The composition of Erythrosins, Fluorescein, Phloxine and Rose Bengal: a study using thin-layer chromatography and solvent extraction

Synopsis Commercial samples of Erythrosin B (CI 45430), Erythrosin Y (CI 45425), Fluorescein (CI 45350), Phloxine (CI 45410) and Rose Bengal (CI 45440) have been analysed by thin-layer chromatography. The Erythrosins were found to be mixtures consisting in the main of 4-iodofluorescein, 4,5-di-iodofluorescein, 2,4,5-triiodofluorescein and 2,4,5,7-tetraiodofluorescein, in some instances together with 2,4,5-tri-iodo-4,5,6,7-tetrachlorofluorescein and 2,4,5,7-tetraiodo-4,5,6,7-tetrachlorofluorescein. Samples of Fluorescein were mixtures of the nominal dye usually with traces of several unidentified, fluorescent components. Those of Phloxine consisted mainly of mixtures of 4-bromo-4,5,6,7-tetrachlorofluorescein, 4,5-dibromo-4,5,6,7-tetrachlorofluorescein, 2,4,5-tribromo-4,5,6,7-tetrachlorofluorescein and 2,4,5,7-tetrabromo-4,5,6,7-tetrachlorofluorescein, often with 4,5,6,7-tetrachlorofluorescein Samples of Rose Bengal were mixtures of 4-iodo-4,5,6,7-tetrachlorofluorescein, 4,5-di-iodo-4,5,6,7-tetrachlorofluorescein, 2,4,5-tri-iodo-4,5,6,7-tetrachlorofluorescein and 2,4,5,7-tetraiodo-4,5,6,7-tetrachlorofluorescein together with some unidentified components.Most of the commercial dye samples gave an insoluble residue when extracted with methanol. This residue was usually inorganic carbonate or halide. Some possible practical consequences of the various impurities are discussed.     

Effect of excess boron on summer and winter squash

The boron tolerance of two summer squash cultivars (Cucurbita pepo L. Aristocrat Zucchini and Peter Pan Scallop) and one winter squash cultivar (Cucurbita moschata Poir. Butter boy) was determined in large, outdoor sand cultures. Boron treatments were imposed by irrigation with culture solutions that contained 1.0, 3.0, 6.0, 9.0, 12.0, or 15.0 mg B L^-1. Relative fruit yields of Zucchini, Scallop, and Butter boy were reduced 5.2%, 9.8%, and 4.3% with each unit (mg L^-1) increase in soil solution B (B_sw)>2.7, 4.9, and 1.0 mg B L^-1, respectively. Reduced yields of all cultivars were attributed to a reduction in fruit number and not fruit size. Boron concentrations in leaves and fruit were directly correlated to B_sw.     

The microbial production of 3aα-H-4α- (3′-propionic acid)-5α-hydroxy-7aβ-methylhexahydro-indan-1-one-δ-lactone from cholesterol

Summary A mutant strain of Rhodococcus australis CSIR-236.457 which accumulates 3a-H-4-(3-propionic acid)-5-hydroxy-7a-methylhexahydro-indan-1-one--lactone from cholesterol, stigmasterol and -sitosterol was studied. The product is produced in a 60% molar yield in a dilute black strap molasses medium containing 6–12g/l cholesterol after a 72 hour fermentation period.     

Isolation of a halobacterial phage with a fully cytosine-methylated genome

Summary A new bacteriophage from Halobacterium halobium has been isolated and partially characterized. It is not homologous to the phage H (Schnabel, et al. 1982) which infects the same bacterium, though it appeared spontaneously in a culture of H adapted to H. halobium NRL/JW. The size and morphology of N are comparable to that of other known halophages. The genome of N consists of linear double-stranded DNA, 56 kb in size, whose dCMP is totally replaced by 5-methyl-dCMP. This is the second case of a fully cytosine-methylated genome, the bacteriophage XP12 from Xanthomonas oryzae, being so far the only one reported. Like H, the N, genome seems to have terminal redundancy and circular permutation. N is the first halobacterial phage which survives prolonged exposure to low ionic strength environments. After 48 h incubation in distilled water a loss in infectivity of less than 50% is observed.     

A new enzymatic route to the synthesis of 12-ketoursodeoxycholic acid

Summary Cholic acid (3,7,12-trihydroxy-5-cholanoic acid) was completely and selectively transformed into 12-ketoursodeoxycholic acid (3,7-dihydroxy-12-oxo-5-cholanoic acid) by means of two consecutive enzymatic steps catalyzed, the first, by 7- and 12-hydroxysteroid dehydrogenase and, the second, by 7-hydroxysteroid dehydrogenase. Coenzyme regeneration was carried out with -ketoglutarate-glutamate dehydrogenase and glucose-glucose dehydrogenase, respectively.     

Expression of the plant sulphite reductase in cell suspension cultures from Catharanthus roseus L.

Sulphur-heterotrophic growth exhibited a dual response to the expression of sulphate-assimilating enzymes. The level of ATP-sulphurylase (EC 2.7.7.4) appeared repressed while sulphite reductase (EC 1.8.7.1) and O-acetyl-l-serine sulphhydrylase (EC 4.2.99.8) were derepressed and coordinated in their occurrence. The capability of the cells to reduce adenylylphosphosulphate or 3-phospho adenylylphosphosulphate to cysteine coincided with the activity of sulphite reductase. The expression of these reducing steps lacked correlation with the regulation of ATP-sulphurylase.Abbreviations APS adenylylphosphosulphate - MVH reduced methylviologen - OAS O-acetyl-l-serine - PAPS 3-phospho adenylylphosulphate     

Effects of Biogenic Amines and Polypeptide Hormones on Protein Kinase A and Adenylyl Cyclase Activities in Muscles of the Mollusc Anodonta cygnea

The effects of biogenic amines, glucagon, and insulin on the cAMP-dependent protein kinase A (PKA) activity have been studied in the muscle tissue of the freshwater bivalve mollusc Anodonta cygnea. It was shown that serotonin, glucagon, and insulin both in vivo and in vitro stimulated PKA activity, whereas isoproterenol inhibited it. The stimulating effect of serotonin and inhibiting effect of isoproterenol was blocked by serotoninergic (cyproheptadine) and adrenergic (propranolol) inhibitors, which confirms specificity of the effect of biogenic amines on the PKA activity. Taking into account participation of adenylyl cyclase system in action of the above hormones, the revealed hormonal effects on the PKA activity produce metabolic effects via the following chain reaction. In the case of serotonin and glucagon: receptor G_s-protein AC cAMP PKA phosphorylation of glycogen synthase (GS) and glucose-6-phosphate dehydrogenase (G6PDH) and inhibition of their activity; in the case of isoproterenol: -adrenoreceptor G_i-protein AC inhibition decreasing PKA inhibition of phosphorylase and stimulation of GSI and G6PDH. A participation is suggested of the insulin-stimulated AC signaling system in the mechanism of the mitogenic insulin effect mediated, as shown in this work, via the PKA activation, but not of the metabolic effect of insulin.     

A deletion derivative of the kalilo senescence plasmid forms hairpin and duplex DNA structures in the mitochondria of Neurospora.

Summary A novel deletion derivative, kal, of the kalilo senescence plasmid from Neurospora intermedia, was recovered from a culture treated with chloramphenicol. The deletion derivative exists in mitochondria as two different, equally abundant forms: a 2.8 kb duplex DNA molecule kal-2.8) and a 1.4 kb hairpin form kal-1.4). The kal-2.8 plasmid contains the 1366 by terminal inverted repeats and a partially duplicated 102 by segment of the unique sequence of the 8.6 kb kalilo plasmid. In contrast, the kal-1.4 hairpin plasmid appears to result from the folding of single strands that are generated during the replication of kal-2.8. Both forms of kal have covalently linked terminal proteins. Sequence analysis suggests that kal was generated either by slippage of the tip of a growing strand during the replication of kalilo, or by illegitimate recombination between two copies of the plasmid at non-homologous palindromic sequences that might form cruciform structures. In either case, the deletion process was mediated at least in part by an inverted repeat of 5 by in the unique region of kalilo. Since the terminal segments of kalilo DNA that are implicated in plasmid integration might also form cruciform structures, it is possible, but improbable, that the process that generated the first kal molecule is related to that which mediates integration of the plasmid into mitochondrial DNA.     

Molecular systematics and genetic differentiation of Pinus sylvestris (L.) and P. densiflora (Sieb. et Zucc.)

Summary Allozyme variation was examined in 22 populations of Pinus densiflora (Sieb, et Zucc.) and four geographic varieties of P. sylvestris (L.): var lapponica (Fries, Hartman), var armena (Komarov), var mongolica (Litvinov) and var sylvestriformis (Takenouchi). In addition, we developed paternal chloroplast (cp) DNA markers that distinguish P. densiflora from var lapponica, var armena and var mongolica. UPGMA cluster analysis based on Nei's distances between all pairwise combinations of the 22 populations revealed patterns corresponding strictly to geographic origin and taxonomic status. Analysis of allozyme variation in var lapponica, var armena and var mongolica demonstrated a high level of intrapopulational variability but a low level of interpopulational differentiation. It appears that the late Pleistocene blending of genetically diverse populations was responsible for the observed variation patterns. The constructed phylogenetic trees also showed late divergence of these three varieties. The var sylvestri formis was genetically distinct from the other three P. sylvestris varieties. The genetic distances separating var sylvestriformis from P. densiflora and the other taxa lend support to a separate taxonomic status for var sylvestriformis and a close relation with P. densiflora. We found that var sylvestriformis harbors admixtures of allozymes and cpDNA from both P. sylvestris and P. densiflora, which suggests an introgressive nature of this variety. Levels of intrapopulational variability were similar in P. sylvestris and P. densiflora, but interpopulational differentiation was much higher in P. densiflora. In the constructed phylogenetic trees, populations of this species were characterized by relatively long internode distances and branch lengths. The present results suggest that P. densiflora has a more advanced evolutionary age than P. sylvestris.     

3α-Hydroxysteroid Dehydrogenase in Animal and Human Tissues

This review analyzes data on the biological role of 3-hydroxysteroid dehydrogenase (3-HSD) in animal and human tissues and describes its main characteristics, mechanism of action, and regulation of activity. Based on published data, a scheme for the actions of androgen, progestin, and glucocorticoids involving the participation of 3-HSD is proposed. According to this scheme, in the mechanism of steroid action 3-HSD not only regulates the concentration of the main effector androgen, 5-dihydrotestosterone, in target cells, but also switches androgen, progestin, and glucocorticosteroid genomic activity to non-genomic activity.     

Treatment of NOE constraints involving equivalent or nonstereoassigned protons in calculations of biomacromolecular structures

Summary Two modifications to the commonly used protocols for calculating NMR structures are developed, relating to the treatment of NOE constraints involving groups of equivalent protons or nonstereoassigned diastereotopic protons. Firstly, a modified method is investigated for correcting for multiplicity, which is applicable whenever all NOE intensities are calibrated as a single set and categorised in broad intensity ranges. Secondly, a new set of values for pseudoatom corrections is proposed for use with calculations employing centre-averaging. The effect of these protocols on structure calculations is demonstrated using two proteins, one of which is well defined by the NOE data, the other less so. It is shown that failure to correct for multiplicity when using r^-6 averaging results in overly precise structures, higher NOE energies and deviations from geometric ideality, while failure to correct for multiplicity when using r^-6 summation can cause an avoidable degradation of precision if the NOE data are sparse. Conversely, when multiplicities are treated correctly, r^-6 averaging, r^-6 summation and centre averaging all give closely comparable results when the structure is well defined by the data. When the NOE data contain less information, r^-6 averaging or r^-6 summation offer a significant advantage over centre averaging, both in terms of precision and in terms of the proportion of calculations that converge on a consisten result.Abbreviations HMG high mobility group - NOE nuclear Overhauser enhancement - NOESY nuclear Overhauser enhancement spectroscopy - rmsd root-mean-square deviation - YASAP yet another simulated-annealing protocol     

Localization and synthesis of an insulin-binding region on human insulin receptor

Seven regions of the subunit of human insulin receptor (HIR) were synthesized and examined for their ability to bind radioiodinated insulin. A peptide representing one of these regions (namely, residues 655–670) exhibited a specific binding activity for insulin. In quantitative radiometric titrations, the binding curves of¹²⁵I-labeled insulin to adsorbents of peptide 655–670 and of purified placental membrane were similar or superimposable. The binding of radioiodinated insulin to peptide or to membrane adsorbents was completely inhibited by unlabeled insulin, and the inhibition curves indicated that the peptide and the membrane on the adsorbents had similar affinities. Synthetic peptides that were shorter (peptide 661–670) or longer (peptide 651–670) than the region 655–670 exhibited lower insulin-binding activity. It was concluded that an insulin-binding region in the HIR subunit resides within residues 655–670. The results do not rule out the possibility that other regions of the subunit may also participate in binding of HIR to insulin, with the region described here forming a face within a larger binding site.     

Adoptions expérimentales de larves entre des fourmis de genres différents:Leptothorax nylanderi Förster etSolenopsis fugax Latreille

Résumé En l'absence de son propre couvain,Solenopsis fugax a élevé des larves deLeptothorax nylanderi, à la température de 22°C. Les ouvrières deSolenopsis détruisirent une partie de ces larves mais nourrirent celles qu'elles épargnèrent; ces dernières grossirent lentement pendant cinq à six mois, sans atteindre le stade prénymphe. Lorsque les ouvrières deS. fugax et les larves deL. nylanderi furent soumises ensemble à un hivernage préalable, elles donnèrent les mêmes résultats que sans hivernage. La présence d'une jeune reine deSolenopsis fut défavorable aux larves deLeptothorax.Inversement,L. nylanderi fut capable d'élever, à la température de 22°C, des larves deS. fugax et de les amener jusqu'au stade adulte. En présence de leurs propres larves, les ouvrières deL. nylanderi détruisirent tapidement toutes les larves deS. fugax introduites dans leur nid. D'autre part, un jeune couvain deLeptothorax remplaçait plus ou moins rapidement les larves deLeptothorax enlevées au préalable; sa présence était alors défavorable au développement des larves deSolenopsis. Un hivernage en début d'expérience fut plutôt favorable auxS. fugax, de même que la présence d'une reine féconde deLeptothorax. LesSolenopsis ainsi obtenus n'ont pas vécu plus de sept semaines. Ils étaient tous de caste ouvrière et de taille très petite.

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Summary When its own eggs and larvae missed,Solenopsis fugax bred larvae ofLeptothorax nylanderi, at a temperature of 22°C. TheSolenopsis workers killed some of this larvae and fed the others; these slowly grew bigger during five or six months but never reached the pre-pupa stage. The result was the same if the workers ofS. fugax and the larvae ofL. nylanderi overwintered together or not at all. A youngSolenopsis queen being there was noxious to the larvae ofLeptothorax.On the contrary,L. nylanderi has been able to breed larvae ofS. fugax up to the imago stage, at a temperature of 22°C. When its own larvae were in the nest, together with larvae ofS. fugax, the workers ofL. nylanderi killed the larvae ofS. fugax. On the other hand, new eggs and young larvae ofLeptothorax had to replace, more or less quickly, the larvae which had been taken away, and that was noxious to the growth ofSolenopsis larvae. An overwintering at the beginning of the experiment was rather favourable toS. fugax as was the presence of a fecundLeptothorax queen. TheSolenopsis thus obtained lived no longer than seven weeks. They all were workers and very small.

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S. Fugax L. Nylanderi 22° . Leptothorax , , , , . . S. Fugax Leptothorax.,L. Nylanderi 22° S. Fugax . L. Nylanderi ( )Leptothorax ; S. Fugax Solenopsis, Leptothorax. S. Fugax . .

     

Adoptions expérimentales de larves entre des fourmis de genres différents (II):Myrmica laevinodis Nylander etAnergates atratulus Schenck

Résumé Nous avons fait élever des larves d'Anergates atratulus par des ouvrières deMyrmica laevinodis à 22°C. Pour y parvenir, il n'est pas utile de faire hivernerensemble les larves d'Anergates et les ouvrières deMyrmica. La présence de larves autochtones n'empêche pas lesMyrmica d'élever des larves d'Anergates. Dans toutes les expériences lesMyrmica ont été soumises au fridavant de recevoir des larves d'Anergates. Aucune reine deMyrmica n'a été utilisée dans ces expériences.Sur les 64 larves d'Anergates que nous avons utilisées, 38 se sont transformées en imagos. C'est au début de l'adoption et au moment des métamorphoses que périrent la plupart des 26Anergates perdus. Les femelles vécurent en général 2 ou 3 jours et cherchèrent très tôt à quitter le nid natal. Les mâles vécurent 2 à 3 semaines.

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Summary Larvae ofAnergates atratulus were experimentally reared by workers ofMyrmica laevinodis, at 22°C. An overwintering of both larvae ofAnergates and workers ofMyrmica is not necessary for the success of that experiment. The presence of larvae ofMyrmica does not keep theMyrmica from rearing larvae ofAnergates. The workers ofMyrmica have been cooled, in all the experiments, before receiving larvae ofAnergates. No queen ofMyrmica have been used in that experiments.38 of the 64 larvae ofAnergates used became imagos. Most of the 26 lostAnergates died at the beginning of the adoption and during the metamorphosis. The females lived generally 2 or 3 days and tried, very early, to leave their native nest. The males lived 2 or 3 weeks.

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Anergates atratulus Myrmica laevinodis, 22 . bmecme Anergates Myrmica. Myrmica Anergates. Myrmica Anergates. Myrmica . 64 Anergates , 38 . 26 Anergates 2 3 . 2 3 .

     

On age morphological changes of males of Chydoridae (Cladocera)

Summary Young and adult males of 11 species of Chydoridae are studied, their figures being published here (fig. 1–15). The necessity is stressed to distinguish young forms of males and gynandromorphic individuals.Pleuroxus balatonicus is considered to be described from the population ofPleuroxus unicatus having under Balaton Lake conditions retarded transformation of young males into adult form, and accordingly having unusually numerous young males. \qO\qs\qn\qo\qv\qn\qy\ye \qr\ye\qz\qu\ql\Qj\qt\qa\qt\qy 11 (. 1–15). . , Pleuroxus uncinatus , Pleuroxus balatonicus.     

Insulin-Regulated Adenylyl Cyclase Signaling System in Rat Skeletal Muscles under Conditions of in vivo Insulin Administration and of Insulin Insufficiency Produced by Streptozotocin Diabetes

Possibility of the appearance of functional defects in the adenylyl cyclase (AC) signaling mechanism (ACSM) of insulin action, which was discovered by the authors earlier [1–3], is studied in skeletal muscles of rats with acute insulin insufficiency produced by streptozotocin diabetes (24 h). This ACSM includes the signaling chain: receptor-tyrosine kinase Gi-protein phosphatidylinositol 3-kinase protein kinase C-zeta Gs-protein adenylyl cyclase protein kinase A. At comparative evaluation of the functional state of individual molecular blocks of ACSM and the entire mechanism as a whole in skeletal muscles of diabetic rats in comparison with control animals, the following facts have been revealed: (1) an increase of the AC basal activity and a decrease of effects of non-hormonal activators of AC (guanine nucleotides, NaF, forskolin) ; (2) reduction of reactivity of the whole ACSM to insulin (10_–8 M, in vitro) and to combined action of the hormone and GIDP (10_–6 M) ; (3) a decrease of the activating action of insulin on key enzymes of carbohydrate metabolism—glycogen synthase and glucose-6-phosphate dehydrogenase (G6PDG). It is concluded that insulin insufficiency leads to several disturbances in the insulin ACSM: at the level of its catalytic component—AC, Gs protein and its coupling with AC, as well as to a decrease of regulatory metabolic effects of the hormone. These data indicate a decrease of sensitivity of skeletal muscles of diabetic rats to insulin and an involvement of this hormone in maintenance of functionally active status of the ACSM of insulin signal transduction.     

In vivo effects of insulin and bis(maltolato)oxovanadium (IV) on PKB activity in the skeletal muscle and liver of diabetic rats

In this study, the in vivo effects of insulin and chronic treatment with bis(maltolato)oxovanadium (IV) (BMOV) on protein kinase B (PKB) activity were examined in the liver and skeletal muscle from two animal models of diabetes, the STZdiabetic Wistar rat and the fatty Zucker rat. Animals were treated with BMOV in the drinking water (0.75–1 mg/ml) for 3 (or 8) weeks and sacrificed with or without insulin injection. Insulin (5 U/kg, i.v.) increased PKB activity more than 10fold and PKB activity more than 3fold in both animal models. Despite the development of insulin resistance, insulininduced activation of PKB was not impaired in the STZdiabetic rats up to 9 weeks of diabetes, excluding a role for PKB in the development of insulin resistance in type 1 diabetes. Insulin-induced PKB activity was markedly reduced in the skeletal muscle of fatty Zucker rats as compared to lean littermates (fatty: 7fold vs. lean: 14fold). In contrast, a significant increase in insulinstimulated PKBa activity was observed in the liver of fatty Zucker rats (fatty: 15.7fold vs. lean: 7.6fold). Chronic treatment with BMOV normalized plasma glucose levels in STZdiabetic rats and decreased plasma insulin levels in fatty Zucker rats but did not have any effect on basal or insulininduced PKB and PKB activities. In conclusion (i) in STZdiabetic rats PKB activity was normal up to 9 weeks of diabetes; (ii) in fatty Zucker rats insulininduced activation of PKB (but not PKB) was markedly altered in both tissues; (iii) changes in PKB activity were tissue specific; (iv) the glucoregulatory effects of BMOV were independent of PKB activity.     

A new metabolic pathway from n-dodecane to α, ω-dodecanedioic acid in a mutant of Candida tropicalis

Summary The metabolic formation of ,-dodecanedioic acid via ,-dodecanediol from n-dodecane using a mutant S76 of Candida tropicalis was studied.It was found that resting cells of S76 produce ,-dodecanediol from n-dodecane. This intermediate was identified by different analytical methods. With n-dodecanol as substrate the quantitative changes in the concentrations of ,-dodecanediol as well as other intermediates, e.g. monoacid, -hydroxy acid and ,-dioic acid produced by resting cells of S76 for different periods of time were determined. With ,-dodecanediol as the sole carbon source, quantitative changes of -hydroxy acid and ,-dioic acid produced by S76 were also recorded.The results confirm the existence of a new metabolic pathway via ,-diol in the course of ,-dioic acid formation from n-alkane in the mutant S76 of C. tropicalis.     

15N natural abundance studies in Australian commercial sugarcane

The measurement of natural ¹⁵N abundance is a well-established technique for the identification and quantification of biological N₂ fixation in plants. Associative N₂ fixing bacteria have been isolated from sugarcane and reported to contribute potentially significant amounts of N to plant growth and development. It has not been established whether Australian commercial sugarcane receives significant input from biological N₂ fixation, even though high populations of N₂ fixing bacteria have been isolated from Australian commercial sugarcane fields and plants. In this study, ¹⁵N measurements were used as a primary measure to identify whether Australian commercial sugarcane was obtaining significant inputs of N via biological N₂ fixation. Quantification of N input, via biological N₂ fixation, was not possible since suitable non-N₂ fixing reference plants were not present in commercial cane fields. The survey of Australian commercially grown sugarcane crops showed the majority had positive leaf ¹⁵N values (73% >3.00, 63% of which were >5.00), which was not indicative of biological N₂ fixation being the major source of N for these crops. However, a small number of sites had low or negative leaf ¹⁵N values. These crops had received high N fertiliser applications in the weeks prior to sampling. Two possible pathways that could result in low ¹⁵N values for sugarcane leaves (other than N₂ fixation) are proposed; high external N concentrations and foliar uptake of volatilised NH₃. The leaf ¹⁵N value of sugarcane grown in aerated solution culture was shown to decrease by approximately 5 with increasing external N concentration (0.5–8.0 mM), with both NO₃ ^– and NH₄ ⁺ nitrogen forms. Foliar uptake of atmospheric NH₃ has been shown to result in depleted leaf ¹⁵N values in many plant species. Acid traps collected atmospheric N with negative ¹⁵N value (–24.45±0.90) from above a field recently surface fertilised with urea. The ¹⁵N of leaves of sugarcane plants either growing directly in the soil or isolated from soil in pots dropped by 3.00 in the same field after the fertiliser application. Both the high concentration of external N in the root zone (following the application of N-fertilisers) and/or subsequent foliar uptake of volatilised NH₃ could have caused the depleted leaf ¹⁵N values measured in the sugarcane crops at these sites.     

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.