Bio-diesel is a fast-developing alternative fuel in many developed and developing countries of the world. The bio-diesel production from vegetable oils during 2004–2005 was estimated 2.36 million ...tonnes globally. Of this, EU countries accounted for about 82% and USA about 6%. Global bio-diesel production is set to reach some 24 billion litres by 2017. Shortage of edible oil for human consumption in developing countries does not favour its use for bio-diesel production. Hence non-edible oil from crops like Jatropha (
Jatropha
curcas) and Pongamia (
Pongamia
pinnata) is favoured for bio-diesel production and the trend is expected to continue. Especially
J. curcas has gained attention in tropical and sub-tropical countries and has spread beyond its centre of origin, because of its hardiness, easy propagation, drought endurance, high oil content, rapid growth, adaptation to wide agro-climatic conditions, and multiple uses of plant as a whole. The full potential of
J. curcas has not been realized due to several technological and economic reasons. One of the major reasons is the lack of high yielding varieties with high oil content. In this review, we attempt to discuss the currently available information on
Jatropha species identity, taxonomy and description, distribution and ecological requirements of the species, possibilities of exploitation of genetic potentiality, exploitation of existing diversity for yield and oil content by direct selection, hybridization and creation of diversity by mutation, and biotechnological interventions.
Vast germplasm collections are accessible but their use for crop improvement is limited—efficiently accessing genetic diversity is still a challenge. Molecular markers have clarified the structure of ...genetic diversity in a broad range of crops. Recent developments have made whole-genome surveys and gene-targeted surveys possible, shedding light on population dynamics and on the impact of selection during domestication. Thanks to this new precision, germplasm description has gained analytical power for resolving the genetic basis of trait variation and adaptation in crops such as major cereals, chickpea, grapevine, cacao, or banana. The challenge now is to finely characterize all the facets of plant behavior in carefully chosen materials. We suggest broadening the use of ‘core reference sets’ so as to facilitate material sharing within the scientific community.
A rapid high-resolution genome-wide strategy for molecular mapping of major QTL(s)/gene(s) regulating important agronomic traits is vital for in-depth dissection of complex quantitative traits and ...genetic enhancement in chickpea. The present study for the first time employed a NGS-based whole-genome QTL-seq strategy to identify one major genomic region harbouring a robust 100-seed weight QTL using an intra-specific 221 chickpea mapping population (desi cv. ICC 7184 × desi cv. ICC 15061). The QTL-seq-derived major SW QTL (CaqSW1.1) was further validated by single-nucleotide polymorphism (SNP) and simple sequence repeat (SSR) marker-based traditional QTL mapping (47.6% R(2) at higher LOD >19). This reflects the reliability and efficacy of QTL-seq as a strategy for rapid genome-wide scanning and fine mapping of major trait regulatory QTLs in chickpea. The use of QTL-seq and classical QTL mapping in combination narrowed down the 1.37 Mb (comprising 177 genes) major SW QTL (CaqSW1.1) region into a 35 kb genomic interval on desi chickpea chromosome 1 containing six genes. One coding SNP (G/A)-carrying constitutive photomorphogenic9 (COP9) signalosome complex subunit 8 (CSN8) gene of these exhibited seed-specific expression, including pronounced differential up-/down-regulation in low and high seed weight mapping parents and homozygous individuals during seed development. The coding SNP mined in this potential seed weight-governing candidate CSN8 gene was found to be present exclusively in all cultivated species/genotypes, but not in any wild species/genotypes of primary, secondary and tertiary gene pools. This indicates the effect of strong artificial and/or natural selection pressure on target SW locus during chickpea domestication. The proposed QTL-seq-driven integrated genome-wide strategy has potential to delineate major candidate gene(s) harbouring a robust trait regulatory QTL rapidly with optimal use of resources. This will further assist us to extrapolate the molecular mechanism underlying complex quantitative traits at a genome-wide scale leading to fast-paced marker-assisted genetic improvement in diverse crop plants, including chickpea.
Late leaf spot (LLS) and rust are two major foliar diseases of groundnut (Arachis hypogaea L.) that often occur together leading to 50-70% yield loss in the crop. A total of 268 recombinant inbred ...lines of a mapping population TAG 24 × GPBD 4 segregating for LLS and rust were used to undertake quantitative trait locus (QTL) analysis. Phenotyping of the population was carried out under artificial disease epiphytotics. Positive correlations between different stages, high to very high heritability and independent nature of inheritance between both the diseases were observed. Parental genotypes were screened with 1,089 simple sequence repeat (SSR) markers, of which 67 (6.15%) were found polymorphic. Segregation data obtained for these markers facilitated development of partial linkage map (14 linkage groups) with 56 SSR loci. Composite interval mapping (CIM) undertaken on genotyping and phenotyping data yielded 11 QTLs for LLS (explaining 1.70-6.50% phenotypic variation) in three environments and 12 QTLs for rust (explaining 1.70-55.20% phenotypic variation). Interestingly a major QTL associated with rust (QTLrust01), contributing 6.90-55.20% variation, was identified by both CIM and single marker analysis (SMA). A candidate SSR marker (IPAHM 103) linked with this QTL was validated using a wide range of resistant/susceptible breeding lines as well as progeny lines of another mapping population (TG 26 × GPBD 4). Therefore, this marker should be useful for introgressing the major QTL for rust in desired lines/varieties of groundnut through marker-assisted backcrossing.
A core collection is a chosen subset of large germplasm collection that generally contains about 10% of the total accessions and represents the genetic variability of entire germplasm collection. The ...purpose of a core collection is to improve the use of genetic resources in crop improvement programs. In many crops the number of accessions contained in the genebank are several thousands, and a core subset consisting of 10% of total accessions would be an unwieldy proposition. In this article we have suggested a two-stage strategy to select a chickpea mini core subset consisting of only about 1% of the entire collection held in trust at ICRISAT's genebank (16,991 accessions). This mini core subset still represents the diversity of the entire core collection. The first stage involves developing a representative core subset (about 10%) from the entire collection using all the available information on origin, geographical distribution, and characterization and evaluation data of accessions. The second stage involves evaluation of the core subset for various morphological, agronomic, and quality traits, and selecting a further subset of about 10% accessions from the core subset. At both stages standard clustering procedure was used to separate groups of similar accessions. A mini core subset consisting 211 accessions from 1,956 core subset accessions, using data on 22 morphological and agronomic traits, was selected. Newman- Keuls' test for means, Levene's test for variances, the chi-square test and Wilcoxon's rank-sum non-parametric test for frequency distribution analysis for different traits indicated that the variation available in the core collection has been preserved in the mini core subset. The most important phenotypic correlations which may be under the control of coadapted gene complexes, were also preserved in the mini core. This mini core subset, due to its drastically reduced size, will prove to be a point of entry to proper exploitation of chickpea genetic resources.PUBLICATION ABSTRACT
The sorghum Sorghum bicolor (L.) Moench germplasm collection at the ICRISAT gene bank exceeds 37,000 accessions. A core collection of 2247 accessions was developed in 2001 to enable researchers to ...have access to a smaller set of germplasm. However, this core collection was found to be too large. To overcome this, a sorghum mini core (10% accessions of the core or 1% of the entire collection) was developed from the existing core collection. The core collection was evaluated for 11 qualitative and 10 quantitative traits in an augmented design using three control cultivars in the 2004-2005 post-rainy season. The hierarchical cluster analysis of data using phenotypic distances resulted in 21 clusters. From each cluster, about 10% or a minimum of one accession was selected to form a mini core that comprised 242 accessions. The data in the mini core and core collections were compared using statistical parameters such as homogeneity of distribution for geographical origin, biological races, qualitative traits, means, variances, phenotypic diversity indices, and phenotypic correlations. These tests revealed that the mini core collection represented the core collection, which can be evaluated extensively for agronomic traits including resistance to biotic and abiotic stresses to identify accessions with desirable characteristics for use in crop improvement research and genomic studies.
•Roots contribute to drought yield in chickpea.•Subsoil water use is critical for enhanced tolerance.•Root QTLs help in drought breeding.
Chickpea (Cicer arietinum L.) is a major grain legume crop in ...South Asia, and terminal drought severely constrains its productivity. In this review, we describe how root systems can improve the productivity of chickpea under the terminal drought that occurs in a receding stored soil water conditions in central and south India and propose possible breeding and screening methods. In chickpea, total root biomass in early growth stages has been shown to significantly contribute to seed yield under terminal drought in central and south India. Maximising acquisition of water stored in 15–30cm soil layer by roots had greater implications as the timing of absorption, available soil water and root size matches well for the complete use of water from this zone. However, deeper root systems and a greater exploitation of subsoil water offers potential for further productivity improvements under terminal drought. As proof of this concept, contrasting chickpea accessions for important root traits, such as root biomass and rooting depth, have been screened in a chickpea germplasm collection which comprises rich diversity for root traits. Through analysing mapping populations derived from crosses between these accessions, a ‘QTL hotspot’ that explained a large part of the phenotypic variation for the major drought tolerance traits including root traits was identified and introgressed into a leading Indian chickpea cultivar. Yield advantages of the introgression lines were demonstrated in multi-location evaluations under terminal drought. As an alternative screening method, that would indirectly asses the root system strength, to identify further promising chickpea genotypes with multiple drought tolerance traits, the leaf canopy temperature and carbon isotope discrimination measurements can be proposed.
Chickpea cropping system is largely rainfed and terminal drought is a major constraint to its productivity. Currently available drought tolerant chickpea genotypes are very few. Considering that a ...large number of traits are collectively needed to confer yield under drought, there is a need to identify more genotypes to introduce diversity in drought tolerance breeding programs. The minicore (
n
=
211) chickpea germplasm collection has been evaluated over three years for drought tolerance index (DTI), calculated as the standard residuals, through a regression approach considering drought yield as a function of days to flowering, yield potential and the residual or drought response, in the short season environment of South-India. The minicore collection accessions exhibited large range of variations for days to 50% flowering (26–78 d) and maturity (70–120 d), shoot biomass (1500–4940
kg
ha
−1) and seed yield (210–2730
kg
ha
−1) under drought. The heritability for the shoot biomass and seed yields under drought stress (shoot biomass 0.118–0.461; seed yield 0.511–0.795) were relatively higher than that under optimally irrigated environment (shoot biomass 0.232–0.447; seed yield 0.322–0.631). Both the seed yield under drought and DTI showed significant accession
×
year interaction. A categorization of the DTI using a cluster analysis has revealed five major groups with 5 accessions in highly tolerant group, 78 in tolerant, 74 in moderately tolerant, 39 in sensitive and 20 in highly sensitive groups. ICC 4958, a previously identified drought tolerant genotype, was among the moderately tolerant while Annigeri, a well-adapted cultivar, was in the tolerant group. Though the heritability of DTI was slightly lesser than that of the yield, the DTI represented terminal drought tolerance
per se, and was independent of phenology and yield potential influences.
Legume crops provide significant nutrition to humans as a source of protein, omega-3 fatty acids as well as specific macro and micronutrients. Additionally, legumes improve the cropping environment ...by replenishing the soil nitrogen content. Chickpeas are the second most significant staple legume food crop worldwide behind dry bean which contains 17%–24% protein, 41%–51% carbohydrate, and other important essential minerals, vitamins, dietary fiber, folate, β-carotene, anti-oxidants, micronutrients (phosphorus, calcium, magnesium, iron, and zinc) as well as linoleic and oleic unsaturated fatty acids. Despite these advantages, legumes are far behind cereals in terms of genetic improvement mainly due to far less effort, the bottlenecks of the narrow genetic base, and several biotic and abiotic factors in the scenario of changing climatic conditions. Measures are now called for beyond conventional breeding practices to strategically broadening of narrow genetic base utilizing chickpea wild relatives and improvement of cultivars through advanced breeding approaches with a focus on high yield productivity, biotic and abiotic stresses including climate resilience, and enhanced nutritional values. Desirable donors having such multiple traits have been identified using core and mini core collections from the cultivated gene pool and wild relatives of Chickpea. Several methods have been developed to address cross-species fertilization obstacles and to aid in inter-specific hybridization and introgression of the target gene sequences from wild
Cicer
species. Additionally, recent advances in “Omics” sciences along with high-throughput and precise phenotyping tools have made it easier to identify genes that regulate traits of interest. Next-generation sequencing technologies, whole-genome sequencing, transcriptomics, and differential genes expression profiling along with a plethora of novel techniques like single nucleotide polymorphism exploiting high-density genotyping by sequencing assays, simple sequence repeat markers, diversity array technology platform, and whole-genome re-sequencing technique led to the identification and development of QTLs and high-density trait mapping of the global chickpea germplasm. These altogether have helped in broadening the narrow genetic base of chickpeas.
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