing crop salt tolerance can mean higher yields on irrigated farmland and salt -affected soils. Three cycles of selection were made for growth of alfalfa seedlings under 7500 ppm NaCl. Comparison of parent and selected populations was made for yield and germination under saline conditions. Yield of the last cycle was significantly improved. Germination of the last two cycles was higher than that of the parent and cycle 1.

Improving the germination salt tolerance of alfalfa will help this crop endure both increasingly saline irrigation water and salt build -up in the soil. Seven previous cycles of selection for salt tolerance at germination plus the parental line, Mesa-Sirsa, were evaluated for percentage germination under various levels of NaCI solutions. Germination improved linearly from the earliest to the latest cycle of selection. Germination salt tolerance can be improved through recurrent selection techniques.

Alfalfa which is extremely salt tolerant during germination has been developed by researchers at the University of Arizona Carbohydrates were analyzed in the original parental gemiplasm 'Mesa- Sirsa' and Cycle₅Syn₂ and Cycle₈Syn₂ seed to determine why this seed could germinate in extremely saline conditions. Raffinose and sucrose were both significantly higher in the salt -tolerant germplasm compared to the parental germplasm; however, the magnitude increase of these free sugars was not sufficient to explain the increased ability of the seed to absorb water in a stress environment. The galactomannan content was not different among the alfalfa germplasms.

Genetic variability must exist for a selection program to be successful. Alfalfa seedlings were selected for salt tolerance after six weeks growth at 7500 ppm NaCl. The selection criteria considered plant height and survival. Variability for each factor within a population of alfalfa was shown. Both criteria were important and facilitated selection from those parents which contributed most to the salt tolerance of the population.

The nondormant alfalfa cultivars now grown in Arizona trace largely to a small number of alfalfas introduced from the Middle East. Middle Eastern alfalfas regrow rapidly primarily from crown shoots following harvest and produce high yields during late fall, winter and early spring. Harvest management may have a significant effect on the persistence and yields of Middle - Eastern alfalfas under Arizona conditions. In the Middle East, alfalfa is frequently harvested at the bud stage and little stubble is left. In this experiment we compared the yield and persistence of Middle Eastern alfalfa ecotypes under traditional Middle - Eastern (bud stage + 2 cm stubble) and Southwestern harvest management (10% bloom + 10-15 cm stubble), and a regime with elements of both primary systems (bud stage + 10-15 cm stubble). Only slight differences in yield or persistence were observed between the management systems in the most nondormant entries, however, some ecotypes produced significantly more forage than Lew. No apparent advantages were noted for harvest leaving 2 cm stubble. Elevated yields of high quality forage would be produced with bud stage harvest and 10-15 cm stubble in most Middle Eastern ecotypes.

Salinity is a persistent problem for alfalfa growers in Arizona that will likely worsen over time. Plant breeding may offer a relatively low-cost short-term solution: varieties bred to remain productive in the presence of moderate levels of salinity. We have developed and released AZ-9ONDC-ST, a broad - based, nondormant alfalfa population with increased forage yield in greenhouse trials under moderate NaCl stress. AZ-90NDC-ST was derived from two cycles of selection for increased forage yield under NaCl stress from AZ-88NDC a composite nondonnant population previously released by the experiment station. AZ-90NDC-ST was developed to provide a source of alfalfa with increased forage production under moderate salt stress and is the only population with these characteristics in existence. This population, which has been made available to the alfalfa breeding community, will provide the basis for improved high yielding and pest- resistant varieties for use in areas in subject to salinity stress.

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In plant breeding, when the objective is to select or recommend genotypes to be planted, the study of the interaction between genotype and environment plays a important role. However, this kind of study does not provide detailed information on the behavior of each cultivar due to environmental variations. Thus become necessary to perform analyzes of stability and adaptability for identification and recommendation superior materials in different environments. Although the literature presents several methods for performing analysis of adaptability and stability, none of them take account of the presence of non-normal phenotype, in other words, phenotypic values asymmetric distributions or heavy tails. Thus, if there is the presence of such phenotypic values, the methods can be influenced and the recommendation may be mistaken, that is, the use of such methods cause inadequate estimates that do not reflect the true relationship between the variation environmental and phenotypic response. An interesting solution for treating this problem in a unified way, that is, the presence of outliers or asymmetry is to use the quantile regression (QR). Such methodology, besides the usual regression methods, using the conditional mean to explain the functional relationship between environmental variation and phenotypic response, makes use of conditional quantile functions. This way the QR possible to choose the quantile which best represents the functional relationship of interest in order to naturally cover the lack of normality cited above. Thus, this paper aims to present the methodology of quantile regression, through a detailed discussion of its theorical foundations, demonstrating it by concrete applications, its use in analysis of adaptability and stability, thus providing a easily and accessible material for readers interested in that subject, contributing researchers and those interested in this area. To the technic evaluation symmetric distributions phenotypic values, symmetric with outliers, right asymmetric, right asymmetric with outliers, left asymmetric and left asymmetric with outliers were simulated. Furthermore, we used data from an experiment on dry matter yield of 92 genotypes of alfalfa (Medicago sativa) evaluated in 20 environments. It is suggested that, for symmetrical phenotypic values should be determined if it has outlier, if it has a QR ( τ = 0,50 ) should be used, if not, should be used either Eberhart and Russell methodology (1966) or QR ( τ = 0,50 ). Since the phenotype is asymmetric, with or without the presence of outlier, it uses QR ( τ = 0,25 ) to right asymmetry and QR ( τ = 0,75) to the left asymmetry. According to the results the QR method was efficient for classifying alfalfa genotypes.
No melhoramento genético de plantas, quando o objetivo é selecionar ou recomendar genótipos para o plantio, o estudo da interação entre genótipo x ambiente é de extrema importância. Entretanto, tal estudo não fornece informações pormenorizadas sobre o comportamento de cada cultivar diante das variações ambientais. Assim, tornam-se necessárias as análises de adaptabilidade e de estabilidade para a identificação e recomendação de materiais superiores em diferentes ambientes. Embora a literatura apresente diversos métodos, para realização da análise de adaptabilidade e estabilidade, nenhum leva em consideração a presença de fenótipos não normais, ou seja, distribuições de valores fenótipos assimétricos ou com caudas pesadas. Desta forma, caso haja a presença desse tipo de valores fenotípicos, os métodos podem sofrer a influência de modo que a recomendação pode ser errônea, ou seja, o uso de tais métodos ocasionam estimativas inadequadas, que não refletem a verdadeira relação existente entre a variação ambiental e a resposta fenotípica. Uma solução interessante para tratar este problema de maneira unificada, isto é, a presença de pontos discrepantes ou assimetria, é a utilização de regressão quantílica (RQ). Tal metodologia, diferentemente dos métodos de regressão usuais, que utilizam a média condicional para explicar a relação funcional entre a variação ambiental e a resposta fenotípica, faz uso de funções quantílicas condicionais. Desta forma, a RQ possibilita escolher o quantil que melhor representa a relação funcional de interesse com o intuito de contemplar naturalmente a mencionada falta de normalidade. Desta forma, o presente trabalho tem como objetivo apresentar a metodologia de regressão quantílica, através de uma discussão detalhada de seus fundamentos teóricos, evidenciando, com aplicações concretas, seu uso em análise de adaptabilidade e estabilidade, fornecendo assim um material de fácil acesso para leitores interessados no assunto, contribuindo com pesquisadores e interessados nesta área. Para avaliação da técnica foram simulados valores fenotípicos, com distribuições simétrica, simétrica com outliers, assimétrica à direita, assimétrica à direita com outliers, assimétrica à esquerda e assimétrica à esquerda com outliers. Além disso, foram utilizados dados provenientes de um experimento sobre produção de matéria seca de 92 genótipos de alfafa (Medicago sativa) avaliados em 20 ambientes. Sugere-se que, para valores fenotípicos simétricos deve-se averiguar se este possui outlier, se sim é utilizada ou a regressão não paramétrica ou a RQ (τ = 0,50) , se não, se utiliza ou a metodologia de Eberhart e Russell (1966) ou a RQ (τ = 0,50) . Já se o fenótipo for assimétrico, com ou sem a presença de outlier, utiliza-se RQ (τ = 0,25) para assimetria a direita e RQ (τ = 0,75) para assimetria à esquerda. De acordo com os resultados encontrados a RQ foi eficiente para classificação de genótipos de alfafa.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1994.
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Lucerne is a deep-rooted perennial pasture that is promoted to land managers in southern Australia to mitigate the effects of dryland salinity, a problem of national significance caused by the replacement of native trees and shrubs with annual crops and pastures. In recent years, the acceptance of climate change has provided further rationale for increasing the use of perennial legumes in our farming systems. Perennial legumes have a role in offsetting C02 emissions by sequestering C and N in soil, and provide new, resilient options for future farming in a warmer and more variable climate. This research has focused on evaluating the diverse range of germplasm found in lucerne (Medicago sativa spp.) for a range of attributes in order to determine its compatibility with existing and future farming systems in southern Australia. Regional field evaluation at 8 sites in southern Australia showed that lucerne is a broadly adapted and robust plant. After 3 years, plant density ranged from 2-55 plants / m2 with differences in persistence attributed to tolerance to a combination of stresses including soil acidity, saline and sodic subsoils, drought conditions and persistent heavy grazing. Highly winter-active lucerne (class 9-10) was confirmed to be the most suitable group for short phase rotations in southern Australia, providing grazing is well managed. This germplasm was less persistent than other winter activity groups, but produces more total herbage yield in environments with winter dominant rainfall patterns. Highly winter-active lucerne has poor persistence under continuous grazing, but this may aid in its removal when used in rotation with crops. Winteractive germplasm (class 6-8) was more grazing tolerant and persistent, making it the most suitable group for longer phase rotations (>4 years), or where more flexible grazing management practices are required (i.e. 35 days grazing followed by 35 days recovery). Individual grazing tolerant plants from this group were selected and randomly inter-mated to form new breeder’s lines in the development of a grazing tolerant cultivar. For the first time, the high water-use of a farming system involving wheat overcropped into lucerne is presented. Lucerne over-cropped with wheat used an additional 43-88 mm of water in comparison to continuous wheat at Roseworthy and Katanning respectively. Over-cropping reduced wheat yield by 13-63%, but it can be more efficient in terms of land area to grow lucerne and wheat as a mixture than on separate parcels of land. Very winter-dormant lucerne (class 1-2) appears to be less competitive with winter cereal crops during wheat establishment. It may also be possible to reduce lucerne’s competition with wheat at the critical stage of anthesis, with low spring yielding lucerne varieties identified in this research (SA37908). This group of plants provides excellent potential for the development of high water-use farming systems because they are grazing tolerant and persistent, and have summer forage production and sub-soil water extraction rates that are equivalent to winter active lucerne. The research has been used to identify the perfect ideotype for lucerne in phase farming and over-cropping systems, which can be used to set targets in future breeding programs. The research also highlights current opportunities for the integration of lucerne into southern Australian farming systems to help curb the spread of dryland salinity and reduce the impact of climate change.
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Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008