Influence of the temperature on runner production in five strawberry varieties

Summary The object of the present experiments was to ascertain whether there are differences in runner production between the strawberry varieties Deutsch Evern, Oberschlesien, Auchincruive Climax, Jucunda and Madame Moutot. To this end runner plants of these varieties were grown at 4 constant temperatures, viz. 17°, 20°, 23° and 26°C, in a natural day.It was found that runners were produced at all 4 temperatures. However, there were differences between the varieties in the number of runners produced.As the temperature became higher the number of runners increased, except in the variety Madame Moutot, which has a lower optimum temperature for runner production than the other varieties tested.Both the degree and duration of runner production were affected by temperature.     

Problems of heat spot in fragaria vesca L. when indexing strawberry selections for viruses

Summary In view of the available labour the testing of strawberry selections for viruses by runner grafting is carried out in autumn and winter. In order to obtain sufficient runners on the test plants these tests were carried out at a constant temperature of 23°C. At this temperature, however, the indicator plants (Fragaria vesca) developed heat spot. The symptoms are reminiscent of virus-infection, which makes it difficult to decide whether the test plant carries a virus or not.It was found that heat spot symptoms became less distinct at a constant temperature of 17°C, and were absent on newly developed leaves. Consequently the indicator plants were transferred to 17°C after 2 successful unions had been obtained at 23°C. In this way it was possible to obtain a reliable impression of the state of health of the test plant.     

Introgression of unique characteristics of floral initiation under 24 hour day-length of Fragaria chiloensis ‘CHI-24-1’ into F. × ananassa

A unique flower initiation of the wild Junebearing strawberry strain ‘CHI-24-1’ in Fragaria chiloensis occurs under 24 h DL and high temperature conditions. To introduce the floral initiation characteristics of ‘CHI-24-1’ into cultivated strawberries of F. × ananassa, a cross pollination was conducted between ‘CHI-24-1’ and the Japanese short-day type strawberry cultivar ‘Nyoho’. The floral initiation of ‘CHI-24-1’ was induced in both parent and daughter plants linked with runners under a 24 h DL and 23/20 ^∘C, but not 8 and 16 h DLs at the same temperatures. Of the 21 F1 hybrids grown under the 24 h DL, 12 showed flower truss production in the parent and/or daughter plants linked with runners. Among 64 F1 hybrids, 26 exposed to 8, 16 and 24 h DLs for 30 days produced no flower trusses. However, 32, one and five F1 hybrids produced flower trusses under the 24 h DL alone, 8 h DL alone and both the 8 and 24 h DLs, respectively. The results of the experiments indicated that none of the F1 hybrids were day-neutral plants, but approximately 60% had the characteristics of floral initiation under 24 h DL, which was inherited from the pollen parent of ‘CHI-24-1’. The importance of the unique floral initiation characteristics under 24 h DL with high temperature for strawberry breeding was discussed.     

Runner formation on strawberry plants in autumn and winter

Summary In order to test strawberry selections for viruses, for which runners are necessary, the second writer tried, in connection with experiments carried out by Borthwick and Parker (1), to produce runners in the autumn and winter of 1952–53 by interrupting the dark period, however, without any result. Experiments carried out in 1953–54 have shown that too low a temperature was the cause of this failure, for runner formation in autumn and winter is dependent not only on day length but also on temperature.In the course of our 1953–54 experiments we found that in 1937 Darrow (2) had already made mention of the interrelation of temperature and day length in runner formation. However, it is not likely that sufficient runner formation would have taken place, had we applied his findings.     

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.     

Effect of temperature on the occurrence of male sterility in onion (Allium cepa L.)

Summary Experiments were made to ascertain whether sex expression in the onion depends on temperature.Some populations were found to be largely male sterile at about 14°C and much less so at 20°–23°C. In other populations this phenomenon did not occur. Besides all the fertile populations produced less and worse pollen at 14°C.The first-mentioned temperature influence may be an essential factor in searching for an explanation for the partially male sterile plants found by various research workers, and for the unexpected segregations for male sterility when A-, B- and C-lines are propagated.     

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.     

Resistance to a single UK isolate ofColletotrichum acutatum in strawberry germplasm from Northern Europe

Summary Colletotrichum acutatum on strawberry was first introduced to the UK on runners of cultivar Brighton, which were imported from California in 1983. Recently further outbreaks have been reported following the importation of infected runner plants from mainland Europe. Phytosanitary precautions have so far been successful in controlling the disease but the current trend in the UK is for increasing late season production. This increases the likelihood of there being fruiting plants when the environmental conditions are favourable toC. acutatum. Fifteen cultivars and 19 HRI breeding lines were tested for susceptibility toC. acutatum using the most pathogenic isolate found on plants imported into the UK. It is likely this isolate was originally of Californian origin. Potted plants were spray inoculated and subsequently rated in the glasshouse using a disease severity rating (DSR) with the range from 0–4, where a rating of 4 indicated severe disease symptoms. In contrast to results from California and Italy standard deviations were variable and often large and consequently it was considered unsafe to classify the susceptibility of the genotypes on the basis of mean DSR alone. Classification was thus based on a combination of the mean value and the distribution of the scores but in some cases the results were inconclusive. It was possible to classify five lines as having a high level of resistance (Elvira, Honeoye, EM99, EM224, EM255); six lines had a useful level of resistance but did show symptoms on some plants (Cambridge Favourite, Gorella, Pandora, Pantagruella, EM17 and EM290); five lines were highly susceptible (Elsanta, Redgauntlet, Tamella, EM237 and EM319). The remaining 18 lines could not be classified with the same degree of certainty but 10 were probably resistant.     

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.     

60Co-γ射线对草莓匍匐茎植株辐照效应

采用3种不同剂量的60Co-γ射线辐照5个草莓品种的匍匐茎植株,对辐照引起的致死、损伤和生长抑制效应以及新的匍匐茎发生情况进行了研究。结果表明,经30-80Gy剂量的60Co-γ射线辐照处理后,5个草莓品种的匍匐茎植株均有死亡,死亡率在22-88.7%,且各品种的死亡率均有随着剂量增加而提高的趋势,但不同品种的死亡率随剂量变化的具体表现不同;植株叶片均有畸型现象发生;植株叶片长度、叶片宽度、植株高度和植株冠径的变化因品种和辐照剂量而异;匍匐茎发生率和匍匐茎数量显著下降。不同草莓品种对60Co-γ射线的辐射敏感性不同,“章姬”最敏感,“宝交早生”、“春旭”、“圣星”次之,“硕丰”最不敏感。章姬的辐照半致死剂量应在30Gy和50Gy之间,宝交早生、春旭和圣星的辐照半致死剂量应在50Gy和80Gy之间,而硕丰的辐照半致死剂量应在80Gy以上。     

Analysis of differences in growth of cucumber genotypes under low light conditions in relation to night temperature

Summary Growth of four breeding lines and two cultivars of slicing cucumber with different growth at low temperature and light intensity was analysed in relation to night temperature. Plants were grown from 17 days after sowing at 20°C day temperature and 20, 15 or 10°C night temperature (NT), a light intensity of 24 W/m² visible radiation and a daylength of 8 hours. Data from six successive harvests, ending 47 days after sowing, were analysed according to a MANOVA procedure.RGR, NAR, LAR, SLA and LWR generally decreased with time. Ln W and RGR were largely similar at 20 and 15°C NT, but reduced at 10°C NT. LAR and SLA decreased at each lower NT, whereas LWR increased. NAR was only marginally affected by NT. Significant genotypic differences occurred for 1n W, LAR, SLA, LWR, stem length and percentage of dry matter in leaves and stems at all NT's and for RGR and NAR only at 20°C. Genotypic differences for 1n W could not be explained by differences for RGR, but by differences for initial plant weight.Significant genotype × night temperature interactions were present for LWR. Breeding lines increased LWR in response to lower NT, while that of cultivars remained fairly constant. Implications for breeding are discussed.Abbreviations and definitions L plant length - LA leaf area - W dry weight of the shoot - RGR relative growth rate (the increase in W per unit of time and unit of W) - NAR net assimilation rate (the increase in W per unit of time and unit of LA) - LAR leaf area ratio (the leaf area at time t per unit of W) - SLA specific leaf area (the leaf area at time t per unit of leaf weight) - LWR leaf weight ratio (the leaf weight at time t per unit of W) - RGR NAR × LAR - LAR SLA × LWR - MANOVA multivariate analysis of variance     

The effect of alternating temperatures on the self-incompatibility of some clones of Brussels sprouts (Brassica oleracea L. var. Gemmifera (DC.) Schulz)

Summary The influence of temperature on self-incompatibility of six S-homozygous clones of Brussels sprouts was studied. The clones were treated with constant temperatures of 14°, 17° and 20°C and alternating day and night temperatures of 17/14°, 20/14°, 23/14° and 26/14°C. To determine the degree of incompatibility the mean number of pollen tubes per style after selfing was calculated.The clone with the weak S-allele S-5 was less self-incompatible in the 23/14° and 26/14°C treatments than in the other treatments. The other clones with the weak S-alleles S-15 and S-45 remained sufficiently self-incompatible during all treatments. The clone with the rather strong S-39 showed the highest level of self-incompatibility at 26/14°C.In the two weakly self-incompatible clones with S-5 and S-39 a clear difference in self-incompatibility was found between young and old flowers. The strongly SI clones with S-39 showed no difference and in the two clones with S-15 the differences were small and significant in one case only.     

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.     

Influence of suboptimal temperature on biomass production of potato populations of Andean and European origin

Summary Plants grown from seed derived by crossing conventional European S. tuberosum material were compared with plants grown from seed derived by crossing S. tuberosum with various, Andean frost resistant tuberbearing Solanum species. Biomass growth at optimal (20°/10°) and suboptimal (10°/4°) temperatures was studied.Differences in increase of fresh and dry matter were found between populations of Andean and European orgins at 10°/4°. At 20°/10° no such differences were found.At suboptimal temperature, Andean hybrids produced significantly more fresh and dry matter than European crosses in two harvests (64 and 178 days old plants). Statistically, Andean hybrids were found to produce the same amount of dry matter per day at both temperatures, over the complete growth period.Height increase and flower development were strongly depressed in European crosses under the suboptimal temperatures, but much less so in Andean crosses.The Andean material appears to be an under utilized resource in potato breeding for cool climates.     

Inheritance of net photosynthesis,dark respiration,stomatal resistance and related characters in tomato (Lycopersicon esculentum Mill.) under low energy conditions

Summary Inheritance of net photosynthesis, dark respiration, specific leaf fresh weight, and stomatal resistance was studied in a diallel cross without reciprocals with 15 tomato genotypes. The plants were grown under low light intensity (24 Wm^-2), short days (8 h) and low temperature (19 °C/10 °C day/night temperature). Significant f-values for GCA were observed for all characters. Smaller, but for most characters also significant f-values for SCA were found. This indicated that the characters were mainly controlled by additive gene action. The relationships between the physiological characters and breeding aspects are discussed.     

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.     

Production and performance of potato mini-tubers

Summary Production of mini-tubers as a source for seed potato was investigated by growing in soil micropropagated plants and micro-tubers produced from micropropagated plants. Cultures of several cultivars were initiated from indexed tubers and multiplied on modified MS medium. Cultures were micropropagated by using a modular system which allowed batch handling. Micropropagated plants produced mini-tubers in glasshouse after 70–115 days of growth in soil. A large proportion of the mini-tubers produced were between 9 and 15 mm diameter. Several factors, e.g., explant number, duration of in vitro culture and genotype influenced mini-tubers production. Micropropagated plants after culture of 86 days or longer produced micro-tubers ca. 2 to 10 mm diameter. Plants, which formed micro-tubers in vitro, produced less number of mini-tubers in soil. Micro-tubers produced 1 to 3 mini-tubers when grown in soil in chain-type paper pots, but produced conventional sized tubers when grown in soil under plastic polytunnel. Mini-tuber number varied widely between potato cultivars; cvs. Bintje and British Queen produced more mini-tubers than the other cultivars. Mini-tubers developed green hard skins when kept in light for 3 weeks, and could be stored in dark at 4° C upto 6 months. In a field trial, small mini-tubers ca. 5–10 mm diameter produced more but smaller tubers than mini-tubers ca. 15–20 mm diameter. The micropropagated plants and the plants grown from mini-tubers were genetically stable, and did not show any morphological aberrations except for one variegated plant among the several thousand produced. It is concluded that the production of mini-tubers by soil planting of micropropagated plants is a rapid and efficient method for producing seed potato tubers.The use of any trade mark and other commercial products mentioned in this paper does not constitute any recommendation or advertisement for such products on behalf of the Agriculture and Food Development Authority, Dublin, Ireland     

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.     

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.     

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.