Genetic analysis of brown planthopper resistance in twenty varieties of rice,Oryza saliva L.

Summary The inheritance of resistance to brown planthopper, Nilaparvata lugens (Stol.), of 20 rice cultivars was studied. Single dominant genes that are allelic to Bph 3 condition the resistance in cultivars Ptb 19, Gangala (Acc. 7733), Gangala (Acc. 15207), Horana Mawee, Kuruhondarwala, Mudu Kiriyal and Muthumanikam. Single recessive genes that are allelic to bph 4 govern the resistance in cultivars Gambada Samba, Heenhoranamawee, Hotel Samba, Kahata Samba, Kalukuruwee, Lekam Samba, Senawee, Sulai, Thirissa and Vellai Illankali. The resistance in Ptb 33, Sudu Hondarwala, and Sinna Sivappu is governed by one dominant and one recessive gene which segregate independently of each other. The dominant resistance genes in these cultivars appear allelic to either Bph 1 or Bph 3. Similarly, the recessive genes in these cultivars seem allelic to either bph 2 or bph 4. Further investigations are needed to conclusively determine the allelic relationships of resistance genes in Ptb 33, Sudu Hondarwala and Sinna Sivappu.     

Spontaneous chlorophyll mutants of Pennisetum americanum: Genetics and chlorophyll quantities

Summary Thirteen spontaneously occurring chlorophyll deficient phenotypes have been described and their genetic basis was established. Ten of these — white, white tipped green, patchy white, white virescent, white striping 1, white striping 2, white striping 4, fine striping, chlorina and yellow virescent showed monogenic recessive inheritance and the remaining three — yellow striping, yellow green and light green seedling phenotypes showed digenic recessive inheritance. The genes for (i) white tipped green (wr) and yellow virescent (yv) and (ii) patchy white (pw) and white striping 1 (wst 1) showed independent assortment. Further, the genes for white (w), white tipped green (wr) and yellow virescent (yv) were inherited independently of the gene for hairy leaf margin (Hm).In the mutants — white tipped green, patchy white, white striping 1, white striping 2, fine striping, chlorina, yellow virescent, yellow striping, yellow green and light green phenotypes total quantity of chlorophyll was significantly less than that in the corresponding controls, while in white virescent there was no reduction in the mature stage. For nine of the mutants the quantity of chlorophyll was also estimated in F₁'s (mutant x control green). In F₁'s of six of the mutants — white tip, patchy white, chlorina, yellow virescent, fine striping and yellow striping the quantity of chlorophyll was almost equal to the wild type. In the F₁'s of three of the mutants — white striping 1, white striping 2 and light green an intermediate value between the mutant and wild types was observed. In yellow virescent retarded synthesis of chlorophyll, particularly chlorophyll a was observed in the juvenile stage. Reduced quantity of chlorophyll was associated with defective chloroplasts. In the mutants — white tipped green, white virescent, fine striping, chlorina, yellow striping, yellow green and light green defective plastids were also observed. In patchy white secondary destruction of chlorophylls and the presence of defective plastids were found to be associated with reduced chlorophyll quantity at maturity.Paper chromatographic studies of leaf flavonoids revealed some variation between the inbreds, but there were three common spots, 7, 8 and 9, except for PDP in which the spot 8 was absent. Chlorophyll deficient mutants differed from their respective controls in the absence of one or more of the spots present in the controls and in the presence of new spots in some of the mutants.Most of the chlorophyll mutants showed higher survival rate in the Kharif season than in Rabi season which was attributed to the higher mean day temperature and longer day light period in the Kharif season than in Rabi season.     

Inheritance of callus formation ability in anther cultures of rice,Oryza sativa L.

Summary Inheritance of ability to form callus in rice anther culture was studied using the diallel technique. Anthers containing uninucleate microspores from two japonica cultivais (Minehikari and Taipei 309), two indica cultivars (Mingolo and Suweon 290), and 12 F₁'s of the diallel crosses involving these four parents were cultured on Chaleffs R₂ medium and evaluated for callus induction. The parents showed significant differences in anther callus formation, from 41.9% (Taipei 309) to 0% (Suweon 290). Callus induction ability was inherited as a recessive character conditioned by a single block of genes. Additive gene effects were predominant. The japonica types seemed to be good combiners for callus induction. The order of dominance among the four parents was Suweon 290, Mingolo, Minehikari and Taipei 309.     

Specialized and generalized dispersal systems: where does ‘the paradigm’ stand?

I explore the specialization versus generalization paradigm in frugivory and seed dispersal. This view predicts that some tropical trees produce nutritious fruits adapted for use by a small coterie of specialized frugivores that provide reliable seed dissemination. Other tree species are expected to offer superabundant fruits of lower nutritional reward, relying instead on common opportunistic frugivores that are individually less reliable, but collectively disperse seeds effectively. Though widely referenced, many aspects of the paradigm are untested with tropical trees and avian frugivores, primarily because plant ecologists rarely determine whether specialist or generalist foragers are responsible for different patterns of seed distribution, while students of foraging behavior rarely determine the effects seed dispersal by different animals for survival of seeds or seedlings of specialist or generalist trees.Ecological paradigms provide alternative hypotheses, without evolutionary arguments. Keystone species have ecological effects disproportionate to their abundance; it is important for management considerations to know whether fruiting trees or frugivores serve as keystone mutualists in tropical forests. Alternatively, the extent to which vertebrate seed dispersers influence density-dependent seed, seedling, sapling, or adult mortality may have important consequences for spatial dispersion and population dynamics of tree species in tropical forests.     

Variability and genetics of tolerance for aluminum toxicity in rice (Oryza sativa L.)

A study was undertaken to investigate the variability among lowland rice cultivars and the mode of gene action of aluminum (Al) toxicity tolerance in rice. Pregerminated seeds were grown in a nutrient solution containing 30 ppm Al and in normal nutrient solution, and relative root length (RRL) was determined at the 14-day-old stage to characterize genotypes for tolerance. Sixty-two traditional rice cultivars grown on lowland acid sulfate soil areas of Asia and West Africa were tested. Tolerant varieties Azucena, IRAT104, and Moroberekan, moderately sensitive IR29 and IR43, and sensitive IR45 and IR1552 were used to investigate the genetics of tolerance by diallel analysis. Of the 62 cultivars tested, only 3 were found to be sensitive to A l toxicity. Among the tolerant cultivars identified, 11 (Siyam Kuning, Gudabang Putih, Siyam, Lemo, Khao Daeng, Siyamhalus, Bjm-12, Ketan, Seribu Gantang, Bayer Raden Rati, and Padi Kanji) were found to possess higher levels of tolerance than the improved tolerant upland cultivar IRAT104. Diallel analysis revealed that high RRL is governed by both additive and dominance effects with a preponderance of additive effects. The trait exhibited partial dominance, and one group of genes was detected. Heritability was high, and environmenal effects were low. Findings suggest that when breeding for A1 toxicity tolerance, selection can be made in early generations. The pedigree method of breeding would be suitable. Combining ability analysis revealed the importance of both general combining ability (GCA) and specific combining ability (SCA) in the genetics of A1 toxicity tolerance in rice. GCA was more prevalent than SCA. Tolerant parens Azucena, IRAT104, and Moroberekan were the best general combiners. The presence of reciprocal effects among crosses suggested the proper choice of parents in hybridization programs. Results indicated that Azucena, IRAT 104, and Moroberekan should be used as the female in crosses for A1 toxicity tolerance.     

Molecular mapping of a new gene Rrs4 CI 11549 for resistance to barley scald (Rhynchosporium secalis)

Doubled haploid (DH) progeny from a cross between the scald susceptible barley (Hordeum vulgare L.) cultivar Ingrid and the resistant accession CI 11549 (Nigrinudum) was evaluated for resistance in the pathogen Rhynchosporium secalis (Oudem) J.J. Davis. Two linked and incompletely dominant loci confer resistance CI 11549 against isolate 4004. One is an allele at the complex Rrs1 locus on chromosome 3H close to the centromere; the other is located 22 cM distally on the long arm. The latter locus is designated Rrs4. In BC₃-lines into Ingrid from CI 2222 (another Nigrinudum) resistance seems governed by one locus close to the telomeric region of chromosome 7H, probably allelic to Rrs2. In neither case did we find any trace of the recessive gene rh8 reported to be present in Nigrinudum. Various resistance donors of Ethiopian origin designated as Nigrinudum, Jet or Abyssinian were identical to a great extent with respect to markers, but differed in resistance to different isolates of scald or in barley yellow dwarf virus (BYDV) resistance. The implications for their use as differentials in scald tests and screening of germplasm collections are discussed.     

Characterization of groups of the zygomycete genusRhizopus

Rhizopus is a zygomycetous genus. Several species of this taxon may infect humans and lower animals. Seventeen isolates ofRhizopus species in three distinct morphological groups were studied: the stolonifer group (sporangiophores greater than 1 mm in height, sporangial diameters of 100–275 µm, branched rhizoids); the arrhizus group (sporangiophores greater than 1 mm in height, branched rhizoids, sporangial diameters of 100–240 µm); and the microsporus group (sporangiophores less than 0.8 mm in height, sporangial diameters less than 100 µm, simple rhizoids). Maximal growth temperatures were characteristic: the stolonifer group grew at 30°C, the arrhizus group grew at 36°C, and the microsporus group grew at 45°C. The DNA mol% G + C base composition of all isolates ranged from 34.9 to 40.2% Species within the three groups were grouped by DNA differences. The arrhizus group was most distinctive with a value of 34.9–36.3%; the stolonifer and microsporus groups had G + C values of 37.0–39.3% and 37.8–40.2%, respectively. Our research clarifies and defines the G-C values of the three important groups ofRhizopus species.     

Effect of Gamma Irradiation on Embryogenic Avocado Cultures and Somatic Embryo Development

Embryogenic avocado cultures were exposed to ionizing irradiation in order to determine its effect on proliferation and subsequent somatic embryo development. The approximate PD₅₀ as determined by linear regression is 35 Gy 2 weeks after irradiation for Fuerte 2.11.1 and 4 weeks after irradiation for T362 2.11.1. Irradiation of embryogenic cultures did not significantly affect the number of early stage Fuerte 2.11.1 somatic embryos that developed directly from irradiated cultures; however, 10–50 Gy inhibited somatic embryo development. Irradiation of T362 2.11.1 embryogenic cultures at 25–50 Gy inhibited the number of intermediate and mature stages of somatic embryos that developed directly from irradiated cultures, and 50 Gy inhibited somatic embryo maturation. Inhibition of somatic embryo development could be partially offset by proliferation of irradiated embryogenic cultures as suspensions. Irradiation up to 10 Gy significantly increased the number of mature Fuerte 2.11.1 somatic embryos that developed from suspension cultures. Irradiation with doses up to 25 Gy stimulated development of heart stage T362 2.11.1 somatic embryos; however, mature somatic embryo development was suppressed at dosages of 10 Gy and greater.     

Study of androgenetic performance and molecular characterisation of a set of wheat-rye addition lines

Rye chromosomes of wheat-rye addition lines were successfully identified by means of an RFLP analysis with 30 probes. Our results are in agreement with previous cytological data concerning the identity of lines F (+1R), D (+2R), C (+3R), A (+4R), E (+5R) and B (+7R). Two categories of chromosomal rearrangements have been distinguished, namely: (1) deletions: the current line D possesses a chromosome 2R deleted on its short arm and the line G a chromosome 3R deleted on its long arm; we have also noticed a deletion on the long arm of wheat chromosome 1A in line F61; and (2) evolutionary reciprocal translocations in rye relative to wheat which have been previously mentioned in the literature. The anther culture response of the different lines was studied. A significant difference between FEC 28 and the addition lines was observed for embryo production and plant regeneration. It appears that genes located on S 10 chromosome arm 3RL and on FEC 28 chromosome arm 1AL increase embryo frequency whereas gene(s) located on S 10 chromosome 5R reduce(s) it. Plant regeneration results suggest that genes increasing regeneration ability and green-plant frequency are located on S 10 chromosome 4R. The long arm of chromosome 1A seems to be involved positively in green-plant regeneration whereas chromosomes 1R and 3R limit plant regeneration.     

Variation in the karyotype of three cultivars of Narcissus tazetta L. (Amaryllidaceae)

Three cultivated varieties of Narcissus tazetta, Grand Soleil d'Or, Chinese Sacred Lily and Cypri, are triploid (2n = 3x+30) with the basic number 10. Grand Soleil d'Or has three homomorphic sets, each comprising 2 long submetacentrics, 4 long acrocentrics and 4 short acrocentrics. Karyotypes of the other two varieties are heteromorphic. Both possess one telocentric satellited chromosome. In addition, Cypri shows translocation between two chromosomes belonging to the seventh and eighth triplets. The number of secondary constrictions varies between 3 (Chinese Sacred Lily) and 4 (Grand Soleil d'Or and Cypri) which is also the number of nucleoli observed in the respective varieties.     

Heritable variation in the phaseolin protein of nondomesticated common bean,Phaseolus vulgaris L.

Summary Crude protein extracts from single seeds of nondomesticated Mexican bean accessions were analysed by SDS polyacrylamide gel electrophoresis for variability in phaseolin protein. Six new phaseolin types; M1, M2, M3, M4, M5, M6, which contained polypeptides within the same range of molecular weights (51,000 to 45,000 daltons) as occur in the S, T and C phaseolin types of cultivated beans were identified. No T and C types were found among the non-domesticated Mexican accessions, and the S type occurred in less than 7% of the seeds screened. Genetic analyses of F₂ progenies from crosses between Sanilac (S), and five of the M types showed that each M phaseolin phenotype was allelic to the S type and expressed codominantly.     

Differential susceptibility in some sorghum (Sorghum vulgar) genotypes to zinc deficiency in soil

Summary Nine genotypes of sorghum were screened for their relative susceptibility to zinc deficiency in soil. All the varieties were highly responsive to zinc application, but behaved differently under zinc stress conditions in respect of dry-matter production, zinc concentration and uptake. The varieties, JS-263, 29/1, JS-20 and Son 127×SL-245 and CSH-1 were relatively more susceptible to zinc deficiency than 3677×6352, Son 3×SL 209, CSH-3 and 2077×1151. re]19730102     

Induction of Somatic Embryogenesis and Plant Regeneration of ‘Ataulfo’ Mango (Mangifera indica)

Nucellar explants from the immature fruit of Ataulfo mango, 3–4 cm long, were used. The process had a very low efficiency (<10%); however, Ataulfo was more embryogenic than other cultivars such as Tommy Atkins or Haden in our hands. Overall, the process from nucellus to plantlet stage took 5 months. Twelve regenerated plants were obtained and are currently growing in the greenhouse. They appear to be normal and free of abnormalities. Some biochemical and molecular tests are currently being carried out.     

Chromosomal location of esterase,peroxidase and phosphoglucomutase isozyme structural genes in cultivated rye (Secale cereale L.)

Summary Isoelectric focusing of esterase (EST), peroxidase (PRX), and phosphoglucomutase (PGM) isozymes in Chinese Spring wheat, Imperial rye and several Chinese Spring/Imperial and Holdfast/King II addition, translocation and substitution lines revealed the chromosomal location of nine Est loci previously described and of one Prx and Pgm locus. Loci Est1, Est2, Est3, Est5, Est6 and Est7 were found on chromosome arm 5RL, Est8 and Est9 on chromosome 6R in Imperial rye, and the Est10 locus on chromosome arm 4RL in Imperial rye and King II rye. A discrepancy was found between the chromosomal location of the Prx locus in Imperial where chromosome 2R was responsible for the expression of the peroxidase enzyme, and King II with chromosome 1R carrying the Prx gene. As a possible explanation, the occurrence of translocation events during the production of wheat/rye aneuploid lines is discussed. The rye Pgm locus could be associated with chromosome 4RS in Imperial and King II rye. Except for the location of Est loci on chromosome 5RL, the results reported in this paper lend further evidence for the assumed homoeology relationships between the chromosomes of Triticinae and for the conservation of gene synteny groups during the evolution of the Triticeae tribe.     

RFLP mapping of three new loci for resistance genes to powdery mildew (Erysiphe graminis f. sp. hordei) in barley

Three new major, race-specific, resistance genes to powdery mildew (Erysiphe graminis f. sp. hordei) were identified in three barley lines, RS42-6*O, RS137-28*E, and HSY-78*A, derived from crosses with wild barley (Hordeum vulgare ssp. spontaneum). The resistance gene origining from wild barley in line RS42-6*O, showed a recessive mode of inheritance, whereas the other wild barley genes were (semi)-dominant. RFLP mapping of these three genes was performed in segregating F₂ populations. The recessive gene in line RS42-6*O, was localized on barley chromosome 1S (7HS), while the (semi)-dominant genes in lines RS137-28*E, and HSY-78*A, were localized on chromosomes 1L (7HL) and 7L (5HL), respectively. Closely linked RFLP clones mapped at distances between 2.6cM and 5.3 cM. Hitherto, specific loci for powdery mildew resistance in barley had not been located on these chromosomes. Furthermore, tests for linkage to the unlocalized resistance gene Mlp revealed free segregation. Therefore, these genes represent new loci and new designations are suggested: mlt (RS42-6*O), Mlf (RS137-28*E), and Mlj (HSY-78*A). Comparisons with mapped QTLs for mildew resistance were made and are discussed in the context of homoeology among the genomes of barley (H-vulgare), wheat (Triticum aestivum), and rye (Secale cereale). Duplications of RFLP bands detected in the neighbourhood of Mlf and mlt might indicate an evolutionary interrelationship to the Mla locus for mildew resistance.     

Cytological characterization,powdery mildew resistance and storage protein composition of tetraploid and hexaploid 1BL/1RS wheat-rye translocation lines

Summary Progenies of a tetraploid 1BL/1RS wheat-rye translocation line, CV 256, selected from the cross Cando x Veery, were analyzed by means of Giemsa C-banding. CV 256 is cytologically stable for the presence of the 1BL/1RS translocation but still segregating for A- and B-genome chromosomes of Cando and Veery. In CV 256, nucleolar activity of the 1RS NOR locus is suppressed, as judged by the absence of a secondary constriction in that rye segment and the capability of organizing nucleoli. PAGE analysis of prolamins confirmed the presence of two 1RS secalins in all single seeds analyzed. SDS-PAGE analysis of reduced glutenins of single seeds indicated that some seeds contained the Cando Glu-B1 locus (subunits 6+8), some contained the Veery Glu-B1 locus (subunits 7+9) while others contained all four subunits, indicating that the material was heterozygous. Pm8 resistance is expressed in the tetraploid 1BL/1RS translocation line based on the reactions of six well-defined powdery mildew isolates. However, Pm8 resistance is not expressed in the hexaploid wheat cultivars Olymp, Heinrich and Florida, which also contain the 1BL/1RS translocation. Obviously, the existence of the 1BL/1RS translocation is not a proof for the expression of the associated genes. PAGE results did not show a clear linkage between powdery mildew resistance and the presence of 1RS secalins.     

Osmotic stress-induced alterations in rice (Oryza sativa L.) and recovery on stress release

In laboratory experiments, rice plants cv Kranti were stressed osmotically using polyethylene glycol 6000 and mannitol, whereas, in pots, plants were drought stressed by withholding water supply. Both osmotic and drought stress influenced different aspects of nitrogen metabolism, resulting in a decline in the activities of aspartate aminotransferase, alanine amino-transferase and an increase in protease activity accompanied by increased free proline and alterations in other amino acid content. An influence on -amylase activity, total free sugars and starch contents was also observed, reflecting the impact of water stress on interconversion between starch and simpler sugars. Effects of polyethylene glycol 6000 as an osmotic agent were more consistent than those of mannitol during short-term (18 h) stress imposition, probably because of slight absorption of mannitol. Since the recovery for most of the parameters was substantial on release of stress, one can infer that the duration and magnitude of stress applied in the present experiments did not cause major permanent alterations in the rice cultivar Kranti. The significant basic information gathered in such experiments, particularly on recovery potential, can be utilised for varietal screening.     

Inheritance of the dwarf plant type in blackgram (Vigna mungo (L.) Hepper)

Summary The inheritance of the dwarf plant type was studied in blackgram (V. mungo (L.) Hepper). Type 9 has erect plant type with normal internode length. The mutant line, EMSD has reduced internode length. The F₁, F₂ and F₃ generations of a cross between Type 9 and EMSD and its reciprocal were studied. The extreme dwarf plant type appeared to be governed by a single recessive gene, dw ₁ dw ₁ with no cytoplasmic effect.Part of Ph.D. Thesis submitted by the first author     

The inheritance of host plant resistance and its effect on the relative infection efficiency of Magnaporthe grisea in rice cultivars

The inheritance of host plant resistance and its effect on the relative infection efficiency for leaf blast was studied in the crosses IR36/CO39 (partially resistant × highly susceptible) and IR36/IR64 (both partially resistant). On the natural scale, gene action appeared multiplicative. After log transformation, additive effects described most of the genetic variation in the cross IR36/CO39, while additive and dominance effects were about equal in magnitude in the cross IR36/IR64. Dominance was towards increased resistance. No transgressive segregation occurred in the cross IR36/CO39. The number of genes that reduce lesion number was estimated to be zero in CO39 and five or more in IR36. The cross IR36/IR64 showed transgressive segregation in both directions, and IR36 and IR64 each contain at least one gene that is not present in the other cultivar. The heritabilities (narrow sense) in the F₂ were low (range 0.06–0.16), while narrow sense heritabilities based on F₃ lines were much higher (range 0.41–0.68). Lesion numbers in F₃ lines were reasonably correlated with those in F₅ progenies derived from the same F₂ plant (r was±0.6 in both crosses). Partial resistance can be effectively improved by selecting the most resistant plants from the most resistant F₃ lines.     

Analysis of the effect of rye chromosomes 4R, 6R and telomeric heterochromatin on 7R on homologous chromosome pairing in pentaploid hybrids (AABBR,AABBD)

Summary Meiotic pairing in Triticum turgidum cv. Ma (4x) with a mean chiasmata frequency of 27.16 per cell was compared with chiasmata frequencies in its hybrids with several triticale strains, Chinese Spring wheat and its addition lines for Imperial rye chromosomes 4R and 6R. In hybrids between Ma and x Triticosecale cv. Rosner the chiasmata frequency was marginally reduced by an average of 1.25%, by 8.8% in hybrids with x Triticosecale cv. DRIRA HH and by 6.7% with DRIRA EE (lacking 90% telomeric heterochromatin from chromosome arm 7RL). In pentaploid hybrids between Ma and T. aestivum cv. Chinese Spring the reduction was an average of 10.30%, while addition lines with rye chromosome 6R reduced chiasmata frequencies by an average of 7.4% and rye addition line for 4R showed the greatest depression in chiasmata frequency in hybrids by a 25.04% reduction. An interchange difference involving long chromosome segments was observed between Ma and Rosner.Contribution No. 819 Ottawa Research Station