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.     

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.     

Factors influencing the isotopically exchangeable phosphate in soils

Summary The labile phosphate in a non-calcareous and a slightly calcareous soil was determined by isotopic exchange in the presence and absence of 0.001 molar solutions of a chelating and a non-chelating organic anion. The rate of isotopic exchange curves were analyzed graphically to sub-divide the labile phosphate into 3 or 4 fractions. The half-lives of exchange for the rapid, medium and slow fractions were between 0.3 to 1.6 hours, 1.8 to 8.6 hours and 25.8 to 46.1 hours respectively. In addition, an instantaneously-exchanging component was sometimes observed.In the presence of the citrate ion, the total labile phosphate was increased in the non-calcareous soil and decreased in the calcareous soil, whereas the diethyl barbiturate ion (DEB) anions decreased the total labile phosphate in both soils. In general, the citrate ion increased the rapid and the medium fractions whereas the DEB anion either did not affect them or decreased them. Again, whereas citrate always increased the phosphate in solution, the effect of DEB anions depended on the soil. The major effect of the organic anions was to greatly decrease the slowly-exchanging fraction in both soils.The half-lives of exchange for the rapid, medium and slow fractions were in the order no organic anion > citrate > barbiturate and the rate constants for a first-order mechanism were in the order no organic anion < barbiturate < citrate.Small but significant differences were observed between the two soils.     

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.     

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.     

Inheritance of resistance to Helminthosporium maydis blight in maize (Zea mays L.)

Summary The nature and mode of inheritance of resistance to Helminthosporium maydis blight was investigated in two maize varieties, RbU-W and DIC. The study of F₁, F₂, and reciprocal backcross populations of crosses between these two varieties on the one hand and two susceptible varieties, UVE and ZPSc-58c on the other, revealed that resistance in the two varieties is monogenic recessive. The genes for resistance in the two varieties are allelic. Resistance was shown to be a lesion-type and measurements revealed that it operated through reduced lesion size and lesion number.     

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.     

Diallel analysis of submergence tolerance in rice,Oryza sativa L.

Summary The genetics of submergence tolerance in rice was studied in a 10 × 10 half-diallel cross set involving 10 lowland rice varieties, four of which were tolerant (FR13A, FR43B, Kurkaruppan, and Goda Heenati) and the remaining six were nontolerant (RD19, IR42, IR17494-32-1, IR19672-24-3, Jagannath, and CR1009). Estimates of genetic parameters following Hayman's method showed significant additive and nonadditive gene action and the latter appeared to be solely due to dominance. Narrow sense heritability (0.70) indicated that additive gene effects were more important in the inheritance of the trait. Tolerance was dominant over nontolerance and the average dominance was within the range of incomplete dominance. Dominant alleles were more concentrated in the three tolerant parents, FR13A, Kurkaruppan, and FR43B in that order. Wr/Vr graphic analysis suggested the involvement of both major and minor genes. Combining ability analysis by Griffing's method also indicated significance of both additive and nonadditive effects, and the former appeared to be more important than the latter. The hybrids involving FR13A with RD19, IR42, and IR17494-32-1, and those of Kurkaruppan with RD19 and CR1009 appeared to be promising for incorporating an adequate level of tolerance to submergence into lowland rice cultivars.     

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.     

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.     

Characterization of protein phosphorylation in acetylcholine receptor-enriched membrane preparations from torpedo fuscomaculata

Summary Erythrocyte soluble phosphodiesterase activities show at least two interconvertible states: aggregated and non-aggregated. In the former state the existence of a high affinity component for cyclic AMP is favoured and the system is more active with cyclic AMP than with cyclic GMP as substrate. When the system is in the non-aggregated state, no activity with cyclic GMP is detected. Conversion to the non-aggregated state is enhanced by dilution or by addition of magnesium ions.Upon isoelectric focusing of erythrocyte soluble extracts, phosphodiesterase activities can be resolved in two peaks: one specific for cyclic AMP located at pH 4.66 and the other specific for cyclic GMP focused at pH 4.95. Evidence would indicate that aggregation affects the enzyme specific for cyclic AMP.     

Genotypic control of pollen plant formation in Nicotiana tabacum L.

Summary Tobacco plants (Nicotiana tabacum L.) of four varieties (Badischer Burley, White Burley, Techne, Kupchunos) were raised at different temperatures and daylengths and the effect of genotype on embryogenic pollen grain formation in situ and on pollen plant formation in anther and pollen cultures from these plants was studied. Genotype controlled embryogenic pollen grain and pollen plant formation by defining productivity under standard growth conditions (long days at 24 °C). Kupchunos was the most productive variety, followed by White Burley, Techne, and Badischer Burley. Furthermore, genotype defined which environmental factor was able to affect embryogenic pollen grain and pollen plant formation and also to which degree. In anther cultures, in addition to these effects, genotype controlled the formation of (an) inhibitory substance(s) in the anther wall in interaction with the plant growth conditions. In Badischer Burley and Techne, inhibitor action could be prevented by isolation of the pollen after one week of anther culture. Finally, direct pollen cultures in Badischer Burley and Techne produced embryos were only when the pollen was isolated from nearly mature anthers, while in White Burley and Kupchunos, embryos also produced at earlier stages and at higher yields. This indicated that genotype controls the time when the embryogenic pollen grains become ready to divide. The results are discussed in relation to strategies to overcome recalcitrance of species and genotypes.     

The mucin profiles of normal gastric mucosa, intestinal metaplasia and its variants and gastric carcinoma

Summary Human gastrectomy specimens, including 48 carcinomas and 25 selected benign cases showing extensive intestinal metaplasia (IM), were examined in detail histologically and histochemically. IM was classified into complete (type I), incomplete without sulphomucins (type IIA) and incomplete with sulphomucins (type IIB). Type IIB was associated with intestinal but not diffuse cancers (P<0.01) or benign lesions (P<0.01). The mucin profiles of IIB IM were similar to intestinal cancers with sulphomucins predominating overN-acetylsialomucins.O-acetylsialomucins were not seen in IIB IM or tumours but were observed in complete or type IIM. These findings suggest a histogenic link between incomplete IM secreting sulphomucins (or colonic metaplasia) and intestinal cancers of the human stomach.     

Local motion processing in the optic tectum of the Japanese toad,Bufo japonicus

Summary The results of previous behavioral studies can be so interpreted that the prey-catching behavior in the toad is elicited if there is a local motion restricted with-in a small part of the visual field, while it is suppressed if there is a global motion over a large part of the visual field. This has led us to design experiments to answer a specific question (yet a very essential one for understanding neural processes underlying this behavior): Are there local motion detectors in the toad's visual system that are not activated by global motion over a large part of the visual field but are activated by local motion confined within a smaller part of it? The present study showed that (1) the majority of the toad's tectal neurons exhibit properties of the local motion detectors as defined above, and (2) these properties can be explained from the receptive field structure revealed in the present experiments. Based on these results, we suggest that the tectal local motion detectors are essential for the detection and localization of small moving prey-objects in the natural environment while ignoring the large moving objects or the self-induced motion of the visual field.Abbreviations ERF excitatory receptive field - G1-5 group 1–5 neurons     

The effects of placing small amounts of phosphate fertilizer close to the seed on growth and nutrient concentrations of lettuce

Summary Two glasshouse experiments are described in which the effects of applying starter phosphate fertilizer, 1 cm beneath the seeds, on early growth and nutrient concentrations of lettuce (Lactuca sativa L. cv. Avondefiance) in well fertilized soil were determined. In Experiment 1 various rates of starter P in the form of NH₄H₂PO₄ were applied to soil containing a range of rates of incorporated triple superphosphate. Although there was little response of lettuce dry weight to the incorporated triple superphosphate there was a large response (about 65% increase after 36 days) to the starter. N and P concentrations within the plants were increased by the starter treatments whereas K concentration was reduced. The per cent P in the plants at 36 days from sowing could account for 60% of the variation in plant dry weight. In Experiment 2 the starter P was added as either the Ca, Na or K salt, with or without added (NH₄)₂SO₄. Adding the starter P without ammonum increased the P concentration of the plants by an average of 12% and the dry weight by an average of 39% at 30 days from sowing. The addition of ammonium ions increased plant concentrations of P, Mg and N but decreased plant K concentration. The effect of the ammonium ions on growth depended on the form of phosphate supplied as the starter. This variation in effect of ammonium ions was attributed to the effects of other starter ions on the relative concentration of ammonium in the soil solution.     

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.     

The importance of PS I chlorophyll red forms in light-harvesting by leaves

We have investigated the importance of the long wavelength absorbing spectral forms (red forms) of Photosystem I in photosynthetic light harvesting by leaves. To this end leaf spectra were simulated by using a linear combination of absorption (OD) spectra of purified Photosystem I, Photosystem II and LHC II, multiplied by an empirical multiple scattering chloroplast/leaf conversion function. In this way it is demonstrated that while the PS I red forms account for only about 4–5% of light absorption in a normal daylight environment, in different shadelight environments these long wavelength pigments may be responsible for up to 40% of total photon capture. In the context of maximising the photosynthetic quantum efficiency under the low light conditions of shadelight, this relative increase in the absorption cross section of PS I can be understood by considering the increased synthesis of the major PS II antenna complex, LHC II, known to occur in plants growing under these light conditions. It is demonstrated that for plants in a moderate to deep shadelight regime the PS II cross section needs to increase by 50% to 100% via LHC II synthesis to balance the increased PS I absorption by the red forms. The possibility that under shade light conditions the increased PS I cross section may serve in cyclic phosphorylation is also discussed.     

Effect of anther orientation on microspore-callus production in barley (Hordeum vulgare L.)

Barley anthers from cold pretreated spikes produced no or few calluses when plated with both loculi in contact with the medium (flat). When anthers were plated with only one loculus in contact with the medium (up), a high proportion of the anthers produced calluses. The top loculus of the up anthers was most productive. Flat anthers, when compared with up anthers, were not only slower to produce multicellular pollen grains (MCPs) and microcalluses, but also produced fewer of them and ceased production earlier. The MCPs and microcalluses in flat anthers grew more slowly and few developed beyond the 30 cell stage. These results establish the importance of anther orientation for barley anther culture.     

The incorporation and characterization of powdery mildew resistance from Aegilops longissima in common wheat (T. aestivum L.)

Summary In the progeny of a hybrid between monotelosomic line 3B of Chinese Spring wheat and Chinese Spring — Aegilops longissima ditelosomic addition line G a cytologically stable strain was selected consisting of 20 wheat chromosome pairs, one pair of telosomic chromosome 3BL and one pair of telosomic longissima chromosome G. Inoculating Chinese Spring — Aegilops longissima addition and substitution lines with ten different powdery mildew isolates, partial resistance was observed. The infection grade as well as the number of spores/cm² leaf area were significantly reduced.