Pollen Output Research Articles

Breeding system in Olea ferruginea Royle (Oleaceae): comparative performance of staminate and perfect flowers in reproductive assurance

ABSTRACT Olea ferruginea, a wild widely distributed species of the olive lineage, exhibits andromonoecy with protogynous perfect (hermaphrodite) and staminate (male) flowers. The present communication elucidates the differential performance of staminate and perfect flowers in reproductive assurance. The flowering chronology and function of perfect and staminate flowers in the breeding system were investigated to understand the breeding behavior of the species. In terms of breeding behavior, pollen from staminate and perfect flowers was used to establish their role in breeding system under different pollination treatments. Results indicate higher pollen viability, germination, and pollen tube growth of staminate than perfect flowers. Results from pollen counts and morphological investigations show slight differences in both types. The species is self-incompatible which is indicated by pollen germination, the average number of pollen tubes in the style, and the fruit set following self and cross-pollination. Hand cross-pollination improves natural fruit set, especially when pollen from staminate flowers was used. Although the relict role of attracting pollinators cannot be fully discarded, it is suggested that the main benefit supplied by the formation of staminate flowers in olives is to promote male fitness by raising pollen output at the population level.

The pollen dispersal ability for cross-pollination in winter wheat (Triticum aestivum L.) is related to anther extrusion capability rather than to pollen output

IntroductionTriticum aestivum is a self-pollinated species with a high proportion of cleistogamous flowers constituting a blockade for out-crossing. Therefore, male parent characteristics are the main goal in the production of hybrid wheat seeds. MethodsIn a two-year study conducted in Lublin (Poland), the features of flowering biology that can be relevant for the cross-pollination ability of the pollen donor were investigated in winter wheat genotypes. In particular, the anther extrusion capacity, pollen production at the anther and spike levels, and pollen biological value were examined. The pollen production in the anthers was established using an electronic particle counter. The pollen biological value was assessed based on viability (acetocarmine staining) and in vitro pollen germination (raffinose medium) assays. ResultsThe inter-genotype effect for anther extrusion was significantly correlated to the post-anthesis filament length. The anther extrusion for the individual genotypes fluctuated significantly between the years of the study; however, the interaction with meteorological factors was not assessed. The considerable inter-genotype variability in the pollen donor capability for cross-pollination was highly significantly correlated with the proportion of extruded anthers rather than pollen production, indicating that anther extrusion plays a more important role in the contribution to the final amount of pollen available for cross pollination. The pollen viability determined by staining was high (between 97.5% and 100%), while the in vitro pollen germination varied substantially among the genotypes (between 17.3% and 87.8%). ConclusionThe pollen dispersal ability for cross-pollination in wheat can be improved mainly by increasing the proportion of extruded anthers; however, the pollen production and pollen germination potential cannot be ignored if complete characterization of the ideal male idiotype is to be achieved.

Reproductive Biology and Pollination Ecology of Berberis lycium Royle: A Highly Valued Shrub of Immense Medicinal Significance.

Study of reproductive biology and pollination ecology helps in understanding the life history patterns of species. Such a study brings to light the bottlenecks, if any, on account of which the individuals of the species are not able to reproduce in nature and ultimately helps in planning appropriate conservation strategies for the species under threat. The present study was aimed at examining the morphological and reproductive variance in Berberis lycium, a threatened ecological specialist growing within shrubberies and open hillsides of the North-Western Himalayas in India. B. lycium displays three different variants. Flowering period ranges from February to September. Pollen viability as reported on fluorescein diacetate and acetocarmine treatments was highest for variant I, while maximum pollen output was obtained for variant III. Pollen pistil interaction is brought by the movement of anther towards stigma. Fluorescence microscopy of hand pollinated club shaped stigma shows that the germinating pollen form a ring over the receptive adaxial surface. Pollination syndrome is entomophily. Variant II attracts a significantly large number of pollinators from diverse insect families. Breeding experiments reflect that plants are self-compatible and cross fertile. Reproductive output (% fruit set) was highest for variant II followed by III and I, respectively. This investigation helped to understand the effect of different biotic and abiotic constraints on the phenology and reproductive biology of the plant. The information generated so will enable conservationists to design appropriate strategies for its long-term survival and sustenance in nature.

Palynological investigations in Jasminum spp.


 
 
 The present investigation was carried out at the Department of Floriculture and Landscape Architecture, Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore during 2017-2019. The study involved nine jasmine genotypes, four falling under the commercially cultivated types and five belonging to underutilized species or ‘lesser-known species’. The study was undertaken to investigate and document the palynological parameters of jasmines which could serve as a reliable reference for future jasmine breeding programmes. The palynological investigations were carried out using Scanning Electron Microscopy (SEM), haemocytometry, acetocarmine test, and in vitro pollen germination. The pollen morphology analysis indicated wide variation among the species for the shape of the pollen grain, ranging from tricolpate to prolate; the exine ornamentation was reticulate in all the genotypes. Pollen output was the highest in J. rigidum (28,660 pollen/flower) and the lowest in (625 pollen/ flower) in J. sambac cv. Ramanathapuram Gundumalli. The maximum pollen germination rate and pollen tube length were recorded in J. rigidum.
 
 

Palynological investigations in Jasminum spp.

The present investigation was carried out at the Department of Floriculture and Landscape Architecture, Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore during 2017-2019. The study involved nine jasmine genotypes, four falling under the commercially cultivated types and five belonging to underutilized species or ‘lesser-known species’. The study was undertaken to investigate and document the palynological parameters of jasmines which could serve as a reliable reference for future jasmine breeding programmes. The palynological investigations were carried out using Scanning Electron Microscopy (SEM), haemocytometry, acetocarmine test, and in vitro pollen germination. The pollen morphology analysis indicated wide variation among the species for the shape of the pollen grain, ranging from tricolpate to prolate; the exine ornamentation was reticulate in all the genotypes. Pollen output was the highest in J. rigidum (28,660 pollen/flower) and the lowest in (625 pollen/ flower) in J. sambac cv. Ramanathapuram Gundumalli. The maximum pollen germination rate and pollen tube length were recorded in J. rigidum.

Geographic mosaic theory of coevolution in plant and pollinator interaction: Process, evidence, prospect

Coevolution refers to evolutionary changes in the traits of two or more interacting species caused by reciprocal natural selection. Geographic mosaic theory of coevolution (GMC) proposes that the dynamics of coevolution between pairs or group of species often occur at different geographic scales. There are three hypotheses on the coevolutionary process. (1) Different evolutionary interaction trajectories among populations are likely to generate a selection mosaic. (2) A mixture of coevolutionary hotspots and coldspots. Hot spots are the subset of communities in which much of the coevolutionary change occurs and coldspots refer to areas where coevolutionary selection hardly occurs or completely does not occur. (3) There is a continual population remixing of the range of coevolving traits, resulting from the selection mosaic, coevolutionary hotspots, gene flow, random genetic drift, and local extinction of subpopulations. Studies of GMC between plants and pollinators indicate that shifts of effective pollinators among different geographic populations may cause divergence in floral traits (i.e., pollination ecotype). Changes of pollinator assemblages or species components have been illustrated coevolving with floral morphology or reward among populations from different altitudes or habitats. Here, recent case studies of GMC between plants and pollinators are grouped into five categories: Floral morphology and pollinator components, corolla tube/nectar spur and pollinator feeding structure, floral color, floral scents, floral rewards and pollinator assemblages. Floral tube or nectar spur length is positively related to pollinator body structures, such as the proboscis and leg length. The adaptation of flower color and pollinator vision provides a series of examples for the GMC. With the increase of altitude, flower color changed from blue and ultraviolet blue adapted to bee vision to blue-green and green adapted to fly vision. Recent study indicated that the difference in cycad odor components related to a shift of beetle species in different regions, suggesting a potential coevolutionary relationship between flower odor and pollinators. Studies showed that where bees foraged more nectar, flowers secreted more nectar, suggesting that floral reward amounts and types coevolve with pollinators among different geographic populations. An examination of GMC in plant-pollinator interactions involves three steps in general: (1) Detection of the relationship between floral traits and pollinator shift or body structure. (2) Transplanting experiments to detect differences in seed set between native phenotypes and transplanted phenotypes. (3) Single pollinator visit experiment to detect pollen output differences between native and transplanted phenotypes. Experimental evolutionary biology not only can test whether floral variation is related to pollinator shifts, but also make people aware of the impact of the reduction or loss of pollinators on the evolutionary consequences. To illustrate GMC between plants and pollinators, it is essential to isolate the evolutionary changes in traits caused by biotic factors or abiotic factors in future. It would be highly appreciated if genome scans and analysis are used in further studies to explore the genome-wide patterns of GMC between plants and pollinators.

Screening for male fertility status in selected banana genotypes

In the present study, twenty-five banana cultivars (eight diploids and seventeen triploids) were screened for their male fertility status with reference to the pollen output per anther, pollen size and pollen viability. The results showed that the pollen output and pollen viability are higher in monospecific diploids than the cultivars having the genome of both Musa acuminata and Musa balbisiana. Pollen size were higher in triploids than the diploids. The cultivars such as ‘Rose’, ‘Hatidat’, ‘Athiakol’, ‘Bhimkol’ and ‘Popoulu’ were reported to be polleniferous similar to proven male fertile parents such as ‘Pisang Lilin’ or ‘Anaikomban’. The complexities arising out of ploidy status and genomic differences not only impact pollen viability but also pollen production.

Direct effects of insecticides on common ragweed-implications for natural enemy exclusion trials.

Experimentally applying pesticides is an important method to assess the efficacy of weed biocontrol agents, but potential direct effects of the chemicals on plant performance are controversial or unknown. We assessed how three broad-spectrum insecticides applied in combination affect the performance of the widely invasive, crop-yield reducing, allergenic common ragweed (Ambrosia artemisiifolia L.) in an insect-free environment. Spraying insecticides had no significant effects on aboveground dry weight, seed and pollen output or pollen allergenicity, and only explained 1-8% of variation in these parameters. Our insecticide treatment can hence be applied to assess biocontrol impact on biomass and reproductive output of common ragweed. As our insecticide treatment delayed senescence, however, other methods of insect exclusion should be preferred when studying common ragweed phenology.

The effects of seasonal and long-term climatic variability on Neotropical flowering phenology: An ecoinformatic analysis of aerial pollen data

The phenological behavior of tropical forests changes in response to seasonal, annual, and long-term variation in temperature, precipitation, and solar irradiance. However, detecting the respective influence of these variables is difficult due to the relatively small range of change that is observed in the tropics. Analysis is further constrained by the limited duration of many phenological datasets. To address these limitations, we developed a predictive ecoinformatic model using multivariate linear regression and slope correlation analysis that can uncover statistically significant biological responses within short, noisy ecological time series. Our approach correlates all possible combinations of climatic and taxonomic variables using a series of random determination trials on shuffled environmental data. Seasonal and annual fluctuations in temperature, precipitation, and sunlight were used to predict the reproductive response of each individual taxon. This predictive model was applied to two seasonally sampled aerial pollen records collected between 1996 and 2006 from two Panamanian forests, Barro Colorado Island and Parque Nacional San Lorenzo. Our results highlight the degree to which pollen output responds to fine-scale variability in climate. Our results lend support to the hypothesis that the pollen output of tropical species is diminished with prolonged periods of heavy rainfall and that pollen output is sensitive to small, seasonal increases in temperature. Our ecoinformatic approach can be expanded to other observational phenological datasets to better understand how communities will respond to climate change and our results demonstrate the ability of aerial pollen data to track long-term changes in flowering phenology.

Northern ragweed ecotypes flower earlier and longer in response to elevated CO2: what are you sneezing at?

Significant changes in plant phenology and flower production are predicted over the next century, but we know relatively little about geographic patterns of this response in many species, even those that potentially impact human wellbeing. We tested for variation in flowering responses of the allergenic plant, Ambrosia artemisiifolia (common ragweed). We grew plants originating from three latitudes in the Northeastern USA at experimental levels of CO2 (400, 600, and 800 µL L−1). We hypothesized that northern ecotypes adapted to shorter growing seasons would flower earlier than their southern counterparts, and thus disproportionately allocate carbon gains from CO2 to reproduction. As predicted, latitude of origin and carbon dioxide level significantly influenced the timing and magnitude of flowering. Reproductive onset occurred earlier with increasing latitude, with concurrent increases in the number of flowers produced. Elevated carbon dioxide resulted in earlier reproductive onset in all ecotypes, which was significantly more pronounced in the northern populations. We interpret our findings as evidence for ecotypic variation in ragweed flowering time, as well in responses to CO2. Thus, the ecological and human health implications of common ragweed’s response to global change are likely to depend on latitude. We conclude that increased flower production, duration, and possibly pollen output, can be expected in Northeastern United States with rising levels of CO2. The effects are likely, however, to be most significant in northern parts of the region.

Pollen production and release in Mesua ferrea Linn. (Guttiferae): a spatio-temporal pattern

Based on a five-year study of pollen production and release in two different natural populations of Mesua ferrea from Indo-Burma region of Northeast India, we determined that pollen output follows a spatio-temporal pattern. Pollen productivity determinations considered various sources of variability, including the number of flowers per branch, flowers per tree, anthers per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and population effects. Anthesis follows a forenoon pattern, whereas anther dehiscence pursues the diurnal pattern. The former was significantly correlated with the timing of floral visitation and pollen deposition on stigmas. The latter, however, had significant relationship with the deposition of pollen grains on microscopic slides. The Apis and Xylocopa bees are the efficient pollinators to achieve the reproductive success in M. ferrea. Annual production of pollen per tree varied from averages of 1.07 ± 0.10 × 1010 and 3.24 ± 0.16 × 1010 in years of low production, with alternate high years, producing 3.85 ± 0.34 × 1010 and 8.22 ± 0.76 × 1010 pollen grains per tree.

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An experiment was conducted during 2010 and 2011 to investigate the impact of fertigation on flowering characters of cocoa at Tamil Nadu Agricultural University, India. The study was laid out in randomized block design with thirteen treatment combinations replicated thrice. The study shown that, fertigation with 125% recommended fertilizer dose as water soluble fertilizer through fertigation by micro sprinkler irrigation (T10) recorded the highest number of flower cushions per tree per season (377.6) as against 16.60% increase over the control (314.9) at 0.05% significance. The same treatment (T10) recorded the best in terms of other flowering characters viz., area of pollen grain (504.1 µm2), equivalent diameter of the pollen grain (27.4 microns), radius of the pollen grain (13.3 microns), pollen output (34.9), pollen viability (89.2%), pollen germination (88.1%) as against 38.39, 23.72, 24.06, 28.65, 17.38 and 36.55% increase over the control (T1) respectively. Fertigation with 125% recommended fertilizer dose as water soluble fertilizer through fertigation by micro sprinkler irrigation recorded the maximum flowering characters.   Key words: Fertigation, drip, micro sprinkler, flowering characters, Theobroma cacao. &nbsp

Monoecy, anemophily, anemochory and regeneration ecology of Hildegardia populifolia (Roxb.) Schott. & Endl. (Malvaceae), an economically important endemic and endangered dry deciduous tree species of southern Eastern Ghats, India

Hildegardia populifolia is a critically endangered tree species. All phenological events—leaf flushing, shedding, flowering, fruit dispersal occur one after the other during the dry season. It is morphologically andromonoecious but functionally monoecious. It produces a strikingly male-biased male and bisexual flower ratio; it is self-incompatible and obligately outcrossing. The flowers are nectariferous and the nectar has hexose-rich sugars, some essential and non-essential amino acids. Trigona bee and Rhynchium wasp were the exclusive foragers, though their foraging activity does not promote cross-pollination. The male flower number, the pollen output, the pollen characteristics and the placement of anthers on the top of androphore conform to anemophily. The natural fruit set does not exceed 5%. The fruit is 5-follicled with one or two seeds. The low fruit set is compensated by the production of more 2-seeded follicles. Fruit characteristics such as wing-like follicles, membranous follicle sheath and being very light weight characterize anemochory. Seeds with a hard coat do not germinate readily during the rainy season and their germination depends on the soil chemicals and nutrient environment. The soil is deficient in nitrogen, potassium and phosphorous. Partly burned seeds due to natural or human-caused fires germinate quickly in water saturated soil. The study suggests that seed germination and seedling growth rates are regulated by intrinsic and extrinsic factors along with natural and anthropogenic fires. We recommend that seedlings should be raised in nurseries and then transferred to natural habitats to build up the population.

The Flowering, Pollen Production, and Insect Visitors in the Ornamental Shrub Potentilla Fruticosa L. (Rosaceae)

Summary Urban areas have a specific ecological environment and may help to sustain local pollinator populations by the cultivation of different ornamental plants with entomophilous flowers. This yearlong study examined the flowering pattern, abundance of flowering, pollen production as well as insect visitation of two cultivars of the ornamental shrub Potentilla fruticosa L. (‘Maanleys’ and ‘Blink’), grown in Lublin; a city in south-eastern Poland. P. fruticosa ‘Maanleys’ bloomed from the middle of May to the first decade of September and P. fruticosa ‘Blink’ from June until October. The pattern of diurnal flowering was similar for both cultivars and showed plasticity in the season. Flowers opened most intensively in the morning hours, and 80 - 90% of the daily installment of newly opened flowers expanded by 8.00 h GMT +2h. A delay in the peak of diurnal flowering was noted between the spring/summer and summer/autumn periods. The most intense blooming fell in the 2nd month of flowering. The mass of pollen produced per flower depended on both the number of anthers and the efficiency of archesporial tissues. The pollen output varied from 1.4 to 7.2 mg per 10 flowers (‘Maanleys’) and from 2.6 to 4.5 mg per 10 flowers (‘Blink’). The mass of pollen produced per individual shrub was substantially related to the abundance of blooming. The average estimated pollen productivity in the full flowering phase was low; 1 g (‘Maanleys’) and 1.5 g (‘Blink’) per 10 m2 of shrub crown. The flowers of Potentilla fruticosa attracted numerous insects, mainly solitary bees (33 - 43%), dipterans (31 - 42%), lepidopterans (4 - 14%), bumblebees (3 - 15%), and honey bees (3 - 4%). The Potentilla fruticosa ‘Maanleys’ and ‘Blink’ are propagated for specific ornamental arrangements and due to a long flowering period may be used in small urban courtyards for both decorative value and as a pollen delivering plants.

Variability within the 10-Year Pollen Rain of a Seasonal Neotropical Forest and Its Implications for Paleoenvironmental and Phenological Research

Tropical paleoecologists use a combination of mud-water interface and modern pollen rain samples (local samples of airborne pollen) to interpret compositional changes within fossil pollen records. Taxonomic similarities between the composition of modern assemblages and fossil samples are the basis of reconstructing paleoclimates and paleoenvironments. Surface sediment samples reflect a time-averaged accumulation of pollen spanning several years or more. Due to experimental constraints, modern pollen rain samples are generally collected over shorter timeframes (1–3 years) and are therefore less likely to capture the full range of natural variability in pollen rain composition and abundance. This potentially biases paleoenvironmental interpretations based on modern pollen rain transfer functions. To determine the degree to which short-term environmental change affects the composition of the aerial pollen flux of Neotropical forests, we sampled ten years of the seasonal pollen rain from Barro Colorado Island, Panama and compared it to climatic and environmental data over the same ten-year span. We establish that the pollen rain effectively captured the strong seasonality and stratification of pollen flow within the forest canopy and that individual taxa had variable sensitivity to seasonal and annual changes in environmental conditions, manifested as changes in pollen productivity. We conclude that modern pollen rain samples capture the reproductive response of moist tropical plants to short-term environmental change, but that consequently, pollen rain-based calibrations need to include longer sampling periods (≥7 years) to reflect the full range of natural variability in the pollen output of a forest and simulate the time-averaging present in sediment samples. Our results also demonstrate that over the long-term, pollen traps placed in the forest understory are representative samples of the pollen output of both canopy and understory vegetation. Aerial pollen traps, therefore, also represent an underutilized means of monitoring the pollen productivity and reproductive behavior of moist tropical forests.

Male Fertility in Uganda Banana Germplasm

Identification of fertility levels in banana germplasm collection at Kabanyolo, Uganda, was conducted by dehiscing the anthers using a glass rod. The study involved 151 accessions. The quantity of pollen grains per anther was ranked 0-5; where 0 had no grains and 5 had abundant pollen grains. A correlation between pollen output and inflorescence characters revealed a positive relationship (r = 0.69, P ≤ 0.01) to inflorescence diagnostic characters. A quantitative determination of pollen output per anther and percentage pollen viability based on starch test using the Heamocytometer method revealed that the amount of starch filled grains did not proportionally vary with the total pollen output. Pollen output varied from cultivar to cultivar. Most East African highland banana cultivars were found to have more pollen than the recently introduced banana cultivars. A few highland banana cultivars were non-polleniferous. The results indicate the relative potential of using various cultivars in hybridization and, anther and pollen culture programmes. Keywords: Bananas, Heamocytometer, fertility, pollen

Cyclic pollen production in Cedrus deodara

Based on a seven-year study of pollen production and release in two different natural populations of Cedrus deodara from Garhwal Himalaya, India, we determined that pollen output follows a two-year cycle. Pollen productivity determinations considered various sources of variability, including the number of pollen strobili per branch, strobili per tree, microsporophylls per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and population effects. Microsporangium dehiscence took from 2.5 to 3.5 days. Maximum dehiscence was observed between 12:00 and 14:00 h, which coincides with diurnal highest temperature and lowest relative humidity. Annual production of pollen per tree varied from averages of 4.7 x 10(9), 7.2 x 10(9) and 5.1 x 10(9) in years of low production, with alternate high years, producing 12.6 x 10(9), 14.1 x 10(9), 13.3 x 10(9) and 14.0 x 10(9) pollen grains per tree. Annual pollen production in individual trees of C. deodara ranged from 1.4 x 10(9) to 22.3 x 10(9).

Pollen production, flowering and insect visits on Euphorbia cyparissias L. and Euphorbia virgultosa Klok

SummaryThis study investigated the morphological features, flower biology, pollen output and insects which foraged on Euphorbia cyparissias L. and Euphorbia virgultosa Klok. The observations were made between 2002 and 2006 on ruderal plots in Lublin, south eastern Poland. Both species formed inflorescences of the pseudantium type, known as cyathia. The number of inflorescences was 117.06 per shoot for E. cyparissias and 84.72 for E. virgultosa. The opening of spathe in the successive cyathia occurred almost simultaneously in both species, as early as at 6.00 h with the peak between 7.00 and 8.00 h. All cyathia of E. cyparissias are hermaphroditic. In the case of E. virgultosa, the bisexual cyathia on the shoots accounted for 58.3%. Hermaphroditic cyathia are protogynous. Dichogamy in Euphorbia virgultosa is strengthened through the occurrence of exclusively male flowers in part of the cyathia. The mean number of anthers per cyathium in E cyparissias and E. virgultosa, was 17.22 and 14.22, respectively. The small stamens of E. cyparissias yielded a mean of 0.38 mg of pollen per 100 anthers while the larger stamens of E. virgultosa yielded 0.51mg per 100 anthers. The weight of pollen per plant averaged 2.64 mg in E. virgultosa and 3.68 mg in E. cyparissias. Several hymenopteran species (Apis mellifera L. and solitary bees) visit E. cyparissias flowers. Additionally, Bombus spp. forages on E. virgultosa. Among the pollinators of both plants taxa, Diptera were present. Over the five-year period of observation, the density of species studied per square unit varied, but the plants renew each year. The associations with E. cyparissiasand E. virgultosa are not subjected to rapid succession. Hence, the studied species should be considered as an important component of the food chain for Apoidea and Diptera.

Use of Quercus ilex subsp. ballota phenological and pollen-production data for interpreting Quercus pollen curves

Although aerobiological data are often used in phenological research as an indicator of flowering, airborne pollen concentrations are influenced by a number of factors that could affect pollen curves. This paper reports on a study of various aspects of reproductive biology in Q. ilex subsp. ballota, together with environmental factors influencing pollen release and transport, with a view of achieving reliable interpretation of Quercus pollen curves in Ourense (NW Spain). Aerobiological data were recorded from 2002 to 2004 at two sites in the province of Ourense. From 1st February to the end of the flowering period, phenological observations were carried out on 19 trees from the Q. ilex subsp. ballota population found in the Ourense area. Pollen production was calculated for the same trees. The chilling and heating requirements for triggering development were also calculated. The mean flowering period lasted 11-15 days. Reduced pollen output per catkin and, especially, a reduced number of catkins per tree in 2003 and 2004, prompted a marked decline in overall pollen production. Major differences observed in Q. ilex subsp. ballota pollen curves were attributed to the considerable influence both of weather conditions during pollination and pollen production. In years with high pollen production and weather conditions favouring pollen release, Q. ilex subsp. ballota contributed almost 10% to the total Quercus pollen curve. Around 20% of the pollen trapped was captured before or after flowering periods.

Problems and Prospects of Banana Breeding in India

Banana breeding programme in India involves maintenance of various genetic resources of banana, of which triploids constitute the maximum share over diploids or tetraploids. RAPD studies conducted in these clones exhibit many distinct genotypes. During a hybridization programme, although many crosses were made, seed set and seed germination were relatively poor in many crosses. Male fertility in banana hybrids could be assessed by pollen output per anther; pollen viability and pollen size, which vary from cross to cross, and also from ploidy to ploidy. Ploidy levels in hybrids are estimated by phenotypic appearance (scoring technique) and confirmed either by stomatal density, size and number of chloroplast per guard cell pair or root tip mitosis. However, flow cytometry appears to be the most reliable method in many disputed cases. Generation of parthenocarpic hybrids depends largely upon selection and utilization of parents with parthenocarpic pedigree in a breeding programme. Evaluation of hybrids and parents indicated the nature of inheritance with respect to plant height and suckering habit but no definite trend could be ascribed to the traits of bunch orientation. Diploid x Diploid breeding approach has led to identification of a superior triploid hybrid, NPH 02-01, while Triploid (with AB)xDiploid approach has led to the development of a promising diploid hybrid H.212 and a triploid hybrid H.96/7 (ABB). Similarly, the Triploid x Diploid breeding programme resulted in development of many potential tetraploids that need further improvement. Innovative breeding approaches through in vitro mutation breeding and in vitro polyploidazation resulted in the development of many potentially useful variants. Breeding for resistance against biotic stresses such as Fusarium wilt and nematodes holds promise in banana, and, biochemical mechanisms for resistance in resistant genotypes/hybrids have been elucidated.