[Truncated abstract] The highly weathered, phosphorus-fixing soils of Western Australia require large amounts of P fertiliser to produce acceptable crop yields. Chickpea (Cicer arietinum L.) is an important leguminous crop that is increasingly used in rotations with wheat (Triticum aestivum L.), Western Australia’s major crop. Chickpea and a range of other species exude P-mobilising carboxylates into the rhizosphere. Plants that exude carboxylates may need less P fertiliser or may use P in the soil that is unavailable to other plants. There is a wealth of information about P mobilisation and carboxylate exudation by white lupin; in contrast, research on carboxylate exudation by chickpea is fairly limited. The major aim of this PhD research project was to investigate the relationships between exudation of carboxylates and soil and plant P status for chickpea ... In conclusion, whereas carboxylate exudation of plants such as white lupin is clearly targeted at P acquisition, chickpea showed constitutive carboxylate exudation mainly of malonate into the rhizosphere in a series of experiments, each with a different design. Unlike white lupin, chickpea forms associations with mycorrhizal fungi that may improve plant P status. Some of the functions of constitutive carboxylate exudation by chickpea may include P acquisition and deterring microorganisms, but the exact reasons and mechanisms remain unresolved.

Income and price affect chickpea trade expenditure and consumption expenditure share respectively. An empirical model was estimated to examine the trade effect through the expenditure channel using Almost Ideal Demand System and thus considering non-homotheticity in preferences. The results of the analysis indicated that global chickpea trade has increased from 100000 metric tons in 1988 to about 2.5 million metric tons in 2015. Between the same period consumption and production of chickpea had an increasing trend. USA and Canada had become part of the top 10 chickpea producers by 2015 signifying the increasing demand of chickpea in western countries. Factors that affected relative chickpea trade to importers income were relative market size of the exporter, bilateral distance and contiguous borders. Also, a percentage increase in the adjusted mean income of chickpea consuming country will lead to 94% decrease in the consumption of chickpea when country pair effects are considered.

MSCAGR / Department of Plant Production / Chickpea (Cicer aritienum L.) is an ancient crop that originated in South-Eastern Turkey and belongs to the genus Cicer, tribe Cicereae, and family Fabaceae. Chickpea has the ability to fix atmospheric nitrogen (N) for its growth. However, chickpea productivity not only depends on N2 fixation or dry matter accumulation, but also the effectiveness of nutrient partitioning to seed, a key component to overall yield. There is a dearth of information on the effect of P with rhizobial inoculation in response of nutrients accumulation in the rhizosphere, shoots and grain of chickpea, especially when determined at different growth stages in the African continent. This study contributes knowledge on this crucial aspect which will likely lead to more other similar research reports in other settings. Therefore, the objectives of this study was to evaluate the effect of P fertilizer rates and rhizobial inoculation on yield and nutrients accumulation in two chickpea genotypes. Field experiments were conducted in winter 2017 and 2018 at University of Venda, Thohoyandou and University of Limpopo’s experiment farm, Syferkuil. Treatments consisted of a factorial combination of two rates of P fertilizer (0 and 90 kg P ha-1), two desi chickpea genotypes (ACC1 and ACC5) and two rhizobial inoculation levels (with and without rhizobiam strain). The treatments were laid out in a randomized complete block design (RCBD) and replicated three times on 22 April 2017 and 11 April 2018 (Syferkuil), 13 April 2017 and 29 April 2018 (Thohoyandou). Macronutrients including P, K, Ca, Mg were determined using the citric acid method. The total N concentration were determined by the micro-Kjeldahl method in both soil, shoots and grain. Zn was extracted using a di-ammonium ethylenediaminetetraacetic acid (EDTA) solution. The content of macronutrients (P, K, Ca, Mg, Ca, and Zn) in soil, shoots and grain was determined by first subjected to wet digestion (Mehlich, 1984). From the digest, various elements were read using relevant procedures. P contents was determined colorimetrically using a spectrophotometer. Yield and yield components were assessed at harvest maturity. Genotypes affected the accumulation of mineral elements in rhizosphere soil, shoots, grain and yield. Accession 5 performed better in most of nutrients elements compared to accession 1 in both seasons and sites. Application of phosphorus alone, and in combination with rhizobium inoculation increased the concentration of majority of nutrients in the rhizosphere. When the test accessions were grown at the Syferkuil and Thohoyandou study location in 2017, they showed significant differences in the concentration of N, P and K while Ca, Mg and Zn were similar in the rhizosphere. The concentrations of N, P and K were markedly higher in the rhizosphere of ACC5 compared to ACC1. In fact, the concentration of P was two-fold greater in the rhizosphere of ACC5 than ACC1. Accession 5 exhibited a markedly higher shoot dry weight, number and dry weight of pods, 100-seed weight, grain yield and harvest index compared to ACC1. P plus rhizobium inoculation, P, rhizobium inoculation affected grain yield and yield components of chickpea genotypes. This preliminary finding show that the combination of P and rhizobium inoculation affected the nutrients accumulation in the rhizosphere, shoots, grain, yield and yield components in both locations. Moreover, Thohoyandou had the highest nutrients accumulation on the rhizosphere, shoots, grain, yield and yield components compared to Syferkuil. / NRF

[Truncated abstract] The genetics of ascochyta blight resistance was studied in five 5 x 5 half-diallel cross sets involving seven genotypes of chickpea (ICC 3996, Almaz, Lasseter, Kaniva, 24B-Isoline, IG 9337 and Kimberley Large), three accessions of Cicer reticulatum (ILWC 118, ILWC 139 and ILWC 184) and one accession of C. echinospermum (ILWC 181) under field conditions. Both F1 and F2 generations were used in the diallel analysis. Almaz, ICC 3996 and ILWC 118 were the most resistant genotypes. Estimates of genetic parameters, following Hayman's method, showed significant additive and dominant gene actions. The analysis also revealed the involvement of both major and minor genes. Susceptibility was dominant over resistance to ascochyta blight. The recessive alleles were concentrated in the two resistant chickpea parents ICC 3996 and Almaz, and one C. reticulatum genotype ILWC 118. High narrow-sense heritability (ranging from 82 to 86% for F1 generations, and 43 to 63% for F2 generations) indicates that additive gene effects were more important than non-additive gene effects in the inheritance of the trait and greater genetic gain by breeding resistant chickpea cultivars using carefully selected parental genotypes. Current simple leaf varieties are often susceptible to ascochyta blight disease whereas varieties of other leaf types range from resistant to susceptible. The inheritance of ascochyta blight resistance and different leaf types and their correlation were investigated in intraspecific progeny derived from crosses among two resistant genotypes with normal leaf type (ICC 3996 and Almaz), one susceptible simple leaf type (Kimberley Large) and one susceptible multipinnate leaf type (24 B-Isoline). ... An interspecific F2 mapping population derived from a cross between chickpea accession ICC 3996 (resistant to ascochyta blight, early flowering, and semi-erect plant growth habit) and C. reticulatum accession ILWC 184 (susceptible to ascochyta blight, ii late flowering, and prostrate plant growth habit) was used for constructing a genetic linkage map. F2 plants were cloned through stem cuttings taken at pre-flowering stage, treated with plant growth regulator powder (0.5 mg/g indole butyric acid (IBA) and 0.5 mg/g naphthalene acetic acid (NAA)) and grown in a sand + potting mix substrate. Clones were screened for ascochyta blight resistance in controlled environment conditions using a 19 scale. Three quantitative trait loci (QTLs) were found for ascochyta blight resistance in this population. Two linked QTLs, located on linkage group (LG) 4, explained 21.1% and 4.9% of the phenotypic variation. The other QTL, located on LG3, explained 22.7% of the phenotypic variation for ascochyta blight resistance. These QTLs explained almost 49% of the variation for ascochyta blight resistance. LG3 had two major QTLs for days to flowering (explaining 90.2% of phenotypic variation) and a major single QTL for plant growth habit (explaining 95.2% of phenotypic variation). There was a negative correlation between ascochyta blight resistance and days to flowering, and a positive correlation between days to flowering and plant growth habit. The flanking markers for ascochyta blight resistance or other morphological characters can be used in marker-assisted selections to facilitate breeding programs.

Ascochyta blight, caused by Ascochyta rabiei (Pass.) Labrousse, is one of the most destructive diseases of chickpea (Cicer arietinum L.) worldwide. Despite the existence of highly resistant uncultivated genotypes, attempts to develop cultivars with a high level of durable resistance have been unsuccessful. This study investigated the chickpea defence response to A. rabiei using a functional genomics approach, which has the capacity to improve the overall understanding of the coordinated defence response at a molecular level. An existing cDNA library was used to generate a resource of Expressed Sequence Tags (ESTs) that, after clustering, comprised 516 unigenes. The unigenes were functionally annotated resulting in the identification of 20 specific defence-related unigenes, as well as numerous transcripts with possible involvement in the coordination of defence responses. To explore the expression patterns of the defence-related unigenes in an A. rabiei resistant and susceptible genotype, the unigenes were employed as probes in microarrays. Resulting expression data was analysed to identify differentially expressed unigenes over a time-course after infection. Comparison of the expression profiles from the resistant and susceptible genotype identified three putative genes that were exclusively up-regulated in the resistant genotype, thus may be involved in an effective defence response. Considering that a defence response can involve hundreds of genes, the entire set of chickpea unigenes were used to construct large-scale microarrays. To supplement the chickpea probes, 156 putative defence-related grasspea (Lathyrus sativus L.) ESTs and 41 lentil (Lens culinaris Med.) Resistance Gene Analogs (RGAs) were also included. Expression profiles for three chickpeas and one wild relative were generated over a time course. 97 differentially expressed ESTs were identified using a robust experimental system that included confirmation by quantitative RT-PCR. The results indicated that genes involved in the active defence response were similar to those governed by R-gene mediated resistance, including the production of reactive oxygen species and the hypersensitive response, down-regulation of 'housekeeping' gene expression, and expression of pathogenesis-related proteins. The comparison between resistant and susceptible genotypes identified certain gene expression 'signatures' that may be predictiv e of resistance. To further characterise the regulation of potential defence-related genes, the microarray was used to study expression profiles of the three chickpea genotypes (excluding the wild relative) after treatment with the defence signalling compounds, ethylene (E), salicylic acid (SA), and jasmonate (JA). 425 ESTs were differentially expressed, and comparison between genotypes revealed the presence of a wider range of inducible defence responses in resistant genotypes. Linking the results with the previous microarray results indicated the presence of other pathogen-specific signalling mechanisms in addition to E, SA and JA. The lower arsenal of defence-related gene expression observed in the susceptible genotype may be a result of 'breaks' in the pathways of defence-related gene activation. To draw together the findings of all experiments, a model was constructed for a hypothetical mechanism of chickpea resistance to A. rabiei. The model was synthesised based on the evidence gathered in this study and previously documented defence mechanisms in chickpea, and identified signal transduction as a key to resistance.

Successful chickpea production in western Canada typically requires multiple applications of fungicides to minimize the severity of Ascochyta blight (AB) caused by <i>Ascochyta rabiei</i>. Although planting resistant cultivars could be economical and environmentally safer than fungicide usage, varieties with a high level of resistance are not available. The objectives of this research were i) to determine the effect of different seeding arrangement treatments on ascochyta blight severity and seed yield of two cultivars (moderately resistant and susceptible) of kabuli chickpea; ii) to compare one and four fungicide applications at recommended and reduced rates and their impact on disease severity and cost; and iii) to assess organ-specific reaction to AB in chickpea in leaves, stems and pods of 12 desi and 12 kabuli varieties that are of economic significance to western Canada. <p>Treatments significantly influenced AB severity on both moderately resistant and susceptible cultivars in a season with a severe epidemic. Seed yield was significantly influenced by treatments for both varieties in both years. Contrast analyses revealed that four fungicide applications significantly reduced the AB severity for both varieties in a season with a severe epidemic and for the susceptible variety in a season with a moderate epidemic. Seed yield of both varieties was significantly higher under four fungicide applications compared to a single application. Solid seeding and paired row arrangements did not differ in their effect on seed yield and AB severity for both varieties in both years, except that the susceptible variety benefited from paired row planting with respect to seed yield and reduced AB severity in the season with a severe epidemic. Reducing fungicide rates and seeding rate could reduce the cost of cultivation without significantly affecting disease control and yield. Economic assessment revealed that in a severe epidemic season, the gross returns were high for the moderately resistant variety under four fungicide applications than one fungicide application. Gross returns for the susceptible variety were higher under four fungicide applications in both years.<p>There were differences among varieties for AB severity on leaves, stems and pods, seed yield and 1000 seed weight at all site-years tested. The variation was greater in kabuli varieties than desi varieties. AB severity on leaves, stems and pods was lower under high fungicide regimes, with few exceptions. Varieties with a fern leaf type had lower AB severity than those with unifoliate leaves. There was a positive correlation among AB severity on leaves, stems and pods. No differences in organ-specific reaction were observed.

Kabuli chickpea (<i>Cicer arietinum</i> L.) has two leaf types, the fern and unifoliate. Yield potential is limited for kabuli chickpea in Saskatchewan. It is limited by a short-season, a semi-arid environment, and end-of-season rainfall. Manipulating plant population, and choosing chickpea cultivars with the best leaf type for biomass production, radiation interception and yield for the early, middle, or late growth season, may increase chickpea yield. Therefore, the objectives of this study were: to (i) determine the relationship between leaf type and key growth parameters of six chickpea cultivars varying in leaf morphology at moderate and high plant population densities; (іі) to characterize the reaction of the fern and unifoliate leaf to altered canopy light environments. Different light environments were created by 50% defoliation at vegetative growth, first flower, and 50% shading from vegetative growth to first flower, as well as two light enrichment treatments initiated at the first flower and pod formation stages.<p> Fern leaf cultivars exhibited higher maximum light interception, seasonal cumulative intercepted radiation and a higher harvest index compared to unifoliate leaf cultivars. However, both leaf type canopies had less than 95% light interception for most of the season. The fern and unifoliate leaf type contributed to similar radiation use efficiency in three out of four location-years. In addition, fern leaf cultivars produced significantly higher seed yield than cultivars with unifoliate leaves.<p>Plant density influenced growth parameters. For example, the 45 plants m-2 treatment had a higher harvest index than the 85 plants m-2 treatment, in two location-years, while both population treatments were similar in the other two location-years. Yield of chickpea was increased by higher plant population in only one location-year, but was not significantly affected by plant population in the other location-years. The effect of canopy light environment manipulation on chickpea yield depended on the stages of plant development when they were applied. Defoliation at vegetative growth and first flower had no effect on yield. However, plants responded significantly to the 50% shade treatment; the crop growth rate, harvest index and yield were less in the shaded treatment compared to the control. Shading also increased plant height. Light enrichment treatments increased the yield. However, the degree of yield increase was greater when light enrichment occurred at first flower, than at the later stage of pod formation. These results highlighted the importance of the amount of irradiance during the flowering stage. It was concluded that chickpea breeders should select lines with fern leaves for improved radiation interception when breeding cultivars for semiarid short-season environments such as in Saskatchewan. Management and breeding practices should ensure that the crop can make efficient use of the solar radiation at flowering to maximize yield. Improvement at the canopy and subsequent yield level is yet to be made in Saskatchewan environments by increased light interception, increased growth before flowering, and increased and stable harvest index.

Chickpea production in the short growing season of the Canadian Prairies is still a challenging task due to excessive and continuous vegetative growth which often results in severe yield and quality reduction. This study examined the effects of three plant growth retardants (PGR), Chlormequat Chloride (CCC), Prohexadione Calcium and Trinexapac Ethyl applied during flowering stage on vegetative growth, seed quality, yield and crop maturity of the Kabuli chickpea cultivar CDC Frontier. Field experiments were conducted at Brooks and Bow Island in southern Alberta in the 2010 and 2011 growing seasons. Four concentrations of each PGR were applied at 10, 20 and 30 days after flowering (DAF) stages. During the 2010 growing season the crop experienced above average moist and cooler temperature conditions. In contrast, later half of the 2011 growing season was above average dry and hot. None of the three PGR tested in this study had a significant effect on plant height at 30 days after treatments or on above ground biomass plant-1 at harvest. Application of PGR had no significant effects on the number of seeds m-2, except at the Brooks rain-fed site in 2011 where the PGR treatment applied at 10 and 20 DAF increased the number of seeds m-2 at harvest. An increase of 1000-seed weight of marketable seeds was obtained with Prohexadione Calcium and Trinexapac Ethyl applications at Bow Island, but the effects were not consistent across sites and years. Results suggested that the effect of PGR on 1000-seed weight of marketable seeds mainly depended upon the growing environment and the type of PGR. In general, PGR applications reduced the total and marketable seed yields. Application of Prohexadione Calcium and Trinexapac Ethyl at the Bow Island site delayed crop maturity in 2011. In contrast, the application of CCC at 6000 mg L-1 at 20 DAF accelerated crop maturity at the Brooks irrigated site in 2011. In addition to this main study, the potential effects of Pyraclostrobin and Prothioconazole fungicides on the activities of the three PGR were compared by a separate experiment conducted at the Brooks irrigated site in 2011. The results of that study revealed that there were no significant differences in the effects of PGR on chickpea vegetative growth, seed yield parameters and maturity when they were applied as a mixture with either Pyraclostrobin or Prothioconazole fungicide. In summary, results revealed that PGR applied during flowering stage were not effective on controlling vegetative growth of chickpea and did not improve seed yield and crop maturity. Their effects on yield-related traits were highly inconsistent. Thus, it can be concluded that the application of PGR is not a reliable agronomic option to handle the production issues associated with continues vegetative growth at the late reproductive stage of the chickpea cultivar CDC Frontier under the western Canadian growing conditions.

Kabuli chickpea (<i>Cicer arietinum</i> L.) has two leaf types, the fern and unifoliate. Yield potential is limited for kabuli chickpea in Saskatchewan. It is limited by a short-season, a semi-arid environment, and end-of-season rainfall. Manipulating plant population, and choosing chickpea cultivars with the best leaf type for biomass production, radiation interception and yield for the early, middle, or late growth season, may increase chickpea yield. Therefore, the objectives of this study were: to (i) determine the relationship between leaf type and key growth parameters of six chickpea cultivars varying in leaf morphology at moderate and high plant population densities; (іі) to characterize the reaction of the fern and unifoliate leaf to altered canopy light environments. Different light environments were created by 50% defoliation at vegetative growth, first flower, and 50% shading from vegetative growth to first flower, as well as two light enrichment treatments initiated at the first flower and pod formation stages.<p> Fern leaf cultivars exhibited higher maximum light interception, seasonal cumulative intercepted radiation and a higher harvest index compared to unifoliate leaf cultivars. However, both leaf type canopies had less than 95% light interception for most of the season. The fern and unifoliate leaf type contributed to similar radiation use efficiency in three out of four location-years. In addition, fern leaf cultivars produced significantly higher seed yield than cultivars with unifoliate leaves.<p>Plant density influenced growth parameters. For example, the 45 plants m-2 treatment had a higher harvest index than the 85 plants m-2 treatment, in two location-years, while both population treatments were similar in the other two location-years. Yield of chickpea was increased by higher plant population in only one location-year, but was not significantly affected by plant population in the other location-years. The effect of canopy light environment manipulation on chickpea yield depended on the stages of plant development when they were applied. Defoliation at vegetative growth and first flower had no effect on yield. However, plants responded significantly to the 50% shade treatment; the crop growth rate, harvest index and yield were less in the shaded treatment compared to the control. Shading also increased plant height. Light enrichment treatments increased the yield. However, the degree of yield increase was greater when light enrichment occurred at first flower, than at the later stage of pod formation. These results highlighted the importance of the amount of irradiance during the flowering stage. It was concluded that chickpea breeders should select lines with fern leaves for improved radiation interception when breeding cultivars for semiarid short-season environments such as in Saskatchewan. Management and breeding practices should ensure that the crop can make efficient use of the solar radiation at flowering to maximize yield. Improvement at the canopy and subsequent yield level is yet to be made in Saskatchewan environments by increased light interception, increased growth before flowering, and increased and stable harvest index.

Successful chickpea production in western Canada typically requires multiple applications of fungicides to minimize the severity of Ascochyta blight (AB) caused by <i>Ascochyta rabiei</i>. Although planting resistant cultivars could be economical and environmentally safer than fungicide usage, varieties with a high level of resistance are not available. The objectives of this research were i) to determine the effect of different seeding arrangement treatments on ascochyta blight severity and seed yield of two cultivars (moderately resistant and susceptible) of kabuli chickpea; ii) to compare one and four fungicide applications at recommended and reduced rates and their impact on disease severity and cost; and iii) to assess organ-specific reaction to AB in chickpea in leaves, stems and pods of 12 desi and 12 kabuli varieties that are of economic significance to western Canada. <p>Treatments significantly influenced AB severity on both moderately resistant and susceptible cultivars in a season with a severe epidemic. Seed yield was significantly influenced by treatments for both varieties in both years. Contrast analyses revealed that four fungicide applications significantly reduced the AB severity for both varieties in a season with a severe epidemic and for the susceptible variety in a season with a moderate epidemic. Seed yield of both varieties was significantly higher under four fungicide applications compared to a single application. Solid seeding and paired row arrangements did not differ in their effect on seed yield and AB severity for both varieties in both years, except that the susceptible variety benefited from paired row planting with respect to seed yield and reduced AB severity in the season with a severe epidemic. Reducing fungicide rates and seeding rate could reduce the cost of cultivation without significantly affecting disease control and yield. Economic assessment revealed that in a severe epidemic season, the gross returns were high for the moderately resistant variety under four fungicide applications than one fungicide application. Gross returns for the susceptible variety were higher under four fungicide applications in both years.<p>There were differences among varieties for AB severity on leaves, stems and pods, seed yield and 1000 seed weight at all site-years tested. The variation was greater in kabuli varieties than desi varieties. AB severity on leaves, stems and pods was lower under high fungicide regimes, with few exceptions. Varieties with a fern leaf type had lower AB severity than those with unifoliate leaves. There was a positive correlation among AB severity on leaves, stems and pods. No differences in organ-specific reaction were observed.