Biotic and abiotic stresses cause significant yield losses in legumes and can significantly affect their productivity. Biotechnology tools such as marker-assisted breeding, tissue culture, in vitro mutagenesis and genetic transformation can contribute to solve or reduce some of these constraints. However, only limited success has been achieved so far. The emergence of “omic” technologies and the establishment of model legume plants such as Medicago truncatula and Lotus japonicus are promising strategies for understanding the molecular genetic basis of stress resistance, which is an important bottleneck for molecular breeding. Understanding the mechanisms that regulate the expression of stress-related genes is a fundamental issue in plant biology and will be necessary for the genetic improvement of legumes. In this review, we describe the current status of biotechnology approaches in relation to biotic and abiotic stresses in legumes and how these useful tools could be used to improve resistance to important constraints affecting legume crops.

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Biotechnology approaches to overcome biotic and abiotic stress constraints in legumes

SummaryRapeseed plants have been regenerated after fusion between protoplasts bearing cytoplasms of different genera. Cybrids combine, in a first experiment Brassica napus chloroplasts and a cytoplasmic male sterility (cms) trait coming from Raphanus sativus, in a second experiment chloroplasts of a triazine resistant Brassica campestris and cms trait from Raphanus sativus. Transfer of chloroplasts has been confirmed by restriction cp DNA analysis and two dimensional thylakoïd protein electrophoresis. These plants may be very useful for Brassica hybrid seed production.

Intergeneric cytoplasmic hybridization in cruciferae by protoplast fusion

Preface


Brassica vegetables continue serving mankind after millennia of use as food, fodder and forage. The quiet mundanity of cabbage yards belies their botanical miracles as exponents of genotypic and phenotypic diversity and flexibility. Brassicas provide one of the finest examples of convergent evolution in the horticultural forms of the European Brassica oleracea and Oriental B. rapa. These mirror each other in a rich spectrum of fresh foodstuffs that have been selected and bred for particular regional preferences over many centuries. Alongside are numerous other taxonomic variants brought about natural genetic manipulation and polyploidy that produce oil rich and condiment crops. 

This book per force concentrates on the vegetable brassicas but has made great use of the science underlying the biggest world Brassica crop on an area basis, oil seed rape or canola. It is impossible to study vegetable brassicas without being influenced by B. napus, to have included it in detail would have required a much larger volume. Only very recently science has begun recognising the nutritional benefits of both vegetables and oil seed brassicas. And in comparative terms only more recently have the properties of some of the wild relatives come to the fore. The tiny weed or rock garden speciality, Arabidopsis thaliana has achieved enormous scientific clout as a model system for molecular biological studies. In coming decades it could outstrip some of the crop vegetable brasicas in economic significance. 

In considering the horticultural science underpinning Brassica crops I have attempted to think forward into those aspects that will be important for students who use this Book and whose working careers may have three or more decades to run. Consequently, there is an emphasis on husbandry as the key tool in pest, pathogen and physiological disorder control. Plant breeding and the potential for genetic manipulation are emphasised. The brassicas are of pivotal significance in providing wholesome and nutritious foodstuffs for our burgeoning world population and are capable of doing even greater service to mankind when tailored to use land with an elevated salt content. 

The view of Vegetable Brassicas as expressed here is entirely mine and I fully accept responsibility for all errors, omissions and unconventional thinking. Tribute is due however, to my very good friend Dr Michael Dickson of Cornell University, New York State USA. He has been a constantly supportive mentor during the overlong gestation of the book. His ever kindly help is greatly valued, he penned parts of Chapter 2 relating to Plant Breeding and Genetics and Sections concerned with pest and pathogen resistance in Chapter 7. Gratitude is also due to Professor Paul Williams of Wisconsin University at Madison, USA, he has offered abiding friendship, deep intellectual sustenance and a common view of science over many decades. 





The roots of this book are set deep in a life - time of scientific fascination in the biology of Brassica allied to their commercial production. These bind together horticultural experiences in the Thames Valley, the broad fenlands of East Anglia, the Scottish Mearns and Fife. These are topped by all too brief acquaintances with the kale yards of Europe, extensive and intensive efficiencies of the Valley Lands of California and the sheer magical diversities of Asian cropping. Founding influences in understanding the true nature of scholarship in the natural sciences based around the concept of "One Foot in the Furrow" were my trio of mentors at Wye College (then London University's Faculty of Agriculture and Horticulture). The true teachers, Professor Herbert W Miles, Dr Edward H Wilkinson and Mr Alan Jackson, entranced young minds in the early 1960s with a rich mixture of ecology, crop physiology, plant breeding and commercial instinct founded firmly in the nascent implications of Rachel Carson's Silent Spring.

Committing this text to paper needed the support and encouragement of many other friends and professional colleagues. Particular gratitude goes to Professors John Watson and John Anderson, previous and current Heads of the Department of Bioscience; Mr Stewart Roy, Faculty Officer in the Faculty of Science and Professor Sir John Arbuthnott, Vice - Chancellor and Principal of the University of Strathclyde in Glasgow. Collectively they provided a haven for scholarship proofed against icy blasts of moronic barbarity. 


Geoffrey R Dixon
2005.

Vegetable Brassicas and Related Crucifers

Suspension-derived protoplasts of Agropyron elongatum irradiated by ultra-violet light (UV) were fused with the suspension-derived protoplasts of Triticum astivum using PEG. Fertile intergeneric somatic hybrid plants were produced and various hybrid lines have been selected and propagated in successive generations. Their hybrid nature was confirmed by analysis of profiles of isozymes, RAPDs, and 5S rDNA spacer sequences, and via GISH analysis. By the procedure described, the phenotype and chromosome number of wheat could be maintained besides transfer of a few chromosomes and chromosomal fragments from the donor A. elongatum. The results above indicated that highly asymmetric fertile hybrid plants and hybrid progenies of wheat were produced via somatic hybridization.

Asymmetric somatic hybridization between wheat (Triticum aestivum L.) and Agropyron elongatum (Host) Nevishi

Related or distant species of cultivated cs are a large pool of many desirable genes. Gene transfer from these species through conventional breeding is difficult owing to post- and pre-zygotic sexual incompatibilities. Somatic hybridization via protoplast fusion is a possible alternative for gene transfer from these species to cultivated crops. Since the early days of somatic hybridization many intergeneric somatic hybrids have been developed through symmetric fusion, asymmetric fusion and microfusion. Somatic hybrids are mainly selected by using markers such as specific media or fusion parents with special features, biochemical mutants, antibiotic resistance and complementation strategy. The hybridity of the regenerants is determined based on morphological, cytological and molecular analysis. The inheritance patterns of nuclear and cytoplasmic genomes in the somatic hybrids are diverse. Nuclear DNA from both fusion parents co-exists congruously in some hybrids with translocation and rearrangement of chromosomes, but spontaneous elimination of chromosomes from either or both fusion parents has been observed very often. In asymmetric fusion, chromosome elimination is an important issue that is a complicated process influenced by many factors, such as irradiation dose, phylogenetic relatedness, ploidy level of fusion parent and regenerants. As for chloroplast genome, uniparental segregation is mainly detected, though co-existence is also reported in some cases. The mitochondrial genome, in contrast to chloroplast, undergoes recombination and very frequent rearrangements. Somatic cell fusion has potential applications for crop genetic improvement by overcoming sexual incompatibility or reproductive barriers, and by realizing novel combinations of nuclear and/or cytoplasmic genomes.

Intergeneric somatic hybridization and its application to crop genetic improvement

Somatic Hybrids between Sinapis alba and rapid-cycling Brassica oleracea were generated for transferring of resistance to Alternaria brassicae to B. oleracea. A. brassicae causes the significant disease black spot in cruciferous crops. A total of 27 plants were regenerated from protoplast fusion using 0, 5, 10, 20 and 30 krad γ-irradiation of the resistance donor and iodoacetate treatment of B. oleracea. All plants showed intermediate morphology with partially divided leaves and some trichomes on stems and leaves. Flow cytometry and banding patterns of the enzymes leucine amino peptidase (LAP) and phosphoglucose isomerase (PGI) confirmed the hybrid status of the regenerated plants. Some of the plants obtained from cuttings from the somatic hybrids showed a resistance to A. brassicae that was similar to that found in S. alba. The flowers of the somatic hybrids had reduced anthers with little pollen production.

Somatic hybrids between Brassica oleracea L. and Sinapis alba L. with resistance to Alternaria brassicae (Berk.) Sacc

Black rot caused by the bacterium Xanthomonas campestris pv campestris is one of the most serious diseases of Brassica oleracea. Since sources of resistance to the disease within B. oleracea are insufficient and control means are limited, the development of resistant breeding lines is extremely desirable. Certain lines of B. napus contain very high resistance controlled by a dominant gene, but crossing the two species sexually is very difficult. Therefore, somatic hybrids were produced by protoplast fusion between rapid cycling B. oleracea and a B. napus line highly resistant to X. campestris pv campestris. Hybrid identity was confirmed by morphological studies, flow cytometric estimation of nuclear DNA content, and analysis of random amplified polymorphic DNA (RAPD). Inoculations with the pathogen identified four somatic hybrids with high resistance. The resistant hybrid plants were fertile and set seed when selfed or crossed reciprocally to the bridge line ‘15’ (Quazi 1988). Direct crosses to B. oleracea were unsuccessful, but embryo rescue facilitated the production of a first-backcross generation. The BC1 plants were resistant to the pathogen. Progeny from the crosses to ‘line 15’ were all susceptible. Embryo rescue techniques were not obligatory for the development of a second-backcross generation, and several resistant BC2 plants were obtained.

L. N. Hansen

Papers

Somatic hybrids between Brassica oleracea L. and Sinapis alba L. with resistance to Alternaria brassicae (Berk.) Sacc

Transfer of resistance to Xanthomonas campestris pv campestris into Brassica oleracea L. by protoplast fusion