Effects of Low Temperature and Ultra-low Temperature on Pollen Viability of Tomato(Lycopersicon esculentum Mill.)

The pollen of two tomato varieties, Ryau961721 and Ryau9327D, was adopted in our research. The two tomato varieties were bred by College of Land- scape and Horticulture, Yunnan Agricultural University. The collected pollen was stored in low-temperature （4 ℃） and ultra-low-temperature （-196 ℃） circumstances. Then it was inoculated to the medium and cultured at 28 ℃ in thermostat incubator. The pollen viability was determined by electron microscope. The results showed that compared to that of pollen stored in control （25 ℃） circumstance, the viability of pollen stored in low-temperature （4 ℃） and ultra-low-temperature （-196 ℃） circum- stances for 1 -3 d did not change significantly. In addition, pollen viability trended to decrease with the increase of freeze-thaw cycle and storage time. The pollen lost basically the viability by the 7th d in the storage.

Study on Pollen Viability and Stigma Receptivity of Very Later-ripening ‘Dongxing' Apricot

[Objective] The primary aims of this study were to understand the characteristic of floralorgan development in ‘Dongxing＇, and analyze its differences with other apricot varieties. [Method] Floral organ morphology, pollen quantity, pollen viability and stigma receptivityof ‘Dongxing＇ and other apricot varieties were observed and measured. [Result] The ratio between the medium style and long style of‘Dongxing＇ was 82.4%, and the ratio of pistillode was lower than that in the other apricot varieties. Its pollen quantity was 32 183.2 grains per flower, and was fewer than the others. The pollen germination of ‘Dongxing＇ in optimum medium（1% agar ＋15% sucrose ＋ 0.01% boric acid） was 53.0%, i.e. its pollen viability was low. The pollen viability increased at first and then decreased following the period of the bud stage to flowering stage, and pollen viability reached maximum value at the 1st d after flowering. Meanwhile the stored pollen viability continuously decreased with the extension of storage time, and pollen viability of the both vivo or vitro stored was decreased to the half of the maximum value at the 3rdd after flowering or storage.The stigma receptivity of ‘ongxing＇ enhanced at first then weakened, maximum stigma receptivity was found at the period of 2 h to 4 h after flowering. The optimum time for artificial pollination was 1 h to 8 h after flowering and it was shorter than the other apricot varieties was. [Conclusion] The ratio between the medium style and long style of ‘Dongxing＇ was higher than the other apricot varieties, while the pollen viability of ‘Dongxing＇ on the contrary. Its pollen viability reached maximum value at the 1st d after flowering and the optimum time for artificial pollination was1 h to 8h after flowering.

A Study on Pollen Viability of Piper colubrinum Link

Pollen viability study on Piper colubrinum Link. carried out to develop interspecific hybridization between P. nigrum L. and P. colubrinum Link.. This plant has good potential as a donor plant in breeding programme for Phytophthora to foot rot resistance in the cultivated species, P. nigrum. This project was carried out to reveal the optimum time to collect pollen of P. colubrinum for artificial pollination. Through this study, anther dehiscence was proved occurred around 9 am. Based on the result obtained from study on the time of anther dehiscence, the pollen was classified into five stages for testing on the viability, i.e., stage 1, before anther dehiscence, i.e., around 7 am （pollen obtained by crushing on the anther）; stage 2： immediately after anther dehiscence, i.e., around 9 am; stage 3： two hours after anther dehiscence, i.e., around 11 am; stage 4： four hours after anther dehiscence, i.e., around 1 pm; and stage 5： six hours after anther dehiscence, i.e., around 3 pm. Data obtained from pollen germination and pollen tube growth study showed that pollen of P. colubrinum was the most viable at two hours after anther dehiscence and onward. It was also proved that the viability can be maintained up to at least eight hours. Pollen obtained before anther dehiscence by crushing on the anther was found less viable with lower percentage of pollen germination and retarded pollen tube growth. In other words, the experiment enlightened that artificial pollination between P. nigrum L. and P. colubrinum Link was ideally to be carded out approximately starting from 11 am until 5 pm, considering the viability of pollen ofP. colubrinum.

Impacts of high temperature,relative air humidity,and vapor pressure deficit on the seed set of contrasting maize genotypes during flowering

Heat stress is a major constraint to current and future maize production at the global scale.Male and female reproductive organs both play major roles in increasing seed set under heat stress at flowering,but their relative contributions to seed set are unclear.In this study,a 2-year field experiment including three sowing dates in each year and 20 inbred lines was conducted.Seed set,kernel number per ear,and grain yield were all reduced by more than 80%in the third sowing dates compared to the first sowing dates.Pollen viability,silk emergence ratio,and anthesis-silking interval were the key determinants of seed set under heat stress;and their correlation coefficients were 0.89^(***),0.65^(***),and-0.72^(***),respectively.Vapor pressure deficit(VPD)and relative air humidity(RH)both had significant correlations with pollen viability and the silk emergence ratio.High RH can alleviate the impacts of heat on maize seed set by maintaining high pollen viability and a high silk emergence ratio.Under a warming climate from 2020 to 2050,VPD will decrease due to the increased RH.Based on their pollen viability and silk emergence ratios,the 20 genotypes fell into four different groups.The group with high pollen viability and a high silk emergence ratio performed better under heat stress,and their performance can be further improved by combining the improved flowering pattern traits.

Study on the Flowering Biological Characteristics of Prunus domestica × armeniaca

[Objective] The aims of this study were to understand the flowering biological characteristics of Prunus domestica ×armeniaca and analyze its differences with other apricot varieties and plum varieties. [Method] Taking three varieties of Prunus domestica ×armeniaca as the research object, the phenophase of blooming,morphology characteristics of floral organs and development characteristics of floral organs were observed, pollen amount, pollen viability and stigma receptivity were measured. [Result] The results showed that three varieties of Prunus domestica×armeniaca were in blossom in early April, the florescence were relatively late for 8-12 d comparing with the varieties of apricot, the florescence were relatively similar to the P. domestica L. Morphology characteristics of floral organs of three varieties of Prunus domestica×armeniaca had few differences, were relatively similar to two varieties of plum, and they all had high percent of middle-style and long-style flower.The pollen amount of three varieties of Prunus domestica ×armeniaca had a little differences comparing with two varieties of plum, but were lower than three varieties of apricot. There were some differences in pollen viability, the germination percentage of pollen of ‘Konglongdan＇ was relatively high, was 51.6%; The pollen amount of ‘Fengweihuanghou＇ was relatively high, was 880.8 per anther; ‘Weidi＇ had fewer pollen amount, and the pollen viability was just 2.1%; Three varieties of Prunus domestica ×armeniaca all had strong stigma receptivity on the bloom day, and the stigma receptivity continued exist until the day that 5 days after blooming. [Conclusion] The florescence of three varieties of Prunus domestica ×armeniaca were relatively concentrated, and the rate of pistil abortion was lowest, the variation intensity of stigma receptivity and sustainable time of three varieties of Prunus domestica×armeniaca almost had a little differences comparing with a variety of plum, but slightly more than three varieties of apricot.

Comparative Study on Floral Organs and Pollen Characteristics of Different Varieties of Sorrel

The floral organ morphology,pollen morphology,quantity,and viability of Rumex,Rumex hanus F1,Rumex hanus 1,and Rumex hanus 2 were compared and analyzed.The results showed that the longitudinal diameter of petals was not significantly different among different varieties of sorrel,and the transverse diameter and corolla diameter showed differences to varying degrees.They all had six stamens and three stigmas.The pollen shape of the four varieties was prolate,and the polar view was trilobated and round.They all had three germinal furrows,and the outer wall of the pollen was decorated with small cavities and spiny patterns,with warty protrusions.The equatorial axis length of pollen of different varieties of sorrel was significantly different(P<0.05).There were no significant differences in pollen amount among different varieties.There were six anthers in a single flower,featuring anther dehiscence.The pollen viability of Rumex hanus 1 was significantly lower than that of the other three varieties(P<0.05).Therefore,through the analysis of the floral organs and morphological characteristics of anthers of sorrel,the varieties of sorrel can be effectively distinguished and identified.

The Flowering Biology of Plum(Prunus domestica L.) in Aksu Region, Xinjiang

[Objective] The aim of this study was to understand the flowering biological characteristics of different varieties Prunus domestica L. in Aksu Jiamu Experi- ment Station. [Method] Three varieties of plum as Prunus domestica L. cv. ＇French＇, Prunus domestica L. cv. ＂Victoria＇ and Prunus domestica L. cv. ＂Stanley＇ were the research subjects. The phenophases of blooming, and the morphological and developmental characteristics of floral organs were observed. The amount and viability of pollen and the stigma receptivity were measured. [Result] Three varieties of plum all blossomed in early April, and the florescence had lasted for 9-10 d. The average number of anthers was 28.48%. The average number of pollen grains in each flower was 28 700.0. The pollen germination rate was 27.4%. 86.75% of the flowers were medium-styled or long-styled. There was no significant difference in the petal shape, color, anther number, calyx color, and flower ovary among the three varieties of plum. The stigma receptivity was strongest on the first day of flowering, and then dropped gradually. Therefore, the flowers of plum were manual pollinated on the first day of flowering. The duration time of stigma receptivity of Prunus domestica L. cv. ＇Victoria＇ was longer than the other cultivars, the duration time of stigma receptivity was about 5 d. [Conclusion] The pollen number and pollen germination rate of Prunus domestica L. cv. ＇Stanley＇ were higher than the other cultivars, which be considered the most suitable pollinizer for plum. In contrast, the complete flower rate of Prunus domestica L. cv. ＇French＇ and Prunus domestica L. cv. ＇Victoria＇ was relatively high, but the pollen number and pollen germination rate of Prunus domestica L. cv. ＇French＇ and Prunus domestica L. cv. ＇Victoria＇ were lower than Prunus domestica L. cv. ＇Stanley＇, which are not suitable to use as a pollinizer for plum.

Preliminary Study of Low Self-fertile Rate of ‘Kuijin' Apricot

To research the self-sterility of apricot, the pollen germination of ‘Kuijin＇apricot was conducted in vitro, and pollen viability was determined by germination on solid medium. Meanwhile, the effects of different media on its pollen germination and the growth of pollen tubes were analyzed. The results showed that the optimum media for pollen germination and growth of pollen tubes were 10% sucrose ＋0.1% boric acid and 5% sucrose ＋ 0.01% boric acid respectively. The self-pollination setting rate of ‘Kuijin＇ apricot was 4.70%, indicating that ‘Kuijin＇ apricot was self-incompatible. The reasons for the self-incompatibility of ‘Kuijin＇ were explored according to its pollen weight and pollen quantity. The results showed that self-pollinate setting rate of ‘Kuijin＇ apricot was closely related to the length of pollen tubes,but it had no direct correlation with pollen quantity.

Visualizing Meiotic Chromosome Pairing and Segregation in Interspecific Hybrids of Rice by Genomic in situ Hybridization

Meiotic disturbances in F1 hybrids and their progenies are still major problems in wide hybridization.To investigate the genome affinity reflected in chromosome pairing and segregation,we studied chromosome behaviors during meiosis in two interspecific F1 hybrids[O.minuta×O.australiensis(Om×Oa,BCE genome)and Oa×O.ridleyi(Or,EHJ genome)]by using both traditional staining methods and genomic in situ hybridization(GISH).GISH analysis has been successfully performed on mitotic chromosomes to distinguish different Oryza genomes,but relatively fewer systematic analyses of meiotic chromosomes of interspecific hybrids have been reported.In the hybrids,highly irregular chromosome behaviors through meiosis resulted in producing microspores with unbalanced genome.At diakinesis of these two hybrids,most chromosomes present as univalent,with low frequency as bivalents and occasionally as trivalents.In a pollen mother cell,2 to 8 bivalents and 0 to 4 trivalents were observed in the hybrid Oa×Or,and 1 to 8 bivalents and 0 to 5 trivalents were observed in the hybrid Om×Oa.GISH results indicated that 51.52%bivalents in Oa×Or and 79.65%bivalents in Om×Oa involved allosyndetic association,which indicates that recombination and introgression should be possible if viable backcrosses can be recovered even from triploid hybrids.In this study,we revealed that the meiotic disturbance due to low affinities between parental genomes is the major reason for the sterility of these two triploid interspecific hybrids.The two hybrids showing vigor in reproductive growth are potential genetic resources in future breeding programs.A better understanding of genomic affinities between these distant Oryza species can facilitate planning an effective breeding program by using wide hybridization,and efficient and routine GISH analysis is helpful to monitor alien introgression in the process.

Cloning and Characterization of Protein Prenyltransferase Alpha Subunit in Rice

Protein prenylation plays a crucial role in plant development and stress response.We report the function of pren yltra nsferase a-sub unit in rice.Protein-protei n in teractions showed that the fam esyl-transferase(OsPFT)/geranylgeranyltransferase-l(OsPGGT l-a)protein interacted together with OsPFT-P and OsPGGT l-p.The a-and p-subunits of OsPFT formed a heterodimer for the transfer of a farnesyl group from famesyl pyrophosphate to the CaaX-box-containing peptide N-dansyl-GCVLS.Furthermore,the tissue expressi on patter ns of the OsPFT and OsPGGT I sub units were similar,and these sub units were localized in the cytoplasm and nucleus.Moreover,OsPFT/OsPGGT/-a-deletion homozygous rice mutants had a lethal phenotype,and the heterozygous mutants exhibited reduced pollen viability.These results indicated that prenylation plays an important role in rice development.

Methods for Improving Hybrid Seed-setting Rate of a Potato Cultivar Linshu 17

[Objective] This study aimed to explore methods for improving hybrid seed-setting rate of a potato cultivar Linshu 17. [Method] L0527-4 was taken as male parent and Linshu 17 was taken as female parent to breed a new potato cul- tivar, so as to take advantage of the excellent characters of Linshu 17. [Result] The optimum pollination time of Linshu 17 was 10：00-12：00 am or after 04：00 pm. Spraying 10 mg/L of 2, 4-D, 50 mg/L of gibberellin or 20 mg/L of 6-BA ＋ 50 mg/L of gibberellin once every 7 days since the 3^rd day after hybridization all could im- prove the hybrid seed-setting rate of Linshu 17. [Conclusion] The hybrid seed-setting rate-improving effect of 2, 4-D sprayed on the 3^rd d after hybridization was best for Linshu 17. This study will provide technical references for other varieties to improve the hybrid seed-setting rate.

Self-incompatibility Characteristics of 34 Apricot Cultivars in Xinjiang

[ Objective] This study aimed to explore the relationship between self-incompatibility strength and characteristics related to pollination and fertilization of different apricot varieties in Xinjiang. [ Method] The pollen amount, pollen germination rate, pollen tube growth status and fruiting setting rate by self-pollina- tion of 34 apricot cultivars in Xinjiang were determined, to analyze the self-incompatibility of different apricot cultivars. [ Result] The average pollen amount per anther of 34 apricot eultivars was 1 213.7, and the average pollen germination rate was 46.0%. There were great differences in the self-incompatlbility of different cuhivars ; most pollen tubes of the euhivars with high self-incompatibility stopped elongating at 1/3 or 1/2 part of the styles, and only a few pollen tubes of the euhivars with low self-incompatibility reached the ovary, and the normal fertilization ratio was significantly lower than that in self-compatible cultivars. [ Conclusion] Among the 34 apricot cuhivars, only 6 cuhivars were self-compatible and the others exhibited gametophyte self-incompatibility. In addition, the fruit setting rate by self-pollination was low.

Effects of Dust on Male and Female Floral Organs and the Pollination of the Walnut

The Tarim Basin,Xinjiang,China,a region important to the walnut industry,is affected by frequent heavy dust storms.Dust,including micro-particles(diameter<10μm),covers the surface of the walnut tree,thereby changing the surface-atmosphere interface microenvironment,which,in turn,influences the exterior and interior structure of the tree.Dust storms occur in spring and summer,during the flowering period of walnut,which is the key developmental stage leading to fruit formation.This study investigated the effects of dust on female flowers,male flowers,and the pollination of walnut.The morphological changes in the stigma during pollination were recorded.Stigma receptivity was studied via the benzidine–H2O2 method.Morphological features of the female floral organs and pollen were investigated using scanning electron microscopy.Pollen germination and pollen tube growth were examined by fluorescence microscopy.The results showed that dust had a significant inhibitory effect on male and female flowers,resulting in decreased catkin growth,reduced pollen viability(pollen viability was 20.13%),blocked pollen apertures,a reduced pollen germination rate on the stigma,and increased time needed for pollen tube appearance.Dust also had an inhibitory effect on stigma length and receptivity of female walnut flowers,with the length of the walnut stigma being reduced by 0.25~0.80 mm during the flowering process.In addition,there was decreased stigma mucus,resulting in stigma atrophy,decreased amount of pollen on the stigma,weakened stigma receptivity,and accelerated drying of female flowers.In the Tarim Basin,walnut flowering occurd at the same time as dust storms do,which had a negative impact on the floral organ,flowering and pollination of walnut.