Pollen viability and incompatibility in indigenous rice bean (Vigna umbellata (Thunb.) Ohwi & Ohashi)

Pollen viability, germination and compatibility are essential in determining the success of pollination and seed setting of high-valued crops. Rice bean (Vigna umbellata (Thunb.) Ohwi & Ohashi) is an underutilized and unexplored indigenous legume with high potential for commercial production. In this study, pollen quality, viability, germination rate and incompatibility among selected six rice bean (V. umbellata) accessions from Barili, Cebu, Philippines were evaluated to determine the barriers and effective pollination habit for increased productivity while retaining the important traits, including high tolerance in poor soils, superior climatic resilience and resistance to pest and diseases. Results of acetocarmine calorimetric assay showed that rice beans’ (V. umbellata) pollens are highly viable, with accessions VU 004 (56.33 ± 4.91%) and VU 007 (54.34 ± 4.53%) having the optimum viability rate. Brewbaker and Kwack medium treated with 0.2 g.l-1 and 0.3 g.l-1 boric acid (H3BO4) enhanced the germination rate in vitro (11.56 ± 5.53% and 9.47 ± 6.50% respectively). Bud (14.96 ± 1.53%) and post-anthesis pollens (10.28 ± 0.94%) have optimum germination rate in 0.2 g.l-1 boric acid media, while anthesis pollens are suitable in media supplemented with sucrose and boric acid alone (12.20 ± 1.50%) and with 0.1 g.l-1 myo-inositol supplementation (8.49 ± 1.86%). Pollination test revealed that rice bean accessions have high self-compatibility (50.76 + 3.45%) and low cross-compatibility (26.57 + 2.49%). The findings provide an important background in understanding the pollen quality and intraspecific interaction among indigenous rice bean (V. umbellata) accessions in Barili, Cebu to improve production and hybridization.

Determining conditions for best pollen quality of red-purple tree tomato (Solanum betaceum Cav.) germplasm

The germination and viability of pollen are characteristics required for fecundation when individuals of different or the same species are crossed. For this reason, assessing these parameters in selected individuals to be used in breeding programs will increase the chances for the obtainment of new progeny. In this study, pollen from different accessions of the red-purple tree tomato (Solanum betaceum Cav.) was used: local cultivar (Morado Puntón), two commercial varieties (Large Red and Oratia Red) and six segregants [(Solanum unilobum x Solanum betaceum) x Solanum betaceum]. Three types of flowers were taken (A-day of anthesis, B-one day after anthesis, and C-two days after anthesis). The pollen was conserved in two temperatures (4° and 22° C) and four storage times (0, 5, 10, 20 days). The percentage of germination and pollen viability of the selected individuals were evaluated. It was observed that the commercial materials showed higher germination percentages than the segregants in flower A and B at a temperature of 4 ° C at all storage times, except for the segregants GT7P47 and GT7P48 at the same temperature on day 0. In addition, high percentages of viability were obtained both in flowers A and B, at both temperatures and at all storage times. However, the immediate use of pollen after it is collected is recommended because better germination is achieved. This study is helpful to improve breeding procedures in the initial stages of directed crosses.

Effect of Genetically Diverse Pollen on Pollination, Pollen Tube Overgrow, Fruit Set and Morphology of Kiwiberry (Actinidia arguta)

Successful pollination and fertilization are crucial processes for obtaining a high yield, especially for dioecious plants such as A. arguta. Determination of pollen tube growth on stigma and fruit development parameters, which were investigated in this study, can enable the evaluation of male–female compatibility—one of the factors of successful pollination. Pollen quality and grain size were analysed for two years on six male cultivars of A. arguta and one of A. chinensis var. deliciosa. Results showed high pollen quality, both with parameters above 80%. Pollen germination in vivo showed differences in pollen–stigma interactions. The highest positive interactions were observed for all female cultivar crosses with male ‘Nostino’ and ‘Rubi’ and the lowest one for A. chinensis var. deliciosa ‘Tomuri’. However, fruit set and average fruit weight were equally high in most of the combinations (fruit set above 75% for the majority of combinations). Some differences were noticed in the average seed number per fruit and weight. All tested male cultivars were able to fertilize tested female cultivars, but taking into account other characteristics such as pollen efficiency, some male cultivars seemed to be more proper for commercial orchards. Using A. chinensis var. deliciosa pollen seems to be unreasonable in tested conditions.

Pollen tube growth from multiple pollinator visits more accurately quantifies pollinator performance and plant reproduction

Pollination services from animals are critical for both crop production and reproduction in wild plant species. Accurately measuring the relative contributions of different animal taxa to pollination service delivery is essential for identifying key pollinators. However, widely used measures of pollinator effectiveness (e.g., single visit pollen deposition) may be inaccurate where plant reproduction is strongly constrained by pollen quality. Here, we test the efficacy of single and multiple pollinator visits for measuring pollinator performance in a model plant species (apple, Malus domestica Borkh) that is strongly limited by pollen quality. We determined pollination success using a suite of measures (pollen deposition, pollen tube growth, fruit and seed set) from single and multiple pollinator visits. We found that pollen deposition from a single pollinator visit seldom resulted in the growth of pollen tubes capable of eliciting ovule fertilisation and never resulted in fruit or seed production. In contrast, multiple pollinator visits frequently initiated the growth of pollen tubes capable of ovule fertilisation and often led to fruit and seed production. Our findings suggest that single visit pollen deposition may provide a poor measure of pollinator performance when linked to reproductive success of plant species that are constrain by pollen quality. Alternatively, pollen tube growth from single and multiple pollinator visits can provide a measure of pollinator performance that is more closely linked to plant reproduction.

Pollen quality, pollen production and yield of some tomato (Solanum lycopersicum) genotypes under high temperature stress in Eastern Mediterranean

Pollen quality, pollen production and yield of different high temperature tolerant tomato genotypes were evaluated under Adana, Turkey conditions in two different periods. The control treatment (normal sown, where day/night temperatures during the vegetative and generative stage are below 32/20 °C) of the first period started on February 20, 2015. The seedlings in the second period were planted on May 15, 2015. The performances of twenty-four tomato genotypes (resistant and sensitive commercial genotypes) were compared to determine high temperature resistant and sensitive tomato genotypes. Significant relationship was obtained between the yield and the number of pollens. The results of the experiment revealed that ‘Tom173’, ‘Tom119’ and ‘F15656’ genotypes were more resistant, while ‘Tom108’ and ‘Tom10’ genotypes were more sensitive compared to the other tomato genotypes tested in the experiment.

Morphological variation of male A. arguta plants affects their flowering potential and pollen efficiency

Actinidia arguta (Siebold et Zucc.) Planch. ex Miq. is functionally a cryptic dioecious plant and successful pollination is crucial for achieving high quality fruit. The extent and bases of morphological variability in female genotypes have been well studied, but here we focus on the males. Mature plants of seven male A. arguta genotypes were studied in 2016 and 2017 during which a suite of phenological and morphological features was measured on ten randomly chosen one-year-old canes on each plant. This analysis was complemented by two other, specialized measures potentially related to pollination efficiency, namely pollen quality, and quantity. The time of bud break was similar each year across all genotypes and the pollen quality was uniformly very high (viability – 95.0–99.9% and germination – 89.0–97.3%). However, the ten genotypes exhibited high variability in both the number of flowers per inflorescence and pollen quantity, indicating marked differences in their flowering potential and efficiency as pollinizers. The male kiwiberry indicators developed in this study – flowering potential and pollen efficiency, appear to be effective tools for the comparative evaluation of male A. arguta genotypes.