Wheat Special Issue 2011: From Evolution to Agronomy
Articles
Special issue 2011 [5(9) 2011]
Table of Contents
Special issue 2011 [5(9) 2011]
Table of Contents
Southern Cross Publishing Group©2011
Australia
Australia
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Bipolaris sorokiniana (Sacc.) Shoem.: The most destructive wheat fungal pathogen in the warmer areas Krishnendu Acharya, Arun K. Dutta and Prakash Pradhan Abstract In recent years, spot blotch disease, caused by Bipolaris sorokiniana (Sacc.) Shoem. syn. Drechslera sorokiniana (Sacc.) Subrm and Jain (syn. Helminthosporium sativum, teleomorph Cochliobolus sativus) have emerged as serious concern for cultivation of wheat in warmer and humid regions of the world. During past two decades, substantial economic loss in wheat production has occurred due to the severity of spot blotch, affecting the livelihood of millions of small-scale farmers. Besides spot blotch, this fungus is also the causal agent of other diseases like common root rot, foot rot, seedling blight and seed rot of wheat. In this review, we have focused on the details of the pathogen and its management approaches. The disease severity is directly related to the humidity, temperature and soil nutrient condition. The greatest yield losses occur when the flag leaf and the leaf below the flag leaf become infected before the emergence of head. Crop rotation and burying wheat stubble by tillage can reduce the level of disease early in the season. Seed treatments are effective in eliminating the fungus on the seed. Application of fungicides is another means of disease prevention. Several sources have also been identified for improving resistance among susceptible commercial cultivars. Although a number of attempts have been made to control the disease, still, field results show that spot blotch continues to cause substantial grain yield reductions and underscore the need for further research. Pages 1064-1071 | Full text PDF |
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Ecogeography, genetic diversity, and breeding value of wild emmer wheat (Triticum dicoccoides Körn ex Asch. & Graebn.) Thell. Abdullah A. Jaradat Abstract Wild emmer wheat (Triticum dicoccoides Körn ex Asch. & Graebn.) Thell. is the allotetraploid (2n=4x=28; genome BBAA) progenitor of cultivated wheat. It is fully compatible with the tetraploid (BBAA) durum wheat (Triticum durum), and can be crossed with the hexaploid (2n=6x=42; BBAADD) wheat (Triticum aestivum). In the Fertile Crescent, the centre of origin and centre of diversity of wild emmer wheat, the wild progenitor exhibits a wide phenotypic and genotypic variation and displays a rich adaptive genetic diversity which is ecologically and genetically structured as an “archipelago.” The fertile hybrids between wild emmer wheat and domesticated durum wheat point to the early, and probably current, extensive gene flow that must have enriched the genetic structure of both subspecies in the Fertile Crescent. Specific alleles and allele combinations predominate, at the macro- and microgeographic scales, as co-adaptive blocks of genes adapted to diverse biotic and abiotic stresses. Wild emmer wheat is recognized as a source of genes for agronomically important traits. These include genes for large spike and grain size, high grain and protein yield, desirable composition of storage proteins, photosynthetic yield, herbicide response, salt tolerance, drought tolerance, disease (leaf rust, stripe rust, powdery mildew, and soil-born mosaic virus) resistance, profuse tillering, and genes for other quantitative traits. For millennia, the vast genetic diversity in wild emmer wheat must have contributed to the spatially and temporally sustainable wheat production as a major component of dynamic cropping systems in the Fertile Crescent. With the advent of, and easy access to, molecular genetics and breeding tools, wild emmer wheat is expected to contribute the full range of its diversity in quantitative and qualitative traits for a more globally sustainable wheat production. It is expected that the current and future detailed records of phenotypes and genotypes and their spatio-temporal variation patterns in the Fertile Crescent will form an integral part of a relational database that can serve future strategies for in situ conservation, collection, evaluation, and utilization by wheat geneticists and breeders. Pages 1072-1086 | Full text PDF |
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Haploid production technology in wheat and some selected higher plants Saikat Kumar Basu, Madhuleema Datta, Manorma Sharma, and Ashwani Kumar Abstract Haploid plants are very important in various realms of research disciplines such as plant biotechnology, molecular genetics and traditional plant breeding. They provide useful information regarding recombination and genetic control of chromosomal pairing. Haploidy expedites the breeding process thereby increasing the crop yield. Researchers have been working on the haploidy approach for more than half a century. Some crops have shown interesting results in producing haploid cultivars include bread wheat and other crops such as maize, oat and onion. This technique also has useful applications in genetic transformation for generating polyploidy wheat. Wheat cultivars developed from doubled haploid from both anther-culture and maize induction systems have been released for cultivation in all the major continents. Several techniques have been adapted for the production of haploid plants such as anther culture, isolated microspore culture some of which have been discussed in this review. With the ability to increase the yield of haploids in bread wheat and durum wheat, the haploidy technique may play an ever increasing role in basic cytogenetic, genetic, and genomic research as well as in applied plant breeding in several crop species in the not so distant future. This review aims to capture few of the great achievements being made in the field of haploid production technology in some selected crop/higher plant species and its implications to modern agriculture and in crop development programs. Pages 1087-1093 | Full text PDF |
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Mechanisms of waterlogging tolerance in wheat: Morphological and metabolic adaptations under hypoxia or anoxia Md. Alamgir Hossain and Sarder Nasir Uddin Abstract Waterlogging is a widespread limiting factor for wheat production throughout the world specially irrigated and high rainfall environments. The important biological consequence of waterlogging is the deficiency (hypoxia) or complete absence (anoxia) of oxygen in soil environment which restricts the growth, development and finally yield in wheat. The tolerant genotypes of wheat can adapt to transient waterlogging by developing mechanisms related to morphology and metabolism to cope with the stress. The morphological mechanisms include the development of adventurous roots with well formed aerenchyma and sometimes with a barrier for ROL. Aerenchyma is a continuous gas filled channel which provides a low resistance internal pathway for the movement of O2 from the aerobic shoots to anaerobic roots to respire aerobically under hypoxia or anoxia. However, Lack of oxygen induces the anaerobic roots to shift the energy metabolism from aerobic to anaerobic mode. Greater activities of glycolytic and fermentative enzymes, increased availability of soluble sugars, and involvement of antioxidant defense mechanism against post-stress oxidative damages are the main metabolic mechanisms for waterlogging tolerance in wheat. Pages 1094-1101 | Full text PDF |
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Parasitoid (Bracon cephi) effects on grain yield of selected genotypes of wheat infested by Cephus cinctus X. Wu, H. Cárcamo, B. Beres, B. Pang Abstract The wheat stem sawfly has been a major pest of spring wheat in the southern prairies of Canada and the adjoining parts of the United States for several decades. Bracon cephi (Gahan) is an important endemic ectoparasitoid of the wheat stem sawfly that can reach very high levels of parasitism. The objectives of this study were to determine the effect of B. cephi on the feeding damage (stem mining) caused by the sawfly and consequences on plant fitness in terms of grain yield in various hollow- and solid-stemmed wheat genotypes. This study was conducted at Coalhurst, west of Lethbridge, Alberta in 2003-2005, and 2008. Uninfested stems had lighter grain heads than those infested by the sawfly. There was no consistent difference in grain head weights between uninfested stems, sawfly infested (but dead), and those parasitized by B. cephi. In 2008, the length of the feeding tunnel was significantly shorter in parasitized stems than those cut or with dead sawfly larvae; in other years the difference between stems with dead larva and those parasitized by B. cephi were not significant. We conclude that although B. cephi reduced stem mining by the wheat stem sawfly it did not affect the stem seed weight. Nevertheless, reduction in stem lodging during the growing season and lower sawfly populations in following years are important reasons to conserve this parasitoid. Pages 1102-1107 | Full text PDF |
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Progress in host plant resistance in wheat to Russian wheat aphid (Hemiptera: Aphididae) in North Africa and West Asia M. El Bouhssini, F. C. Ogbonnaya, H, Ketata, M. M. Mosaad, K. Street, A. Amri, M. Keser, S. Rajaram, A. Morgounov, F. Rihawi, A. Dabus and C. M. Smith Abstract Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is an important pest of wheat and barley in several countries of North Africa and West Asia, e.g., Morocco, Algeria, Tunisia, Ethiopia, Yemen, Turkey and Iran. Host plant resistance is the most economical and practical means of controlling this insect. Field and greenhouse screening of introduced and local wheat germplasm at ICARDA resulted in the identification of several sources of resistance which were subsequently incorporated into ICARDA elite wheat germplasm and distributed as RWA gene pool to NARS (National Agricultural Research Systems) in affected countries. Crosses were initiated in 1998 to introgress resistance into winter/facultative bread wheat and the segregating populations were evaluated for RWA resistance and agronomic performance at the ICARDA Experiment Station at Tel Hadya. Selected advanced lines were sent to North African, and West Asian countries for evaluation of RWA and disease resistance and agronomic adaptation under local conditions. Additional identified sources of RWA resistance are now in use in the ICARDA wheat breeding program. Haplotype analysis using molecular markers previously identified as diagnostic for Dn resistance genes revealed that some recently identified resistance sources are unrelated to previously described Dn1-Dn9 genes, and may represent new genes for deployment in RWA breeding. These apparent novel resistance gene(s) could be effective against some of the more virulent biotypes and could be deployed in breeding programs to increase the diversity of available genetic resistances. The reaction of wheat differentials containing different Dn genes indicates that the Syrian RWA biotype is less virulent than US RWA2 biotype. Pages 1108-1113 | Full text PDF |
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Scope and challenges of organic wheat cultivation in Bangladesh MA. Sarker, Y. Itohara, M. Hoque and Sarder N. Uddin Abstract Due to continuous health awareness of the consumers towards organic food, organic wheat is being popular globally. Western Europe, North America, Japan and Australia are considered major markets for organic wheat where there to be few export opportunities for developing countries like Bangladesh in these markets. On the other hand, Bangladeshi farmers are producing organic wheat by default as many of them do not have affordability to costly chemicals. Moreover, the country has a wide range of wheat varieties those are tolerant to disease and insect pests, surplus labors, and an abundance of indigenous knowledge to manage their farm organically. However, there is no active initiative from the public sector extension organizations to promote organic wheat cultivation among the general farmers. Organic farmers are organized here by the initiatives of some NGOs and there are no controlling systems and certification bodies for organic produces except organic shrimp and tea. Despite of having these sorts of major challenges, Bangladesh has good prospects in organic wheat cultivation. Our study reveal that the key to translate the possibilities into realities is the better partnership and cooperation among organic wheat farmers, NGOs, certifiers, marketing people (both local and export), state and the programs that will support organic wheat cultivation and ultimately it will contribute in reducing poverty of the poor farmers of Bangladesh. Pages 1114-1119 | Full text PDF |
Invited Review Paper Edited by Saikat Kumar Basu Co-edited by Ardashir Kharabian Wheat genome phylogeny and improvement Ashwani Kumar and Manorma Sharma Abstract Poaceae (formerly known as Gramineae) is often considered to be the most important of all plant families to human economies. From evolutionary point of view, wheat is a young polyploid and its genetic configuration is a classical example of cereals phylogenic relationship. Studies of genetic diversity of the elite germplasm have been used by plant breeders for numerous reasons viz. germplasm management, genetic relationships, parent selection, and protection. Hence the knowledge of genetic diversity and relationship among a set of germplasm is of great importance in present scenario for crop improvement and genetic security of food grains. Similarity of wheat genome with rice and maize pave a way to develop more improved verities’ of wheat. Many good stress tolerance wheat verities’ have developed in the light of phylogenic study of these species. The main focus of this review paper is to highlight phylogenic relation of elite wheat genome as well as laconically describe the new stress tolerance wheat verities’ development. Pages 1120-1126 | Full text PDF |
Invited Review Paper Edited by Aakash Goyal Co-edited by Ardashir Kharabian Wild emmer wheat, Triticum dicoccoides, occupies a pivotal position in wheat domestication process Junhua Peng, Dongfa Sun and Eviatar Nevo Abstract Domestication of plants and animals is the major factor underlying human civilization. Cultivated wheats refer mainly to two types: the hexaploid bread wheat (Triticum aestivum) accounting for about 95% of world wheat production, and the tetraploid durum wheat (T. durum) accounting for the other 5%. T. aestivum derived from a cross between domesticated emmer T. dicoccum and the goat grass Aegilops tauschii most probably originating in the south or west of the Caspian Sea about 9,000 years ago. T. dicoccoides, the wild emmer wheat, is the progenitor of cultivated wheats, has the same genome formula as durum wheat and has contributed two genomes to bread wheat, and has played core role to wheat domestication. This process of wheat domestication fits the gradual and multi-site model other than the fast and single-site model. Domestication has genetically not only transformed the brittle rachis, tenacious glume and non-free threshability, but also modified yield and yield components in wheat. Wheat domestication is only involved in a limited number of chromosome regions, or domestication syndrome factors, though many relevant quantitative trait loci were detected. The available crop genome sequences and genome sequencing of wheat can transform today’s biology, dramatically advancing both theory and application of wheat domestication study. The nonrandom adaptive processes and complexes in T. dicoccoides and other wheat relatives could provide the basis for wheat improvement as single genes, QTLs, and interacting biochemical networks. Genome sequencing of diploid wild wheat, either T. urartu or Ae. tauschii, could be helpful for isolation of domestication syndrome factors and other relevant genes. The distinct adaptive complexes of T. dicoccoides to environmental stresses is of great importance for improvement of bread wheat. Pages 1127-1143 | Full text PDF |
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