In vitro pollen germination in Hypericum perforatum L. and Hypericum rumeliacum Boiss

In vitro pollen germination and pollen tube growth investigations are valuable tools used in identification of the effects of environmental factors and genotypic differences on pollen viability, pollen germination and tube elongation. In this study pollen viability, in vitro pollen germination capacity, abnormality ratios and tube length in germinated pollens of Hypericum perforatum L. and H. rumeliacum Boiss. were investigated. Both of these species has spheroid-shaped and tricolporate pollen grains. The diameters of Hypericum perforatum and H. rumeliacum pollens were found as 24 +/- 3 microm and 19 +/- 2 microm, respectively. Pollen viability of H. perforatum and H. rumeliacum was found as 83% and 72%, respectively. The germination percentages were found as 12.85% for H. perforatum and 64.42% for H. rumeliacurm. Tube lengths in germinated pollens of both taxa were measured approximately as 95.25 +/- 38 microm in H. perforatum and 165.92 +/- 53 microm in H. rumeliacium 4 h after inoculation. In germinated pollen grains of H. perlbratum and H. rumeliacumn abnormality percentages were determined as 13.23% and 43.97%, respectively. In germinated pollens of these two species, highly significant (P < 0.00001) differences in in vitro germination percents and abnormality percents were observed. Abnormalities such as swollen tube tip, branched tube, spiralled tube and excessive tube formation were observed in pollen tubes. The results of this study showed that there were obvious differences in pollen germinability between these two species growing under the same environmental conditions.     

Genetic variation for in vitro sesame pollen germination and tube growth

  In vitro pollen germination and tube length studies are valuable in elucidating mechanisms (germination capacity and rate, tube growth rate) possibly associated with genetic differences in male transmission. On each of two collection dates, the percentage germination and tube length of the binucleate pollen grains from five diverse sesame (Sesamum indicum L.) genotypes were determined at eight times (30, 60, 90, 120, 150, 180, 240, 300 min) after inoculation on a semisolid medium containing 10% (100 g l^-1) sucrose (C₁₂H₂₂O₁₁), 0.4% (4 g l^-1) purified agar (Fisher Lot 914409), 0.1% (1 g l^-1) calcium nitrate [Ca(NO₃)₂ ⋅ 4H₂O] and 0.01% (100 mg l^-1) boric acid (H₃BO₃). Before heating, the pH of the medium was adjusted to 7.0 with a 0.1 N potassium hydroxide (KOH) solution. Over the five genotypes, 5% germination was found 30 min after inoculation and a maximum of 37% germination 120 min after inoculation with no significant changes thereafter. As indicated by the highly significant genotype×time after inoculation interaction, the genotypes differed in the time at which germination was initiated and maximum germination attained. Over all five genotypes, the tube length was 91 μm 30 min after inoculation, reaching a maximum of 1000 μm 300 min after inoculation. As shown by the highly significant genotype×time after inoculation interaction, the genotypes differed in the time at which tube length was observed and the maximum tube length was attained. Little or no relationship between percent germination and tube length was observed among the genotypes. For both percent germination and tube length, the statistical significance of collection date and its interactions with genotype and time after inoculation indicated that environment in the form of collection date was also an influencing factor. These results indicated that genetic differences among genotypes were present for in vitro germination capacity, germination rate and tube growth rate and that these factors singly or in combination could alter male transmission of genetic elements. Received: 5 February 1997 / Accepted: 23 June 1997     

Quantitative trait loci (QTLs) for pollen thermotolerance detected in maize

Pollen thermotolerance is an important component of the adaptability of crops to high temperature stress. The tolerance level of the different genotypes in a population of 45 maize recombinant inbred lines was determined as the degree of injury caused by high temperature to pollen germinability (IPGG) and pollen tube growth (IPTG) in an in vitro assay. Both traits revealed quantitative variability and high heritability. The traits were genetically dissected by the analysis of molecular markers using 184 mapped restriction fragment length polymorphisms (RFLPs). Significant genetic correlation between the markers and the trait allowed us to identify a minimum number of five quatitative trait loci (QTLs) for IPGG and six QTLs for IPTG. Their chromosomal localization indicated that the two characters are controlled by different sets of genes. In addition, IPGG and IPTG were shown to be basically independent of the pollen germination ability and pollen tube growth rate under non-stress conditions. These results are discussed in relation to their possible utilization in a breeding strategy for the improvement of thermotolerance in maize.     

Screening for High-Temperature Tolerant Cotton Cultivars by Testing In Vitro Pollen Germination, Pollen Tube Growth and Boll Retention

With radical global climate change and global warming, high temperature stress has become one of major factors exerting a major influence on crop production. In the cotton (Gossypium hirsutum L.)-growing areas of China, especially in the Yangtze River valley, unexpected periodic episodes of extreme heat stress usually occur in July and August, the peak time of cotton flowering and boll loading, resulting in lower boll set and lint yield. Breeding programs for screening high temperature-tolerant cotton germplasm and cultivars are urgent in order to stabilize yield in the current and future warmer weather conditions. In the present study, 14 cotton cultivars were quantified for in vitro pollen germination and pollen tube growth in response to temperatures ranging from 10 to 50 ℃ at 5 ℃ intervals. Different cotton genotypes varied in their in vitro pollen germination and pollen tube length responses to the different temperatures. Maximum pollen germination and pollen tube length ranged from 25.2% to 56.2% and from 414 to 682 μm, respectively.The average cardinal temperatures (Tmin, Topt, and Tmax) also varied among the 14 cultivars and were 11.8,27.3, and 42.7 ℃ for pollen germination and 11.8, 27.8, and 44.1 ℃ for maximum pollen tube length. Variations in boll retention and boll numbers per plant in field experiments were found for the 14 cotton cultivars and the boll retention and boll retained per plant on 20 August varied considerably in different years according to weather conditions. Boll retention on 20 August was highly correlated with maximum pollen germination (R2=0.84) and pollen tube length (R2=0.64). A screening method based on principle component analysis of the combination of pollen characteristics in an in vitro experiment and boll retention testing in the field environment was used in the present study and, as a result, the 14 cotton cultivars could be classified as tolerant, moderately tolerant, moderately susceptible and susceptible to high temperature.     

Variation in pollen viability among Picea abies genotypes – potential for unequal paternal success

An in vitro germination method was used to study variation in pollen viability, that is pollen-tube growth rate together with germination percentage, among the Picea abies genotypes in a seed orchard. The method permits easy, rapid screening of large numbers of genotypes. Significant variation in pollen viability among the genotypes was evident, the differences among the pollen-lot means being 7–10–fold in different years. No correlation was found between the average pollen viability and the phenology, growth or growing-site characteristics of the pollen donors. However, there appeared to be pollen lots that either benefit from a higher germination temperature or else germinate faster at lower temperatures. The significant variation in pollen viability among the pollen donors indicates a potential for male gametophyte competition. This, together with the observed genotype-environment interactions in pollen performance, may contribute to the variable genetic composition of seed produced in the seed orchard. Received: 9 December 1999 / Accepted: 22 December 1999     

Mapping quantitative trait loci for heat tolerance of reproductive traits in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis>)

Global warming has become a worldwide concern due to its adverse effects on agricultural output. In particular, long-term mildly high temperatures interfere with sexual reproduction and thus fruit and seed set. To uncover the genetic basis of observed variation in tolerance against heat, a bi-parental F₂ mapping population from two contrasting cultivars, i.e. Nagcarlang and NCHS-1, was generated and phenotyped under continuous mild heat conditions for a number of traits underlying reproductive success, i.e. pollen viability, pollen number, style length, anther length, style protrusion, female fertility and flowering characteristics, i.e. inflorescence number and flowers per inflorescence. Quantitative trait loci (QTLs) were identified for most of these traits, including a single, highly significant one for pollen viability, which accounted for 36% of phenotypic variation in the population and modified pollen viability under high temperature with around 20%. QTLs for some traits colocalised, indicating trait dependency or pleiotropic-effect loci. We conclude that a limited set of major genes determines differences in performance of reproductive traits under continuous mild heat in tomato. The results contribute to our fundamental understanding of pollen thermotolerance and may support development of more heat-tolerant tomato varieties.     

Response of in vitro pollen germination and pollen tube growth of groundnut (Arachis hypogaea L.) genotypes to temperature

Air temperatures of greater than 35 °C are frequently encountered in groundnut‐growing regions, especially in the semi‐arid tropics. Such extreme temperatures are likely to increase in frequency under future predicted climates. High air temperatures result in failure of peg and pod set due to lower pollen viability. The response of pollen germination and pollen tube growth to temperature was quantified in order to identify differences in pollen tolerance to temperature among 21 groundnut genotypes. Plants were grown from sowing to harvest in a poly‐tunnel under an optimum temperature of 28/22 °C (day/night). Pollen was collected at anther dehiscence and was exposed to temperatures from 10° to 47·5 °C at 2·5 °C intervals. The results showed that a modified bilinear model most accurately described the response to temperature of percentage pollen germination and maximum pollen tube length. Genotypes were found to range from most tolerant to most susceptible based on both pollen characters and membrane thermostability. Mean cardinal temperatures (T_min, T_opt and T_max) averaged over 21 genotypes were 14·1, 30·1 and 43·0 °C for percentage pollen germination and 14·6, 34·4 and 43·4 °C for maximum pollen tube length. The genotypes 55‐437, ICG 1236, TMV 2 and ICGS 11 can be grouped as tolerant to high temperature and genotypes Kadiri 3, ICGV 92116 and ICGV 92118 as susceptible genotypes, based on the cardinal temperatures. The principal component analysis identified maximum percentage pollen germination and pollen tube length of the genotypes, and T_max for the two processes as the most important pollen parameters in describing a genotypic tolerance to high temperature. The T_min and T_opt for pollen germination and tube growth, rate of pollen tube growth were less predictive in discriminating genotypes for high temperature tolerance. Genotypic differences in heat tolerance‐based on pollen response were poorly related (R² = 0·334, P = 0·006) to relative injury as determined by membrane thermostability.     

In vitro pollen competitive ability in Viola tricolor: temperature and pollen donor effects

In this study on Viola tricolor pollen, the competitive ability of 16 pollen donors originating from a wild population was analysed in a set of greenhouse and germination temperatures. The aim was to examine the consistency in donor pollen performance across temperatures and to see whether variation in performance was random or due to individual differences in the plastic response to temperature. Pollen tube growth rate in vitro was investigated in two greenhouse temperatures (on the day pollen was collected) and in four germination temperatures. In addition, pollen tube growth rate was assessed in vivo (in one temperature) to examine the relationship between in vivo and in vitro growth. A temperature difference of 5 K - corresponding to natural variation in time and space detected in the field - affected pollen tube growth rate. For both temperature components, significant pollen donor by temperature interactions were found and rank order of pollen donors changed across treatments. Although pollen competitive ability in violets was strongly influenced by both temperature components, the occurrence of pollen donor by temperature interactions indicates that donor siring ability varies with temperature. This, in turn, may suggest a means to maintain pollen competitive ability despite selection for this trait.     

Soybean (Glycine max) pollen germination characteristics, flower and pollen morphology in response to enhanced ultraviolet-B radiation

BACKGROUND AND AIMS: Ultraviolet-B (UV-B) radiation effect on reproductive parts of the plants has received little attention. We studied the influence of UV-B radiation on flower and pollen morphology, pollen production and in vitro pollen germination and tube growth of six genotypes of soybean (Glycine max). METHODS: Soybean genotypes were investigated by growing them under four levels of biologically effective UV-B radiation of 0 (control), 5, 10 and 15 kJ m(-2) d(-1) in sunlit controlled-environment chambers. KEY RESULTS: Reductions in lengths of flower, standard petal, and staminal column along with reduced pollen production, germination and tube growth were observed in all genotypes with increasing UV-B radiation. Combined response index (CRI), the sum of percentage relative responses in flower size, pollen production, pollen germination and tube growth due to UV-B radiation varied with UV-B dosage: -67 to -152 with 5 kJ m(-2) d(-1), -90 to -212 with 10 kJ m(-2) d(-1), and -118 to -248 with 15 kJ m(-2) d(-1) of UV-B compared to controls. Genotypes were classified based on the UV-B sensitivity index (USI) calculated as CRI per unit UV-B, where D 90-9216, DG 5630RR and D 88-5320 were classified as tolerant (USI > -7.43), and DP 4933RR, Stalwart III and PI 471938 were sensitive (USI < -7.43) in their response to UV-B radiation. Pollen grains produced in plants grown at 15 kJ m(-2) d(-1) UV-B radiation were shrivelled and lacked apertures compared to control and other UV-B treatments in both sensitive and tolerant genotypes, and the differences were more conspicuous in the sensitive genotype (PI 471938) than in the tolerant genotype (D 90-9216). The number of columellae heads of the exine was reduced with increasing UV-B radiation. CONCLUSIONS: Soybean genotypes varied in their reproductive response to UV-B radiation. The identified UV-B tolerant genotypes could be used in future breeding programmes.     

In vitro pollen maturation and successful seed production in detached spikelet cultures in wheat (Triticum aestivum L.)

Summary Two spring wheat genotypes (cv Orofen and Chinese Spring) were compared for their in vitro pollen maturation capacity in detached spikelet cultures in a defined solid medium. Under these in vitro conditions Chinese Spring produced normal trinucleate pollen in 66.8% and Orofen in only 37.5%. In both cultivars the pollen maturation process from the middle uninucleate stage took approximately 3 days longer in vitro than in vivo. The pollen maturation time depended on the microspore developmental stage at the time that the culturing started. The viability, germination capacity, and fertilizing ability of the in vitro matured pollen also differed between the two genotypes. The seed set achieved in vitro (averagely 12.8%) offers promise for the practical application of this method for producing controlled or selected offspring.     

Tomato pollen respiration in relation to in vitro germination and pollen tube growth under favourable and stress-inducing temperatures

Tomato pollen germination, pollen tube growth and respiratory activity were recorded during incubation in a liquid medium for 7 h over a temperature range of 15–35°C. Although the initial rate of respiration was highest at 30°C, both at 30°C and 35°C respiration decreased after the first hour of incubation due to high temperature impairment of germination and pollen tube growth. The total per cent germination of pollen over the 7-h period was maximal at 15°C whereas pollen tube length was maximal at 25°C. Although the production of CO₂ measured at hourly intervals throughout the incubation period did not correlate to a statistically significant level with either the per cent pollen germination or the length of the pollen tubes alone, nevertheless from 2 h after the start of incubation, it closely correlated with the values for germination × pollen tube length, indicating that the respiratory activity of tomato pollen at a given time is a function of both the per cent germination and the pollen tube growth. We suggest therefore that the rate of respiration might be preferable to a simple germination test for the assessment of pollen germination ability since it expresses not only the pollen germination potential but also the growth vigour of the pollen tubes. In addition, where in vitro tests are designed to assess pollen germination–temperature interactions, they should employ a long incubation period (e.g. 7 h) to permit differences in sensitivity to temperature to be observed.     

Evolution of mating system and the genetic covariance between male and female investment in Clarkia (onagraceae): selfing opposes the evolution of trade-offs

Sex allocation theory has assumed that hermaphroditic species exhibit strong genetically based trade-offs between investment in male and female function. The potential effects of mating system on the evolution of this genetic covariance, however, have not been explored. We have challenged the assumption of a ubiquitous trade-off between male and female investment by arguing that in highly self-fertilizing species, stabilizing natural selection should favor highly efficient ratios of male to female gametes. In flowering plants, the result of such selection would be similar pollen:ovule (P:O) ratios across selfing genotypes, precluding a negative genetic correlation (r(g)) between pollen and ovule production per flower. Moreover, if selfing genotypes with similar P:O ratios differ in total gametic investment per flower, a positive r(g) between pollen and ovule production would be observed. In outcrossers, by contrast, male- and female-biased flowers and genotypes may have equal fitness and coexist at evolutionary equilibrium. In the absence of strong stabilizing selection on the P:O ratio, selection on this trait will be relaxed, resulting in independence or resource-based trade-offs between male and female investment. To test this prediction, we conducted artificial selection on pollen and ovule production per flower in two sister species with contrasting mating systems. The predominantly self-fertilizing species (Clarkia exilis) consistently exhibited a significant positive r(g) between pollen and ovule production while the outcrossing species (C. unguiculata) exhibited either a trade-off or independence between these traits. Clarkia exilis also exhibited much more highly canalized gender expression than C. unguiculata. Selection on pollen and ovule production resulted in little correlated change in the P:O ratio in the selfing exilis, while dramatic changes in the P:O ratio were observed in unguiculata. To test the common prediction that floral attractiveness should be positively genetically correlated with investment in male function, we examined the response of petal area to selection on pollen and ovule production and found that petal area was not consistently genetically correlated with gender expression in either species. Our results suggest that the joint evolutionary trajectory of primary sexual traits in hermaphroditic species will be affected by their mating systems; this should be taken into account in future theoretical and comparative empirical investigations.     

In vitro pollen germination and transient transformation of<Emphasis Type="Italic">Zea mays</Emphasis> and other plant species

To study pollen-specific gene expression, fast and convenient methods involving in vitro pollen germination and bombardment with promoter deletion constructs are needed. Unfortunately, because of variation of pollen germability and tube growth, conducting these experiments is often unsatisfying for many plant species, including maize, especially when pollen is collected at different times of the day or season. We have overcome these problems by defining a novel medium (PGM) that guarantees germination efficiencies of more than 90% for maize pollen from at least 7 genotypes (A188, AC 3572 C, B73, H99, Hi-II, Q2, Tx232). This medium is also suitable to germinate pollen of other monocot species, such asPennisetum americanum andTradescantia species, and dicot species, such asArabidopsis thaliana, Arachis hypogaea, Columnea oesterdiana, Nicotiana tabacum, Phaseolus vulgaris, Pisum sativum, Solanum lycopersicum, Solanum tuberosum, andVicia faba. On average, reproducible germination rates ranging from 50–100% were observed with all plant species tested. In addition, we report a transient transformation assay using the luciferase (Luc) reporter gene. Biolistic parameters were defined to obtain reproducibleLuc activity measurements after bombarding thick-walled pollen, such as maize pollen. For comparison, samples of germinated maize and tobacco pollen were bombarded with the reporter gene under control of the constitutive ubiquitin-and pollen-specificZmMADS2 maize promoters. The important parameters necessary to apply both in vitro pollen germination and transient transformation for a large range of plant species are discussed. An erratum to this article is available at .     

The vitality of the Serbian spruce (Picea omorika) pollen during the long-term cryopreservation

Abstract

This article studies differences in the vitality (germination rate and pollen tube length) of fresh pollen and pollen stored at ?20 °C for 14 years of Serbian spruce (Picea omorika [Pan?i?] Purkyne). Fresh pollen was sampled from 24 trees from a Serbian spruce seed stand area on the site of Bela zemlja (43° 48′ 32″ N, 19° 44′ 25″ E) in the area of Mount Zlatibor (Serbia) in two successive years. Six nutrition media with different sucrose concentrations (0%, 5%, 10%, 15%, 20% and 25% aqueous solution) were used to assess the vitality of the pollen. Variance analysis shows significant differences among years of pollen sampling, years of cryopreservation, trees, and sucrose treatments for pollen germination for both germination rate and pollen tube length. The results indicate that climate conditions preceding the pollen maturation period had an impact on the pollen quality as well as on the pollen vitality during the years of cryopreservation. Inter-individual variability (differences between trees genetic variability) was very pronounced and enabled selection of pollinator trees that retained their initial vitality during the period of cryopreservation. This periodicity in Serbian spruce full flowering might have significant practical application in the breeding of this important species.     

Differences in in vitro pollen germination and pollen tube growth of cotton cultivars in response to high temperature

* BACKGROUND AND AIMS: High-temperature environments with >30 degrees C during flowering reduce boll retention and yield in cotton. Therefore, identification of cotton cultivars with high-temperature tolerance would be beneficial in both current and future climates. * METHODS: Response to temperature (10-45 degrees C at 5 degrees C intervals) of pollen germination and pollen tube growth was quantified, and their relationship to cell membrane thermostability was studied in 12 cultivars. A principal component analysis was carried out to classify the genotypes for temperature tolerance. * KEY RESULTS: Pollen germination and pollen tube length of the cultivars ranged from 20 to 60 % and 411 to 903 microm, respectively. A modified bilinear model best described the response to temperature of pollen germination and pollen tube length. Cultivar variation existed for cardinal temperatures (T(min), T(opt) and T(max)) of pollen germination percentage and pollen tube growth. Mean cardinal temperatures calculated from the bilinear model for the 12 cultivars were 15.0, 31.8 and 43.3 degrees C for pollen germination and 11.9, 28.6 and 42.9 degrees C for pollen tube length. No significant correlations were found between pollen parameters and leaf membrane thermostability. Cultivars were classified into four groups based on principal component analysis. * CONCLUSIONS: Based on principal component analysis, it is concluded that higher pollen germination percentages and longer pollen tubes under optimum conditions and with optimum temperatures above 32 degrees C for pollen germination would indicate tolerance to high temperature.     

Influence of the pH of the stigmatic exudate on male-female interaction in Rosa hybrida L

Summary The in vitro germination of rose pollen is influenced by the pH of the medium. Both germination percentage and length of emitted pollen tubes were maximal for in vitro germination and tube elongation at pH 5 and minimal at pH 3 and 9 (Rosa hybrida L. var P 30 pollen). Three varieties characterized by having a stigmatic exudate of pH = 5 and another three varieties having one of pH = 9 were pollinated with the same pollen. Pollination effectiveness, as indicated by hip set (number of hips/pollmated flowers × 100) and mean number of achenes per hip, were significantly different: it was much higher for the varieties with the stigmatic exudate of pH = 5. pH control on pollination efficiency and subsequent fecundation success is proposed and discussed.     

Rice (<i>Oryza sativa</i> L.) Breeding among Hassawi Landrace and Egyptian Genotypes for Stem Borer (<i>Chilo agamemnon</i> Bles.) Resistance and Related Quantitative Traits

Rice stem borer (Chilo agamemnon Bles.) is a primary insect pest of rice and is a major limiting factor to rice production. Breeding for insect-resistant crop varieties has been an economic way of integrated pest management (IPM) as it offers a viable and ecologically acceptable approach. This study was aimed to evaluate rice genotypes for their resistance against rice stem borer. Seven parental genotypes with twenty one F1 crosses were evaluated for genotypic variation in field experiments. Analysis of variance revealed significant differences for the studied traits in almost all crosses and parents. In addition, the mean squares of parents versus their crosses were signifi- cant for stem borer resistance and other associated traits. Moreover, both general combining ability (GCA) and specific combining ability (SCA) variances were highly significant for all characters studied in the F1 generation. Based on GCA, 4 genotypes (Sakha101, Gz6903-3-4-2-1, Gz9577-4-1-1 and Hassawi) exhibited highly significant negative values for stem borer resistance (–0.53, –1.06, –0.18 and –0.49, respectively) indicating they are the best combiners for stem borer resistance. Based on SCA analysis, nine cross combinations showed highly significant negative effects for stem borer resistance. Similarly, the cross Giza178 Hassawi was the best combination with significantly highest value for early maturity. In addition, seven crosses showed highly significant negative SCA for plant height trait. On the other hand, for panicle length, number of primary branches/panicle, panicle weight and 1000-grain weight, seven, four, eight and six crosses showed highly significant positive SCA, respectively. The result further revealed that the non-additive dominance genetic variance was higher than the additive variance for all evaluated traits indicating that non-additive genetic variances have a role in their inheritance. The broad-sense heritability estimates were high for all the studied traits. The stem borer resistance was significantly correlated with panicle weight and 1000-grain weight, which also showed a highly significant correlation with grain yield/plant. Thus these traits can be effectively employed in a breeding program to confer resistance against stem borer infestation in rice. It was further supported by biplot analysis, which clustered these potentially important traits into two quadrants showing their importance in any future breeding program to control stem borer infestation. This study has contributed valuable information for evaluation of genetic diversity in the local rice germplasm and its utilization in futuristic rice genetic improvement programs.     

The structure of phenotypic variation in gender and floral traits within and among populations of Spergularia marina (Caryophyllaceae)

We sampled four wild populations of the highly autogamous Spergularia marina (Caryophyllaceae) in California to detect and to measure the magnitude of within- and among-population sources of phenotypic variation in gender and floral traits. From flowers and fruits collected from field and greenhouse-raised plants, we measured ovule number, seed number, mean seed mass, pollen production (greenhouse families only), mean pollen grain volume (greenhouse families only), anther number, anther/ovule ratio, pollen/ovule ratio (estimated using different flowers for pollen than for ovules; greenhouse families only), petal number, and petal size. Using greenhouse-raised genotypes, variation among maternal families nested within populations was evaluated for each trait to determine whether populations differ in the degree of maternally transmitted phenotypic variation. For each population, we used 15 greenhouse-raised maternal families to estimate the broad-sense heritability and genetic coefficient of variation of each floral trait. The magnitude and statistical significance of broad-sense heritability estimates were trait- and population-specific. Each population was characterized by a different combination of floral traits that expressed significant maternally transmitted (presumably genetic) variation under greenhouse conditions. Flowers representing two populations expressed low levels of maternally transmitted variation (three or fewer of nine measured traits exhibited significant maternal family effects on phenotype), while flowers representing the other two populations exhibited significant maternal family effects on phenotype for five or more traits. Our ability to detect statistically significant differences among the four populations depended upon the conditions under which plants were grown (field vs. greenhouse) and on the floral trait observed. Field-collected flowers exhibited significant differences among population means for all traits except anther number. Flowers sampled from greenhouse-raised maternal families differed among populations for all traits except ovule number, seed number, and petal size. We detected negligible evidence that genetic correlations constrain selection on floral traits in Spergularia marina.     

SSR and AFLP based genetic diversity of soybean germplasm differing in photoperiod sensitivity

Forty-four soybean genotypes with different photoperiod response were selected after screening of 1000 soybean accessions under artificial condition and were profiled using 40 SSR and 5 AFLP primer pairs. The average polymorphism information content (PIC) for SSR and AFLP marker systems was 0.507 and 0.120, respectively. Clustering of genotypes was done using UPGMA method for SSR and AFLP and correlation was 0.337 and 0.504, respectively. Mantel's correlation coefficients between Jaccard's similarity coefficient and the cophenetic values were fairly high in both the marker systems (SSR = 0.924; AFLP = 0.958) indicating very good fit for the clustering pattern. UPGMA based cluster analysis classified soybean genotypes into four major groups with fairly moderate bootstrap support. These major clusters corresponded with the photoperiod response and place of origin. The results indicate that the photoperiod insensitive genotypes, 11/2/1939 (EC 325097) and MACS 330 would be better choice for broadening the genetic base of soybean for this trait.     

The effects of ethyl methanesulfonate treatment on <Emphasis Type="Italic">Eucalyptus</Emphasis> pollen behaviour in vitro

Treating pollen with mutagens prior to controlled pollination may facilitate the production of mutant trees for developmental studies and eventual plantation improvement. To establish a suitable dose of the chemical mutagen ethyl methanesulfonate (EMS) for the testing of this hypothesis, pollen of Eucalyptus globulus ssp. globulus and E. grandis was studied in vitro. Pollen germination, pollen tube elongation and generative cell division were examined after 48 h of culture, following exposure to between 0 and 1,000 ppm EMS. Doses of 600 to 1,000 ppm EMS reduced pollen germination in vitro in both species. Doses of up to 1,000 ppm EMS were not observed to significantly impact on either pollen tube length, or generative cell division in vitro of either species. A dose of 600 ppm EMS in paraffin oil is predicted to induce mutation in Eucalyptus species whilst impacting minimally on seed production based on the effect on pollen germination.