Storage of avocado pollen

Summary Avocado pollen was stored at a range of temperatures and relative humidities (RH) for up to one year and the pollen was tested for viability in vivo.Pollen stored for one month was capable of germination on the stigma and penetrating the ovule when stored at 4°C with <1,23,55 and 75% r.h. and at -196°C with 0% r.h. Most pollen samples stored at 25 and -15°C at a range of r.h. would germinate on the stigma but none would penetrate the ovule.After one year of storage, pollen at 4°C and <1 and 23% r.h. would germinate on the stigma but would not penetrate the ovule. There was no germination of pollen stored at 4°C and 55 and 75% r.h. Only pollen stored at -196°C and 0% r.h. would penetrate the ovule, but thawing and refreezing once during the year destroyed the viability.     

Benzyladenine induces foliar adventitious shoot formation on young plants of two sugarbeet (Beta vulgaris L.) cultivars

Summary Benzyladenine (BA) at concentrations from 33–2000 mg/l caused development of adventitious shoots on subsequent leaves of sugarbeet plants when sprayed once onto cotyledon-stage seedlings. Cultivar EL44 produced more adventitious shoots and greater fresh weight reduction in response to BA treatment than cultivar EL40. Related anomalies caused by BA included dissected leaves, and bumps and rods on petioles.     

Cryopreservation of pollen from two rose cultivars

Summary An investigation was undertaken on the storage characteristics of pollen collected from two English rose cultivars. A rapid decline in viability was observed in pollen stored at +4° C and –20° C, whereas the viability of pollen, stored at ultra-low temperature (–196° C), remained constant. Cryopreserved pollen was shown to retain its ability for fertilisation. The effects of the stage of flower development and anther dehiscence were assessed on both pre-and post-cryopreservation viabilities. Successful long-term storage of pollen will facilitate hybridisation of rose species and cultivars that do not flower synchronously.     

Breeding for tolerance to beet-cyst eelworm Heterodera schachtii Schm. in sugarbeet

Summary Successive mass selections were made in sugarbeet varieties (Beta vulgaris L.) and in B. vulgaris × B. maritima L. hybrids for tolerance to wilting caused by beet-cyst eelworm attack. The selected lines showed improved tolerance to wilting, but no evidence of resistance to eelworm infection was demonstrated. By repeated back-crossing of the selected lines with the commercial varieties and concurrent selection root yield could be improved without substantially decreasing the tolerance to eelworm attack. These results indicate that tolerance is partly conditioned by complete and incomplete dominant genes.     

Polyploid and maternal effects on Rhizoctonia root rot resistance in sugarbeet

Summary Three sugarbeet breeding lines partially resistant to the root-rotting fungus, Rhizoctonia solani, were converted to the tetraploid condition without selection. These three diploid and tetraploid lines were crossed with three diploid male-sterile lines to produce equivalent diploid and triploid hybrids. The triploid hybrids were significantly more resistant to Rhizoctonia than were the diploid hybrids. However, the tetraploid resistant limes were no different than their diploid equivalent lines. Reciprocal crosses provided no evidence of maternal effect on resistance. Cytoplasm that included the male-sterility factor had no influence on resistance. Triploid hybrids, where the resistant parent is tetraploid, should be advantageous in the breeding of rhizoctonia-resistant hybrid varieties.Joint contribution of the Agricultural Research Service, U.S. Department of Agriculture, the Colorado State University Experiment Station, and the Beet Sugar Development Foundation. Published with the approval of the Director of the Colorado State University Experiment Station as Scientific Paper Series No. 2072.     

Viability and storage of bromeliad pollen

Several bromeliad species from two different subfamilies, were used to develop a reliable method to evaluate pollen viability. Pollen germination on a medium containing 20% sucrose, 0.001%H₃BO₃ and 0.5% agar was comparable to germination on a compatible stigma. Maximum germination was reached within 2 to 10 hours depending on the species. Based on this test, six species were considered as being good pollen donors with germination percentages between 49%and 83%. Furthermore, pollen from these species and cultivars could be stored in liquid nitrogen (–196 ^°C) without a considerable loss of viability. For all species, a dehydration period of 4 hours prior to cryopreservation and a rehydration period of 1 hour after cryostorage were essential. Greenhouse humidity influenced anther moisture content and cryostorability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Linkage maps for nine isozyme and four marker loci in sugarbeet (Beta vulgaris L.)

Summary An analysis of linkage in sugarbeet (Beta vulgaris L.) was conducted for nine isozyme loci, Ak ₁, Gdh ₂, Idh ₁, Lap, Mdh ₁, Mdh ₃, Pgi ₂, Pgm ₁,and Skdh ₂,and four marker loci, annuality (B), red hypocotyl-color (R), pollen fertility restorer (X), and monogermity (m). Four linkage groups were identified; R-B-Idh ₁, Gdh ₂-Mdh ₁, Ak ₁ -Lap, and Mdh ₃-Pgm ₁.In addition, X was linked to Mdh ₁and Skdh ₂with a recombination value of 13.4% and 34.7%, respectively, and m was linked to Pgm ₁with a recombination value of 35.8%. Pgi ₂was inherited independently of the four linkage groups. This locus showed a skewed ratio in F₂ progeny of a cross between self-compatible and self-incompatible lines and the allele derived from self-incompatible parents decreased markedly. On the other hand, the expected segregation ratio was observed in the backcrossed progeny and also in F₂ progeny of a cross between self-compatible lines. The results obtained suggest that Pgi ₂may be linked to a self-compatibility locus (S ^f)and the two loci may be assigned to an additional linkage group.     

Long-term storage of Narcissus anthers and pollen in liquid nitrogen

Summary Three methods for the long-term storage of narcissus pollen were compared; anthers in glass vials held in a desiccator with calcium chloride at 2°C, and polypropylene straws containing either anthers or naked pollen immersed in liquid nitrogen. Pollen from all storage treatments showed 15–16% germination in vitro after 3 days, compared with 27.4% for fresh pollen. Seed set per pod using pollen stored for 3 days was comparable to that of fresh pollen. However, after 351 days, pollen from anthers at 2°C exhibited only 0.1% germination and failed to set seed whereas no further change in germination rate was recorded for pollen from the two liquid nitrogen treatments and seed set was still equivalent to fresh pollen.     

Partial resistance of sugarbeet to beet cyst eelworm (Heterodera schachtii Schm.)

Summary Within Beta vulgaris and B. maritima origins some partial resistance to beet cyst eelworm was found which could be raised to a very limited extent by selection. However after the second backcross to commercial sugar beet varieties and successive selection of the inbreds this resistance was lost. It was demonstrated that in the rootsystem of resistant plants as much nematodes penetrate and develop as in susceptible ones but the ratio between males and females is different. It was therefore quite probable that this resistance is polyfactorial and merely recessive.     

Cryopreservation of English walnut (Juglans regia L.) pollen

Summary Pollen from eight clones of English walnut (Juglans regia L.) was stored in liquid nitrogen (LN₂) at-196°C for one year. Pollen was monitored for percent germination in vitro before being frozen. Pollen was frozen within two hours of anther dehiscence and subsequently at 24 hr intervals until germination assays indicated that the ability to germinate was lost. Survival after one year was evaluated by determining percent germination in vitro. Freshly collected pollen of only five of the eight clones survived LN₂. By contrast, when the same pollen was held for 24 and 72 hr before freezing, pollen of all eight clones survived. Survival is correlated with moisture content (MC) of the pollen. Pollen samples with MC greater than 7.5% were killed by freezing in LN₂. All pollen samples with MC between 4 and 7.5% survived as did most of the samples with MC between 3.2 and 4%.     

Storage of broccoli pollen in liquid nitrogen

Summary Broccoli pollen which had been stored in liquid nitrogen retained its viability, but seed produced using this pollen rapidly lost its germinability. Plants raised from this seed, and their progenies, gave no indication of genetic damage resulting from the low temperature treatment of pollen.     

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.     

Dehydration accelerates respiration in postharvest sugarbeet roots

Sugarbeet (Beta vulgaris L.) roots lose water during storage and often become severely dehydrated after prolonged storage and at the outer regions of storage piles which have greater wind and sun exposure. Sucrose loss is known to be elevated in dehydrated roots, although the metabolic processes responsible for this loss are unknown. To identify processes that contribute to sucrose loss in dehydrated roots, respiration rate, cellular electrolyte leakage, and sucrolytic enzyme activities were determined in roots of two varieties (VDH 66156 and Beta 4797R) during 4 weeks of 10 °C storage at high (85%) and low (40%) relative humidities. Roots stored at 40% relative humidity dehydrated significantly and lost almost 50% of their weight after 4 weeks of storage. Electrolyte leakage increased in these roots, indicating that dehydration damaged cellular membranes. Respiration rate generally increased in roots stored at 40% relative humidity compared to roots stored at 85% relative humidity. The increase in respiration rate was positively correlated with root weight loss and electrolyte leakage. Respiration rate was most closely associated with electrolyte leakage, however, suggesting that elevations in respiration rate were not due to dehydration, but to the membrane damage that occurred in response to dehydration. Activities of the sucrose-degrading enzymes, sucrose synthase, alkaline invertase and soluble acid invertase, were unaltered by dehydration. Alterations in sucrolytic enzyme activities, therefore, were not needed to provide for the increased demand for respiratory substrates in dehydrated roots. These results suggest that storage at low relative humidity alters the postharvest physiology of sugarbeet roots by increasing the rate of weight loss, reducing membrane integrity, and accelerating root respiration rate.     

Storage of maize (Zea mays L.) pollen at −196°C in liquid nitrogen

Summary The water content of pollen has a decisive influence on its storability in liquid nitrogen. Pollen with an initial high water content cannot be stored successfully at extremely low temperatures, so a certain degree of drying must be carried out before storage. Provided the viability of the pollen is not significantly reduced during drying, the pollen remains viable and fertile when kept at –196°C.     

Freeze preservation of gladiolus pollen

Viability and fertility profiles of cryopreserved gladiolus pollen from 7 cultivars have shown that it is possible to use cryogenic methods for conservation and management of the haploid gene pool in this species. There was no decline in pollen viability (in vitro) levels after 1 and 10 years of cryogenic storage. Field pollinations with cryogenic stored pollen induced capsule and seed set in varying capacities. Long-term cryogenic storage of gladiolus pollen could enhance breeding efficiency through better management of the haploid gene pool resources. Pollen parents could be made available throughout the breeding programme, ensuring guaranteed supply at the time of peak stigma receptivity. A pollen cryobank facility established for this species would increase genetic diversity conservation at the haploid stage.IIHR Contribution No. 112/93     

Hybrid Tea-rose pollen. I. Germination and storage

Summary Germination and storage trials were carried out with pollen of several rose varieties. The pollen grains germinated well in a 15% sucrose solution with 40 ppm boric acid. Staining the pollen with a 0.1% tetrazolium solution and standardizing the degree of colour at which the pollen grains are counted as viable, provided a good viability estimate, simpler to carry out than in vitro germination. Germination capacity and staining ability of the pollen were greatly impeded-about halved-by dehydration during storage in desiccators at low humidity. This effect could be corrected by humidifying the pollen beforehand for about one hour, though this pre-treatment increased the percentage of germinated pollen grains more than the percentage stained. There was no difference between the two percentages in fresh or in deep-frozen pollen.Pollen stored at 1°C and high relative humidity soon lost its germination capacity: between 0 and 20% humidity a considerable proportion of the pollen remained viable for 9 months and longer. Storage for the same period in vacuum-sealed glass tubes at –24°C maintained viability as well or better and would probably prolong it further. Some of the cold-stored pollen induced a reasonable seed set after one year, a low seed set was obtained even after two years of storage at 1°C and low humidity.     

Resistance to Heterodera schachtii in patellares section of the genus Beta

Summary Fifty-two accessions of the section Patellares wild beet (including 26 Beta patellaris Moq., 13 B. procumbens Chr. Sm and 13 B. webbiana Moq.) and 14 progeny families were selected and tested against sugarbeet cyst nematode, Heterodera schachtii Schm. All Patellares species tested were highly resistant, but not immune, to the development of H. schachtii, after infection. This is the first report that mature female nematodes developed in the roots of B. webbiana plants. The occasional development of nematode cysts in roots of juvenile wild beets was, however, not a heritable genetic factor.Mention of a trademark, vendor, or proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Genetic and environmental effects on chromosome doubling of sugarbeet (Beta vulgaris L.) haploids

Summary Chromosome doubling has been a limiting factor for production of doubled-haploids, a means of obtaining fruly homozygous individuals, and a time-saving alternative to repeated selfing for the creation of inbred lines. The existence of genetic, environmental and genotype × environment interaction effects on chromosome doubling ability of sugarbeet (Beta vulgaris L.) haploids was investigated. Haploids were derived from four distinct, highly heterozygous diploid populations through in vitro culture of unpollinated ovules. Ovule-derived plants were treated with colchicine to double their chromosome complement. Environmental effects were determined from replication of the experiment at seven dates. Both genetic and environmental factors were found to affect chromosome doubling ability of sugarbeet haploids. No significant interaction between genotype and environment was identified. The presence of genetic effects on chromosome doubling ability is discussed with regard to its implications on breeding programs.     

Cryopreservation of Delphinium pollen at –30 °C

Pollen of garden varieties and species of Delphinium that was cryopreserved at –30 ^°C after 3 hours of air drying and storage on silica gel, had high germination and pollen tube growth in vitroeven after 180-day storage. On the other hand, pollen stored at 25 ^°C showed a marked decrease in the germination rate within 10 days. The best in vitro germination of Delphinium pollen was on a 1% water agar containing 15% sucrose and 0.005 to 0.01% boric acid and at 15 to 20 ^°C. Field pollination with the cryopreserved pollen showed higher fruit and seed set than pollination with pollen stored at 25 ^°C, and was not significantly different from fresh pollen. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cytochemical investigation of long-term stored maize pollen

Summary Maize pollen quality was investigated after long-term storage both in a refrigerator and in liquid nitrogen by a combination of viability tests and cytochemical methods. Determination of the activities of a number of enzymes involved in important metabolic pathways was carried out. Quinone formation was also studied, as some products of secondary metabolism affect pollen grain viability. One year of pollen storage in liquid nitrogen had little effect on the activities of oxidoreductases and hydrolases and had no significant effect on pollen grain viability evaluated by acetocarmine, neutral red and acridine organe. Only the FCR test showed slightly decreased viability. After one and two years of storage in a refrigerator, pollen grain viability, tested using acetocarmine, neutral red and acridine orange, did not change substantially. Simultaneously the FCR test showed a considerable decrease in pollen grain viability. Long-term storage in a refrigerator resulted in the loss of cytochrome oxidase activity and rise of alcohol dehydrogenase, lactate dehydrogenase, peroxidase and polyphenoloxidase activities as well as of quinone formation.Abbreviations ADH Alcohol dehydrogenase - DOPA L-3,4-Dihydroxyphenylalanine - FCR Fluorochromatic reaction - FDA Fluorescein diacetate - GDH Glutamate dehydrogenase - IDH Isocitrate dehydrogenase - LDH Lactate dehydrogenase - NADI reaction with -NAphthol and DImethyl-p-phenylenediamine hydrochloride - 6-PGDH 6-phosphogluconate dehydrogenase