Morphology,cytology and forage potential of Pennisetum americanum (L.) K. Schum. x P. Purpureum Schum. amphidiploids

Summary F₁ hybrids between short-day photoperiod- sensitive maiwa bulrush millet, Pennisetum americanum (2n=14), and elephant grass, P. purpureum (2n=28), are triploid (2n=21), sterile, and can only be propagated vegetatively. Fertile amphidiploids, (2n=42, with 21 bivalents) were produced by colchicine treatment. Good seed set was obtained upon selfing the amphidiploids and the progeny exhibited variable pollen fertility and bivalent univalent and multivalent formation.Reciprocal crosses between elephant grass and the colchicine-induced amphidiploid failed to produce seeds. The maiwa millet x amphidiploid cross resulted in poor seed set and the reciprocal failed. Maiwa x amphidiploid hybrids were pollen sterile with 2n=21, rather than the expected 2n=28, indicating chromosome elimination.Morphologically, the amphidiploids and maiwa x amphidiploid hybrids closely resembled elephant grass and the F₁ hybrid. The amphidiploids showed no superiority over the F₁ hybrid and elephant grass in either forage yield or quality but one maiwa x amphidiploid genotype surpassed a promising local elephant grass selection in forage dry matter yield and flowered for a relatively short period.     

The black currant leaf curling midge,Dasyneura tetensi Rübs.; its host range,and the inheritance of resistance

Summary Established Western European black currant cultivars are susceptible to Dasyneura tetensi but the Scandinavian Sunderbyn II, Kangosfors and Hedda, and 10 out of 33 Russian cultivars showed very slight or no leaf symptoms of midge attack in the field.Of species within the black currant Section Eucoreosma, Ribes dikuscha, R. pauciflorum (probably=syn R. ussuriense), and R. americanum were not attacked, but an accession of R. bracteosum proved very susceptible. Species within other sections of the genus were not attacked.A strong dominant resistance gene in R. dikuscha, designated Dt, appeared to be linked with (a) gene(s) controlling resistance to American gooseberry mildew, Sphaerotheca mors-uvae. Resistance in Sunderbyn II and, probably, in R. pauciflorumwas oligogenic and dominant.     

Cytoplasmic relatedness of apple landraces and cultivars: a molecular analysis

Summary Mitochondrial DNA (mtDNA) diversity has been determined in apple landraces and cultivars, based upon restriction fragment length polymorphisms (RFLPs) for several mitochondrial genes. Our analysis includes three cultivars, Golden Delicious, McIntosh and Delicious, which represent the various patterns of mtDNA polymorphisms previously described (Ishikawa et al., 1992). A total of five RFLPs were detected, allowing classification of the apple genotypes into four cytoplasmic groups: GroupI, Golden Delicious-type; GroupII, McIntosh-type; GroupIII, Delicious-type; and Group IV, Dolgo Crab-type. European landraces and cultivars were assigned to Groups I, II, and III, while chinese crab apples were placed in either Group III or IV.     

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

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

Effect of ploidy on stomatal and other quantitative traits in plantain and banana hybrids

Summary Ploidy polymorphism occurs in the hybrid offspring derived from interspecific crosses between triploid plantains (Musa spp. AAB group) and diploid bananas (M. acuminata). Therefore,Musa breeders are interested in the determination of ploidy and its effects on phenotypic expression of quantitative traits. The aim of this research was to examine the reliability of stomatal and other phenotypic traits to determine ploidy in segregating plantainbanana hybrid families. Stomatal density and size were significantly correlated (P<0.01) with ploidy, although the correlation coefficients were not high (r=–0.49 and r=0.47, for stomatal density and size, respectively). High density of small stomata was correlated with low ploidy level, and vice versa. However, stomatal size and density were also influenced by a significant genotype effect (P<0.001) within the same ploidy level. Ploidy had an important effect on fruit traits and plant height in the hybrids of Obino l'Ewai×Calcutta 4, but this was not so clear in Bobby Tannap×Calcutta 4 hybrids. Obino l'Ewai derived tetraploids have medium to tall plants with large bunches and big fruits. Most of the tetraploids derived from Bobby Tannap have short stature due to the gene action of the dwarf,dw, allele. Also, a few selected diploids derived from Bobby Tannap outyielded their non-selected tetraploid full-sibs. In conclusion, chromosoem counting remains the only accurate proof of ploidy levels inMusa germplasm.     

Comparison of leaf and pod disease reactions of beans (Phaseolus vulgaris L.) inoculated by different methods with strains of Xanthomonas campestris pv. Phaseoli (Smith) dye

Summary Common blight disease in beans (Phaseolus vulgaris), caused by the bacterium Xanthomonas campestris pv. phaseoli, reduces crop yield and seed quality. Information is needed on the variation of leaves and pods disease reaction to strains of the bacterium after different inoculation methods. Phaseolus vulgaris cultivars Red Kidney Charlevoix, GN Harris, GN 1140, and GN Emerson were inoculated with three different strains of Xanthomonas campestris pv. phaseoli at two inoculum concentrations (10⁸ and 10⁶ bacterial cells/ml) using water soaking, multiple needle, and razor blade inoculation on leaves, and razor blade scratch, dissecting needle, and razor blade cut inoculation on pods. Differential cultivar disease reactions of leaves, pods, or both to the bacterial strains were observed in some cases. Significant interactions among cultivars, inoculation methods, strains, and inoculum concentrations (leaves) were found. A rapid leaf chlorosis developed 6 to 7 days after inoculation. Strains of bacteria did not show specificity in inducing this reaction, but rapid leaf chlorosis was associated with high inoculum concentration and with the water soaking and multiple needle methods. Another experiment was conducted to count the number of living bacterial cells deposited in the leaf tissue after inoculation by different methods. The number of bacteria deposited by water soaking or multiple needle was higher than that deposited by razor blade.Published as Paper No. 8584, Journal Series, Nebraska Agricultural Experiment Station. Research was conducted under Project No. 20–36.     

Traditional seed maintenance and origins of the French lucerne landraces

Summary As for other forage crops the notion of variety is quite recent in lucerne (Medicago sativa L.). Up to 1950 in France, farmers cultivated landraces whose origins were geographically defined. Seed production was a by-product of forage production. Usually, seeds were harvested on the second or third crop, in old lucerne fields. Natural selection created landraces adapted to local conditions. In some years, climatic conditions, especially in northern regions, were unfavourable to seed production. In the exchanges and trades of seeds between French regions, the genetic origin of the seeds was omitted, the geographical origin was only mentioned. Even if France usually exported lucerne seeds, imports occurred in bad years. Seeds were imported from European countries and from North and South America. Varieties from America were poorly adapted to the French conditions for forage production. These foreign varieties have probably intercrossed with the local landraces but no data is available to know to what extent. Among the various French landraces, five main types were defined using morphological characters: Flamande in the north, three types (Poitou, Marais de Luçon, Marais de Challans) in the west, and Provence in the south. These landraces have been widely used in breeding since 1950. Even though these five landraces are, up to now, maintained, the other landraces have probably been lost (no more cultivated and not in genebanks), replaced by registered varieties.     

Chromosome location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L.) 1. Mlk and other alleles at the Pm3 locus

Summary Several wheat cultivars/lines were inoculated with isolates of Erysiphe graminis tritici to identify new genes/alleles for resistance. The wheats were tested with 13 isolates that had been characterized from responses on differential lines with known resistance genes. Gene Mlk which occurs in cultivars Kolibri, Syros, Ralle and several other European common wheats was found to be an allele at the Pm3 locus and is now designated Pm3d. The mildew resistance in an old Australian wheat, W150, is conferred by a single gene also allelic to Pm3 and now designated Pm3e. The near-isogenic line Michigan Amber/8^*Cc possesses another allele now designated Pm3f. A Syrian land variety of common wheat shows mildew resistance that is conditioned by the combination of genes Pm1 and Pm3a. Finally, two accessions of Triticum aestivum ssp. sphaerococcum appeared to possess the Pm3c allele.     

Genetic variation and changes with ontogeny of osmotic adjustment in sunflower (Helianthus annuus L.)

Summary Intraspecific variation for osmotic adjustment in sunflower was examined using a collection of 33 genotypes of different origin which were exposed to water stress at the 8-leaf stage. Changes in osmotic adjustment with ontogeny were also evaluated in the pre- and post-anthesis phases using seven genotypes drawn from this collection. Estimates of osmotic adjustment were derived from measurements of leaf relative water content (RWC) and osmotic potential () during a period in which the soil was allowed to dry out gradually. The degree of osmotic adjustment, expressed as the value of RWC for a of –1.7 MPa (RWCe), was derived from the ln RWC/ln relationship. Both monophasic and biphasic ln RWC/ln relationships were found. Irrespective of the form of the relationship, all genotypes at the 8-leaf stage showed some degree of osmotic adjustment. This was also true for the cultivars included in the subset examined in pre- and post-anthesis phases. Significant differences (P=0.05) in RWCe were found between extreme genotypes in all three phases.Significant (P=0.05) linear relationships were found between RWCe measured in the 8-leaf stage and that measured in the pre- and post-anthesis phases, establishing the viability of measurements in the 8-leaf stage as a means of selection for osmotic adjustment in later developmental stages. Genotype rank order was stable (P=0.01) across the three ontogenetic phases examined.Abbreviations ETp potential evapotranspiration - osmotic potential - RWC relative water content - RWCe value of RWC for a of –1.7 MPa     

Breeding for resistance to yellow disease of hyacinths. II. Influence of flowering time,leaf characters,stomata and chromosome number on the degree of resistance

Summary Analysis of an incomplete diallel design with 14 hyacinth cultivars and 4 wild accessions of Hyacinthus orientalis showed a significant GCA component for resistance to yellow disease. The late flowering hyacinth cultivars King of the Blues and Marconi and the early flowering Hyacinthus orientalis 70129 were found to be the best combiners for yellow disease resistance. Within a cultivar, the degree of earliness itself was not associated with the degree of resistance. Correlation coefficients of leaf characters and degree of resistance showed that hyacinths with short and/or narrow leaves are generally more resistant than those with long and/or broad leaves. Tetraploid cultivars with few, large stomata tend to be susceptible, diploid ones with many small stomata tend to be the more resistant.     

Resistance to the glasshouse whitefly (Trialeurodes vaporariorum Westw.) in sweet pepper (Capsicum annuum L.)

Summary Fourteen cultivars, one F₁-hybrid and one half-wild type (Cind) of sweet pepper were tested on resistance to glasshouse whitefly. Several mutually significant levels of resistance were found. Most resistant appeared to be California Wonder, Severka M, Korál and Yolo Wonder. During the test sweet pepper plants were infested both with whiteflies and their parasite — Encarsia formosa, which caused the blackening of whitefly puparia. The blackened puparia are easily seen, enabling an easier and more rapid evaluation of the number of puparia present.     

Race-specific effects in major genic and polygenic resistance of barley to barley leaf rust in the field: identification and distinction

Summary Six partially resistant spring barley cultivars were exposed to four barley leaf rust (Puccinia hordei) races in the field and in the greenhouse. The 24 cultivar-race combinations were tested in field plots of 1.5×1.5 m² in two replications over two years. To reduce the interplot exchange of urediospores each plot was surrounded by winter rye.The level of barley leaf rust varied among cultivars, races and years. In both years the variance for cultivar-race interactions was highly significant and originating largely from the cultivar-race combinations Berac-22. Armelle-22, Armelle-A and Tyra-A. The Berac-22 interaction was towards higher, the other three interactions towards a lower level of barley leaf rust. The reduced rust levels of these three combinations were not due to interactions between the partial resistance of these cultivars and the aggressiveness of the races but to major genes for hypersensitivity not effective to the races 1-2-1 and F, common in Western Europe, but effective against the rare races 22 and A. This was revealed in the greenhouse experiments where all combinations had a susceptible infection type except Armelle-22, Armelle-A and Tyra-A, which showed low infection types in both the seedling and adult plant stages. The urediosori present in the field plots of these three combinations apparently arose from spores derived from other plots; this interplot interchange suggesting partial resistance.The interaction of Berac with race 22 truly was a small race-specific effect within the polygenic, partial resistance of barley to barley leaf rust like the one reported before between Julia and race 18.     

Inheritance of aroma in rice

Summary Inheritance of an aroma was worked out in crosses between Brimful from Nepal as an aromatic rice and leading Japanese varieties Koshihikari and Nipponbare as non-aromatic ones. The F₂ pattern of segregation for aroma to non-aroma was 3:13 indicating one dose gene for aroma and one dose inhibitor gene in two crosses. This ratio was confirmed by genetic behavior of F₃ populations.     

Development of a triticale resistant to the greenbug: An historical perspective

Summary A greenbug [Schizaphis graminum (Rondani)] resistant strain of rye (Secale cereale L.) Insave F.A. from Argentina was crossed with Chinese Spring wheat (Triticum aestivum L.) and also with Elbon and Balbo cultivars of common rye. Juvenile plants of the primary wheat X rye hybrid were treated with colchicine. Partially fertile amphidiploids were obtained that are resistant to greenbug Biotypes B and C. F₁ and F₂ populations of seedling plants derived from crosses of Insave F.A. with Elbon and Balbo rye were tested for reaction to the greenbug to determine the genetic basis of inheritance. The results confirmed previous reports that resistance in Insave F.A. is conditioned by a single dominant gene.Deceased     

Genetics and histology of powdery mildew resistance in apple

Summary Eight scab-resistant cultivars and selections along with eight commercial apple cultivars were evaluated for powdery mildew resistance in greenhouse and nursery tests. Dayton, Liberty, Delicious and Tolman Sweet were rated moderately resistant to infection in both greenhouse and nursery tests. Segregation of seedlings among 14 progenies for mildew reaction indicated that mildew resistance is polygenically controlled in this material with additive gene effects. Recovery of mildew resistant seedlings from crosses involving a scab-resistant parent(s) suggested that this material can be useful in developing scab- and mildew-resistant apple cultivars. Histological investigations were conducted to describe mildew symptoms of infected leaves.     

Inheritance studies of characters associated with floating habit and their linkage relationship in rice

Summary Deep water rice varieties in general have certain peculiar characters which are associated with floating habit. These characters are (i) early nodal differentiation, (ii) nodal rooting, (iii) spreading habit, (iv) awned grains, (v) brown hull colour, (vi) red pericarp (red rice), and (vii) seed dormancy. Inheritance of these characters and linkage relationship of genes governing these characters were studied in a cross between Pankaj (non floating) and Nageribao (floating) rice varieties. Nageribao, a cultivar from Assam possesses these characters.Early nodal differentiation was observed to be controlled by a single dominant gene, designated as Nd. Nodal rooting was controlled by two dominant complementary genes, designated as Nr ₁ and Nr ₂. We found an inhibitory factor for spreading habit and one for brown hull colour in Pankaj; the operation of two dominant duplicate genes An ₁ and An ₂ for controlling awning characters, a single dominant gene Rd for red pericarp colour and a single dominant gene Gd for grain dormancy. Joint segregations between these characters resulted in the assignment of genes in the X linkage group of indica rices with estimated map distances based on the cross-over values. The genes An (awning), Es (spreading habit), Nr (nodal rooting) and Nd (nodal differentiation) were observed to be associated with each other. The gene for red pericarp (Rd) was observed to be linked with the grain dormaney gene Gd.     

Low light intensity and flower bud abortion in Asiatic hybrid lilies. I. Genetic variation among cultivars and progenies of a diallel cross

Summary When Asiatic lilies are forced during the winter period, additional light is needed to prevent flower bud abscission and flower bud blasting. Growth room experiments showed considerable differences among eight lily cultivars in their response to low light. Among these cultivars, Connecticut King and Enchantment appeared to be the most sensitive to low light conditions while Uncle Sam and Scout were the least sensitive.Analysis of an incomplete diallel cross between nine cultivars showed significant differences in general combining ability (GCA) for flower bud abortion, number of buds, forcing time, plant height and leaf scorch under winter greenhouse conditions. Enchantment had the highest positive GCA for bud abortion, indicating a high sensitivity to low light conditions. Uncle Sam had the lowest GCA. Pirate and Scout appeared to have a high GCA for sensitivity to leaf scorch. Connecticut King was found to be a probable source of cytoplasmic male sterility. The data suggest that male sterility is associated with better response to low light conditions.     

Genetic nature of low capsaicin content in the variant strains induced by grafting in Capsicum annuum L.

Summary The genetic nature of low capsaicin content in variant strains induced by grafting was elucidated by crossing the G₅S₂₃ strain with the two cultivars, Yatsubusa (Capsicum annuum L. var. fasciculatum Ilish) and Spanish Paprika (C. annuum L. grossum Sendt) originally used for grafting. Decreased capsaicin synthesis was a stable characteristic for at least several generations from G₅S₁₆ to G₅S₂₃ and was transmitted to the progenies of crosses. This fact shows that the decreased capsaicin synthesis is a genetic trait in the graft-induced variant strains. The genetically dependent characteristic of pungency of the G₅S₂₃, Yatsubusa and Spanish Paprika were analysed by High Perfomance Liquid Chromatography measurement and tasting assay.Cross experiment between the G₅S₂₃ strain, hot parent Yatsubusa and sweet parent Spanish Paprika showed that pungent and sweet for pungency chracteristics are generally controlled by at least two pairs of genes. Although segregation of capsaicin content and pungency was clearly demonstrated in F₂ progenies from reciprocal crosses between the G₅S₂₃ strain and Spanish Paprika, F₂ progenies from reciprocal crosses between G₅S₂₃ and Yatsubusa were all hot and did not develop low capsaicin plants.     

Genes for resistance to stripe rust in four spring wheat varieties

Summary Four spring wheat (Triticum aestivum L.) varieties differing in origin and reaction in the seedling stage to pathotype CDL-6 (extant in California) were intercrossed and examined in greenhouse conditions in F₁, F₂, and F₃ generations. Digenic and transgressive segregation was found in all crosses. The four varieties each had infection types (1 immune, 9 susceptible) and putative resistance genes as follows: Anza, IT 7, YrA; Glennson 81, IT 2, Yr9; Yecora Rojo, IT 6, YrC; and Ollanta, IT 4–6, YrL. Anza was classified as susceptible, Yecora Rojo and Ollanta as intermediate in seedling resistance, and Glennson 81 as resistant in the seedling stage.     

Molecular and biological studies on male sterile cytoplasm in Cruciferae. II. The origin of Ogura male sterile cytoplasm inferred from the segregation pattern of male sterility in the F1 progeny of wild and cultivated radishes (Raphanus sativus L.)

Summary To determine the origin of Ogura male sterile cytoplasm in radish (Raphanus sativus L.), wild and cultivated radishes were crossed. Three types of progeny resulted from the F₁ hybrids between the wild radish from Kushikino with Ogura-type mtDNA and the cultivars (Uchiki-Gensuke or Comet). The segregation patterns of the male sterility were compared with those of Ogura cytoplasm. The male sterility induced in the F₁ hybrid was maintained by crossing with Uchiki-Gensuke, that maintains Ogura male sterility. In the two types of progeny, in which Comet (a restorer of Ogura cytoplasm) was used as one of the parents, both fertile and sterile plants segregated at the predicted ratio on the assumption that a single dominant fertility restoring gene exists in the restorer. From these results, we concluded that the Ogura cytoplasm is identical to that of the wild radish, and the former originated in a population of Japanese wild radish.