Sources of resistance to broomrape (Orobanche crenata Forsk.) in narbon vetch

Little is known about the levels of resistance to Orobanche crenata available in narbon vetch. A germplasm collection of 200 accessions of narbon vetch (Vicia narbonensis L.) originating from different countries was screened for resistance to crenate broomrape under field conditions. Thirteen accessions were selected for more detailed screening under controlled conditions and for additional field testing. Resistance to O. crenata was manifested by lower germination of broomrape seeds, reduced emergence of Orobanche shoots and fewer root attachments per narbon vetch plant. Differences in pod yield among narbon vetch accessions were also found in response to Orobanche infestation. Finally, eight accessions were selected and identified as new sources of narbon vetch resistant to broomrape.     

Variation of resistance to broomrape (Orobanche ramosa) in tomatoes

Summary Twenty five tomato cultivars and one accession of wild tomato were evaluated for their resistance to branched broomrape (Orobanche ramosa) infestation. Tomato cultivars were found different in their resistance to Orobanche based on different growth parameters. Total Orobanche number, haustoria development and number of emerged Orobanche shoots were all different between tomato cultivars. Differences in the growth and fruit yield among tomato cultivars were also found in response to Orobanche infestation. Ranking tomato cultivars for Orobanche resistance indicates the existence of different resistance mechanisms in these cultivars. Relatively high to moderate levels of resistance were obtained in Tiny Tim, Acora, Castler, Pomodora, Orient, Red Alert and the accession LA 1478 of L. pimpinellifolium. The cultivar Tiny Tim showed the highest level of resistance for all measured parameters and in all experiments.     

Characterization of a novel tomato mutant resistant to the weedy parasites <Emphasis Type="Italic">Orobanche</Emphasis> and <Emphasis Type="Italic">Phelipanche</Emphasis> spp.

Orobanche and Phelipanche, commonly known as broomrape, are dicotyledonous holoparasitic flowering plants that cause heavy economic losses in a wide variety of plant species. Breeding for Orobanche resistance is still one of the most effective management strategies for this weed. However, previous efforts to find broomrape-resistant tomato (Solanum lycopersicon) genotypes have been unsuccessful. Here, we report on the isolation and characterization of a fast-neutron-mutagenized M-82 tomato mutant, Sl-ORT1. The Sl-ORT1 mutant showed resistance to Phelipanche aegyptiaca as compared to cultivar M-82; segregation analysis suggested a single recessive ort1 allele. Sl-ORT1 broomrape resistance was reflected in a lower number of broomrapes per plant, reduced P. aegyptiaca fresh weight per plant, and the absence of broomrape’s negative effect on plant host growth and yield. Sl-ORT1 was shown to be resistant to high concentrations of P. aegyptiaca seeds, and to another three broomrape species: Phelipanche ramosa, Orobanche cernua, and Orobanche crenata. Grafting experiments demonstrated that roots, rather than shoots, are necessary for Sl-ORT1 broomrape resistance. In addition, Sl-ORT1 was shown to be resistant to broomrape under field conditions. Since yield parameters are slightly affected by the mutation, this resistance gene should be introduced into tomato varieties with different genetic backgrounds; this newly identified Orobanche-resistant mutant may be further utilized in breeding programs for Orobanche resistance.     

Selection in Faba Bean for Tolerance to Broomrape, Orobanche crenata Forsk.

Six populations of faba bean (Vicia faba L.) were developed through various selection schemes to examine the influence of selection In improving tolerance to Orobanche crenata (Forsk.) in local faba bean stocks. All populations trace their origin to 209 farmers’ seed lots that were collected from Egypt. The entries of each population were grown during the 1982/1983 season in the Orobanche nursery located at Giza in Egypt. Comparison among means of the selected, populations showed that more progress in improving Orobanche tolerance could be achieved from combined selection between and within lots. Between-lots selection was less efficient than single-plant selection. Results, of this study show that considerable progress could be achieved from selection for Orobanche tolerance in local faba bean germplasm. There was sufficient residual genetic variation in the selected populations to expect substantial progress from further selection for most tolerance traits.     

Simulating crop–parasitic weed interactions using APSIM: Model evaluation and application

The parasitic weed Orobanche crenata inflicts major damage on faba bean, lentil, pea and other crops in Mediterranean environments. The development of methods to control O. crenata is to a large extent hampered by the complexity of host–parasite systems. Using a model of host–parasite interactions can help to explain and understand this intricacy. This paper reports on the evaluation and application of a model simulating host–parasite competition as affected by environment and management that was implemented in the framework of the Agricultural Production Systems Simulator (APSIM). Model-predicted faba bean and O. crenata growth and development were evaluated against independent data. The APSIM-Fababean and -Parasite modules displayed a good capability to reproduce effects of pedoclimatic conditions, faba bean sowing date and O. crenata infestation on host–parasite competition. The r² values throughout exceeded 0.84 (RMSD: 5.36 days) for phenological, 0.85 (RMSD: 223.00 g m⁻²) for host growth and 0.78 (RMSD: 99.82 g m⁻²) for parasite growth parameters. Inaccuracies of simulated faba bean root growth that caused some bias of predicted parasite number and host yield loss may be dealt with by more flexibly simulating vertical root distribution. The model was applied in simulation experiments to determine optimum sowing windows for infected and non-infected faba bean in Mediterranean environments. Simulation results proved realistic and testified to the capability of APSIM to contribute to the development of tactical approaches in parasitic weed control.     

Antibiosis and antixenosis to Rhopalosiphum padi among triticale accessions

Tests for antibiosis and antixenosis resistance to Rhopalosiphum padi L., the bird cherry-oat aphid, were conducted among four wheat (Triticum aestivum L.) and eight triticale (XTriticosecale Wittmack) accessions. Tests for antibiosis included measuring R. padi-population growth over 13 days, number of days to reproduction of individual R. padi, and number of aphid progeny produced in the first 7 days of adulthood. Antixenosis was measured in no-choice nymphiposition tests and in choice tests of host selection by winged R. padi. Three of seven triticale accessions limited R. padi populations relative to control accessions. Lower R. padi-population growth on N1185 and Okto Derzhavina could be explained partially by increased developmental times. Lower R. padi-population growth on triticale accessions N1185, N1186 and Okto Derzhavina could be explained at least partially by fewer aphid progeny on these accessions. Developmental time of R. padi on N1185 and Okto Derzhavina was greater than that on Stniism 3 triticale, identified previously as resistant to R. padi. There were less R. padi progeny on N1185 than on Stniism 3, and comparable numbers of R. padi progeny among N1186, Okto Derzhavina, and Stniism 3. None of the accessions limited nymphiposition by R. padi. Choice tests revealed heterogeneity in host selection by R. padi but an overall trend that triticale accessions Okto Derzhavina, N1185, N1186 and Stniism 3 were less preferred hosts than Arapahoe wheat. Relatively strong resistance in these triticale accessions warrant consideration of their future use in breeding programs for cereal-aphid resistance.     

Resistance in spelt wheat to yellow rust

Summary Seven spelt wheat accessions of different origin were hybridized with the susceptible bread wheat cultivar Taichung 29 in order to study the genetics of their resistance to yellow rust (Puccinia striiformis Westend. f. sp. tritici). One Iranian and five European accessions were found to carry Yr5 of Triticum aestivum ssp. spelta var. album, whereas a factor for resistance in the Iranian accession 415 was confirmed to be genetically distinct from Yr5. The alleles for resistance in each of the accessions studied showed a monogenic dominant mode of inheritance. Twenty-eight spelt wheat accessions, including those studied for their resistance to yellow rust, were subjected to polyacrylamide-gel-electrophoresis to study variation for gliadin storage protein patterns. Thirteen distinct patterns were revealed, implying the presence of duplicates within the studied spelt wheat collection.     

Screening for Greenbug Resistance in Hordeum chilense Roem et Schult.

Schizaphis graminum (Rondani) is a serious pest of cultivated wheat (Triticum aestivum L.) and resistance is only available in other related species such as Hordeum chilense. Amphiploids between H. chilense and Triticum spp. have been obtained, and addition lines of H. chilense in wheat have been developed. Thirty-five accessions of H. chilense were screened to identify greenbug antixenosis, antibiosis and tolerance. Antixenosis was determined in a conventional host free choice test; antibiosis was measured by aphid life cycle and fecundity rate, and tolerance was tested in a conventional infestation test of 4 weeks. Two commercial barley cultivars were used as susceptible and resistant controls. Eight H. chilense accessions showed higher degrees of antixenosis than the resistant check, 19 were similar and the rest were lower. All accessions were more resistant than the susceptible check. Measured by aphid life cycle, 22 H. chilense accessions showed higher antibiosis than the resistant cv., and all exhibited a higher antibiotic effect on fecundity rates than the control. A similar degree of tolerance to that of the resistant control was observed in six accessions, the remaining entries ranged between the controls. The presence of one mechanism did not exclude the existence of other mechanisms in the same entry and therefore, independence of the different mechanisms is proposed. Most of the accessions showed higher variability than both controls for the three mechanisms, and it appears to be genetic variability within entries for the three mechanisms.     

Characterisation of resistance to crenate broomrape (<Emphasis Type="Italic">Orobanche crenata</Emphasis> Forsk.) in <Emphasis Type="Italic">Lathyrus cicera</Emphasis> L.

Field, pots and mini-rhizotrons experiments revealed the existence of useful levels of avoidance and resistance to Orobanche crenata Forsk. within Lathyrus cicera L. accessions, in addition to escape due to precocity or to reduced root biomass. This resistance was characterized by several phenotypic mechanisms of defence which acted alone or in combination, including low stimulation of parasitic seed germination, prevention of the radicle penetration inside the root and prevention of a correct connection by the parasite with the host vascular tissue being visible by reduced development of established parasitic tubercles or abortion of the parasitic tubercles formed.     

Population genetic structure of the clonal plant Zingiber zerumbet (L.) Smith (Zingiberaceae), a wild relative of cultivated ginger, and its response to Pythium aphanidermatum

Zingiber zerumbet (L) Smith, a wild clonal species related to the cultivated ginger (Zingiber officinale Roscoe), is a potential resistance donor for soft rot disease in ginger caused by Pythium aphanidermatum (Edson) Fitzp. In this study we evaluated the genetic diversity and P. aphanidermatum resistance of 74 Z. zerumbet accessions belonging to 15 populations from eight districts in Kerala state, India. The disease index (DI) of the accessions varied from 0% to 72.24% and the accessions could be separated into six frequency classes according to their DI values. More than 65% of the accessions had a DI < 20%. Eight accessions were found to be immune to the infection. The relative frequency of resistant accessions was higher in the central and northern regions of Kerala. Amplified fragment length polymorphism (AFLP) analysis of Z. zerumbet accessions using five primer combinations yielded 215 bands in total, of which 175 (81.4%) were polymorphic. Nei’s genetic diversity (h) of 0.2738 and Shannon information index (I) of 0.4012 revealed a high genetic diversity in Z. zerumbet unexpected for a clonal species. In the UPGMA dendrogram, accessions were clustered mostly according to their geographical origin and no clear correspondence was observed between the clustering pattern of accessions and their responses to Pythium aphanidermatum. The study revealed high genetic diversity and variability for pathogen resistance among Z. zerumbet accessions and confirmed the value of Z. zerumbet as a potential donor for soft rot resistance for the genetic improvement of ginger.     

Reactions of Hordeum spontaneum to infection with two cultures of Puccinia hordei from Israel and United States

Summary The reactions to infection with two cultures of Puccinia hordei were determined for 292 Hordeum spontaneum (syn. H. vulgare ssp. spontaneum) accessions, collected at 16 sites which encompassed the ecological range of H. spontaneum in Israel. Culture Tel-Aviv was from Israel and culture 57.19 was from the United States. Fifty-two percent of the accessions were resistant to culture Tel-Aviv and 67% were resistant to culture 57.19. Forty-three percent of the accessions were resistant to both cultures. The average infection type (IT) of accessions within sites ranged from 2.7 to 7.5 on a 0–9 rating scale. The results showed that the presence of Ornithogalum species, the alternate hosts of P. hordei, may increase the percentage of H. spontaneoum accessions resistant to P. hordei. More accessions were resistant at sites where humidity at 1400 was higher, the annual evaporation was lower, and where the glumes were shorter. Kernel weight and annual rainfall was not correlated with resistance. A lower percentage of H. spontaneum accessions were resistant to P. hordei culture Tel-Aviv from Israel than to culture 57.19 from the United States. In a previous study a lower percentage of H. spontaneum accessions also was found to be resistant to a culture of Erysiphe graminis hordei from Israel than to cultures from other countries. Previous studies also have shown that cultures of P. hordei and E. graminis hordei from Israel have many genes for virulence on barley, and that H. spontaneum accessions from Israel have many genes for resistance to these two pathogens. Previous results and the results reported in this paper support the hypothesis of coevolution of resistant host genes and virulent pathogen genes where hosts and pathogens have coexisted for many thousand years.     

Estimation of phenotypic divergence in a collection of <Emphasis Type="Italic">Capsicum</Emphasis> species for yield-related traits

Phenotypic divergence among the 24 accessions belonging to a collection of six species of Capsicum from different geoclimatic regions available in field gene bank of CIMAP, Lucknow, India, was quantified by multivariate analysis for 12 quantitative and qualitative traits. Based on their values, all 24 accessions were grouped into six clusters such that the genetic stocks within cluster had smaller D ² values among themselves than those belonging to different clusters. The accessions of Capsicum annuum were distributed in different clusters in morphotyping representing different species, suggesting that taxonomic characteristics are not always related to agronomic traits. No parallelism/association was found between geographical and phenotypic diversity. Accessions 15 and 23 (clusters V and VI, respectively) had distinct identity. The three characteristics that played the greatest role in differentiation were fruit diameter, number of fruits per plant, and leaf diameter, which can be utilized as conventional/morphological markers for the improvement of chilli yield and obtaining good segregants in chilli breeding programs.     

Evaluation of a collection of wild wheat relative Aegilops geniculata Roth and identification of potential sources for useful traits

A collection comprising 157 Aegilops geniculata accessionsoriginating from different ecogeographical regions was established atENSA-INRA, Montpellier. The accessions were studied for physiologicaltraits related to drought and heat stress and screened for resistance tobarley yellow dwarf virus (BYDV) and rusts. Some accessions were alsotested for resistance to Hessian fly and cereal cyst nematodes (CCN). The study allowed to distinguish different adaptive strategies to theclimatic constraints encountered by Aegilops populations in theirregion of origin. They led to significant differences in biomass and grainproduction and should be taken into account in the utilisation of Ae.geniculata germplasm in wheat breeding programs. Two accessions withresistance to BYDV were found. Both originated from South of France. Theinterest of Ae. geniculata as a source of rust resistance was confirmedand accessions with resistance to the three rusts were identified. Highresistance against populations of Heterodera avenae and H.latipons was found in accessions from Spain, Bulgaria, Jordan and Tunisia.Sources of resistance to Hessian fly were also identified.     

Evaluation and verification of resistance to Meloidogyne hapla Chitwood in a Cannabis germplasm collection

A collection of Cannabis accessions was evaluated for resistance to the root-knot nematode Meloidogyne hapla Chitwood in a seedling test. After inoculation with a larval suspension, significant variation was found for the number of galls and egg masses on the seedling roots. These parameters were considered as estimates for nematode infection and larval multiplication, respectively. A subset of the tested accessions was grown on a naturally infested arable field to study the relation between the test results and host characteristics in the field. The ranking order of accessions for the number of galls in the seedling test agreed well with that for the number of root galls on juvenile plants in the field. Therefore the test provides a useful indication for nematode infection. The number of egg masses in the seedling test and the population density of Meloidogyne measured in post-treatment soil samples of the field trial, showed a comparable ranking of accessions. Differences between accessions in the field were however smaller and not statistically significant.     

Genetic variability of Striga asiatica (L.) Kuntz based on AFLP analysis and host-parasite interaction

AFLP analysis was used to estimate genetic variability within and among 14 populations of Striga asiaticaL. Kuntze collected from different locations within the Republic of Benin. The mean within-population genetic distances ranged from 0.028 to 0.038, while the mean among-population genetic distances ranged from 0.019to 0.088, with an assumed minimum genetic distance of0.01 in each case. Intra- and inter-population variation was reflected by a highly significant R² of 0.61for the regression of geographic distance versus genetic distance. Interactions of the different Strigapopulations with susceptible host genotypes, 8338-1 (Zea mays) and CK60B (Sorghum bicolor),indicated a high degree of host-specialization, with CK60B failing to support growth of the parasite from any of the populations. The various Striga populations also exhibited different degrees of virulence on susceptible host plants. Our results support the hypothesis that different populations of this parasite may well be considered and treated as ecotypes in plant breeding programs developing resistance to S. asiatica. This revised version was published online in August 2006 with corrections to the Cover Date.     

Prehaustorial resistance to the wheat leaf rust fungus, Puccinia triticina, in Triticum monococcum (s.s.)

Diploid wheat, Triticum monococcum s.l., is a host for the wheat leaf rust fungus, Puccinia triticina. Some accessions have been reported to show a high degree of prehaustorial resistance. This is non-hypersensitivity resistance, which acts before the formation of haustoria by the pathogen. To assess the frequency of prehaustorial resistance 598 accessions of diploid wheat were inoculated with the wheat leaf rust isolate Felix. Most T. monococcum s.s. accessions (84%) were resistant whereas all T. urartu and all but three T. boeoticumaccessions were susceptible. Histological components analysis revealed that a high percentage of prehaustorial resistance to P. triticina was found in only three T. monococcum accessions. No haustoria were observed in such infection units confirming the prehaustorial nature of the resistance. Prehaustorial abortion of certain infection units in an accession always coincided with posthaustorial abortion of the other infection units. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of Resistance to Striga in Sorghum Genotype SRN39

Striga hermonthica (Del.) Benth., a parasitic weed of grasses, causes major yield reductions in the principal cereal crops of semi-arid Africa. Cultivar resistance is the most economic control measure, since adapted, resistant cultivars can be grown without additional input from the subsistence farmer. Information on the genetics of resistance to S. hermonthica is scant. This is partially attributable to the rarity of germplasms which exhibit stable resistance across geographical regions. The objective of this study was to determine if the stable resistance observed in sorghum [Sorghum bicolor (L.) Moench] cultivar SRN39 is heritable. Crosses were made between SRN39 and a susceptible parent, P954063. Parental, F₁, F₂ and backcross generations were grown in infested pots and development of both host and parasite was monitored. Significant variation among genotypes was observed for both host traits and effects on parasite populations. The F₁ did not differ significantly in Striga resistance from the susceptible parent, suggesting recessive inheritance. However, hybrid vigor was exhibited by the F₁ which yielded and developed as well as the resistant parent. Broad sense heritability ranged from 0.23 to 0.55 for host traits and from 0.10 to 0.43 for effect of genotypes on the Striga population. Joint scaling tests showed that observed variation in each host or parasite trait consisted of additive and dominance components, suggesting possible progress could be made with appropriate selection schemes.     

Variation in response to infection with Erysiphe graminis hordei and Puccinia hordei in some wild barley populations in a centre of diversity

Summary The Near East Fertile Crescent extending from Iran to Israel is the centre of origin of cultivated barley and a region of great genetic diversity in wild barley, Hordeum spontaneum C. Koch (syn. H. vulgare ssp. spontaneum (C. Koch Thell)). Wild barley accessions collected from different parts of this region were evaluated for their reactions to infection with three isolates of Erysiphe graminis hordei and two of Puccinia hordei. One culture of each pathogen was isolated in Israel and the others, either in Japan or the United States. Out of a total of 330 wild barley accessions collected from 14 sites in Iran, Turkey and Syria, only 18.8% were resistant to the Israeli culture, and 14.8% were resistant to a composite of the Japanese and American cultures of E. graminis hordei. Out of 105 accessions collected from six sites in Iran and Turkey, none was found to be resistant to the Israeli culture and 34.3% were resistant to the American culture of P. hordei. Considerable variation was observed both within and among sites for reactions to infection with different cultures of each of the two pathogens. The results of this study were compared with those of an earlier study involving wild barley accessions from Israel to illustrate the relative importance of different subregions in the Near East Fertile Crescent as sources of new genes for resistance to E. graminis hordei and P. hordei. Implications of these studies for in situ conservation of genetic diversity in wild barley are discussed.     

Diversity in root architecture and response to P deficiency in seedlings of <Emphasis Type="Italic">Cucumis melo</Emphasis> L.

Breeding for more phosphorus (P)-efficient crops is one strategy to reduce the use of P fertilizers, thus mitigating the environmental and economic impacts of agriculture. Variation in root architecture and the response to P deficiency were studied in C. melo. Forty accessions representing genetic diversity within the species were screened for their root systems in normal and deficient P conditions at the seedling stage. Various parameters of P-uptake and P-use were analyzed in a subset of accessions at 40 days. Significant differences in root architecture were observed, with the taproot systems prevailing among the wild and exotic accessions, and more branched root systems in cultivated stocks. Moreover, differences in the plastic response of roots to P starvation were observed. Variation in different P-use and -uptake traits correlated with the root architecture. Within ssp. melo, the inodorus and flexuosus landraces had larger and more branched roots and more efficient P-uptake, thereby providing a close genepool for breeding. Within ssp. agrestis, conomon and momordica accessions can be sources of interest for the enhancement of variation in root architecture and P-use efficiency into cultivated melons. Therefore, the diversity observed within C. melo species could be useful in breeding P-efficient melon cultivars.