Kadambot H. M. Siddique

Polyamines: Natural and engineered abiotic and biotic stress tolerance in plants

Polyamines (PAs) are ubiquitous biogenic amines that have been implicated in diverse cellular functions in widely distributed organisms. In plants, mutant and transgenic plants with altered activity pointed to their involvement with different abiotic and biotic stresses. Furthermore, microarray, transcriptomic and proteomic approaches have elucidated key functions of different PAs in signaling networks in plants subjected to abiotic and biotic stresses, however the exact molecular mechanism remains enigmatic. Here, we argue that PAs should not be taken only as a protective molecule but rather like a double-faced molecule that likely serves as a major area for further research efforts. This review summarizes recent advances in plant polyamine research ranging from transgenic and mutant characterization to potential mechanisms of action during environmental stresses and diseases.

Heat Stress in Wheat during Reproductive and Grain-Filling Phases

Ambient temperatures have increased since the beginning of the century and are predicted to continue rising under climate change. Such increases in temperature can cause heat stress: a severe threat to wheat production in many countries, particularly when it occurs during reproductive and grain-filling phases. Heat stress reduces plant photosynthetic capacity through metabolic limitations and oxidative damage to chloroplasts, with concomitant reductions in dry matter accumulation and grain yield. Genotypes expressing heat shock proteins are better able to withstand heat stress as they protect proteins from heat-induced damage. Heat tolerance can be improved by selecting and developing wheat genotypes with heat resistance. Wheat pre-breeding and breeding may be based on secondary traits like membrane stability, photosynthetic rate and grain weight under heat stress. Nonetheless, improvement in grain yield under heat stress implies selecting genotypes for grain size and rate of grain filling. Integrating physiological and biotechnological tools with conventional breeding techniques will help to develop wheat varieties with better grain yield under heat stress during reproductive and grain-filling phases. This review discusses the impact of heat stress during reproductive and grain-filling stages of wheat on grain yield and suggests strategies to improve heat stress tolerance in wheat.

A review of the potential of Lathyrus sativus L. and L. cicera L. grain for use as animal feed

The use of two closely related species, Lathyrus cicera and L. sativus, as grain legumes for human and animal consumption, dates to the Neolithic period. Due to its tolerance to harsh environmental conditions L. sativus is still used widely for human food in Ethiopia and the Indian sub-continent, although cultivation has diminished in many other regions. The grain of both L. cicera and L. sativus contains a neurotoxin, 3-(-N-oxalyl)-L-2,3-diamino propionic acid (ODAP), which can cause a paralysis of the lower limbs (lathyrism). Due to the occurrence of lathyrism in humans recent plant breeding has produced cultivars with low ODAP concentrations. The susceptibility of animal species to lathyrism is poorly understood, although horses and young animals are more susceptible. Older published animal feeding studies are of limited use, since the presence and role of ODAP was unknown until the 1960s. More recent feeding studies indicate that low ODAP lines of L. cicera or L. sativus can be safely incorporated at inclusion rates up to 40, 30 and 70% of the diet of poultry, pigs and sheep, respectively, without growth reductions. The compositions of both L. cicera and L. sativus are similar to other commonly used feed grain legumes, respective protein contents are 25 and 27%. Antinutritional factors (ANFs), other than ODAP, are present in both L. cicera and L. sativus at concentrations similar to those found in other grain legumes; including trypsin inhibitors, chymotrypsin inhibitors, amylase inhibitors, lectins, tannins, phytate and oligosaccharides. The effect of ANFs in L. cicera and L. sativus on animal performance is not well understood and sometimes confounded with ODAP effects. Heating of grain will reduce levels of the proteinaceous ANFs and in some cases ODAP as well. Variation recorded in the germplasm of L. cicera and L. sativus has not been greatly utilised in plant breeding to lower levels of ANFs, with the exception of ODAP, leaving considerable potential for rapid improvement of cultivars. L. cicera and L. sativus are low production cost legumes

Physiological responses of chickpea genotypes to terminal drought in a mediterranean-type environment

Two field experiments were carried out to investigate the eVects of terminal drought on chickpea grown under water-limited conditions in the Mediterranean-climatic region of Western Australia. In the first experiment, five desi (small angular seeds) chickpeas and one kabuli ( large round seeds) chickpea were grown in the field with and without irrigation after flowering. In the second experiment, two desi and two kabuli cultivars were grown in the field with either irrigation or under a rainout shelter during pod filling. Leaf water potential (Y l ), dry matter partitioning after pod set and yield components were measured in both experiments while growth before pod set, photosynthesis, pod water potential and leaf osmotic adjustment were measured in the first experiment only. In the first experiment, total dry matter accumulation, water use, both in the pre- and post-podding phases, Y l and photosynthesis did not vary among genotypes. In the rainfed plants, Y l decreased below ’3 MPa while photosynthesis decreased to about a tenth of its maximum at the start of seed filling. Osmotic adjustment varied significantly among genotypes. Although flowering commenced from about 100 days after sowing (DAS) in both experiments, pod set was delayed until 130‐135 DAS in the first experiment, but started at 107 DAS in the second experiment. Water shortage reduced seed yield by 50 to 80%, due to a reduction in seed number and seed size. Apparent redistribution of stem and leaf dry matter during pod filling varied from 0 to 60% among genotypes, and suggests that this characteristic may be important for a high harvest index and seed yield in chickpea.

A comprehensive resource of drought- and salinity- responsive ESTs for gene discovery and marker development in chickpea (Cicer arietinum L.)

BackgroundChickpea (Cicer arietinum L.), an important grain legume crop of the world is seriously challenged by terminal drought and salinity stresses. However, very limited number of molecular markers and candidate genes are available for undertaking molecular breeding in chickpea to tackle these stresses. This study reports generation and analysis of comprehensive resource of drought- and salinity-responsive expressed sequence tags (ESTs) and gene-based markers.ResultsA total of 20,162 (18,435 high quality) drought- and salinity- responsive ESTs were generated from ten different root tissue cDNA libraries of chickpea. Sequence editing, clustering and assembly analysis resulted in 6,404 unigenes (1,590 contigs and 4,814 singletons). Functional annotation of unigenes based on BLASTX analysis showed that 46.3% (2,965) had significant similarity (≤1E-05) to sequences in the non-redundant UniProt database. BLASTN analysis of unique sequences with ESTs of four legume species (Medicago, Lotus, soybean and groundnut) and three model plant species (rice, Arabidopsis and poplar) provided insights on conserved genes across legumes as well as novel transcripts for chickpea. Of 2,965 (46.3%) significant unigenes, only 2,071 (32.3%) unigenes could be functionally categorised according to Gene Ontology (GO) descriptions. A total of 2,029 sequences containing 3,728 simple sequence repeats (SSRs) were identified and 177 new EST-SSR markers were developed. Experimental validation of a set of 77 SSR markers on 24 genotypes revealed 230 alleles with an average of 4.6 alleles per marker and average polymorphism information content (PIC) value of 0.43. Besides SSR markers, 21,405 high confidence single nucleotide polymorphisms (SNPs) in 742 contigs (with ≥ 5 ESTs) were also identified. Recognition sites for restriction enzymes were identified for 7,884 SNPs in 240 contigs. Hierarchical clustering of 105 selected contigs provided clues about stress- responsive candidate genes and their expression profile showed predominance in specific stress-challenged libraries.ConclusionGenerated set of chickpea ESTs serves as a resource of high quality transcripts for gene discovery and development of functional markers associated with abiotic stress tolerance that will be helpful to facilitate chickpea breeding. Mapping of gene-based markers in chickpea will also add more anchoring points to align genomes of chickpea and other legume species.

Ridge-Furrow Mulching Systems—An Innovative Technique for Boosting Crop Productivity in Semiarid Rain-Fed Environments

Increasing food demands by a growing human population require substantial increases in crop productivity. In rain-fed arid and semiarid areas where the water supply is limited, an increase in the precipitation use efficiency (PUE) is the key to reach this goal. This chapter examines the scientific basis of a ridge-furrow mulching system (RF system) for increasing PUE, and summarizes the effects of this system on crop performance, microclimates, soil attributes, and environmental sustainability. Studies have shown that using crop straw, plastic film, or gravel–sand materials to mulch the soil surface significantly reduces the evaporation of soil moisture, increases water availability to crop plants, and decreases soil erosion caused by wind and water. Plastic mulching increases topsoil temperature during cool spring, promoting plant growth; during hot summer, straw mulching can moderate soil temperature, preventing the topsoil from reaching temperatures that inhibit plant growth. Ridge furrows with plastic mulching on the ridges and crop straw covering the furrows channel water to the furrows, and enhance soil water infiltration and water availability to the crop. Microclimates under mulched ridges and furrows favor soil microbial activity, increase soil biodiversity, and improve environmental benefits. The effectiveness of ridge-furrow systems is reflected in increased crop yields (20–180%) compared with that of the conventional-flat planting. Although more research is required to document physiochemical strengths, technique details and potential drawbacks, and more importantly to define long-term sustainability, we strongly suggest that RF systems are an innovative approach for increasing crop water availability, improving soil productivity, and enhancing food security for arid and semiarid rain-fed areas.

Chickpea molecular breeding: New tools and concepts

SummaryChickpea is a cool season grain legume of exceptionally high nutritive value and most versatile food use. It is mostly grown under rain fed conditions in arid and semi-arid areas around the world. Despite growing demand and high yield potential, chickpea yield is unstable and productivity is stagnant at unacceptably low levels. Major yield increases could be achieved by development and use of cultivars that resist/tolerate abiotic and biotic stresses. In recent years the wide use of early maturing cultivars that escape drought stress led to significant increases in chickpea productivity. In the Mediterranean region, yield could be increased by shifting the sowing date from spring to winter. However, this is hampered by the sensitivity of the crop to low temperatures and the fungal pathogen Ascochyta rabiei. Drought, pod borer (Helicoverpa spp.) and the fungus Fusarium oxysporum additionally reduce harvests there and in other parts of the world. Tolerance to rising salinity will be a future advantage in many regions. Therefore, chickpea breeding focuses on increasing yield by pyramiding genes for resistance/tolerance to the fungi, to pod borer, salinity, cold and drought into elite germplasm. Progress in breeding necessitates a better understanding of the genetics underlying these traits. Marker-assisted selection (MAS) would allow a better targeting of the desired genes. Genetic mapping in chickpea, for a long time hampered by the little variability in chickpea’s genome, is today facilitated by highly polymorphic, co-dominant microsatellite-based markers. Their application for the genetic mapping of traits led to inter-laboratory comparable maps. This paper reviews the current situation of chickpea genome mapping, tagging of genes for ascochyta blight, fusarium wilt resistance and other traits, and requirements for MAS. Conventional breeding strategies to tolerate/avoid drought and chilling effects at flowering time, essential for changing from spring to winter sowing, are described. Recent approaches and future prospects for functional genomics of chickpea are discussed.

Water use and water use efficiency of cool season grain legumes in low rainfall Mediterranean-type environments

Abstract The water use ( E t ) and water use efficiency ( WUE ) of a range of cool season grain legume species (field pea [ Pisum sativum L.], faba bean [ Vicia faba L.], chickpea [ Cicer arietinum L.], lentil [ Lens culinaris Med.], albus lupin [ Lupinus albus L.], dwarf chickling [ Lathyrus cicera L.], ochrus chickling [ Lathyrus ochrus L.], grass pea [ Lathyrus sativus L.], narbon bean [ Vicia narbonensis L.], common vetch [ Vicia sativa L.], and purple vetch [ Vicia benghalensis L.]) were examined on fine textured neutral to alkaline soils in the low to medium rainfall Mediterranean-type environments in south-western Australia at Merredin and Mullewa in two seasons. There was no difference in the total E t between grain legumes at either site in either year. There was also no variation in soil water extraction between species on the shallow sandy loam soil at Merredin. However, C. arietinum , L. sativus and L. cicera had greater water extraction and P. sativum the least water extraction at Mullewa where soil conditions were less hostile and root penetration was not restricted. The pattern of water use varied markedly between the grain legume species examined. Grain yield was positively correlated with post-flowering water use ( E tpa ) in both erect ( r =0.59) and prostrate ( r =0.54) grain legume species. Water use efficiencies for dry matter production ( WUE dm ) of up to 30 kg ha −1 mm −1 for V. faba and V. narbonensis at Merredin, and water use efficiencies for grain yield ( WUE gr ) of up to 16 kg ha −1 mm −1 for P. sativum and 13 kg ha −1 mm −1 for V. faba at Mullewa, were comparable to those reported for cereals and other grain legumes in previous studies in this and other environments. Potential transpiration efficiencies ( TE ) of 15 kg ha −1 mm −1 together with soil evaporation ( E s ) values of 100–125 mm were estimated in this and associated studies, and can be used as benchmark values to assess the yield potential of cool season grain legume crops in low rainfall Mediterranean-type environments. The major traits of adaptation for grain legume species producing large yields in this short season environment are early flowering, and pod and seed set before the onset of terminal drought. Early phenology together with rapid ground cover and dry matter production allows greater water use in the post flowering period. This leads to greater partitioning of dry matter into seed, which is reflected in greater harvest index (HI) and WUE gr , as was observed for V. faba and P. sativum . Improvement in the adaptation of other grain legume species to short season Mediterranean-type environments requires increased early growth for rapid ground cover and improved tolerance to low temperatures (especially for C. arietinum ) during flowering and podding.

Ascochyta blight of chickpea (Cicer arietinum L.): a review of biology, pathogenicity, and disease management

Ascochyta blight (AB), caused by Ascochyta rabiei is a major disease of chickpea (Cicer arietinum L.), especially in areas where cool, cloudy, and humid weather persists during the crop season. Several epidemics of AB causing complete yield loss have been reported. The fungus mainly survives between seasons through infected seed and in infected crop debris. Despite extensive pathological and molecular studies, the nature and extent of pathogenic variability in A. rabiei have not been clearly established. Accumulation of phenols, phytoalexins (medicarpin and maackiain), and hydrolytic enzymes has been associated with host-plant resistance (HPR). Seed treatment and foliar application of fungicides are commonly recommended for AB management, but further information on biology and survival of A. rabiei is needed to devise more effective management strategies. Recent studies on inheritance of AB resistance indicate that several quantitative trait loci (QTLs) control resistance. In this paper we review the biology of A. rabiei, HPR, and management options, with an emphasis on future research priorities.

Flower numbers, pod production, pollen viability, and pistil function are reduced and flower and pod abortion increased in chickpea (Cicer arietinum L.) under terminal drought.

Terminal drought during the reproductive stage is a major constraint to yield of chickpea in many regions of the world. Termination of watering (WS) during podding in a small-seeded desi chickpea (Cicer arietinum L.) cultivar, Rupali, and a large-seeded kabuli chickpea cultivar, Almaz, induced a decrease in predawn leaf water potential (LWP), in the rate of photosynthesis, and in stomatal conductance. Compared to well-watered (WW) controls, the WS treatment reduced flower production by about two-thirds. In the WW treatment, about 15% of the flowers aborted and 42% (Rupali) and 67% (Almaz) of the pods aborted, whereas in the WS treatment 37% and 56% of the flowers aborted and 54% and 73% of the pods aborted, resulting in seed yields of 33% and 15% of the yields in WW plants in Rupali and Almaz, respectively. In vitro pollen viability and germination in Rupali decreased by 50% and 89% in the WS treatment, and pollen germination decreased by 80% in vivo when pollen from a WS plant was placed on a stigma of a WW plant. While about 37% of the germinated pollen tubes from WW plants and 22% from the WS plants reached the ovary in the WW plants, less than 3% of pollen grains reached the ovary when pollen from either WS or WW plants was placed on a stigma of a WS plant. It is concluded that, in addition to pod abortion, flower abortion is an important factor limiting yield in chickpea exposed to terminal drought and that water deficit impaired the function of the pistil/style more than the pollen.