Species relationships in the subgenus Ceratotropis (genus Vigna) as revealed by RAPD analysis

Summary The genetic variation among 23 accessions of 5 species in the subgenus Ceratotropis, genus Vigna, were investigated by random amplified polymorphic DNA (RAPD) analysis. A total of 404 fragments amplified with 24 primers were scored and analyzed by cluster analysis. The accessions used were separated into two main groups with an average of 70% differences. Within the main groups, five subgroups were recognized, which are in complete agreement with taxonomic species. Wild forms were always grouped with their most closely related cultivated forms and they showed variation in each species. The largest intraspecific variation was found in V. radiata (mungbean), in which wild forms (V. radiata var. sublobata) were highly different from each other and from cultivated forms. V. angularis (adzuki bean) showed the least variation and thus, was probably differentiated in relatively recent times.     

Proteinase inhibitor polymorphism in the genus Vigna subgenus Ceratotropis and its biosystematic implications

The diversity of components for fourproteinase inhibitors found in species ofthe genus Vigna subgenus Ceratotropis are described. Trypsin,chymotrypsin, subtilisin and cysteineproteinase inhibitors were analyzedby isoelectric focusing followed by thegelatin replica method. Of these proteinaseinhibitors, trypsin inhibitors showedmost polymorphism both within and betweenspecies. Many trypsin inhibitor componentswere also active to chymotrypsin. Severalaccessions had very low levels or absenceof some inhibitors, such as very low levelsof trypsin inhibitor in two accessions ofthe V. tenuicaulis and absence ofchymotrypsin inhibitors in V.grandiflora and V. subramaniana.Proteinase inhibitor polymorphism broadlyagreed with the taxonomic system for thesubgenus Ceratotropis. Based oninhibitor variation species analyzed couldbe divided into three groups whichcorresponding to sections Aconitifoliae, Angulares and Ceratotropis. Some species have verylittle variation in trypsin inhibitorsdespite wide distribution, such as, V.radiata and V. reflexo-pilosa.Accessions of other species showedconsiderable intraspecific variation fortrypsin inhibitors, such as, V.grandiflora, V. aconitifolia andV. stipulacea. Proteinase inhibitorpolymorphism provides an indication of thespecies that may have contributed a genometo the tetraploid species, V. reflexo-pilosa.     

Inheritance of seed resistance to bruchids in cultivated mungbean (Vigna radiata, L. Wilczek)

Bruchid beetles or seed weevils are the most devastating stored pests of grain legumes causing considerable loss to mungbean (Vigna radiata (L.) Wilczek). Breeding for bruchid resistance is a major goal in mungbean improvement. Few sources of resistance in cultivated genepool were identified and characterized, however, there has been no study on the genetic control of the resistance. In this study, we investigated the inheritance of seed resistance to Callosobruchus chinensis (L.) and C. maculatus (F.) in two landrace mungbean accessions, V2709BG and V2802BG. The F₁, F₂ and BC generations were developed from crosses between the resistant and susceptible accessions and evaluated for resistance to the insects. It was found that resistance to bruchids in seeds is controlled by maternal plant genotype. All F₁ plants derived from both direct and reciprocal crosses exhibited resistance to the bruchids. Segregation pattern of reaction to the beetles in the F₂ and backcross populations showed that the resistance is controlled by a major gene, with resistance is dominant at varying degrees of expressivity. Although the presence of modifiers was also observed. The gene is likely the same locus in both V2709BG and V2802BG. The resistant gene is considered very useful in breeding for seed resistance to bruchids in mungbean.     

The importance of wild potato species resistant to the potato cyst nematode,Globodera pallida,pathotypes P4A and P5A,in potato breeding. II. The crossability of resistant species

Summary Over 2400 pollinations were made to investigate the crossability relationships between cultivated potatoes, and wild diploid species from Series Tuberosa and Circaeifolia, as well as wild polyploid species in Series Tuberosa and Longipedicellata resistant to potato cyst nematode, Globodera pallida pathotypes P₄A and P₅A. Wild diploids in Series Tuberosa crossed easily with cultivated diploid species, except with Solanum lignicaule where most pollinations failed, and seed set was extremely low (0.2 seeds per pollination or less). It is suggested that this species is 1EBN. S. capsicibaccatum is clearly isolated from Series Tuberosa, but can form hybrids with S. lignicaule, which can act as a bridging species to S. tuberosum haploids. S. gourlayi and S. oplocense can be crossed with both subspecies of S. tuberosum, but S. papita, Series Longipedicellata is reproductively isolated from the tetraploid cultigens. The crossability data are discussed in the light of germplasm utilisation for breeding potato varieties resistant to potato cyst nematode.     

The breeding potential of wild potato species resistant to the potato tuber moth,Phthorimaea operculella (Zeller)

Summary The potato tuber moth, Phthorimaea operculella (Zeller) is an important pest of potatoes in the field and in stores in warm environments throughout the world. In this study genetic resistance to potato tuber moth was identified in clones of Solanum sparsipilum (coded MBN) originally developed for resistance to bacterial wilt and root-knot nematode. Resistance to this pest in S. sucrense and S. tarijense as well as S. sparsipilum was exploited in wide crosses with diploid and tetraploid cultivated potatoes, and haploids derived from S. tuberosum; hybrid progenies were produced. Crosses between resistant S. pinnatisectum or S. commersonii and cultivated potatoes failed completely, although S. commersonii did hybridise with two bridging species S. lignicaule and S. capsicibaccatum which are slightly compatible with cultivated potatoes. Resistance to potato tuber moth was transferred to all progenies except those in which S. tarijense was the resistant parent. The development of potatoes resistant to potato tuber moth is discussed in the context of population breeding for the lowland tropics.     

Reaction of wild species of the geneus Lens to drought

Summary Susceptibility to drought stress is a key factor in dry land lentil (Lens culinaris Medikus) production in the Mediterranean region of West Asia and North Africa. This study examined the response to drought stress of 121 accessions representing all subspecies of the genus Lens; cultivated, and the wild L. culinaris ssp. orientalis (Boiss.) Ponert, L. culinaris ssp. odemensis (Ladiz.), L. nigricans M.B. Godr. ssp. nigricans Godr. and L. nigricans ssp. ervoides (Brign.) Ladiz. for their potential use in breeding for dry land conditions. Accessions were grown under two moisture regimes (dry land and dry land plus supplemental irrigation) at Breda, Syria during the 1990–91 and 1991–92 seasons. The cultivated lentil had markedly superior seed and straw production than did the wild Lens species. Time to flowering accounted for less than 10% of the variation in yield of wild accessions under rainfed conditions in the two seasons, showing that, in contrast to the cultivated germplasm, drought escape was relatively unimportant in wild lentil. Performance under drought in wild lentil, measured in terms of dry land seed yield or drought susceptibility index (S), was randomly distributed among collection locations with little relation to collection site aridity. Direct selection of wild lentil germplasm for biomass yield under dry conditions is of little value and an evaluation of wild accessions in hybrid combination is needed.     

Heritability and gain from selection for field resistance against multiple root-knot nematode species (Meloidogyne incognita race 1 and M. javanica) in carrot

Heritability and gain from selection of traits associated with field resistance to multiple root-knot nematode species were estimated in carrot (Daucus carota L.). Experimental plots were uniformly and simultaneously infested with Meloidogyne incognita race 1 and M. javanica. Forty-seven half-sib families derived from the cv. ‘Brasília’ were evaluated for: (1) percentage of commercial roots with non-galling symptoms (%RNG); (2) percentage of commercial roots with gall symptoms (%RGS) and (3) percentage of non-commercial roots (%NCR). The cultivars ‘Brasília’ (resistant), ‘Carandaí’ (intermediate) and ‘Nova Kuroda’ (susceptible) were employed as standards. Broad-sense heritability estimates were 61.9 % for %RNG; 30.6 % for %RGS and 67.9 % for %NCR. However, the gains from selection were very small for all traits. The genotypic correlation between %RGS and %NCR was –0.38 and the correlation between %RNG and %RGS was 0.13. Selection on increasing %RNG resulted in a negative correlated response on %NCR (genotypic correlation = –0.99) indicating repulsion phase linkage(s) between the genetic factor(s) controlling these traits. The phenotypic correlation of –0.88 between %RNG and %NCR suggested that incomplete penetrance and dosage effects might be involved in the expression of these traits. Selection of superior genotypes (i.e. high %RNG, low %RGS, and low %NCR) can be achieved. ‘Brasília’ was among the genotypes selected for the following cycle of recombination reinforcing the notion that this cultivar is one of the most promising sources of stable, wide-spectrum field resistance to Meloidogyne species in D. carota. This revised version was published online in July 2006 with corrections to the Cover Date.     

Frost tolerance in wild potato species: Assessing the predictivity of taxonomic, geographic, and ecological factors

The use of genetic resources could be more effective and efficient if we were able to predict the presence or absence of useful traits in different populations or accessions. We analyzed the extent to which taxonomic, geographic and ecological factors can predict the presence of frost tolerance in wild potatoes. We used screening data for 1646 samples from 87 species that had been collected in 12 countries in the Americas. There was a strong association of frost tolerance with species and to a lesser extent with taxonomic series. There was significant geographic clustering of areas with wild potatoes with similar levels of frost tolerance. Areas with a high level of frost tolerance are the central and southern Peruvian Andes, the lowlands of Argentina and adjacent areas, and a small area in the central Chilean Andes. There is a greater chance of finding wild potatoes with high levels of frost tolerance in areas with a yearly mean minimum temperature below 3 ^°C than there is in warmer areas. However, temperature is only a weak predictor of frost tolerance. Temperature data alone did not predict observed frost tolerance in eastern Argentina/Uruguay and falsely predicted it in the southwestern United States. Because many wild potato species occur over small areas, taxonomic, ecological, and geographical factors are difficult to disentangle. This revised version was published online in July 2006 with corrections to the Cover Date.     

The location and characteristics of novel sources of resistance to Bremia Lactucae Regel (downy mildew) in wild Lactuca L. Species

Summary Twenty-one accessions of 3 wild Lactuca species which could be hybridised with L. sativa, the cultivated lettuce, were inoculated at different stages of plant development with 3 multivirulent isolates of Bremia lactucae. Nineteen sources of resistance to B. lactucae, not attributable to the previously recognised resistance factors 1–11 were identified. Two lines of L. serriola showed similar resistance patterns as lines carrying R11. The resistance of some accession was incomplete particularly at the seedling stage and this phenomenon may be race specific.Tests on segregating F₂ populations of crosses between 2 different L. serriola accessions and L. sativa cultivars showed that the resistance in one line (LSE/18) appears to be inherited as a single dominant gene, which is sometimes incomplete in expression and allelic to either Dm6 or R7. The segregation patterns for resistance in PI 281876 did not give readily interpretable ratios.To assess the frequency of occurrence in B. lactucae populations of virulence factors to overcome this novel resistance, 11 of the novel sources of resistance were inoculated with numerous collections of the pathogen from the UK, Czechoslovakia and elsewhere and found to show a high level of resistance.     

Evaluation of resistance to verticillium wilt in diploid,wild potato interspecific hybrids

Summary Verticillium wilt (V. albo-atrum Reinke & Berthold or V. dahliae Kleb) threatens potato (Solanum tuberosum L.) production in most growing areas of the world. Genetic resistance offers the most cost-effective and environmentally-sound control measure. However, there is a dearth of genetic and breeding information on resistance to verticillium wilt in potato, because of obscure parentage of some standard cultivars and the complex segregation at the tetraploid level. The wide range of genetic variability in wild relatives of potatoes can be potentially useful as a source of disease resistance, such as verticillium wilt resistance. Six diploid, wild, interspecific Solanum hybrids involving resistant x resistant and susceptible x resistant crosses, were assayed for verticillium wilt resistance under greenhouse conditions to evaluate their potential as sources of verticillium wilt resistance. The cross between S. gourlayi Oka. and S. chacoense Bitt. and its reciprocal had the most resistant progenies based on mean colony counts. No simple mode of inheritance can be proposed based on the observed segregation ratios. However, the continuous distributions observed on verticillium wilt disease response among hybrid families indicate that inheritance of resistance may be polygenic and complex. In addition, skewness of colony count distributions toward the resistance parents were characteristic of all resistant x susceptible crosses suggesting that resistance may be dominant. By contrast, the susceptible x susceptible cross showed a more normal distribution. Overall, the cross between S. gourlayi and S. chacoense showed the most potential as a source of verticillium wilt resistance.     

Selection of wild Cicer accessions for the generation of mapping populations segregating for resistance to ascochyta blight

In order to determine genetically diverse parents for the generation of mapping populations segregating for resistance to ascochyta blight in wild Cicer species, the genetic diversity between a selection of resistant and susceptible accessions was assessed using molecular markers. Twenty Cicer accessions — comprising eight C. reticulatum accessions, six C. echinospermum accessions, five C. bijugum accessions, and one C. arietinum accession — were compared using a combination of seven RAPD primers and seven ISSR primers. A total of 231 polymorphic bands were scored and used to determine the genetic distances between accessions using Jaccard similarity coefficients. The most genetically diverse parents for the generation of intraspecific and interspecific populations segregating for resistance to ascochyta blight are reported. This revised version was published online in July 2006 with corrections to the Cover Date.     

Differences in resistance of wild Lactuca species to natural infection of lettuce powdery mildew (Erysiphe cichoracearum)

Summary The natural infection of Erysiphe cichoracearum on 29 accessions of five wild Lactuca species (L. serriola, L. saligna. L. virosa, L. aculeata and L. dentata) and on one hybrid of L. serriola x L. sativa has been investigated for two and three years, respectively. No infection was observed on L. serriola (PI 255665), L. saligna (LSA/92/1 and LSA/92/2), L. virosa (LVIR/26 and LVIR/57/1) and L. dentata (PI 234204). The level of susceptibility of the control cultivars of L. sativa was found to be moderate (Fila) to fairly high (Hilde).     

Genetic resistance to cereal cyst nematode Heterodera avenae Woll. in wild oat Avena sterilis I. 376

Summary Three dominant genes A, B and C are involved in the resistance of Avena sterilis I. 376 to Heterodera avenae. When associated, genes A and B are responsible for the high level of resistance in I. 376. In the absence of the first two genes, gene C confers intermediate resistance characterized by the presence of a limited number of cysts on the roots. Only the completely recessive genotype allows the nematode to develop normally.     

The use of polyacrylamide gradient gel electrophoresis to identify variation in isozymes as markers for Lactuca species and resistance to the lettuce root aphid Pemphigus bursarius

Summary This paper describes simple, routine polyacrylamide gradient gel electrophoresis of allozyme patterns surveyed in wild populations of four Lactuca species, obtained from the Wellesbourne Vegetable Gene Bank. Using multivariate statistical techniques, four allozyme bands were identified, which distinguished the four species, and an additional two bands, which were related to the resistance of Lactuca species to the lettuce root aphid.     

Race differentiation and search for sources of resistance to Rhynchosporium secalis in barley in Italy

Summary Barley in Italy has recently been seriously affected by Rhynchosporium secalis. The pathogenic variation of the fungus was studied and 17 races were differentiated on 13 barley cultivars carrying most of the currently known genes for resistance. RC 1, the most virulent and most frequent race, was virulent on 10 out of the 13 differentials and the remaining races proved to be less virulent variants of RC 1. Atlas (C.I. 4118), Atlas 46 (C.I. 7323) and Osiris (C.I. 1622) were the only three differentials resistant to all the analyzed single-spore isolates.Differential cultivars previously assumed to have identical resistance factors did not react in the same way to all the Italian races, thereby revealing either undisclosed differences in the genes described or the presence of additional unidentified ones.Our findings were compared with previous data about virulence of scald populations from different countries, on the basis of tests with common differentials: fundamental differences were found between the Italian population and those of other countries with regard to virulence patterns.The susceptible reactions to race RC 1 of most barley cultivars grown in Italy indicate the urgent need for resistance genes to be incorporated in the cultivated material. Seventy-one barley accessions, known as sources of resistance in different parts of the world, were screened for their behaviour to races RC 1 and RC 13. Twenty-two appeared resistant to both of them.     

Influence of vernalization and photoperiod to the vegetation period of wild species of oats (Avena spp.)

This paper presents the results of a six year field study of wild Avenaspecies and their response to vernalization and photoperiod. The accessions of twenty one wild and weedy species were tested under 12-hr and 18-hr daylength and cold temperatures (for 40 days at +2 ^°C) treatments and without it (as a control). The results demonstrate that for the majority of species evaluated, cold temperature requirements had a greater influence on heading date and the duration of the vegetative period than daylength. Genotypes with neutral, weak and strong reactions to all treatments were found and spring and winter types were selected. The results further demonstrated that daylength-insensitive forms occurred in the south Mediterranean region and adjacent southern territories.     

Genetic analysis of phosphoglucoisomerase isozymes in cultivated and wild species of section Cepa in Allium

Phosphoglucoisomerase (PGI) was studied to establish the genetic system of the isozymes in section Cepa of Allium. The results of isozyme analyses using 15 cultivars and clones in two cultivated species A. fistulosum and A. cepa, eight strains in four wild species A. altaicum, A. galanthum, A. oschaninii and A. vavilovii and a total of 10 hybrids between A. fistulosum and A. cepa and between the cultivated and wild species revealed that: 1) PGI was a dimeric enzyme; 2) the two cultivated and four wild species had a common gene locus Pgi-1 where six alleles were identified; and 3) A. fistulosum had Pgi-1 ^F-1 and Pgi-1 ^F-2, A. cepa had Pgi-1 ^A-1 and Pgi-1 ^A-2, A. altaicum had Pgi-1 ^F-1, A. galanthum and A. vavilovii had Pgi-1 ^A-1, and A. oschaninii had Pgi-1 ^A-1, Pgi-1^O-1 and Pgi-1 ^O-1. The intra- and inter-specific polymorphisms of PGI isozymes are expected to be valuable tools for the genetics and practical utilization of the wild species in section Cepa.     

Development of SCAR markers linked to a scald resistance gene derived from wild barley

The F₂ progeny of a third backcross(BC₃) line, BC line 240, derived from a Turkish accession of wild barley (Hordeum vulgare ssp. spontaneum),segregated for resistance to scald (Rhynchosporium secalis) in a manner indicating the presence of a single dominant resistance gene. Two SCAR marker slinked to this resistance were developed from AFLP markers. Screens of disomic and ditelosomic wheat-barley addition lines with the SCAR markers demonstrated that the scald resistance gene is located in the centromeric region of barley chromosome 3H,a region previously reported to contain a major scald resistance locus, Rrs1. Markers that flank the Rrs1 locus were used to screen the wild barley-derivedBC₃F₂ population. These markers also flank the wild barley-derived scald resistance, indicating that it maps to the same locus as Rrs1; it may beallelic, or a separate gene within a complex locus. However, BC line 240 does not respond to treatment with the Rhynchosporium secalis avirulence factorNIP1 in the same way as the Rrs1-carrying cultivar Atlas46. This suggests that the scald resistance gene derived from wild barley confers a different specificity of response to theRrs1 allele in Atlas46.In order to increase the durability of scald resistance in the field, we suggest that at least two scald resistances should be combined into barley cultivars before release. The scald resistance gene described here will be of value in the Australian environment, and the several markers linked to it will facilitate pyramiding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation for resistance to head blight caused by Fusarium graminearum in wild emmer (Triticum dicoccoides) originating from Israel

Head blight of wheat (FHB, scab) caused by Fusarium spp. has been associated with yield and quality losses in many wheat-growing regions. In tetraploid wheat sources of resistance are scarce. In the search for novel sources of resistance, 151 Triticum dicoccoides genotypes, originating from 16 habitats in Israel and one habitat in Turkey together with several control genotypes, were evaluated for reaction to fungal spread (Type II resistance) in replicated greenhouse experiments. Significant genetic diversity was found among the tested genotypes, the broad sense heritability for Type II FHB resistance was 0.71. Most of the tetraploid accessions were highly susceptible, only a few showed moderate resistance. Among the eight T. dicoccoides lines with the lowest relative infection rates, five originated from the Mt. Gerizim population, and three from the Mt. Hermon population. None of the T. dicoccoides lines reached the level of resistance present in the common wheat cultivar Sumai3. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of resistance sources and inheritance of resistance in kidney bean to Indian virulences of Colletotrichum lindemuthianum

Summary Forty nine common bean lines comprising of exotic accessions and locally grown cultivars evaluated against Colletotrichum lindemuthianum exhibited differential resistance to its races in Himachal Pradesh, a north-western Himalayan state of India. Some exotic accessions like G 2333, Cornell 49242, PI 207262, Mexique 222, TO, Perry Marrow, Kaboon and Widusa were resistant to more than five Indian races, whereas two Indian accessions KRC-5 and Hans showed resistance to six and four races, respectively. However, nine accessions KRC-8, KR-40, KR-43, KR-81, KR-62-2, KR-90, KR-142, KR-148, and KR-216 were resistant to three races. Race specific resistance has been observed in different bean cultivars. Studies on inheritance of resistance in exotic accession G 2333 and Indian accession, KRC-5 showed that two independent dominant genes conferred resistance in G 2333 to race 3 and 515 and a single dominant gene controlled resistance in KRC-5 to race 775, indicating resistance from these sources is easily transferable to the locally adapted susceptible cultivars.