Compatibility and incompatibility in witloof-chicory (Cichorium intybus L.). 1. The influence of temperature and plant age on pollen germination and seed production

Summary For the production of inbred lines and F₁ hybrids in witloof-chicory information is wanted on characteristics such as the incompatibility system. These characteristics can only be studied properly if the influence of temperature and physiological status of the plant on pollen germination and seed production is known. Investigations were carried out with 9 self-incompatible (SI) and 6 self-compatible (SC) clones in glasshouses of the IVT phytotron at constant temperatures of 10, 14, 17, 20, 23 and 26°C. In general, in vivo pollen germination percentages were rather low after self pollination with an optimum for germination around 17–20°C. No seeds were formed at the lowest temperature (10°C) while seed production for SC clones was usually (rather) good at higher temperatures. At 26°C seed production in some clones decreased. Both pollen germination and seed production decreased at the end of the flowering period. There was a rather positive relationship at e.g. 17 and 20°C between pollen germination after selfing and seed production. When no pollen germination was observed, no seed formation occurred. When pollen grains did germinate, seed development would not necessarily occur in all cases. So this relationship only enables negative mass selection for SC.     

Use of irradiated pollen as mentor pollen to induce self-fertilization of two self-incompatible Upper Amazon cacao clones

Summary Two self-incompatible Upper Amazon cacao clones, T85/799 and T79/501, were pollinated with compatible Amelonado pollen subjected to varying doses of gamma irradiation (10–100 Gy). The proportion of flat non-viable beans to fully formed, viable beans in the pods increased with an increase in dosage of gamma rays. At 60 Gy all the beans produced were flat and non-viable, beyond this dosage fruit set was zero. Pollinating the self-incompatible cacao clones with a 1 : 1 mixture of compatible mentor pollen irradiated at 60 Gy and normal self pollen produced a mixture of flat, non-viable beans and fully-formed viable beans. Similar experiments using irradiated pollen with a marker gene suggested that the fully-formed viable beans resulted from selfing. Increasing the proportion of the radiation-treated compatible pollen in the mixture increased the number of fully-formed beans. However, when compatible pollen which had been treated either at 80 Gy or with temperatures of 35° C, 40° C and 45° C for periods of five, ten and fifteen minutes in factorial combination were mixed with self pollen, no successful pollinations were achieved. Pollen viability tests indicated that, whilst pollen treated at 60 Gy were about 50% viable, those treated at either 80 Gy or with temperatures of 35–45° C were mostly not viable. This suggests that, to overcome the incompatibility in cacao, the tubes of the mentor pollen grains used should at least grow into the style. The possible causes for overcoming the self-incompatibility in cacao are discussed.     

Low temperature tolerance of biomass and pollen germination in potato clones of Andean and European origin

Summary The temperature-related performances of six tetraploid potato clones, two Andean, three European, and one hybrid, were compared by cultivating them in growth chambers under one of two temperature regimes: 10°C day/4°C night or 20°C day/10°C night. Preformance was measured in terms of biomass production and pollen germinability.For dry matter yield at second harvest, the temperature-related performance ratios (performance at 10°C/4°C divided by performance at 20°/10°C) were highest for the Andean clones, intermediate for the Andean/European hybrid clone 201₅×S₁₂, and lowest for the European cultivars. The ability of the European cultivars to maintain their normal rates (i.e. rates at 20/10°C) of biomass production when cultivated at low temperatures varied greatly, with clone S₃ performing most poorly at 10/4°C.For pollen germinability in vitro, performance ratios were highest for the hybrid clone 201₅×S₁₂ and lowest for the European clones.The high tuber yield of hybrid 201₅×S₁₂ at 10/4°C can be attributed to its low-temperature tolerance and it being daylength neutral.     

Breaking breeding barriers in Lycopersicon. 2. Breakdown of self-incompatibility in L. peruvianum (L.) Mill.

Summary Attempts were made to break the self-incompatibility in L. peruvianum by selection of mutated S-alleles through large-scale self-pollination on clones with pollen which was mutagenically treated in different stages of development. Besides self-compatibility was searched for in inbred lines.The self-incompatibility in L. peruvianum was found to be very strict indeed. From more than 22,000 self-pollinations on 5 clones 1527 seeds were obtained, seed set being very erratic. The possible causes of this seed set are discussed. From 1527 seeds 1036 plants were raised and tested for self-compatibility.In the progenies of 4 clones from 823 plants tested, 7 were more or less self-compatible. It is concluded that this self-compatibility was spontaneous and not the result of the mutagenic treatment.In the progeny of the fifth clone plants were found which reacted as self-compatible at a temperature of about 40°C and as self-incompatible at lower temperatures. It is suggested that this character—a high temperature sensitive incompatibility reaction—is governed by one recessive gene.In inbred lines plants were found with a stable form of self-compatibility and also plants with a high temperature sensitive incompatibility reaction.The problems of an incompatibility research on inbred material are discussed. A brief survey is given of some of the characters found in inbred L. peruvianum.     

Incompatible pollen tube growth and protein composition in styles of Japanese pear following high temperature treatments

Summary Immersing the excised-prepollinated styles of self-incompatible Japanese pear, Pyrus serotina Rehd., into distilled water at 45°C for 1.5–2.5 min promoted the growth of self-pollen tubes; both the number of styles penetrating the pollen tubes through styles to cut ends and of pollen tubes protruding from cut ends were increased. The subsequent growth of the protruded pollen tubes on agar media was also enhanced by the treatments. Treatments at 40°C did not promote the growth of self-pollen tubes and those at 50°C led the styles to necrosis. In the stylar proteins analyzed by isoelectricfocusing polyacrylamide gel electrophoresis, several changes in banding pattern were found following the heat treatment; one of the bands was a glycoprotein that increases in quantity in developing styles as self-incompatibility of the style becomes stronger (Hiratsuka et al., 1986). This protein band was stained more weakly by Coomassie Brilliant Blue-G250 dye. Antigenic substances in the styles examined by immunodiffusion seemed not to be denatured by high temperature treatments.Abbreviations IEF-PAGE isoelectricfocusing polyacrylamide gel electrophoresis - CBB Coomassie Brilliant Blue     

Overcoming the self-incompatibility of Lilium longiflorum Thunb. by application of flower-organ extract or temperature treatment of pollen

Summary The application of flower organ extracts to stigmas and the temperature treatment of pollen were tried to overcome self-incompatibility of Lilium longiflorum cv. Georgia.Substances in stigma, style, ovary and anther were extracted with ethanol and fractionated with ethylacetate into the acidic, basic and aqueous fractions. The extracs melted in a small volume of distilled water were applied to stigmas prior to self-pollination. Hinomoto stigma extract, self-pollinated and cross-pollinated Georgia stigma extracts of high concentrations and Georgia anther extract of high concentration were effective in overcoming the self-incompatibility and resulted in a high percentage of fruit set and many normal seeds. Extracts from Hinomoto ovary, style and anther were ineffective, except a basic fraction, which was very slightly effective.Pollen was treated with 40°C for 60 or 90 minutes and 50°C for 30 or 60 minutes, and a half of each lot was followed by –20°C for 24 h, prior to self-pollination. All treatments were effective, especially at 40°C for 60 minutes or 50°C for 30 minutes, and 40°C for 90 minutes or 50°C for 60 minutes followed by –20°C for 24 h.     

Effects of photoperiod and temperature on flowering in mungbean (Vigna radiata (L.) Wilczek)

Summary Forty strains of mungbeans, including all of the entries in the 1st and 2nd International Mungbean Nurseries (IMN), were grown in plant growth chambers in photoperiods of 12, 13, 14, 15, and 16 hours and mean temperatures of 18, 23, and 28°C. Results show that (1) mungbean strains differ in their flowering response to photoperiod and to mean temperature; (2) increasing the photoperiod of reducing the mean temperature delayed flowering, the amount of delay varied with the strain: (3) variations in mean temperature may alter the effect of the photoperiod on flowering in particular strains. Twenty-five strains which flowered in all photoperiod-temperature treatments could be divided into four groups, each group being successively later in flowering. The remaining 15 strains could be divided into four groups, according to their failure to flower within 105 days in specific photoperiod-temperature treatments. Flowering response in the growth chamber is useful in explaining flowering response in the 2nd IMN at three locations varying from 14°N to 49°N latitude.Contribution No 7516 from the Missouri Agricultural Experiment Station.     

Partial control of chromosome elimination by temperature in immature embryos of Hordeum vulgare L. x H. bulbosum L.

Summary Embryos derived from Hordeum vulgare L. x H. bulbosum L. were subjected in vivo to a range of temperatures, and the proportions of hybrid plants which retain both parental sets of chromosomes were determined. Elimination of the H. bulbosum genome was significantly increased at temperatures greater than 20°C and resulted in fewer hybrid plants compared with temperatures below 17.5°C. Embryos were also allowed to develop in situ at 15°C and then transferred to 26°C for 8, 16 or 24h during the first 7 days after pollination. A period of 16 h at 26°C (equivalent to at least one complete mitotic cycle) at 2–5 days after pollination was found to be sufficient to increase chromosome elimination significantly above the levels obtained at a constant 15°C. At this stage (2–5 days after pollination at 15°C) the mean embryonic cell number was 2.3–223.     

Parthenogenetic monohaploids (2n=x=12) from Solanum tuberosum L. and S. verrucosum Schlechtd. and the production of homozygous potato diploids

Summary Dihaploid and dihaploid derived clones of Solanum tuberosum and diploid genotypes of S. verrucosum produced 85 viable monohaploids by female parthenogenesis. All were induced using diploid S. phureja clones, homozygous for embryo spot, as pollinator. Frequency of S. tuberosum monohaploids per 100 berries was rather constant in three successive years (14, 17 and 17 respectively). No male and female fertility was found in flowering monohaploids.Colchicine-induced chromosome doubling yielded homozygous s. tuberosum diploids with low pollen quality but good seed fertility.Two diploid self-incompatible species (S. multidissectum and S. berthaultii) produced no monohaploids. The presence of genes for female parthenogenesis in some dihaploids is discussed.     

Breeding of the cultivated potato species Solanum x juzepczukii Buk. and Solanum x curtilobum Juz. etBuk.

Summary This study investigated the possibility of recombining anew the genomes of the wild and cultivated progenitors of triploid S. juzepczukii and pentaploid S. curtilobum by following the known evolutionary pathway of these two species. Before starting the actual breeding work, the natural variation of S. juzepczukii, S. curtilobum and their wild progenitor S. acaule was studied from the point of view of morphology, quantitative and qualitative tuber glycoalkaloid content and frost resistance. The morphological study was supplemented by a study of the soluble tuber proteins employing polyacrylamide slab-electrophoresis. From 137 accession of S. juzepczukii only 19 morphotypes were identified, 18 of which were also different in their protein spectra. The only red-tubered S. juzepczukii revealed a protein spectrum identical to that of the largest white-tubered group. On phylogenetic grounds, the occurrence of a red-tubered S. juzepczukii cannot be explained. It is concluded that this red clone is a somatic mutant for tuber colour which arose from a whitetubered clone. S. curtilobum was restricted in its variation to just two morphotypes differing only in tuber colour which are, however, identical chemotypes. This would be the case if one of the clones was a somatic mutant for tuber colour from the other one. The glycoalkaloids -solanine, -chaconine, tomatine, demissine and - and -solamarine are shown to be useful taxonomic characters which confirm earlier hypotheses on the origin of S. juzepczukii and S. curtilobum. Laboratory tests showed the two cultivated species to be resistant to about –3°C whereas S. acaule is resistant to temperatures sometimes below–5°C. The diploid progenitor of S. juzepczukii, S. stenotomum, also has forms resistant to –3°C. The results of this study demonstrate that the proposed breeding scheme is possible.     

Differential cold sensitivity of pollen grain germination in two Prunus species

Summary Pollen grains from selected cutivars of almond [Prunus dulcis (Mill.) D. A. Webb] and peach (Prunus persica Batsch L.) were exposed to a range of temperatures between 1°C and 34°C on a thermogradient plate. Pollen germination at temperatures below 9°C was conspicuously greater in almond than peach. Miximal germination percentages were attained at about 16°C (almond) and 23°C (peach). The two species did not differ in their capacity for pollen tube elongation over a broad range of temperatures. Maximal pollen tube elongation occurred at temperatures 5°C to 8°C higher than maximal pollen germination. Species affiliation appeared to be of much greater consequence than chilling requirement or bloom date of the sporophyte in predicting gametophytic response to temperature.     

Low temperature storage of pistachio pollen

Summary Pollen from four male pistachio (Pistacia vera L.) clones was stored at –196°C and –20°C for up to 12 months and tested for ability to germinate in vitro following a period of hydration at high humidity. Germination of fresh pollen was high (>80%) for each clone. At –196°C, pollen of cv. Peters survived freezing, storage and thawing with no loss of germinability; pollen of the other three clones had sharp declines in germination possibly attributable to cellular lesions incurred during freezing or thawing. When the relative humidity of the –20°C storage environment was maintained at or near 33%, Peters pollen had high rate of germination through 12 months storage. Without control of relative humidity, Peters pollen germination was high at 4 months, but declined at 12 months. Germination requirements became more exacting for pollen stored at –20°C for 12 months at suboptimal humidity conditions. Pollen of the other three clones did not tolerate storage at –20°C as well as Peters pollen regardless of the storage humidity environment.     

Physiological studies on grass-dwarf selection lines in wheat (Triticum aestivum L.)

Summary Low power heating wires insulated in a flexible plastic strip were used to heat the shoot meristematic region of grass-dwarf genotypes to a precise temperature. The results indicate that the shoot apical meristem is the region requiring 26°C for the initiation of reproductive development in these genotypes. A secondary effect of the reproductive growth induced by high temperature treatments, was a reduction in the high levels of peroxidase enzymes found in vegetative grass-dwarf plants. The heating wire provides a precise method to identify Type I, II and III grass-dwarf genotypes according to their temperature requirements, of 26°C, 21°C and 16°C respectively, for reproductive growth under the same temperature (16 C) and photoperiod (12 hours).     

Breakdown of self-incompatibility in perennial ryegrass at high temperature and its uses in breeding

Summary The maximum temperature (34°C) at which perennial ryegrass plants from one breeding population successfully shed pollen was determined and the seed set of ten clones taken from the same population and self-pollinated both in an unheated glasshouse and at a constant 34°C during anthesis was compared. Seed set by selfing of all ten clones was markedly increased by heat treatment, from a mean of 2.3% to 30.7%. Heat treatment of anthers, but not stigmas, greatly enhanced pollen tube growth on stigmas from the same genotype. Germination of progeny was not affected by the heat treatment. Heat treatment of ten clones from a breeding population with contrasting morphology and growth rate was not so successful. Only one clone shed pollen freely at 34°C and showed a marked improvement in subsequent seed set. The advantages to the breeder of routinely producing full-sib families of elite perennial ryegrass parents by selfing are outlined.     

Selection for high self-incompatibility in inbred lines of brussels sprouts

Summary An attempt to improve the self-incompatibility of an advanced inbred line of Brussels sprouts by selection has been unsuccessful. The apparent plant-to-plant variation in self-incompatibility has little or no genetic basis. It results from environmental effects and from intrinsic physiological differences between flowers on a single plant. A temperature rise from 17°C to 26°C markedly increases the self-compatibility of the lines tested, but no evidence was found for end-of-season compatibility. The best methods for producing inbreds with high and consistent self-incompatibility are discussed.     

Characterisation and origin of rust and powdery mildew resistance genes in VPM1 wheat

Summary The expression of rust resistances conferred by closely linked genes derived from VPM1 varied with environmental conditions and with genetic backgrounds. Under low light and low temperature conditions seedlings carrying Yr17 showed susceptible responses. Stem rust and leaf rust resistance genes Sr38 and Lr37 tended to confer more resistance at 17±2° C than at normal temperatures above > 20° C. These studies supported the hypothesis that Yr17, Lr37 and Sr38 were derived from Aegilops ventricosa, whereas Pm4b was probably derived from T. persicum. Studies on certain addition lines and parental stocks indicated that wheat cytoplasm may enhance the expression of Sr38.     

In vitro selection of strawberry (Fragaria × ananassa Duch.) clones tolerant to salt stress

The method of in vitro selection for increased salt tolerance at the seed germination and early growth phase of strawberry seedlings is proposed. Clone Pau/27 was selected on medium containing 200 mM of NaCl from population obtained by free pollination of cv. ‘Paula2019;. Subsequently, on the same medium 18 salt tolerant clones were attained from the population of seeds collected from self pollinated Pau/27 plants. In the next step we examined the influence of a mild salt stress (75 mM of NaCl) on vegetative growth parameters of selected clones and two cvs.; ‘Paula2019; and ‘Senga Sengana’. All materials in the study on the basis of calculated indexes were divided into four groups differing in reaction to salt. First group (clustered together cv. ‘Paula’, Pau/27 and three second generation clones: Pau/27/11, Pau/27/24, Pau/27/30) represents sensitive genotypes. Second group, including ‘Senga Sengana’, Pau/27/06, Pau/27/10, Pau/27/12, Pau/27/13, Pau/27/15, Pau/27/18, Pau/27/20, Pau/27/21, Pau/27/26, Pau/27/27, Pau/27/31 and Pau/27/32 was designated tolerant. Third group contains only one highly tolerant clone Pau/27/08. The last group comprises two highly sensitive clones (Pau/27/01 and Pau/27/03). This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of vernalization and photoperiod to the vegetation period of wild species of oats (Avena spp.)

This paper presents the results of a six year field study of wild Avenaspecies and their response to vernalization and photoperiod. The accessions of twenty one wild and weedy species were tested under 12-hr and 18-hr daylength and cold temperatures (for 40 days at +2 ^°C) treatments and without it (as a control). The results demonstrate that for the majority of species evaluated, cold temperature requirements had a greater influence on heading date and the duration of the vegetative period than daylength. Genotypes with neutral, weak and strong reactions to all treatments were found and spring and winter types were selected. The results further demonstrated that daylength-insensitive forms occurred in the south Mediterranean region and adjacent southern territories.     

A genetic analysis of self-incompatibility and double flowers in Potentilla fruticosa L.

Summary The self-incompatibility system in Potentilla fruticosa was investigated by examining pollen cytology, and by analysing intercrosses between two self-incompatible, cross-compatible cultivars of the species. The pollen was found to be binucleate, which is consistent with a single locus self-incompatibility system acting gametophytically in the pollen. This was confirmed by the results of the intercrosses. A proposed model for the inheritance of extra petals was tested by backcrossing selected F₁ hybrid plants to both of their parents. Non-random segregation of the double modifier (Dm) locus suggested linkage to the self-incompatibility locus (S). The model was accordingly modified to include this linkage.     

Influence of the temperature on growth and alkaloid content of first-year Atropa belladonna L.

Summary In breeding Atropa belladonna for high alkaloid content it is of importance to know whether the alkaloid content is affected by the environment. Therefore some experiments on the influence of temperature were carried out in the phytotron of our Institute. As the results were in agreement with each other only one experiment is discussed in which the influence of three constant temperatures, viz. 20°, 23° and 26°C, on growth rate, dry matter, and alkaloid content of yellow-flowered Atropa belladonna L. was studied.It was found that development was quickest at 23°C, followed by 26° and 20°C. Temperature had little or no effect on the height of the plants and weight of dry matter in the corresponding developmental stages. The highest alkaloid content was reached at 23°C; at 26° and 20°C the alkaloid content was lower. The differences were slight but mathematically reliable.