Lucerne for Acid Soils: A Field Evaluation of Early Generation Aluminium Tolerant Genotypes

The development of lucerne germplasm tolerant of acidic soil conditions has long been a research objective of international significance. Many initiatives have previously failed to produce genotypes with adequate improvement in tolerance to be deemed economically viable and as a consequence, still no cultivar of lucerne exists that has improved adaptation to acidic soils. An Australian research program spanning the previous decade sought to redress this issue by developing lucerne genotypes with significantly enhanced tolerance to aluminium (Al) toxicity. Using recurrent selection in hydroponic solution culture, populations selected comprised individuals which displayed enhanced seedling root growth following a pulse of Al toxic solution (Scott et al. 2008). A subsequent pot experiment showed that these populations exhibited up to 40% increase in seedling root length when grown in an acidic soil with high Al concentration, though there was a differential response observed between the elite populations (Hayes et al. 2011). The current study tested the hypothesis that lucerne establishment in the field would be higher in populations selected in high Al solution culture when grown in an acidic soil environment

Cytogenetic manipulation and anther culture of wheat

The experiments in this thesis manipulated the breeding system of wheat and triticale first toward outcrossing with male sterility systems, and then toward homozygosity with anther culture systems. To provide a visible marker that could be used to distinguish male-sterile plants from male-fertile plants, 'chromosome engineering' was attempted via two distinct crossing procedures to generate two translocation chromosomes, 5AL.5AS-5RS and 4EL-5AS. These would then be recombined (via an intercrossing procedure) into another translocation chromosome 4EL.5AS—5RS which would link the blue aleurone gene Ba on chromosome 4EL with the dominant male sterility allele Ms3 on chromosome arm SAS, while chromosome arm segment SRS would prevent pairing and crossing over with other SAS arms in heterozygous breeding lines. The procedure to develop the first translocation chromosome consisted of crossing dominant male-sterile (DMS) Selkirk wheat with the 5R(5A) substitution line in Chinese Spring wheat. The progeny were further crossed with ph1b mutant in Chinese Spring wheat to allow homoeologous pairing and recombination to occur between chromosomes 5A and 5K Morphological, cytological and genetic markers were used to evaluate the progeny derived from these crosses. The required traits were 1. Presence of 2n = 41, 2. Speltoid heads indicating monosomy for chromosome 5A 3. Sterile anthers indicating the presence of M33. 4. Presence of B-Amy—AZ bands and IBF bands indicating the presence of chromosome arm SAL. 5. Lack of 'hairy neck' phenotype, B-Amy-R2 and [bf—R1 bands indicating the absence of chromosome arm SRL. 6. Positive dot-blot for the rye-specific DNA probe indicating the likely presence of a rye segment or arm from chromosome arm 5R8. One progeny which had a combination of these characteristics was consistent with the required translocation chromosome. The procedure for the second translocation chromosome involved crossing DMS-Selkirk with the chromosome 4E addition line 'Blue Tordo' and backcrossing with N5AT5D in Chinese Spring. This enabled the maintenance of chromosomes 5A and 4E as monosomes thus providing an opportunity for them to misdivide and reunite (centric fusion). The progeny were evaluated using morphological and cytological markers. The required characters were 1. Blue seed color. 2. Sterility of anthers. 3. Speltoidy of heads. 4. 2n = 42 chromosomes. The results obtained indicated that although one plant with most of the above mentioned traits was recovered, its anthers were partially fertile. In addition, M33 segregated independently of Ba indicating that the required translocation chromosome was not obtained. The restoration of partial fertility is the first instance of partial restoration of DMS which was previously considered to be obligate male sterility. In general it is recommended that the translocation obtained from the first crossing procedure be further confimed by analyses with the C-banding technique or by in situ hybridization methods to confim the presence of chromosome arm SRS and to evaluate the length of rye segment. Further, alternative sources of the blue aluerone marker such as T. boeoticum should also be investigated. The potential for using the DMS gene Ms3 in triticale was also investigated. Wheat-rye amphihaploids derived from crosses between Selkirk DMS wheat and four rye populations (Chapter 4) were treated with colchicine, and DMS triticales were derived from only two S. cereale selections. Male sterility was expressed in both wheat-rye amphihaploids as well as in primary and secondary triticales inspite of the presence of rye chromosomes. The stability of expression of male sterility in these triticales indicated that dominant male sterility could be used in breeding programs. Experiments to enhance the efficiency of anther culture for use as a wheat breeding tool were conducted using cv. Grebe and MC17 medium as model systems. The media were modified using alternative support substrates, carbohydrate sources and plant growth regulators. The data quantified were induction of embryoids, direct plant production, green and albino plant regeneration, proportion of green plants to total regenerants. In addition, the survival of green regenrants upon transfer to soil was evaluated together with the seed set obtained probably due to spontaneous doubling

Development of In Vitro Anther Culture for Doubled Haploid Plant Production in Indica Rice (<i>Oryza sativa</i> L.) Genotypes

Anther culture is an efficient biotechnological tool in modern plant breeding programs to produce new varieties and parental lines in hybrid seed productions. However, some bottlenecks—low induction rate, genotype dependency, albinism—restrict the widespread utilization of in vitro anther culture in rice breeding, especially in Oryza sativa ssp. indica (indica) genotypes, while an improved efficient protocol can shorten the process of breeding. Three different induction media (N6NDK, N6NDZ, Ali-1) and four plant regeneration media (mMSNBK1, MSNBK3, MSNBKZ1, MSNBKZ2) were tested with five indica rice genotypes to increase the efficiency of in vitro androgenesis (number of calli and regenerated green plantlets). The production of calli was more efficient on the N6NDK medium with an average 88.26 calli/100 anthers and N6NDZ medium with an average of 103.88 calli/100 anthers as compared to Ali-1 with an average of 6.96 calli/100 anthers. The production of green plantlets was greater when calli was produced on N6NDK medium (2.15 green plantlets/100 anthers) compared when produced on to N6NDZ medium (1.18 green plantlets/100 anthers). Highest green plantlets production (4.7 green plantlets/100 anthers) was achieved when mMSNBK1 plant regeneration medium was used on calli produced utilizing N6NDK induction medium. In the best overall treatment (N6NDK induction medium and mMSNBK1 plant regeneration medium), four tested genotypes produced green plantlets. However, the genotype influenced the efficiency, and the green plantlets production ranged from 0.4 green plantlets/100 anthers to 8.4 green plantlets/100 anthers. The ploidy level of 106 acclimatized indica rice plantlets were characterized with flow cytometric analyses to calculate the percentage of spontaneous chromosome doubling. Altogether, 48 haploid-, 55 diploid-, 2 tetraploid- and 1 mixoploid plantlets were identified among the regenerant plantlets, and the spontaneous chromosome doubling percentage was 51.89%. Utilization of DH plants have been integrated as a routine method in the Hungarian rice breeding program. The tetraploid lines can be explored for their potential to offer new scopes for rice research and breeding directions in the future

Statistical methods for analysis of multi-harvest data from perennial pasture variety selection trials

Variety selection in perennial pasture crops involves identifying best varieties from data collected from multiple harvest times in field trials. For accurate selection, the statistical methods for analysing such data need to account for the spatial and temporal correlation typically present. This paper provides an approach for analysing multi-harvest data from variety selection trials in which there may be a large number of harvest times. Methods are presented for modelling the variety by harvest effects while accounting for the spatial and temporal correlation between observations. These methods provide an improvement in model fit compared to separate analyses for each harvest, and provide insight into variety by harvest interactions. The approach is illustrated using two traits from a lucerne variety selection trial. The proposed method provides variety predictions allowing for the natural sources of variation and correlation in multi-harvest data