Current status and future strategy in breeding chickpea for resistance to biotic and abiotic stresses

Chickpea (Cicer arietinum L.) production has remained static for the past two decades. One major limiting factor has been susceptibility of cultivars to several biotic and abiotic stresses that adversely affect yield. In recent years, cultivars resistant to Ascochyta blight (Ascochyta rabiei [Pass.] Lab.), Fusarium wilt (Fusarium oxysporum f. sp. ciceris), and cold have been bred and released in many countries. Some progress has been made in breeding for resistance to drought, insects, and cyst nematode, but not for viruses, heat, and salinity. Two or more stresses are of equal importance in most chickpea growing areas. Therefore, future efforts should be directed toward the development of cultivars with multiple-stress resistance. Proper understanding of important stresses in different countries and the genetics of resistance should lead to more systematic approaches to resistance breeding. Wild Cicer species hold promise and deserve attention in resistance breeding.     

Current and future strategies in breeding lentil for resistance to biotic and abiotic stresses

Lentil production is limited by lack of moisture and unfavorable temperatures throughout its distribution. Waterlogging and salinity are only locally important. Progress has been made in breeding for tolerance to drought through selection for an appropriate phenology and increased water use efficiency and in breeding for winter hardiness through selection for cold tolerance.The diseases rust, vascular wilt, and Ascochyta blight, caused by Uromyces viciae-fabae, Fusarium oxysporum f. sp. lentis, and Ascochyta fabae f. sp. lentis, respectively, are the key fungal pathogens of lentil. Cultivars with resistance to rust and Ascochyta blight have been released in several countries and resistant sources to vascular wilt are being exploited. Sources of resistance to several other fungal and viral diseases of regional importance are known. In contrast, although the pea leaf weevil (Sitona spp.) and the parasitic weed broomrape (Orobanche spp.), and to a lesser extent the cyst nematode (Heterodera ciceri), are significant yield reducers of lentil, no sources of resistance to these biotic stresses have been found. Directions for future research in lentil on both biotic and abiotic stresses are discussed.     

Present status and future strategy in breeding faba beans (Vicia Faba L.) for resistance to biotic and abiotic stresses

Progress is being made, mainly by ICARDA but also elsewhere, in breeding for resistance to Botrytis, AScochyta, Uromyces, and Orobanche; and some lines have resistance to more than one pathogen. The strategy is to extend multiple resistance but also to seek new and durable forms of resistance. Internationally coordinated programs are needed to maintain the momentum of this work.Tolerance of abiotic stresses leads to types suited to dry or cold environments rather than broad adaptability, but in this cross-pollinated species, the more hybrid vigor expressed by a cultivar, the more it is likely to tolerate various stresses.     

Inheritance of resistance to pea blight (Ascochyta pinodella) and induction of resistance in pea (Pisum sativum L.)

Summary Pea blight caused by Assochyta pinodella does considerable damage to the pea crop every year. To ascertain the inheritance of resistance to pea blight and incorporate resistance in the commercial cultivars, crosses were made between Kinnauri resistant to pea blight and four highly susceptible commercial pea cultivars — Bonneville, Lincoln, GC 141 and Sel. 18. Studies of the F₁'s, F₂'s, back crosses and F₃'s indicated that Kinnauri carries a dominant gene imparting resistance to pea blight.     

Lathyrus improvement for resistance against biotic and abiotic stresses: From classical breeding to marker assisted selection

Summary Several Lathyrus species and in particular Lathyrus sativus (grass pea) have great agronomic potential as grain and forage legume, especially in drought conditions. Grass pea is rightly considered as one of the most promising sources of calories and protein for the vast and expanding populations of drought-prone and marginal areas of Asia and Africa. It is virtually the only species that can yield high protein food and feed under these conditions. It is superior in yield, protein value, nitrogen fixation, and drought, flood and salinity tolerance than other legume crops. Lathyrus species have a considerable potential in crop rotation, improving soil physical conditions; reducing the amount of disease and weed populations, with the overall reduction of production costs. Grass pea was already in use in Neolithic times, and presently is considered as a model crop for sustainable agriculture. As a result of the little breeding effort invested in it compared to other legumes, grass pea cultivation has shown a regressive pattern in many areas in recent decades. This is due to variable yield caused by sensitivity to diseases and stress factors and above all, to the presence of the neurotoxin β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP), increasing the danger of genetic erosion. However, both L. sativus and L. cicera are gaining interest as grain legume crops in Mediterranean-type environments and production is increasing in Ethiopia, China, Australia and several European countries. This paper reviews research work on Lathyrus breeding focusing mainly on biotic and abiotic resistance improvement, and lists current developments in biotechnologies to identify challenges for Lathyrus improvement in the future.     

Genetical analysis of resistance to Mycosphaerella pinodes in pea seedlings

Summary In studies of the inheritance of resistance, pea seedlings of seven lines in which stems and leaves were both resistant to Mycosphaerella pinodes were crossed with a line in which they were both susceptible. With seven of the crosses resistance was dominant to susceptibility. When F₂ progenies of five crosses were inoculated on either stems or leaves independently, phenotypes segregated in a ratio of 3 resistant: 1 susceptible indicating that a single dominant gene controlled resistance. F₂ progenies of one other cross gave ratios with a better fit to 9 resistant: 7 susceptible indicating that two co-dominant genes controlled resistance. The F₂ progeny of another cross segregated in complex ratios indicating multigene resistance.When resistant lines JI 97 and JI 1089 were crossed with a susceptible line and leaves and stems of each F₂ plant were inoculated, resistance phenotypes segregated independently demonstrating that leaf and stem resistance were controlled by different genes. In two experiments where the F₂ progeny of the cross JI 97×JI 1089 were tested for stem and leaf resistance separately, both characters segregated in a ratio of 15 resistant:1 susceptible indicating that these two resistant lines contain two non-allelic genes for stem resistance (designated Rmp1 and Rmp2) and two for leaf resistance (designated Rmp3 and Rmp4). Evidence that the gene for leaf resistance in JI 1089 is located in linkage group 4 of Pisum sativum is presented.     

Common bean breeding for resistance against biotic and abiotic stresses: From classical to MAS breeding

Summary Breeding for resistance to biotic and abiotic stresses of global importance in common bean is reviewed with emphasis on development and application of marker-assisted selection (MAS). The implementation and adoption of MAS in breeding for disease resistance is advanced compared to the implementation of MAS for insect and abiotic stress resistance. Highlighted examples of breeding in common bean using molecular markers reveal the role and success of MAS in gene pyramiding, rapidly deploying resistance genes via marker-assisted backcrossing, enabling simpler detection and selection of resistance genes in absence of the pathogen, and contributing to simplified breeding of complex traits by detection and indirect selection of quantitative trait loci (QTL) with major effects. The current status of MAS in breeding for resistance to angular leaf spot, anthracnose, Bean common mosaic and Bean common mosaic necrosis viruses, Beet curly top virus, Bean golden yellow mosaic virus, common bacterial blight, halo bacterial blight, rust, root rots, and white mold is reviewed in detail. Cumulative mapping of disease resistance traits has revealed new resistance gene clusters while adding to others, and reinforces the co-location of QTL conditioning resistance with specific resistance genes and defense-related genes. Breeding for resistance to insect pests is updated for bean pod weevil (Apion), bruchid seed weevils, leafhopper, thrips, bean fly, and whitefly, including the use of arcelin proteins as selectable markers for resistance to bruchid seed weevils. Breeding for resistance to abiotic stresses concentrates on drought, low soil phosphorus, and improved symbiotic nitrogen fixation. The combination of root growth and morphology traits, phosphorus uptake mechanisms, root acid exudation, and other traits in alleviating phosphorus deficiency, and identification of numerous QTL of relatively minor effect associated with each trait, reveals the complexity to be addressed in breeding for abiotic stress resistance in common bean.     

Field screening ofPisum accessions to evaluate their susceptibility to the pea weevil (Coleoptera: Bruchidae)

Summary Seventeen unreplicated field trials over nine sites and four years were used to classifyPisum germplasm (P. sativum L. &P. fulvum Sibth. & Sm) as potential sources of resistance to the pea weevil,Bruchus pisorum (L.). The emergence of adult weevils from <10% of harvested seed was used as the selection criterion to indicate possible resistance. A total of 1900Pisum accessions were assessed using the field trials and 1754 of theP. sativum accessions were eliminated. However in the 18P. fulvum accessions screened, the level of infestation by pea weevil was always below the arbitrary resistance threshold selected. This suggests thatP. fulvum accessions could be a valuable source of resistance to the pea weevil.     

Genetic analysis of adult plant resistance to powdery mildew in pea (Pisum sativum L.)

Summary An analysis of adult plant resistance of powdery mildew in 15 F₁, F₂ and F₃ populations of pea derived from crossing 15 diverse and susceptible lines with one resistant line revealed that resistance to powdery mildew is controlled by duplicate recessive genes. The genes were designated as er₁ and er₂.Disease reaction showed independent segregation with three known markers in the resistant parent, namely, af (afila, chromosome 1), st (stipule reduced, chromosome 3) and tl (clavicula, chromosome 7).Contribution form the Department of Genetics and Plant Breeding Banaras Hindu University, Varanasi-221005, India.     

Sources of variation for sustainable field pea breeding

The pea crop (Pisum sativum L.) is a convenient source of plant protein for animal feeding. The objective of this research was to evaluate field pea breeding lines for agronomic performance and seed quality focussed to their use in a sustainable production. Thirty-five field pea breeding lines and six elite cultivars were evaluated for their agronomic value in field in Spain upon 20 traits related to flower, cycle, plant architecture, productivity and seed quality. The lines showed significant differences in all the quantitative traits evaluated and three of them, namely MB-0307, MB-0308, and MB-0319 were chosen to be evaluated, together with the advanced cultivar ZP-1233, in field and in growing chamber for agronomic performance, seed quality and ability for sustainable production. The four accessions displayed high seed protein content that had significant effect of cropping density with averages of 253.6 g kg⁻¹ under low cropping density of 60 plants m⁻² and 259.1 g kg⁻¹ under high cropping density of 90 plants m⁻², therefore, the low cropping density should be regarded as the most convenient. Average yield of the lines MB-0307, MB-0308 and MB-0319 and the cultivar ZP-1233 was fair (197.5 g m⁻²), probably due to the absence of fertilizers and irrigation, aiming for the sustainability of the crop. Intercropping with rye and herbicide application resulted in no differences on the seed yield; therefore, the ability of the breeding lines to grow without herbicide seems to be demonstrated, while the germination of the seeds at low temperature was very good. These results indicate that field pea could be a new protein crop in the North of Spain to satisfy the demand of plant protein for animal feed, based upon adapted breeding lines that combine the ability for growing under sustainable conditions with other desirable agronomic traits maintaining an adequate productivity.     

Heterosis for yield and related characters in pea

Summary To determine the levels of heterosis in F1 hybrids, four current pea (Pisum sativum L.) cultivars from southern Australia were used as female parents and crossed with 18 introduced genotypes. The 22 parents, 72 F1 hybrids and, depending on the environment, either 54 or all 72 F2 families were grown in replicated plots in four environments. Grain yield, total dry matter, harvest index, branches per plant, pods per plant, seeds per pod, hundred seed weight, plant height, onset of flowering and flowering periods were evaluated. For both the F1 and F2 generation, heterosis was determined as the superiority over the mid-parent and also over the better parent. In addition, the superiority over the best commercial cultivar was calculated. Most hybrids were higher yielding than their mid-parent but were less stable in yield across environments. Four F1 hybrids were significantly higher yielding than the best parent, by up to 26%. There were significant correlations between F1 hybrid and mid-parent value for plant height, pods per plant and hundred seed weight but not for yield. Overall, grain yield heterosis was mainly due to more pods per plant in the hybrids. The level of heterosis for yield in a poor yielding environment was higher than that in a high yielding one. Both additive and non-additive gene effects were important in the expression of all studied traits. The average level of heterosis for grain yield and total dry matter in the F2 population was half of that in F1 hybrids. The low level of inbreeding depression from the F1 to the F2 generation suggested that epistatic gene action also contributed to the expression of grain yield. Some F2 populations maintained the high yield levels of the corresponding F1 hybrids.     

Faba bean breeding for resistance against biotic stresses: Towards application of marker technology

Summary Faba beans are adversely affected by numerous fungal diseases leading to a steady reduction in the cultivated area in many countries. Major diseases such as Ascochyta blight (Ascochyta fabae), rust (Uromyces viciae-fabae), chocolate spot (Botrytis fabae), downy mildew (Peornospora viciae) and foot rots (Fusarium spp.) are considered to be the major constraints to the crop. Importantly, broomrape (Orobanche crenata), a very aggressive parasitic angiosperm, is the most damaging and widespread enemy along the Mediterranean basin and Northern Africa. Recent mapping studies have allowed the identification of genes and QTLs controlling resistance to some of these diseases. In case of broomrape, 3 QTLs explained more than 70% of the phenotypic variance of the trait. Concerning Ascochyta, two QTLs located in chromosomes 2 and 3 explained 45% of variation. A second population sharing the susceptible parental line also revealed two QTLs, one of them likely sharing chromosomal location and jointly contributing with a similar percentage of the total phenotypic variance. Finally, several RAPD markers linked to a gene determining hypersensitive resistance to race 1 of the rust fungus U. viciae-fabae have also been reported. The aim of this paper is to review the state of the art of gene technology for genetic improvement of faba bean against several important biotic stresses. Special emphasis is given on the application of marker technology, and Quantitative Trait Loci (QTL) analysis for Marker-Assisted Selection (MAS) in the species. Finally, the potential use of genomic tools to facilitate breeding in the species is discussed. The combined approach should expedite the future development of lines and cultivars with multiple disease resistance, one of the top priorities in faba bean research programs.     

The response of Pisum sativum L. germplasm to high concentrations of soil boron

Summary Tolerance to high levels of boron in the soil is an important aspect of the adaptation of crop varieties to southern Australian conditions. This paper reports investigations aimed at exploring the extent of genetic variation in Pisum sativum and at defining appropriate selection criteria for selection for boron tolerance in breeding programs.A collection of 617 accessions of Pisum was screened in controlled conditions and visually assessed for symptoms of boron toxicity. A high proportion of accessions were sensitive with only 3.5% being more tolerant than any of the Australian varieties. Relatively high proportions of tolerant and moderately tolerant accessions originated from Asia and South America.In a second experiment the responses of selected tolerant accessions were evaluated with respect to different parameters. The objectives were to confirm the performance of the putative boron tolerant accessions and identify appropriate parameters for selecting boron tolerant genotypes. In addition to the visual assessment of boron toxicity, measurements at the time of harvest included dry matter yield and concentration of boron in tissues. Symptom expression was highly correlated with dry matter yield and concentration of boron in tissues under high boron conditions and so could be used as a non-destructive selection criteria. A low degree of symptom expression by tolerant accessions could usually be attributed to low levels of boron in the vegetative tissues. The results of this study indicate that considerable genetic variation exists among exotic accessions of Pisum sativum and tolerance to boron could be transferred to sensitive varieties.     

Somatic embryogenesis in pea (Pisum sativum L. and Pisum arvense L.): Diallel analysis and genetic control

Summary Six lines of Pisum were tested in vitro for their ability to produce somatic embryos from apices. Significant quantitative variation was observed. Inheritance of the ability to form somatic embryos was studied using a diallel cross among six different lines. About 80% of the observed genotypic variation was due to additive effects. There is a tendency for the favourable genes to be recessive. It appears that there are two genetic systems involved. Analysis of the distribution of F₃ families means from a cross among two extreme lines seems to indicate the presence of a few major genes in the control of somatic embryogenesis of pea.     

Study of the variation in the somatic embryogenesis ability of some pea lines (Pisum sativum L. and Pisum arvense L.)

Summary Thirty lines of pea were tested in vitro to evaluate their ability to produce somatic embryos. Three distinct genotypic classes were detected (strong, medium and weak). The best responses were obtained in Pisum sativum. Abnormal somatic embryos and secondary embryogenesis seem to constitute the principal obstacle to the development of these structures.     

Genetic male sterility in the pea (Pisum sativum L.)

Summary Genetic male sterility has been described in the pea (Pisum sativum L.), but no comprehensive effort has been made to study the phenomenon. A preceding companion paper reported the inheritance, allelism and linkage relations of thirteen male sterile mutants obtained from seed mutagen treatments. In the present study, the same male sterile mutants were investigated cytologically to determine the cause of sterility. Normal microsporogenesis and microgametogenesis was compared to that of the mutants. The ms-2, ms-3, and ms-4 mutants exhibited meiotic abnormalities similar to those described by Gottschalk and colleagues except that ms-3 had a high degree of female sterility. Chromosome clumping and spindle abnormalities leading to formation of coenocytic microspores and degeneration were characteristic of ms-2 and ms-4. The ms-2 and ms-4 mutants were previously found to be allelic, and were nearly identical cytologically in the present study. The ms-3 mutant exhibited a lack of chromosome condensation in meiosis I, and a lack of spindle formation in both meiotic divisions. Two mutations (ms-6 and ms-10) affected meiosis, with univalents at metaphase, and asynchronous divisions during meiosis II. Microspores of ms-6 completely degenerated whereas those of ms-10 showed some development. Sticky chromosomes, bridges and fragments, tripolar spindles, and lack of a second division were characteristic of ms-10. The ms-10 mutant also showed reduced female fertility. Two male steriles (ms-5 and ms-9) had abnormalities associated with premature degeneration of the tapetum. Three others (ms-7, ms-8, and ms-11) aborted pollen during meicrogametogenesis. Pollen grains of ms-11 had thinner walls than normal and lacked sculptured exine. The ms-10 mutant, and those affecting microgametogenesis (ms-5, ms-7, ms-8, ms-9, and ms-11) produced some stainable and viable pollen.     

Maintenance breeding and multiplication of pea and faba bean cultivars. Maintenance of protein peas (Pisum sativum) and field beans (Vicia faba)

Summary The maintenance of protein pea (Pisum sativum)and field bean (Vicia faba)cultivars is a part of the breedingscheme of these pulses at CEBECO-ZADEN. As soon as the cultivar is pure breeding a large quantity ofseed is stored under conditioned circumstances.     

Analysis of tissue culture-derived variation in pea (Pisum sativum L.)-preliminary results

Summary The possibility of producing agronomically-useful somaclones via organogenesis and somatic embryogenesis from callus cultures of pea (Pisum sativum L.) was studied. Organogenic calli were induced from immature leaflets on MSB medium with NAA and BAP. Embryogenic calli were derived either from immature zygotic embryos (using 2,4-D) or from shoot apices (using picloram) of aseptically-germinated seedlings.The seed progenies (T₁ to T₃-generation) of primary regenerants were grown in field conditions and their phenotypic variation was evaluated and compared with control, non-tissue culture-derived plant material. In addition, electrophoretic analyses of selected isoenzyme systems and total proteins have been done. The results do not show dramatic changes in qualitative and quantitative traits. The evaluation of at least two future generations (T₄, T₅) is planned.Abbreviations BAP 6-benzylaminopurine - IBA indole-3-butyric acid - MSB medium (mineral salts after Murashige & Skoog, 1962, vitamins after Gamborg et al., 1968) - NAA -naphthalene-acetic acid, picloram-4-amino-3,5,6-trichloro picolinic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - ORG organogenesis - SE somatic embryogenesis     

Selection for partial resistance to downy mildew in peas by means of greenhouse tests

Summary A partially downy mildew resistant pea line was back-crossed to a susceptible cultivar with more pods per node and lower seed weight. Breeding lines with different degrees of infection in a greenhouse test were selected. These lines and the two parental lines were investigated in field trials and tested in the greenhouse for four generations. Significant genetic variation among lines was found for infection of seedlings in greenhouse tests, and infection of pods, pod set and seed weight in field-trials. Infection of seedlings in the greenhouse was correlated with infection of pods in the field. In greenhouse tests, the non-genetic variance component was large in comparison with the genetic component and a significant genotype trial interaction was found. Significant repeatability was obtained for downy mildew on seedlings and pods, number of pods per node and seed weight. An unfavourable correlation between susceptibility to downy mildew and number of pods per node was found. No single breeding line showed the ideal combination of good resistance, high number of pods per node and small seeds. However, one line showing better resistance than the susceptible parent, with smaller seeds and more pods per node than the resistant parent was found. The susceptible parent also carries some resistance factor that is not present in the resistant parent.     

Screening techniques and sources of resistance to foliar diseases caused by fungi and bacteria in cool season food legumes

Screening techniques are an important component of the overall strategy of breeding for resistance to diseases in cool season food legumes. Suitable screening methods have been developed for several major foliar diseases of chickpea, pea, faba bean, and lentil, and sources of resistance have been identified. International cooperation plays an important role in promoting research and keeping collections of cultivated species and their wild relatives. New biotechnological approaches are promising for enhancing the practical use of genes for resistance.