The effect of temperature on fruit set,seed set and seed germination in ‘Sonia’ × ‘Hadley’ hybrid Tea-rose crosses

Summary The effect of temperature on fruit set, seed set and seed germination was studied in Sonia × Hadley Hybrid Tea-rose crosses. Sonia mother bushes were grown at constant temperatures (10, 14, 18, 22, 26°C) in the greenhouses of the phytotron until fruit ripening. Fruit set, fruit weight and number of seeds increased as temperature was higher. Optimum temperatures were found for days to fruit ripening (18°C), seed germination (22°C) and number of seedlings per pollinated flower (22°C). Fruit weight and number of seeds were positively correlated. For crossing and the subsequent growing of seed-bearing plants 22°C was the most favourable temperature. Effects of temperature on pollen tube growth, fertilization and seed germination are discussed.     

Cytoplasmic-genetic male sterility in radish (Raphanus sativus L.). Identification of maintainers,inheritance of male sterility and effect of environmental factors

Summary Research has been carried out on identification of maintainers for cytoplasmic-genetic male sterile lines in Japanese and European radish, on the mode of inheritance of male sterility and on the effect of environmental factors on the expression of this character.In a Japanese radish population and in most early European radish populations maintainers were found in high frequency. Segregations for male sterility in full-sib families, obtained by crossing male sterile and male fertile plants, and in backcross generations, indicated that male sterility is probably determined by one dominant and two recessive independently acting genes, but also minor genes may be involved.The expression of male sterility was not affected by seasonal influences. In some populations a reversible temperature effect was found, most ms plants occurred at 10, 14 and 26°C and most mf plants at 17 and 20°C.     

The effect of temperature during growth and flowering on the seed set of tetraploid freesia

Summary Phytotron experiments have been carried out to study the effect of different temperatures on the seed set of tetraploid freesias during the raising of the plants and at the time of flowering and pollination.The effect of a relatively low temperature during the growth period is reflected in a comperatively greater number of flowers as a result of an increase in number of ramifications of the peduncle. This sometimes promotes the seed yield notwithstanding that the lower temperature reduces the fertility of each seperate flower. It is clearly proved that the temperature during flowering and pollination affects the fertility of the flower and the ultimate seed yield of the plant. Experiments in our phytotron showed 14°C during the growth period and 20°C at the time of pollination to be the optimum combination for a good seed yield.The effect of a lower night temperature was generally favourable, particularly so when measured by the number of seeds per pollinated flower.     

The effect of temperature on seed set and embryo development in reciprocal crosses of wheat and barley

Summary The effect of temperature on seed set and embryo development in reciprocal crosses of barley and wheat was assessed in crosses involving two spring barley varieties (Betzes, Martonvásári 50) and one wheat variety (Chinese Spring). Detached tillers placed in nutrient solution were pollinated in controlled environments at constant day-night temperature regimes (12, 15, 18 and 21° C) with a light intensity of 30,000 lux and a relative humidity of 80%. When barley was used as the female, lower temperatures (12 and 15° C) produced the maximum seed set, whereas for the reciprocal cross, the highest temperature (21° C) produced the best seed set in the Chinese Spring × Betzes combination.Low temperature retarded the embryo development. The highest numbers of hybrid plants were produced at 18° C and 21° C in the barley × wheat cross and in the wheat × barley cross, respectively. Embryos of about 1.5 mm length in the barley × wheat cross, and of about 1.0 mm length in the wheat × barley cross germinated successfully. The smallest embryo giving rise to hybrid plants was 0.57 mm in the barley × wheat cross and 0.51 mm in the wheat × barley cross.     

Some causes of poor fruit set in Jucunda strawberries

Summary A study was made of the possible causes of poor fruit set occurring in the strawberry variety Jucunda. In experiments in which plants were exposed to different constant temperatures from the beginning of flowering it was found that fruit set in Jucunda was normal at temperatures of 17°C and higher, but decreased rapidly at lower temperatures to a very low level at 10°C. In other experiments, in which in each case the temperature treatments were started a different number of days before the begining of flowering, fruit set was always lower than in the experiments mentioned above, but here too the unfavourable effect of lower temperatures was quite distinct. The experimental results indicate that poor fruit set is Jucunda results from inadequate pollen production and that it will occur if temperatures during the period of flowering are below 17°C, and possibly also if temperatures at some time before flowering are higher than the normal temperatures prevailing in the field during that period.Fruit set in the variety Juspa which originated from a cross between Jucunda and the American variety Sparkle, showed sensitivity to temperatures before and during flowering which was identical, if less pronounced, with that of Jucunda. Thus it was confirmed that poor fruit set in Jucunda can be passed on to its progeny. The results of these experiments indicate under which conditions selection against poor fruit set can be effectively carried out in progenies derived from Jucunda.     

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.     

A non-destructive selection method for faster growth at suboptimal temperature in common bean (Phaseolus vulgaris)

Summary A non-destructive method has been developed to select common bean (Phaseolus vulgaris L.) plants whose growth is less effected at a suboptimal temperature. Shoot weight was determined at a suboptimal (14°C) and optimal temperature (20°C), 38 days after sowing and accessions identified with a significantly lower than average weight reduction at 14°C compared to their weight at 20°C. Weight of primary leaves and of the shoot was correlated with seed weight at both temperatures, but no correlation was found between shoot weight reduction at 14°C and seed weight.     

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.     

Inactivation of self-incompatibility following temperature pretreatments of styles in Lilium longiflorum

Incompatible (self) pollen tube growth in styles of six cultivars of L. longiflorum is strikingly influenced by treatment of the styles for six minutes in 50°C distilled water prior to pollination. In pretreated detached styles the incompatible pollen tubes reach lengths normally attained by compatible pollen whereas in untreated styles they grow to only approximately two-thirds the length normally reached by compatible tubes. Pretreatment at either 25°C or 45°C for six minutes does not affect incompatible pollen tube growth. Both compatible and incompatible tubes grow only a few millimeters into styles treated at 55°C for six minutes. Stigmatoid cells in these styles appear necrotic. Pretreatment of attached styles at 50°C for six minutes resulted in fruit set following self-pollination. Seed number per capsule ranged from 6 to 114. Stylar pretreatment appears to be a highly promising approach to further investigation concerning the nature of the self-incompatibility reaction. It also appears to offer a suitable means of obtaining seed from self-incompatible plants.Paper No. 1096 from the Laboratory of Genetics, University of Wisconsin. Supported in part by a grant from the National Science Foundation.     

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.     

Effects of temperature pre-treatments on the forcing of strawberry plants (cv. Glasa)

The results of an experiment, designed to study the effects of certain temperature treatments during the autumn season on the subsequent development of strawberries (cv. Glasa) during forcing, have been presented in this paper. This study was under-taken in the interest of both breeding new varieties suitable for forcing and improving the present forcing methods.Practical experience has shown that the chance of success is small when forcing is started before the 15th of January.In a recent publication it has been suggested to provide plants with strong artificial light for assimilation, which would make it possible to start forcing at an earlier date.In the present experiment, however, in which forcing was started as early as the 5th of January, good results were obtained under ordinary light conditions by previously exposing the plants to 12°C for three weeks in November. The pre-treated plants showed earlier flowring and fruiting, better fruit set and a higher yield than the control plants.These observations indicate that in order to obtain satisfactory results the inflorescences must have attained a certain stage of development at the beginning of forcing, and that this stage was reached at an earlier date by the accelerating effect of the temperature treatment.     

Exogenous Application of Abscisic Acid Improves Cold Tolerance in Chickpea (Cicer arietinum L.)

Chickpea suffers cold stress (<10 °C) damage especially during reproductive phase resulting in the abortion of flowers and pods, poor pod set, and reduction in seed yield and seed quality. One of the ways in modifying cold tolerance involves exogenous treatment of the plants with chemicals having established role in cold tolerance. In the present study, the chickpea plants growing under optimum temperature conditions (28/12 °C, as average maximum and minimum temperature) were subjected to cold conditions of the field (10–12/2–4 °C; day/night as average maximum and minimum temperature) at the bud stage. Prior to exposure, these plants were treated exogenously with 10 μm abscisic acid (ABA) and thereafter again after 1 week of exposure. The stress injury measured in terms of increase in electrolyte leakage, decrease in 2,3,5-triphenyl tetrazolium chloride reduction %, relative leaf water content and chlorophyll content was observed to be significantly mitigated in ABA-applied plants. A greater pollen viability, pollen germination, flower retention and pod set were noticed in ABA-treated plants compared with stressed plants. The seed yield showed considerable improvement in the plants treated with ABA relative to the stressed plants that was attributed to the increase in seed weight, greater number of single seeded pods and reduction in number of infertile pods. The oxidative damage measured as thiobarbituric acid-reactive substances was lesser in ABA-treated plants that was associated with greater activities of superoxide dismutase, catalase, ascorbate peroxidase, ascorbic acid, glutathione and proline in these plants. It was concluded that cold stress effects were partly overcome by ABA treatment because of the improvement in water status of the leaves as well as the reduction in oxidative damage.     

文冠果种子产量影响因素分析

作为木本能源植物,文冠果的种子产量问题是制约其大力开发利用的主要因素。通过观测357个单株树形树势、叶片性状、果实性状、种子性状、产量相关性状、含油率等方面共26个性状,进行相关、多元回归和通径分析,找出影响其产量的主要因素。结果表明：产量与地径、冠幅、叶长、叶面积、果长、果宽、每果种子数、果实鲜重、结果个数呈极显著正相关,与果皮厚、心皮数、种长、种宽、百果重显著正相关,与枝下高呈极显著负相关。果实鲜重、出籽率、结果个数、每果种子数、种宽是影响单株种子产量的主要因素。果实鲜重、结果个数和出籽率对种子产量的贡献较大,是选择高产单株的主要选择性状。     

‘Thermally aided pollination’: A new method of breaking self-incompatibility in Brassica oleracea L.

Summary Application of heat during self-pollination of open flowers by means of an electric mini soldering iron resulted in seed set in self-incompatible Brassica oleracea varieties. Temperatures of 60, 70 and 80°C were tested. Compared with bud-pollination, in some cases the so-called thermally aided pollination (TAP) method, gave a considerably higher seed yield at 70 and 80°C. In view of the ease and rapidity of TAP it should be ascertained how far this method can replace bud-pollination in maintaining inbred lines. The possible mechanism behind the TAP response is briefly discussed.     

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.     

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).     

Relations between biomass maintenance of potato clones and the growth and yield of their progeny seedlings at low temperatures

Summary The main purpose of the research reported in this article was to see if the biomass maintenance of parental potato clones was correlated with the growth and yield of their progeny. Seedling populations with parents of European and of Andean origin were cultivated at a temperature of 10°C during the day and 4°C at night. The biomass maintenance of the parents was defined as the ratio between the total biomass yield at 20°C day/10°C night and the total biomass yield at 10° C day/4°C night. The Andean parents had good maintenance ability at the lower regime compared to the Eurpean parents.Biomass maintenance appears to be hereditary. Significant correlation was found between the dry matter maintenance of the parents and the growth rate of seedlings, especially during the second month after potting. In populations with only Andean or only European parents, differences in height increase and leaf formation rate between seedling populations were correlated to the dry matter maintenance of the parents cultivated at the temperature regime 10/4°C. In the hybrid population between an Andean and an European parent only differences in height increase during the second month after potting correlated well to the average dry matter maintenance of the parents. It appears therefore that the rate of height increase during the second month after potting can be used as a criterion for selection.     

Impact of High Night‐Time and High Daytime Temperature Stress on Winter Wheat

High temperature is a major environmental factor that limits wheat (Triticum aestivum L.) productivity. Climate models predict greater increases in night‐time temperature than in daytime temperature. The objective of this research was to compare the effects of high daytime and high night‐time temperatures during anthesis on physiological (chlorophyll fluorescence, chlorophyll concentration, leaf level photosynthesis, and membrane damage), biochemical (reactive oxygen species (ROS) concentration and antioxidant capacity in leaves), growth and yield traits of wheat genotypes. Winter wheat genotypes (Ventnor and Karl 92) were grown at optimum temperatures (25/15 °C, maximum/minimum) until the onset of anthesis. Thereafter, plants were exposed to high night‐time (HN, 25/24 °C), high daytime (HD, 35/15 °C), high daytime and night‐time (HDN, 35/24 °C) or optimum temperatures for 7 days. Compared with optimum temperature, HN, HD and HDN increased ROS concentration and membrane damage and decreased antioxidant capacity, photochemical efficiency, leaf level photosynthesis, seed set, grain number and grain yield per spike. Impact of HN and HD was similar on all traits. Greater impact on seed set, grain number and grain yield per spike was observed at HDN compared with HN and HD. These results suggest that HN and HD during anthesis cause damage of a similar magnitude to winter wheat.     

Problems in breeding the legume Indigofera spicata for tropical pastures

A survey of I. spicata introductions showed the majority to be tetraploid perennials and similar to each other with red stems, strongly stoloniferous habit, and poor seeding ability. The rest were green stemmed annuals or biennials which were either diploid or tetraploid and which were free seeding and almost non-stoloniferous.Crosses were attempted using several green stemmed introductions as the female parents with a representative red stemmed one as the male. The ploidy of a diploid parent was raised with colchicine treatment before crossing. F₁ seed was obtained in all crosses except in that involving the induced tetraploid. The F₁ generations were sterile except for one cross from which a small quantity of F₂ seed was obtained. A high degree of sterility was maintained in the F₂ and F₃ generations but fertile F₃ selections produced mostly fertile progeny. The sterility could be followed by the percentage stained pollen and appeared to be controlled by genetic factors.Normal types of distribution of the phenotypic classes for yield and stoloniferous development were obtained for the F₃ population which contained 26.3 per cent perennial plants. Two F₃ lines were obtained which combined the desirable characters of the two parents.The effect of temperature and photoperiod on all introductions used as parents and the two promising lines was investigated in a phytotron. All types flowered at both the 8 hour and 16 hour photoperiods and temperatures 27°/22°C and 30°/25°C favoured flowering. The better flowering of the green stemmed parent had apparently been transferred to the selected F₃ lines. The highest plant dry weights occurred at 30°/25°C and the effect of photoperiod on yield was reversed as the temperature increased.