Field resistance to late blight (Phytophthora infestans (Mont.) De Bary) in potato (Solanum tuberosum L.) somaclones associated with instability and pleiotropic effects

Summary Adventitious regenerants (somaclones) of Bintje and their vegetative progeny were screened for field resistance to Phytophthora infestans as follows: the area under the disease progress curve was computed and correlated with resistance rating in Bintje and reference varieties. The resistance rating of the somaclones was determined from this relationship.Clones with stable improved field resistance in successive years' trials were detected, however, most of such clones were also maturation mutants. Variation in resistance rating in clone replicates and between years was detected in most clones.The possible basis of the field resistance and reasons for its instability are discussed.Abbreviations AUDPC area under the disease progress curve     

Stability of bacterial leaf spot resistance in peach regenerants under in vitro,greenhouse and field conditions

Summary Phenotypic stability of bacterial leaf spot resistance in peach (Prunus persica (L.) Batsch) regenerants, either selected at the cellular level for insensitivity to a toxic culture filtrate of Xanthomonas campestris pv. pruni or screened at the whole plant level for resistance to X. campestris pv. pruni, was investigated. A detached-leaf bioassay was used to evaluate the original regenerants again after three years in the greenhouse and also after a two to three year cycle of tissue culture propagation. Peach trees derived through micropropagation from the original regenerants were also evaluated after one to three years growth in the field. Although leaf spot resistance was retained in some regenerants over time in the greenhouse, following in vitro propagation, and under field conditions, resistance was either lost or not expressed in others. Regenerants # 19-1 and #156-6, derived from embryo callus of bacterial spot susceptible Sunhigh, were significantly more resistant than Sunhigh. High levels of resistance were exhibited in greenhouse plants and field-grown trees of regenerant #122-1, derived from embryo callus of moderately resistant Redhaven. This research provides additional evidence that selecting or screening for somaclonal variants with disease resistance is a feasible approach to obtaining peach trees with increased levels of bacterial spot resistance.Abbreviations TC Tissue-Cultured - TF Toxic culture Filtrate     

Improved frost tolerance and winter survival in winter barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.) by <Emphasis Type="Italic">in vitro</Emphasis> selection of proline overaccumulating lines

Embryogenic calli derived from anther cultures of the two-rowed winter barley cultivar Igri were plated on solid L3 medium containing the proline analogue hydroxyproline (Hyp), 10–20 mmol l^–1. Exposure to Hyp caused severe degeneration of most of the calli. Hyp resistant calli, distinguishable by their lighter colour and higher growth rate, and control calli not exposed to Hyp were plated on L3 regeneration medium. From 22,500 anthers exposed to Hyp 46 Hyp resistant regenerates were obtained, which were transferred to soil. After cultivation for 5–10 weeks at normal growth conditions they were cold hardened at 2 C under short day conditions together with control regenerates. Frost tolerance assays with segments of fully grown leaves of unhardened and cold hardened plants revealed that Hyp resistant regenerants were significantly more frost tolerant than the control regenerants. Improved frost tolerance was found also in the progenies R₁ to R₉, and genotypic segregation in the R₁ generation in a 1:2:1 ratio was indicated. Increased proline content was observed in the R₂ generation and in subsequent generations and was significantly (P 0.001) correlated with increased frost tolerance in the Hyp lines. Comparative studies of R₉ progenies from homozygous R₂ plants with the wild type Igri under field conditions in winter at three locations in Europe as well as crossing experiments confirmed the heritable improvement of frost tolerance and winter survival, respectively, in the Hyp lines. The results support the hypothesis that proline accumulation in cold acclimated winter barley plants is causally related to the acquisition of frost tolerance. Moreover, the described biotechnological procedure may be applicable in breeding programs for improved winter hardiness and possibly also for other stress tolerances.     

Genotypic and exogenous factors affecting shoot regeneration from anther callus of linseed (Linum usitatissimum L.)

Summary The objective of this study was to investigate factors affecting the regeneration capacity of linseed anther culture. Four different environmental conditions in a phytotron were tested with regard to their effects on anther donor plants of cv. Hella. Anther response and shoot regeneration from anther callus was maximal when donor plants were grown in a 16 hrs-day at 14°C day/8°C night temperature. Anthers of four linseed genotypes were cultured on different media. Maximum shoot regeneration was achieved when the induced calli were transferred onto a modified N6 medium containing zeatin (1 mg l^-1). Most of the calli regenerated shoots in the second subculture on regeneration media. Shoots were rooted on modified B5 or MS media containing NAA (0.1 mg l^-1). Cytological examinations of incubated anthers and root tips of regenerated plants indicated that the anther calli were derived from microspores.Abbreviations B5 Gamborg's (1975) medium - BAP 6-benzylaminopurine - 2,4D dichlorophenoxyacetic acid - N6 Chu's (1978) medium - NAA -naphthaleneacetic acid - MS Murashige & Skoog's (1962) medium - ZEA zeatin     

Analysis of tissue culture-derived variation in pea (Pisum sativum L.)-preliminary results

Summary The possibility of producing agronomically-useful somaclones via organogenesis and somatic embryogenesis from callus cultures of pea (Pisum sativum L.) was studied. Organogenic calli were induced from immature leaflets on MSB medium with NAA and BAP. Embryogenic calli were derived either from immature zygotic embryos (using 2,4-D) or from shoot apices (using picloram) of aseptically-germinated seedlings.The seed progenies (T₁ to T₃-generation) of primary regenerants were grown in field conditions and their phenotypic variation was evaluated and compared with control, non-tissue culture-derived plant material. In addition, electrophoretic analyses of selected isoenzyme systems and total proteins have been done. The results do not show dramatic changes in qualitative and quantitative traits. The evaluation of at least two future generations (T₄, T₅) is planned.Abbreviations BAP 6-benzylaminopurine - IBA indole-3-butyric acid - MSB medium (mineral salts after Murashige & Skoog, 1962, vitamins after Gamborg et al., 1968) - NAA -naphthalene-acetic acid, picloram-4-amino-3,5,6-trichloro picolinic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - ORG organogenesis - SE somatic embryogenesis     

In vitro Separation of Chimeral Pears into their Component Genotypes

Summary An adventitious shoot regeneration system for Pyrus communis was used to separate two chimeral pears into their component genotypes. The two cultivars were a variegated type, Louise Bonne Panachée and a red fruited mutant, Red Hardy. Leaves of these cultivars were placed onto a regeneration medium consisting of Nitsch & Nitsch (1969) salts supplied with various levels of Thidiazuron (TDZ) and NAA. After two months the regenerants were moved onto a proliferation medium of Lepoivre salts. Later they were evaluated for their chimeral status. Among the regenerants of the variegated type, 100% segregation occurred, most shoots were green, a few were albino. Regeneration was more efficient for dissociating the variegated chimera than rapid shoot multiplication and physical injury. In Red Hardy, after two months on the regeneration medium, 20 to 33% of the regenerants were green, the rest were red. The stability of the red and the green regenerants were assessed on media supplemented with various levels of sucrose and by total anthocyanins measurement. Both types were stable.     

High frequency somatic embryogenesis with a pampeana-derived genotype of alfalfa (Medicago sativa L.)

Summary Somatic embryos of genotype R11 of the alfalfa variety Pampeana were produced from embryogenic calli derived from leaf sections. They were induced by an auxin shock and its development was attempted on six different media. The best condition for somatic embryo production was inducing callus on MS medium plus 10 M 2,4-D and 4,6 M KIN and transferring them, after the auxin shock, to MS with 10–20 mM NH₄ ⁺ and 30 mM proline. More than 500 somatic embryos per plate were produced. Embryos were grown to plants on MS or half strength MS media and all regenerated plants resembled the original R11 genotype. This technique could be useful in alfalfa Pampeana improvement using genetic modification.     

Identification of tetraploid regenerants from cotyledons of diploid watermelon cultured in vitro

Summary Adventitious shoots were obtained from the diploid watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] cultivars Dixielee, Jubilee II, Mickylee, Minilee, and Royal Sweet by culturing excised cotyledons on shoot regeneration medium for six weeks. Tetraploid and diploid regenerants were identified by counting the number of chloroplasts per guard cell pair from leaves of regenerated plants. Cross fertilization of putative tetraploids with diploid pollinators and the production of triploid seed confirmed the efficacy of this approach. The mean number of chloroplasts for tetraploid regenerants was 19.1 whereas diploids averaged 11.2. These values were similar to tetraploid and diploid plants from seed. Ovary diameter, petal, and anther diameter of male flowers, and leaf length by width ratio were also good indicators of plant ploidy. Progeny obtained from self-fertile tetraploids of Mickylee were crossed with various diploid pollinators to produce triploid hybrid seed. All triploid plants from tissue culture-derived tetraploids produced fruit comparable in quality to fruit produced by currently-available triploid hybrids, demonstrating that in vitro tetraploid induction can be used to produce high quality tetraploid plants for use in triploid hybrid seed production.     

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.     

The effect of anther orientation on microspore-derived plant production in barley (Hordeum vulgare L.)

Summary The effect of anther orientation on culture response has been examined in a range of barley cultivars of agronomic importance. Anther orientation did not significantly affect the percentage of anthers responding. However, orientation of the anthers in the up position with one lobe in contact with the medium significantly increased the number of green plants produced when compared to anthers cultured in the flat position. Green plantlet production was observed directly from embryoids i.e. without an intermediate callus phase. Cytological examination of the regenerants indicated that the majority of the plantlets possessed the normal barley karyotype. The implications of these results for Barley breeding are discussed.     

Genetics of resistance in the wheat cultivar chhoti lerma against stem rust race 122

Summary Genetics of rust resistance against stem rust race 122 in Chhoti Lerma was studied both by conventional and aneuploid analysis. Observations on F₁, F₂ and F₂ backcross progenies revealed the operation of two recessive genes, controlling resistance in Chhoti Lerma. Monosomic analysis confirmed the operation of two recessive genes conferring resistance to race 122 located on chromosomes 1D and 7D. A minor gene or modifier was also located on chromosome 1B. This was concluded from the fact that F₂ of mono's x Chhoti Lerma exhibited skewness in favour of resistant plants.     

Chromosomal location of genes controlling 6-phosphogluconate dehydrogenase,glucose-6-phosphate dehydrogenase and glutamate dehydrogenase isozymes in cultivated rye

Summary The 6-phosphogluconate dehydrogenase (6-PGD), glucose-6-phosphate dehydrogenase (G-6-PD) and glutamate dehydrogenase (GDH) zymogram phenotypes of wheat, rye and their aneuploid derivates were determined. At least three genes involved in the production of 6-PGD isozymes were located on chromosome arms 4RL, 6RL and 2RL of Imperial rye, King II rye and Dakold rye. Evidence was obtained that at least one gene located on chromosome arm 5RS controls G-6-PD isozyme activities in these varieties of rye and one gene involved in the production of GDH isozymes was located on chromosome arm 2RS of Imperial, King II and Dakold rye. The results indicate that the 6-PGD isozymes exist as dimers and monomers. No possible structure of the G-6-PD and GDH could be determined.     

In vitro morphogenetic capacity of Nicotiana tabacum L. var. BEL W3 upon cyclic culture and regeneration

Summary Variation in the capacity to regenerate shoots and morphogenetic potential were investigated by cyclic culture and regeneration of Nicotiana tabacum var. BEL W3. Explants were excised from different shoots formed by the same callus line. Differences in the organogenetic in vitro response among regenerated plantlets was observed in two subsequent regenerate generations. A progressive decrease of the regenerative capacity was observed across callus line generations.     

The effect of the ‘Golden Promise’ dwarfing gene on partial resistance to leaf rust and powdery mildew in spring barley

Summary F₂-plant progenies, derived from seven crosses between susceptible erectoides breeding lines and conventional, nutans breeding lines with partial resistance to leaf rust incited by Puccinia hordei Otth., derived from Vada x Cebada Capa, were examined in a field and a glasshouse experiment. In the field experiment, the nutans plant progenies generally were more resistant to leaf rust and powdery mildew than the erectoides progenies. In the glasshouse experiment, the components of partial resistance to leaf rust of six erectoides and six nutans progenies derived from one cross were studied. The nutans progenies generally had lower infection frequencies than erectoides progenies with a similar infection level in the field experiment. The variation for leaf rust and powdery mildew infection in the field was similar for the nutans and erectoides progenies. This suggests that erectoides lines with a fairly high level of partial resistance to leaf rust and powdery mildew can be selected from these populations.     

Genetic analysis of hexaploid wheat,Triticum aestivum using intervarietal chromosome substitution lines—protein content and grain weight

Summary The 21 intervarietal chromosome substitution lines of the cultivar Hope in Chinese Spring were used to analyse the genetic differences between the two cultivars Hope and Chinese Spring in grain protein content and grain weight.Only one chromosome of Hope, 5D, significantly influenced grain protein content of Chinese Spring. Its influence was of only minor effect and was to decrease protein content expression of Chinese Spring. It has been postulated that the genetic control of protein content, in this instance, is most likely due to many genes each of small effect.Five chromosomes of Hope influenced the 1000 grain weight value of normal Chinese Spring, all increasing its expression. Chromosomes 1A, 4A and 5B were of major effect and 3A and 6A of comparatively minor effect. A minimal estimate of five genes determines the difference in grain size between these cultivars. The possible evolutionary significance of the contribution of the A genome of bread wheat to grain size determination is discussed. On the basis of certain findings of this study, proposals are made for breeding for increased grain size in hexaploid wheat.     

Monosomic analysis of fertility restoration in common wheat ‘Prof. Marchal’

Summary In common wheat (Triticum aestivum L.) a monosomic set of Chinese Spring and male-sterile Janus (with cytoplasm of T. timopheevi Zhuk.) were used to determine the chromosomal location of Rf-genes in Professeur Marchal. As revealed by test cross data, a major gene cofeerring fertility restoration was present in Prof. Marchal on chromosome 1B. A significant deviation towards sterility was observed in some fest cross progenies. Chromosome 1B of Chinese Spring appeared to carry a dominant restoring gene, which caused partial restoration of fertility.     

In vitro propagation of Japanese garden iris,Iris ensata Thunb.

Summary Explants of young scapes of Iris ensata were cultured on MS medium with 1 mg/l NAA, 1 mg/l 6-BA, 30 g/l sucrose and 10 g/l agar, and this species was characterized by high variety specificity for callus, shoot and root induction. Among 23 varieties and one wild form tested, Okichidori, Miyukisudare and Meiji-l exhibited a considerable rate of shoot induction, although these induced poorly rooted shoots. In addition, two types of callus induction such as green and white calli were observed, and the induction of green-type calli was significantly correlated with that of shoots. Surprisingly, the only modification, half-strength MS inorganic salts, for the above medium proved to be very effective for shoot induction in the scape culture. For shoots obtained from the scape culture, effects of sucrose concentrations and activated charcoal on root induction were examined by using 1/2 MS with 1 mg/l NAA, 1 mg/l 6-BA, 30 g/l sucrose and 10 g/l agar as the basic medium. The addition of 1% activated charcoal to the media had a marked effect for root induction independent of sucrose concentrations and varieties tested. The in vitro propagation technique of I. ensata is discussed.     

Association of gene for grain colour with monosome XIV of Avena sativa L.

Summary The F₂'s from crosses between Dyfed (S.240; a black grained cultivar) and monosomics of Sun II (non-black cultivar) were analysed. With the exception of F₂ progenies involving monosomes, II, VI, VII, X, XI, XII, XIII and XIV, all other deviated from the genetic ratio 3 black: 1 non-black. The cytological examination of the non-black individuals belonging to those families that did not deviate from the 3:1 ratio showed that they were either 41- or 42-chromosome plants. However, non-black individuals involving monosome XIV were 40-chromosome plants. The gene conferring the black colour to the grains in Avena sativa cv. Dyfed (S.240) is located on chromosome XIV.Department of Plant Breeding and Genetics, Sind Agriculture University. Tando Jam. Pakistan.     

Determining levels of resistance to Tulip Breaking Virus (TBV) in tulip (Tulipa L.) cultivars

Summary The resistance of seven tulip cultivars to tulip breaking virus (TBV) was studied after mechanical inoculation by determining the number of infected plants and the level of virus in these plants over a period of one and a half years. Three cultivars (Apeldoorn, Kees Nelis and Lustige Witwe) appeared to be susceptible. Four cultivars (Cantata, Juan, Madame Lefeber and Princeps) showed a high degree of resistance. The number of infected plants of the latter cultivars was low and virus could not always be detected in the plants at the different sampling dates. Virus could not be detected in these plants after storage. These results indicate that the virus may disappear from or was not detectable in these plants. The levels of infection found are discussed with respect of its significance in studies of TBV in tulips.     

Lilium x ‘Black Beauty’—a potential bridging hybrid in Lilium

Summary Lilium Black Beauty, a rare intersectional hybrid previously reported sterile, was re-examined for pollen and ovule fertility. No pollen tubes were detected following incubation of styles pollinated with Black Beauty pollen. However, embryos varying in size from small globular to long boat-shaped and only rarely associated with endosperm, were found in 0.1–1.0% of the ovules in Black Beauty pistils pollinated with Oriental or Aurelian division lilies. Aseptic extraction and culture of these embryos on a nutritive medium resulted in growth, germination, and plantlets. It is apparent that with embryo culture, Black Beauty has unique value as a species bridge in that it accepts pollen of both Oriental and Aurelian lilies, two of the major commercial lily divisions.Scientific Journal Series Paper Number 9197 of the Minnesota Agricultural Experimental Station.