Inter-subspecific maps of non-brittle rachis genes btr1/btr2 using occidental, oriental and wild barley lines

Brittle rachis of wild barley is controlled by two dominant complementary genes, Btr1 and Btr2, and mutation in either locus (btr1 or btr2) results in the non-brittle rachis of cultivated barley. In this study, a simple monogenic inheritance of non-brittle rachis was demonstrated, and moreover differentiation of multiple dominant alleles for either Btr1 or Btr2 among cultivated and wild barley lines was suggested. Two amplified-fragment-length polymorphism (AFLP) linkage maps of the genes were constructed using wild × btr1-type cultivar and wild × btr2-type cultivar F₂ populations. The order of AFLPs and the btr1/btr2 locus was constant between the wild × cultivar maps and a cultivar × cultivar map previously constructed. No suppression of recombination due to the inter-subspecific crosses was noticed in the interval studied. The btr1 locus and all AFLP loci were separated in the wild × btr1-type cultivar F₂ map, but the btr2 locus and eight AFLP loci did not recombine in the wild × btr2-type cultivar F₂ map, thus slightly different levels of affinity between parental cultivars with the wild line was suggested at the btr1/btr2 locus.     

Selection for resistance to Plasmodiophora brassicae Wor. in oriental subspecies of Brassica rapa L.

Summary Selection for resistance to Plasmodiophora brassicae Wor. in oriental groups of Brassica rapa L.Two hundred and sixty-five cultivars of leafy, oriental bassicas were tested for resistance to 18 collections of Plasmodiophora brassicae, the causal agent of clubroot. The tests were conducted in the greenhouse at low and high level inoculum concentrations. Eleven cultivars of B. rapa pe-tsai, five cultivars of B. rapa pak-choy and three cultivars of B. rapa choy-sum consistently segregated for resistance at the lower concentration of inoculum (1000 spores/ml). All 265 cultivars were susceptible at the higher concentration (1 000 000 spores/ml). Three cultivars were used in pedigree and recurrent selection schemes for increased resistance. After three cycles of selfing resistant individuals, significantly more resistant S₃ lines were derived from each cultivar. Lines derived from two cultivars. Chinese White and PI 257236, continued to improve with each cycle of selection and demonstrated increased resistance to higher levels of inoculum (up to 1 000 000 spores/ml) New cultivars based on intercrosses of S₂ resistant individuals also had significantly better resistance than the original cultivar. After two cycles of selection in the third cultivar, PI 419007, resistance did not increase and its S₂ mass did not differ significantly from the original cultivar. Evidence that indicates resistance is pathotype-non-differential and offers an alternative to major gene, pathotype-differential types of resistance currently being introduced to the leafy oriental brassicas from other Brassica rapa groups.     

Crossability and cytology of hybrid progenies in the cross between Brassica campestris and three wild relatives of B. oleracea,B. bourgeaui,B. cretica and B. montana

Summary Crossability and cytology were examined in F₁, F₂, B₁ and hybridsplants of F₁ hybrids of Brassica campestris and three wild relatives of B. oleracea, B. bourgeaui, B. cretica and B. montana, respectively. The F₂ plants were obtained after self-and open pollination of the F₁ hybrids. The B₁ and hybrid plants were produced after the F₁ hybrids backcrosses with B. campestris and crossed with B. napus, respectively. After crossing the F₁ hybrids, many seeds of the F₂, B₁ and hybrid plants were harvested. Multivalent formation was high in the chromsome configuration for the PMCs of F₂, B₁ and hybrid plants, suggesting that crossing over might occur between them. Many different types of aneuploids were obtained in the progenies of the F₂, B₁ and hybrid plants. It is suggested that different types of normal egg cells may be produced by one-by-one or little-by-little chromosome addition. The possibility is discussed of gene transfer from B. bourgeaui, B. cretica and B. montana, to cultivated plants, B. campestris and B. napus.     

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.     

Genetic control of isozymes in eggplant and its wild relatives

Summary This study was conducted to elucidate the inheritance and linkage relationships of isozymes in aspartate aminotransferase (AAT, EC 2.6.1.1), alcohol dehydrogenase (ADH, EC 1.1.1.1), phosphogluconate dehydrogenase (PGD, EC 1.1.1.43), phosphoglucomutase (PGM, EC 2.7.5.1) and shikimate dehydrogenase (SKDH, EC 1.1.1.25) in eggplant and its wild relatives. Segregating populations were generated by backcrossing of hybrids among the species. Evidence of Mendelian inheritance was obtained for seven loci: Aat-1, Adh-1, Adh-2, Pgd-1, Pgm-1, Pgm-2 and Skdh-1. Twenty-one pairs of loci were tested for independent assortment, suggesting three linked pairs, Aat-2 with Pgd-2 (R=0.35±0.07), Adh-2 with Pgm-1 (R=0.33±0.07) and Pgd-2 with Pgm-2 (R=0.32±0.06).Abbreviations AAT aspartate aminotransferase - ADH alcohol dehydrogenase - PGD phosphogluconate dehydrogenase - PGM phosphoglucomutase - SKDH shikimate dehydrogenase     

Resistance toPhytophthora porri in leek and some of its wild relatives

Summary Winter leek and related plant material was evaluated for resistance to white tip disease (Phytophthora porri) in the Netherlands. Significant differences in partial resistance were found between winter leek accessions in field tests with zoospore and natural inoculation. These differences were consistent over three years, and indicate that resistance can be improved through mass selection in winter leek cultivars. Some accessions of wild or cultivated relatives of winter leek with higher levels of resistance were found in a glasshouse test with zoospore inoculation. These sources of resistance were also highly resistant in field experiments over a two year period.     

Sources and inheritance of resistance to stemphylium leaf spot of lettuce

Summary None of the tested cultivars of lettuce was found resistant to Stemphylium leaf spot, a common disease in Israel. Within a Lactuca saligna population collected in wild lettuce in Israel, resistance was traced. Interspecific crosses of L. saligna x L. sativa were made and the mode of inheritance of resistance to this disease was studied. Resistance is apparently controlled by two genes: one dominant (Sm₁) and one recessive (sm₂).Contribution No. 1176-E 1984 series, from the ARO.     

Variation of prezygotic barriers in the interspecific hybridization between oilseed rape and wild radish

Escape of transgenes from genetically modified oilseed rape, Brassica napus, into wild radish, Raphanus raphanistrum, depends on sexual compatibility. The variation in prezygotic barriers of two different cultivars for interspecific hybridization with a population of wild radish was investigated by hand crossing and fluorescence microscopy of pistils. Significant differences were observed between oil seed rape cultivars in their ability to accept wild radish pollen germinating onto their stigma and the rate of fertilization of ovules. Some differences among the pollen donor plants were also detected. These results suggest that the rate of interspecific hybridization in the field would depend upon the oilseed rape cultivar and the genotype composition of the local wild populations. The implication of S-related genes, as revealed through identification by pistil tissue prints of class I and II S-types of SLG (S-Locus Glycoprotein) and SLR1 (S-Locus Related),and immuno-IEF, was not significant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Overcoming hybridization barriers between pea and some of its wild relatives

Pea would benefit from the plasticity and adaptability of its cross-incompatible relatives Pisum fulvum and Lathyrus sativus L., and we have tested reciprocal sexual crossings by manually cross-pollinating plants of genotypes of these three species. Studies of in situ germination of pollen grains on stigmata showed that pollen tubes were generally unable to germinate or could not reach the ovary. A few putative hybrid pods were nevertheless harvested, with one grain per pod germinated in vitro, then micropropagated for flow cytometry, isoenzyme, molecular (ribosomal ITS PCR-RFLP) and genomic in situ hybridization (GISH) studies. One such grain was recovered from an inter-generic cross of P. sativum x L. sativus and four from an inter-specific P. sativum x P. fulvumcross. A strong cross-incompatibility was shown between pea and grass pea, where the putative hybrid turned out to be pea. Conversely, with the interspecific, P. sativum x P. fulvum cross, flow cytometry and isoenzymes with leaf tissues strongly suggested hybridity, while molecular approaches and GISH confirmed the production of inter-specific hybrids, and without the need for a wild type P. sativum accession as a bridging cross.     

Identification and polymorphism of cultivars and wild ecotypes of safflower based on isozyme patterns

Summary Acid phosphatase and cathodal peroxidase isozyme patterns were used to identify nine introduced and five local cultivars of common safflower (Carthamus tinctorius L.) and seven ecotypes of wild safflower (C. oxyacantha Bieb.). Nineteen and nine bands, respectively, were readily observed for the phosphatase and peroxidase systems in the extracts from seedling shoots. Results indicated that both systems could be used jointly for complete identification of all the 21 seed sources used.Band frequencies and polymorphic indices (PI) were determined from acid phosphatase patterns using at least 92 individual seedlings of five introduced and five local cultivars and three wild ecotypes. Band frequencies ranged from complete absence in some to total presence in other populations. The mean PI for the introduced, local and wild safflowers were found to be 0.069, 0.052 and 0.058, respectively.The banding patterns of either enzyme system were similar in some instances for the cultivated and wild safflowers and there was as much variation between two cultivars as between a cultivar and a wild ecotype, indicating close genetic relationships between C. oxyacantha and C. tinctorius.     

Increase in grain protein percentage in high-yielding common wheat breeding lines by genes from wild tetraploid wheat

Summary Forty-one breeding lines of common wheat, derived from crosses between the Israeli cultivars Miriam and Lakhish and high-protein lines of wild tetraploid wheat, Triticum turgidum var. dicoccoides, were tested for various protein and yield parameters in field trials, under typical agronomic conditions. All lines had a higher grain protein percentage (GPP) than the leading Israeli cultivar Deganit, which was grown as a control. Grain yield (GY) ranged in the breeding lines from a low of 2.44 t/ha to as high as that of Deganit (6.95 t/ha). Despite the weak negative correlation between GPP and GY, several lines excelled both in GPP and in GY. The grain protein yield (GPY) of some of these selected breeding lines was higher than that of Deganit; e.g., 1.19 t/ha in the best line vs. 1.02 t/ha in Deganit. The 16.7% increase in GPY in this line reflected a more efficient utilization of nitrogen.     

Chromosomal location of Hwc2, one of the complementary hybrid weakness genes, in rice

A hybrid weakness phenomenon is controlled by a set of complementary genes, Hwc1 (hybrid weakness c) and Hwc2, in rice. The Hwc2 gene is prevalent among temperate Japonica but not among tropical Japonica or Indica. In this study, the chromosomal location of the Hwc2 locus was determined from the segregation in the F₁ hybrids made between 127 recombinant inbred lines and the cultivar ‘Jamaica’. Hwc2 was located between the two restriction fragment length polymorphism loci, XNpb264 and XNpb197 on chromosome 4. Further analysis indicated that Hwc2 was closely linked to Ph (phenol staining). The genetic and phylogenetic significance of the Hwc2 locus and the surrounding chromosomal region is discussed.     

Genetics of Cyst Nematode Resistance in Soybean PIs 467312 and 507354

Soybean Cyst nematode (SCN) Heterodera glycines Ichinohe is the most serious pest of soybean [Glycine max (L.) Merr.] in the world and genetic resistance in soybean cultivars have been the most effective means of control. Nematode populations, however, are variable and have adapted to reproduce on resistant cultivars over time due mainly to the narrow genetic base of SCN resistance in G. max. The majority of the resistant cultivars trace to two soybean accessions. It is hoped that new sources of resistance might provide durable resistance. Soybean plant introductions PI 467312 and PI 507354, are unique because they provide resistance to several nematode populations, i.e. SCN HG types 0, 2.7, and 1.3.6.7 (corresponding to races 3, 5, and 14) and HG types 2.5.7, 0, and 2.7 (corresponding to races 1, 3, and 5), respectively. The genetic basis of SCN resistance in these PIs is not yet known. We have investigated the inheritance of resistance to SCN HG types 0, 2.7, and 1.3.6.7 (races 3, 5, and14) in PI467312 and the SCN resistance to SCN HG types 2.5.7 and 2.7 (races 1 and 5) in PI 507354. PI 467312 was crossed to ‘Marcus’, a susceptible cultivar to generate F₁ hybrids, 196 random F₂ individuals, and 196 F_2:3 families (designated as Pop 467). PI 507354 and the cultivar Hutcheson, susceptible to all known SCN races, were crossed to generate F₁ hybrids, 225 random F₂ individuals and 225 F_2:3 families (designated as Pop 507). The F_2:3 families from each cross were evaluated for responses to the specific SCN HG types in the greenhouse. Chi-square (χ²) analyses showed resistance from PI 467312 to HG types 2.7, and 1.3.6.7 (races 5 and 14) in Pop 467 were conditioned by one dominant and two recessive genes (Rhg rhg rhg) and resistance to HG type 0 (race 3) was controlled by three recessive genes (rhg rhg rhg). The 225 F_2:3 progenies in Pop 507 showed a segregation of 2:223 (R:S) for response to both HG types 2.5.7 and 2.7 (corresponding to races 1 and 5). The Chi-square analysis showed SCN resistance from PI 507354 fit a one dominant and 3 recessive gene model (Rhg rhg rhg rhg). This information will be useful to soybean breeders who use these sources to develop SCN resistant cultivars. The complex inheritance patterns determined for the two PIs are similar to the three and four gene models for other SCN resistance sources known to date.     

Phylogenetic differentiation of cultivated rice,XXIII. Potentiality of wild progenitors to evolve the Indica and Japonica types of rice cultivars

Summary Studies of intermediate wild-cultivated plants suggested that the Indica-Japonica differentiation of cultivars of Oryza sativa L. has taken place with the domestication of wild plants. The wild progenitor, which is considered to be the Asian form of O. perennis Moench, shows no trace of differentiation into two such types as the Indica and Japonica. To elucidate the potentiality of the wild progenitor to evolve the two types when domesticated, the selfed progenies from an Indica × wild and a japonica × wild cross were examined with regard to three characters known to be useful for distinguishing between the two types. The data showed that Japonica-like plants were derived from the Indica × wild cross and Indica-like plants from the Japonica × wild cross. The Indica-Japonica differentiation was considered to have resulted from selection of incipient domesticates having such potentiality under different climatic conditions; the dynamics was discussed.     

Cytology and leafspot resistance in Arachis hypogaea x wild species hybrids

Summary Introgression of germplasm from diploid wild Arachis species to A. hypogaea has great potential for improving pest resistance in cultivated peanuts. This investigation evaluated methods for incorporating exotic germplasm into cultivated peanuts, especially for Cercospora arachidicola Hori resistance. Interspecific hybrids between A. hypogaea (cvs. NC 2 and NC 5) and the wild species A. cardenasii Krap. et Greg. nom. nud. and A. chacoense Krap. et Greg. nom. nud. were analyzed cytologically and for leafspot resistance. All F₁ hybrids were sterile, had irregular meiosis, and very few multivalents. They were highly resistant to C. arachidicola in field tests and had a 10-fold reduction of conidia per lesion in the greenhouse as compared to A. hypogaea cultivars. After colchicine treatments of F₁ hybrids, hexaploids (2n=60) and aneuploids (2n=54, 56, 63) were observed. The hexaploids had up to 18 univalents per pollen mother cell and very few multivalents, indicating a low frequency of intergenomic chromosome pairing. For C. arachidicola resistance, significant differences were not found among wild species parents, F₁ hybrids and two generations of hexaploids. Most hexaploids were stable at 2n=60 and embryos aborted when backcrosses with the respective wild species were attempted. However, when hexaploids were backcrossed to A. hypogaea, several fertile pentaploid (2n=50) offspring were obtained. Use of self-pollinating pentaploids is believed to be the quickest method to recover 40-chromosome hybrid derivatives in these hybrids.     

Postulation of resistance genes to yellow rust in wild emmer wheat derivatives and advanced wheat lines from Nepal

Summary Seedlings of 38 wild emmer derivatives, and a total of 53 advanced wheat varieties/lines introduced from the International Maize and Wheat Improvement Centre (CIMMYT) or other sources, Nepalese breeding lines and local cultivars were inoculated with 18 different yellow rust isolates to postulate yellow rust resistance genes (Yr). Many wild emmer wheat derivatives used were resistant to all isolates indicating the presence of undescribed genes. Some derivatives carried Yr9, Yr6 and/or YrSU. Genes Yr1, Yr2, Yr6, Yr7, Yr8, Yr15, YrSU and YrA+ are no longer effective in Nepal; Yr4, Yr5, Yr9, Yr10, YrSP and YrSD are still effective; the effectiveness of Yr3 remains unclear. This study shows that stripe rust resistance in seedling stage of most Nepalese cultivars and advanced materials is based on Yr9 with combinations of Yr2, Yr6, Yr7, and YrA+, of which only Yr9 is still effective in Nepal. In many countries Yr9 has lost its effectiveness. Therefore the introduction of new Yr-genes from wild emmer wheat in Nepalese cultivars is highly important.     

Resistance of lettuce (Lactuca) to the leaf aphid Nasonovia ribis nigri. 2. Inheritance of the resistance

Summary The inheritance of resistance to Nasonovia ribis nigri in L. sativa was investigated. Parents and F₁ and F₂ populations from crosses between the susceptible cultivar Ravel and two resistant breeding lines were tested. In both breeding lines one dominant gene appeared responsible for resistance.     

Location of genes for high grain protein percentage and other quantitative traits in wild wheat Triticum turgidum var. dicoccoides

Summary The genetic control of grain protein percentage (GPP) in the wild tetraploid wheat, Triticum turgidum var. dicoccoides, was determined by crossing four accessions of this taxonomic variety with durum cultivar Inbar, and analyzing the parents, F₁ and F₂ populations. Reciprocal crosses indicated no cytoplasmic effect on GPP. The F₂ variation was continuous in all crosses, showing no transgressive segregation. However, crosses between different accessions of var. dicoccoides showed transgressive segregation indicating the presence of different genes for high GPP in these accessions. Grain protein percentage was mostly codominant with high GPP, showing either no dominance, or a weak dominance. Heritability coefficients (broad sense) ranged from 0.30 to 0.53. Correlation coefficients between GPP and yield components were usually significantly negative, with the exception of the number of spikelets per spike, and in some crosses, grain weight.The number and chromosomal location of genes coding for high GPP were determined by the association between GPP and 27 markers (23 morphological and 4 biochemical markers). For this purpose, the genetic control of these markers, their linkage groups and chromosomal location were studied. At least four loci for high GPP that segregated in the F₂ populations are suggested: one on chromosome arm 1AS, marked by the black glume gene (Bg); one on 1BS, marked by the HMW gliadin locus Gli-B1; one on group 5, marked by the genes for beaked glume (Bkg) and toothed palea (Tp); and one on group 7, marked by the kinky neck gene (Kn). The relationship between GPP and several yield components was studied in a similar manner. In general, loci of markers that correlated positively with high GPP were not correlated with a decrease in yield components. Moreover, several loci of var. dicoccoides were associated with an increase in yield components.The utilization of markers for chromosomal location of genes coding for quantitative traits is compared to the technique of aneuploid analysis, commonly used in wheat. The significance of the above findings for breeding is discussed.     

Inheritance of trichomes and resistance to pod borer (Helicoverpa armigera) and their association in interspecific crosses between cultivated pigeonpea (Cajanus cajan) and its wild relative C. scarabaeoides

The legume pod borer, Helicoverpa armigera, is one of the most devastating pests of pigeonpea. High levels of resistance to pod borer have been reported in the wild relative of pigeonpea, Cajanus scarabaeoides. Trichomes (their type, orientation, density and length) and their exudates on pod wall surface play an important role in the ovipositional behavior and host selection process of insect herbivores. They have been widely exploited as an insect defense mechanism in number of crops. In the present investigation, inheritance of resistance to pod borer and different types of trichomes (A, B, C and D) on the pod wall surface in the parents (C. cajan and C. scarabaeoides) and their F₁, F₂, BC₁ (C. cajan × F₁), and F₃ generations has been studied. Trichomes of the wild parents (high density of the non-glandular trichomes C and D, and glandular trichome B and low density of glandular trichome A) were dominant over the trichome features of C. cajan. A single dominant gene as indicated by the segregation patterns individually will govern each trait in the F₂ and backcross generation. Segregation ratio of 3 (resistant): 1 (susceptible) for resistance to pod borer in the F₂ generation under field conditions was corroborated with a ratio of 1:1 in the backcross generation, and the ratio of 1 non-segregating (resistant): 2 segregating (3 resistant: 1 susceptible): 1 non-segregating (susceptible) in F₃ generation. Similar results were obtained for pod borer resistance under no-choice conditions. Resistance to pod borer and trichomes associated with it (low density of type A trichome and high density of type C) are governed individually by a dominant allele of a single gene in C. scarabaeoides. Following backcrossing, these traits can be transferred from C. scarabaeoides into the cultivated background.     

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.