Induction of Tetraploidy in the Tanier Cultivar 'Inglesa' [Xanthosoma saghtifolium (L.) Schott]

Induction of tetraploidy in commercial tanier was successfully achieved in vitro. Tissue cultures of a tanier [Xanthosoma sagittifolium (L.) Schott cv. ‘In-glesa’, 2n 26] were established and maintained on modified nutrient media containing various concentrations of MURASHIGE and SKOOG basal salts, vitamins, sucrose, BA and IAA or 2,4-D. Cultures were exposed continuously for 8 days to 0, 12.5, 25 and 50 mg/1 colchicine incorporated in the media. The colchicine-treated tissue cultures yielded di-ploids (2n 26), tetraploids (2n 52) and aneuploids (2n – 2 24) respectively. The diploids produced on average one leaf and 4 suckers more per plant than the tetraploids, while plant height increased at about the same rate. Continuous exposure of tanier tissue cultures tocolchicine is an effective method for the production of synthetic tetraploids that may be hybridized with non-commercial root rot-resistant tetraploids.     

Non-Destructive Estimation of Leaf Area in Cocoyam (Xanthosoma sagktifolium [L.] Schott)

Leaf area of cocoyam ( Xanthosoma sagittifolium ) can be estimated quickly and accurately using the mathematical relationship between linear measurements of leaves which relate leaf area (Y) to the product of length (L) and breadth (B).The most accurate relationship is Y = K (LB) with K = 0.923 + 0.004.     

Colocasia esculenta (L.) Schott,Colocasia antiquorum Schott,how many species? 1. A preliminary investigation

Summary The taxonomy of edible Colocasia (Cocoyam) is confusing. The existence of one species, C. esculenta var. antiquorum or C. esculenta and C. antiquorum as two separate species is controversial. Nine high yielding Nigerian cultivars of cocoyam made up of members of the two taxa were grown under the same environmental conditions. As a preliminary investigation, 17 characters were monitored and recorded to help in the classification of the cultivars. Results showed that cocoyams can be grouped into two separate species. The qualities possessed by TCe 23, Nwine and Ukpon cultivars which include pink tuber skin, long or club shaped cormels and non-irritation in the throat when boiled and eaten, clearly distinguished them from those of Tce 15, 19, 27, 36, Ede-ofe and Kochuom.     

Control pollination and pollen management in Sesbania sesban (L.) Merr.

Sesbania sesban was amiable to controlled cross pollination when the emasculation and pollination operations were performed in the morning. A medium of 10% sucrose solution was found to be optimal for in vitro germination of the pollen grains. The pollen is quite tolerant of orthodox storage conditions enabling controlled crosses to be performed among accessions that flower in differing seasons of the year.     

Some consequences of pollen storage in the raspberry (Rubus idaeus L.)

Summary Raspberry pollen was stored at 5°C and –13°C for six months and then tested for its ability to induce pyrene set and the production of viable seedlings, and for its effect upon the segregation of a major gene s. Only pollen stored at –13°C gave a pyrene set and germination percentage adequate to produce sufficient seedlings for a breeding programme. It is suggested that tests of pollen viability in the raspberry should include studies of pollen germination, and the effect of this pollen on pyrene set and seed germination. Possible causes of the loss of viability in the pollen stored at 5°C are discussed.     

Variation in pollen viability in the onion (Allium cepa L.)

Summary The pollen viability of onions in a glasshouse was recorded from May to October 1975, using the fluorescein test. The average viability was 60–95% for most of this period but fell to less than 1% during the last two weeks of August. There was great variation in pollen viability between anthers within a flower and between flowers within a head. Attempts to induce pollen inviability by low temperature treatments at various stages of inflorescence development were unsuccessful. Low levels of pollen inviability appear to be a characteristic feature of onions, but the high level of inviability which was found both in this and in a previous season was associated particularly with the August period.     

Pollen competition in onion (Allium cepa L.)

Summary Pollen mixtures with two components, one of which carried a dominant marker gene for red or white bulb skin colour, were used to pollinate flowers on onion umbels from several cultivars. Scoring progenies for the marker revealed that pollen components differed in their ability to effect fertilization, suggesting that gametophytic competition can occur in onions. In many cases, self-pollen appeared to have a competitive advantage over cross-pollen. Both of the male components and the female parent played a part in determining the final ratio obtained from a mixed pollination.Crossed seeds were slightly but significantly heavier than selfed seeds in nine out of ten umbels studied.     

Pollen storage of Fragaria and Potentilla

Summary Low temperature and humidity were used for the storage of pollen of four species of Fragaria (2n=14, 42 and 56) and two species of Potentilla (2n=14). The stainability of Fragaria pollen was assessed over a number of years by use of aceto-carmine stain and its viability by cross-pollinations; stainability of Potentilla pollen was assessed by acetocarmine. Fragaria pollen so stored remained stainable for seven years and showed the ability to set seed for three years. over the latter period, aceto-carmine staining gave a reasonable prediction of seed set produced by the stored pollen of Fragaria and so is of value in estimating pollen viability in that genus. Potentilla pollen remained stainable for three years.     

Isozyme variation in taro (Colocasia esculenta (L.) Schott) from Asia and Oceania

Summary Isozyme variation was studied in 1,417 cultivars and wild forms of taro collected in Asia and Oceania. Seven polymorphic enzyme systems (MDH, IDH, PGI, 6-PGD, ME, SkDH, and ADH) revealed 143 isozyme phenotypes, or zymotypes, each uniquely characterized by the presence or absence of 56 electromorphs. Results showed greater isozyme variation in Asia than in Oceania, with Indonesia being the area of greatest diversity. No correlations were found between zymotypes and morphotypes or ploidy levels (as described by other investigators). Multivariate analyses of the isozyme data indicated that the majority of the Indonesian cultivars were different from the Philippine and Oceanian taro cultivars. Oceanian cultivars constituted a continuum of clusters and are thought to have originated from a narrow genetic base introduced from Indonesia. If taro breeding is to have any future in Oceania, it is important to exchange genotypes to broaden the base of existing breeding programmes.     

Effect of pollen storage by drying and deep-freezing on the expression of different agronomic traits in maize (Zea mays L.)

Summary Pollen from the inbred maize line HMv 1645 was used to study the effect of pollen treatments (drying and deep-freezing) on the phenotypic performance of the next generation. Fresh and artificially dried pollen samples with different water contents (56%, 18%, 13% and 10%) were used for sib pollinations immediately after collection or drying. Samples containing low amounts of water were then stored in liquid nitrogen for 7 days. Fertilization ability of the samples with 13% water was the highest after storage. Plant characteristics of the next generation originated from the seeds set by differently treated (fresh, dried to 13% water and deep-frozen) pollen were examined and statistically analysed. Pollen treatments due to the pollen storage procedure did not cause detectable changes in quantitative characters of the next generation.     

Pollen grain germination inside the anthers of two chasmogamous angiosperms: Almond (Prunus amygdalus L. Batsch) and apple (Malus pumila Mill.)

Summary Pollen grain germination inside anthers has so far been known in only eleven chasmogamous angiospermous species. The discovery of this phenomenon in some varieties of Prunus amygdalus (almond) and Malus pumila (apple) is therefore significant. The anomaly appears to be genetically controlled, the gene expression occurring under specific environmental conditions.     

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.     

Pollen mother cell and anther wall development in a photoperiod-insensitive male-sterile mutant of pigeon pea (Cajanus cajan (L.) Millsp.)

Summary The development of the pollen mother cells (PMC's) and anther wall of a male-sterile mutant was microscopically compared with that of fertile sib plants in pigeon pea (Cajanus cajan). Male-sterility was complete and caused by breakdown of microsporogenesis at prophase I. Delayed and incomplete development of the anther wall appeared to be responsible for PMC degeneration. The sterile mutant also differed from the fertile plants in the size and number of the PMC's.On leave from International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Hyderabad, India.     

Pollen longevity and artificial cross-pollination in Coffea arabica L

Summary Various aspects of pollen longevity, in vitro germination of pollen and controlled pollination in Coffea arabica were investigated. High pollen viability could be maintained for more than two years, much longer than previously reported, by storing it under vacuum at 18°C. The most satisfactory method of in vitro germination of pollen was the hanging drop in a Van Tieghem cell, with a 10°, sucrose solution. For artificial cross-pollination it is necessary to carry out emasculation and bagging at the latest one day before anthesis. The stigmas of unpollinated flowers remained receptive for at least nine days.This paper is published with permission of the Director, Coffee Research Station, Ruiru, Kenya     

Pollen–style compatibility in cashew (Anacardium occidentale L.)

The role of pollen–stigma interaction and pollen tube growth as a measure of genetic compatibility was studied in eleven clones of cashew under a tropical rainforest ecology in Southwestern Nigeria between 1999 and 2002. Diallel cross of the clones showed that 55.00% of the cross-pollinated crosses showed high pollen cross-compatibility (CC) indicating moderate genetic distance in the population. About 54.55% of the clones showed evidence of self-compatibility, therefore confirming that cashew is self-fertile. Cytological examination however suggests possible postzygotic self-incompatibility in the crop as no evidence of tube growth inhibition was recorded in both cross- and self-pollinated styles. Correlation between maternal compatibility (pollen recipients) and fruit set shows that more attention need to be focused in this direction during selection. Based on the data from this study, the use of combinations of floral quality characteristics like high pollen fertility, prolific flowering, and high flower sex ratio plus high cross-compatibility as reliable selection criteria for cashew yield improvement is therefore suggested.     

Pollen and pollination experiments. III. The viability of apple and pear pollen as affected by irradiation and storage

Summary Apple and pear pollen was irradiated with doses of 0, 50, 100, 250 and 500 krad (gamma rays) and stored at 4°C and 0–10% r.h. From the in-vitro germination percentages an average LD 50 dose of about 220 krad was estimated. For both irradiated and untreated pollen a close and corresponding lineair relationship existed between germination percentage and pollen tube growth.Irradiated pollen was much more sensitive to dry storage conditions than untreated pollen, resulting in less germination and more bursting. Apparently, irradiation caused the pollen cell membrane to lose its flexibility faster than normal. Rehydration of dry-stored, irradiated pollen in water-saturated air restored germination percentages up to their initial levels. The importance of this procedure in germination trials is stressed.     

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.     

Pollen selection in breeding tomato (lycopersicon esculentum Mill.) for adaptation to low temperature

Summary F₂ and BC₁ progenies from crosses between tomato (Lycopersicon esculentum) varieties differing for growth capacity at low temperature were produced under controlled conditions by hand pollination under two temperature regimes (22°C D/15°C N, normal temperature (N), and 15°C D/8°C N, low temperature (L)) with pollen formed under both regimes, resulting in four pollination treatments: NN, NL, LN and LL. Vegetative growth of the offspring was compared under a rather low temperature regime (19°C D/10°C N). Populations from different treatments within the progeny of a particular F₁ often differed significantly for average dry weight of 7 weeks old plants, the average of the NN population always being higher. Variances for dry weight were sometimes larger for LN populations, but this never resulted from a larger number of vigorous plants. Differences between populations within each progeny seemed to result in part from differences in the conditions for embryo development. Pollen selection at low temperature did not appear to be efficient for sporophyte breeding in this experiment.     

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.     

Field bean (Phaseolus vulgaris L.) cultivar identification by electrophoregrams of cotyledon storage proteins

Summary Electrophoretic procedures were developed for seed proteins which can discriminate cultivars of field beans. Proteins were extracted from seven varieties and the extracts were analysed using acid and SDS polyacrylamide gel electrophoresis. Electrophoregrams are presented to illustrate the results that can be obtained with the methods described. Results indicate that sufficient variation is present among the seven cultivars examined to afford unambiguous discrimation and identification of the cultivars. Banding patterns were stable for each genotype.Joint publication of the Department of Plant Science, University of Manitoba (No. 747) and Centro Internacional de Agricultural Tropical-CIAT.