The identification and evaluation of hybrid plants among open pollinated tkue seed families

An increase in the proportion ofhybrid vs. selfed plants improves the performance ofopen pollinated (OP) true potato seed (TPS) families. Strategies to increase the proportion ofhybrid seeds were investigated. A marker gene for yellow tuber flesh in a diploid clone, interplanted as the male parent, permitted identification of 4x × 2x hybrids among the OP progeny. Only 5% of the OP progeny were 4x × 2x hybrids. The proportion of 4x × 2x hybrid plants among the OP progeny was increased when the female parent had low male fertility and when only the largest 25% of the seeds were planted. The hybrid 4x × 2x plants were superior for all traits evaluated on the OP seedling transplant families. Traits included vigor, flowering, pollen stainability, OP fruit set, and tuber yield. Effects of the female parent were significant only for vigor and flowering, while seed size did not affect values for any trait consistently: With the limited outcrossing observed, the low seed set obtained when using parents with low male fertility and the work involved in selecting the largest seeds within individual fruits were not justifiable. However, research with OP true seed families asa low cost planting material should be continued, since high yielding OP families have been identified.     

The male fertility of primary and further generation dihaploids ofSolanum tuberosum

Summary Male sterility in dihaploids ofSolanum tuberosum is often a barrier to their utilization in breeding and genetical studies. Although the male fertility of primary dihaploids (obtained directly from tetraploids) was generally low, a few were produced by the author which produced seed when used as pollen parents on female fertile dihaploids. The population of further generation dihaploids (from dihaploid intercrosses) produced from the showed a marked improvement in male fertility. Comparative data from measurements of different aspects of male fertility in dihaploids are presented. These showed that the weight of pollen per anther, the percentage of (iodine) stainable pollen and the number of seeds per berry were greater in further generation dihaploids than in primary dihaploids. It is suggested that interspecific crosses using dihaploids are not necessarily useful for increasing male fertility in diploid potatoes. The advantages of breeding at the diploid level withinS. tuberosum are discussed. Rare male-fertile dihaploids could be used to generate diploids with a high frequency of male fertility. These could then be used to cross with any other flowering dihaploids to combine characters at the diploid level, so exploiting the simpler genetic ratios associated with disomic inheritance.     

木薯二倍体及其同源四倍体开花结实特性的比较

以木薯品种‘新选048’和‘华南205’的二倍体及其同源四倍体为材料,采用定株观察的方法,比较二倍体及其同源四倍体开花结实特性的差异,探究染色体加倍后对木薯开花结实特性的影响,为开展木薯多倍体材料创制及鉴定提供科学参考。结果表明：2个木薯品种四倍体的开花结实物候期都要迟于二倍体,且四倍体的雌花、雄花、花药、果实、种子的形态大小均大于二倍体;2个木薯品种不同倍性间花药分布情况存在差异,‘新选048’的四倍体会出现两性花且其雌花花被颜色与二倍体存在明显差异;2个木薯品种不同倍性间开花及坐果数量也存在不同程度的差异,其中‘新选048’四倍体的单序总花量和雌、雄花总量显著大于二倍体的,但2个品种在不同倍性间开花及坐果数量的差异中呈现不同的规律。因此,木薯染色体加倍,可延迟开花结实的时间,增加生殖器官的大小,改变花形态特征和雌雄花的数量及花总量,但这种改变具有品种依赖性。     

Crossability ofSolanum tuberosum Gp. Andigena haploids

The crossability of Group Andigena haploids was investigated in this study. Groups Phureja, Stenotomum and Tuberosum haploids were crossed to Gp. Andigena haploids reciprocally to estimate the female and male fertility of the latter. The male fertility of Gp. Andigena haploids was reflected by the average seed set from crosses to Gps. Phureja Stenotomum and Tuberosum haploids (69, 43 and 21 seeds per fruit, respectively); female fertility was expressed when Gps. Phureja or Stenotomum served as the male, yielding 48 and 38 seeds per fruit, respectively. To contrast Gp. Andigena and Gp. Tuberosum haploid male fertility, they were crossed among and between themselves. As males, Gp. Andigena haploids gave three to four times the seed set of Gp. Tuberosum haploids. Pollen tube growth was analyzed in various Gp. Andigena haploid crosses to determine the site of cross failure. The results presented provide the basis for the first step in determining the potential of Gp. Andigena haploids in the development of diploid breeding stocks and the 2n gamete approach to potato improvement.     

Seed set in 4x x 2x crosses as related to 2n pollen frequency

Seeds per fruit following 4x × 2x crosses in potato are roughly related to the frequency of 2n pollen. Our goal was to examine precisely the relationship between frequency of stainable 2n pollen and seeds per fruit (s/f) in 4x × 2x crosses. A 4x cultivar with high female fertility and 21 2n pollen producing 2x hybrids were used as seed and pollen parents, respectively. 2n pollen frequencies varied from 1 to 99% in the 2x hybrids and seed set ranged from 0 to 305 s/f in 4x×2x crosses. Mean seeds per fruit increased in response to increases from 1 to 50% 2n pollen, but did not increase in response to using a pollen sample with a 2n pollen frequency over 60%. Seed set averaged 11 s/f corresponding to pollen samples with 1–5% 2n pollen, 50 s/f at 10–20%, 125 s/f at 20–30%, and over 170 s/f at 2n pollen frequencies over 60%. Seed set in 210 control 4x × 4x crosses indicated that equivalent seed set occurs in 4x × 2x crosses when 2n pollen frequencies are over 20–30%. The 2x hybrids differed in mean and variation of 2n pollen frequencies and seed set in 4x × 2x crosses. One 2x hybrid with a meiotic aberration (sy-3) resulting in all univalents at Metaphase I (ordinarily leading to male sterility) and parallel spindles (ps) at Anaphase II had close to 100% 2n pollen (of the stainable pollen) and gave equivalent s/f in 4x × 2x crosses to s/f in 4x × 4x crosses. It is apparent that ample seed set occurs for using the 4x × 2x breeding scheme with 2n pollen frequencies over 10% and that even very low 2n pollen frequencies (1–10%) provide seed for the 4x×2x breeding approach.     

Screening potato (Solanum) species for male fertility under heat stress

Heat stress limits botanical seed production by inhibiting flowering, pollen production and pollen viability. Three accessions (PIs) of each of 23 diverseSolanum species were screened for stability of fertility parameters under heat stress. Seedlings were grown to flowering in temperate conditions (16–25 C), then treated with three weeks of heat stress of up to 45 C for 4–6 hours per day at midday with nighttime lows of 18 C, and compared to temperate-grown controls. A highly significant effect of species, temperature, and their interaction was detected for flowering. This means species were inherently different and heat had a general depressing effect, but the degree of that effect varied among species. While most species had little flowering in the hot house,S. commersonii andmicrodontum flowered significantly more there than in the temperate house. Of species which flowered in hot conditions, some shed no pollen and some had good shed of mostly dead pollen, but onlyS. commersonii, jamesii, kurtzianum andmegistacrolobum had good flowering, pollen shed and viability. This work is expected to contribute to the study of the genetic and physiological bases of heat stress fertility, true potato seed (TPS) breeding, and possibly improvement of tomato production under heat stress.     

Pollination Services of Mango Flower Pollinators

Measuring wild pollinator services in agricultural production is very important in the context of sustainable management. In this study, we estimated the contribution of native pollinators to mango fruit set production of two mango cultivars Mangifera indica (L). cv. ‘Sala’ and ‘Chok Anan’. Visitation rates of pollinators on mango flowers and number of pollen grains adhering to their bodies determined pollinator efficiency for reproductive success of the crop. Chok Anan failed to produce any fruit set in the absence of pollinators. In natural condition, we found that Sala produced 4.8% fruit set per hermaphrodite flower while Chok Anan produced 3.1% per flower. Hand pollination tremendously increased fruit set of naturally pollinated flower for Sala (>100%), but only 33% for Chok Anan. Pollinator contribution to mango fruit set was estimated at 53% of total fruit set production. Our results highlighted the importance of insect pollinations in mango production. Large size flies Eristalinus spp. and Chrysomya spp. were found to be effective pollen carriers and visited more mango flowers compared with other flower visitors.     

中国特有产甜蛋白植物——马槟榔花果及种子形态学

对中国特有产甜蛋白植物--马槟榔(Capparis masaikai Levl.)花果及种子的形态、结构进行解剖和显微观察.描述了马槟榔花的花萼、花瓣、子房、花药、花粉和果实的大小、外中内果皮以及种子的内外种皮、胚、胚乳等的结构和形态.马槟榔为圆锥花序,花瓣、萼片各4个,上位子房,侧膜胎座,4个心皮,1个心室,雄蕊多个,胚珠多数,多为肾形,沿心皮腹缝线成2～3纵行排列,花粉囊4囊纵裂,底着药,花粉粒球形,三孔沟型萌发,花程式为:K2+2C4A∞G(4:1:∞);果实大小差异较大,最小果纵横径3.1 cm×2.8 cm,最大果纵横径11.2 cm×9.4 cm,果实含种粒数平均8～9粒,最多的达40粒;果皮分外、中、内3层,外果皮有8～10条不规则棱及粗短的棘状突起,中果皮石细胞居多,内果皮晶莹剔透;种子形状多样,不同区域马槟榔种粒大小存在极显著差异,种皮有内外2层,外种皮质硬而脆,内种皮薄而透明,种子胚乳被吸收仅留遗痕,胚由胚根、胚轴、子叶和胚芽组成.     

Pollen fertility in relation to open pollinated true seed production in potatoes

The cost and difficulty of producing hybrid true potato seed (TPS) currently limits their use for commercial production. Twelve clones, selected in preliminary trials for low pollen stainability but high fruit and seed set, initially seemed promising for inexpensive production of mostly hybrid open-pollinated (OP) TPS. However, in subsequent tests, pollen stainability of these clones appeared to be highly variable and fruit and seed set were not as high. Bumblebees favored the most fertile clones, especially during periods when pollen stainability was the highest. Amounts of OP fruit and seed set correlated with maximum observed pollen stainability levels of the clones. Most of the OP seeds produced by these clones were probably the result of self-pollination; therefore, other methods must be used to obtain hybrid TPS.     

Effect of functional female and male fertilities on crossability in diploid potato breeding

Summary Functional female fertility (FFF) and functional male fertility (FMF) were studied in diploid potato clones, includingS. tuberosum haploids, F₁ hybrids between haploids and otherSolanum species, and in progenies from subsequent hybridisations. The results of 402 crosses between 91 diploid potato clones revealed that 60% of all genotypes had low levels of FFF as well as low levels of FMF regardless of their origin and degree of hybridity. Failed crosses (without any fruits at all) and those with a low level of success (with less than 3 seeds per pollinated flower) constituted 69% of all studied crosses. Most of these had resulted from parents with low levels of FFF and FMF, and these two characteristics were expressed independently. Functional female fertility affected crossability behaviour no less than FMF, therefore both FFF and FMF should be controlled in diploid potato clones involved in breeding. Reliable FFF and FMF estimates can be based only on crossing results. The coefficient of multiple correlation between seeds per pollinated flower in crosses and FFF and FMF estimates of the parental clones was 0.80 (P<0.01). Hence the compilation and analysis of the results of diploid potato crosses allow a reliable assessment of FFF and FMF and consequently the prediction of crossability with a degree of sufficient accuracy.     

东乡野生稻南昌异位圃内的开花习性

于2009年采用常规野外考察的方法,对南昌异位圃东乡野生稻的开花习性进行了调查。结果表明,南昌异位圃东乡野生稻开花时间比预期提前了近一个月,异位圃内各方向开花时间差异较大,异位圃南部开花高峰期在9月2日～9月4日,同一穗头上的可育度从上到下一般是逐渐递增,上部与下部育性差异达极显著,结实率40%左右。     

Self -Compatibility in a Diploid Hybrid Population of <Emphasis Type="Italic">Solanum phureja</Emphasis> – <Emphasis Type="Italic">S. stenotomum</Emphasis>

Recently proposals have been made in both Europe and North America to try to radically change potato breeding strategy from a tetraploid, heterozygous crop to a diploid inbred crop. As part of that effort, clones from the long-day adapted, late blight resistant diploid hybrid Solanum phureja – S. stenotomum population were selfed to begin the process of developing inbred lines. In March of 2016 and 2017, 42 diploid clones from the above-mentioned population were selfed in the greenhouse in Beltsville, MD. In 2016 and 2017, 10 and 13 clones failed to flower, respectively. Among the remaining clones, 716 pollinations were made in 2016, resulting in 57 fruit from 17 clones, and 3742 seeds; 801 pollinations were made in 2017, resulting in 34 fruit from 12 clones, and 1903 seeds. Nine clones were successfully selfed both years. Percent successful selfs was significantly higher in 2016 (7.96%) than in 2017 (4.24%). The most prolific clones in 2016 were BD1241–1 (34% successful selfs, 1090 seed), BD1218–3 (25% successful selfs, 638 seed), BD1215–1 (5% successful selfs, 411 seed), BD1243–1 (23% successful selfs, 232 seed). In contrast, the most prolific clones in 2017 were BD1230–2 (25% successful selfs, 537 seed), BD1203–3 (23% successful selfs, 391 seed), and BD1229–1 (11% successful selfs, 388 seed). These results indicate that there is sufficient self-compatibililty in this population to generate large numbers of inbred individuals, but that genotype x environment interactions are large. Attempts to generate selfed seed should be made over several years to maximize the genetic base of the selfed population.     

Effect of thinning flower buds on fruit and seed traits and root yield of Panax ginseng C.A. Meyer

Panax ginseng C.A. Meyer, commonly known as ginseng, is a perennial herb. Agricultural practices have an influence on growth and yield of P. ginseng plants. Effect of thinning flower buds (treatment A (TA) the outermost whorl of flower buds in the umbels was retained while all other buds were excised; treatment B (TB) the two outer whorls of flower buds in the umbels) on fruit traits, which include number of fruits per plant, single fruit: double fruit ratio, fruit weigh (FW) per square meter, weight of 100 fruits, vertical length of fruit (VLF), horizontal diameter of the fruit (HFD) and thickness of the fruit (TF), seed traits, which include number of seeds per square meter, weight of 1000 seeds, number of different seed grading categories (extremely large seeds (ELS), large seeds (LS), medium-sized seeds (MS), small seeds (SS)) per square meter, vertical length of the seed (VLS), horizontal diameter of the seed (HSD), thickness of the seed (TS), and the root yield and total ginsenosides content of root of four- and five-year-old cultivated P. ginseng was studied in Fusong region of north-eastern China. The results showed that the FW and VLF, the weight of 1000 seeds, number of ELS per square meter, VLS and HDS of ELS, HDS and TS of MS and root yield were increased significantly by TA and TB (p < 0.05), whereas the number of MS and SS were significantly reduced (p < 0.05) in four- and five-year-old plants. The number of ELS and LS in TB and control were higher than that of in TA, and not significant was observed between TB and control. The root yield in TB was significantly higher than that in control of five-year-old plants. Number of the seeds per square meter of five-year-old plants was higher than that of four-year-old plants. The results indicated that the method of thinning flower buds, which was the two outer whorls of flower buds in the umbels, on five-year-old cultivated P. ginseng plants was a favourable method to promote the production of high-quality seeds and maximise the root yield.     

海南油茶不育株花器发育生物学特性及解剖学观察

从解剖学、细胞生物学及遗传学角度对海南油茶不育株花器发育过程导致不育的原因进行研究。以海南油茶正常株和不育株为实验材料,对其花芽发育过程外部形态特性进行阶段性比较观察,并应用花粉原位萌发技术检测其花粉萌发及花粉管发育差异;应用石蜡切片法对花芽分化过程中雌雄蕊进行解剖学观察,分析雌雄蕊发育时期与其花芽外部形态的相关性。结果表明：不育花与正常花外部形态上并无明显差异,但不育株开花后子房即脱落,表明没有正常授精,不育株柱头授粉后花粉粒不萌发,花粉管并不伸长;从雌雄蕊石蜡切片可以看出,不育株花器发育失常,其花药的绒毡层降解异常,无法形成成熟花粉粒,而在其胚珠发育过程中不育株未能形成成熟胚囊,导致空心胚珠。     

Genetic variation in the sensitivity of anther dehiscence to drought stress in rice

Field-based screens for genetic variation in reproductive-stage drought tolerance are often confounded by genetic variation in root depth, flowering date and biomass at flowering. To reduce these confounding effects and to impose drought stress more precisely, we grew contrasting genotypes of rice (Oryza sativa L.) in shallow containers of flooded soil. When water was withheld from the shallow-rooted indica genotype IR64 for 6 days starting at −17, −7, 0, 10 and 20 days after heading (DAH), the impact on grain yield was greatest at −7 and 0DAH. The most sensitive yield component was filled grain percentage (spikelet fertility). Data on yield and spikelet fertility were also obtained for another shallow-rooted lowland indica (BRRI Dhan 31) and two deep-rooted upland tropical japonicas (Azucena and Moroberekan). Compared with well-watered controls, withholding of water for 6 days reduced spikelet fertility by ∼80% in IR64, BRRI Dhan 31 and Azucena but by 22% in Moroberekan. In a detailed comparison, water was withheld from IR64 for 5 days and from Moroberekan for 6 days, starting 3 days before the heading date of well-watered controls. Under these stress conditions, heading was delayed for 4 days in IR64 and 6 days in Moroberekan. Spikelet fertility in the top four rachis branches was reduced by 80% in IR64 and 16% in Moroberekan, a difference attributable principally to reduced anther dehiscence and lower stigma pollen density in IR64. Two properties of Moroberekan may contribute to high anther dehiscence after stress/re-watering: (i) constitutively superior development of fibrous structures in the endothecium at the anther apex and base and (ii) better maintenance of pollen size. All ovaries of Moroberekan received pollen—an average of 60 grains in well-watered plants and 42 grains in stressed/re-watered plants. In well-watered IR64, all ovaries received an average of 31 grains, whereas in stressed/re-watered IR64, 67% of ovaries received no pollen and the remainder received an average of eight grains. Moroberekan may, therefore, be a source of reproductive-stage drought tolerance through genes that maintain anther dehiscence during recovery from low water status.     

水稻花器官发育基因DPS2的鉴定和精细定位

【目的】鉴定和克隆花器官发育相关基因,为进一步研究水稻花发育的分子机制奠定基础。【方法】在大田常规种植条件下比较了突变体dps2 (Defective pistil and stamens 2)和野生型春江06的主要农艺性状及花器官形态特征差异;扫描电镜及石蜡切片观察花药结构并用染色法观察花粉和胚囊的育性;利用图位克隆方法进行基因精细定位;qRT-PCR分析了花发育相关基因在野生型和突变体中的表达水平。【结果】dps2突变体抽穗期变长,不能正常扬花,雄蕊和雌蕊皱缩且花药和柱头数目增多;进一步研究发现,dps2突变体花药腔室塌陷,内无可见小孢子,即使部分花药形成腔室,花粉粒也无淀粉积累呈干瘪状。此外,突变体胚囊育性也受到影响;遗传分析表明该突变性状受一对隐性核基因控制,该基因位于第4染色体短臂上91.2 kb的区间内,区间内未见花器官发育相关基因的报道。qRT-PCR检测发现,水稻ABCDE模型中的B类、C类和E类基因的表达在突变体中显著升高。【结论】dps2突变体的雄蕊及雌蕊均发育异常,最终导致完全不育,推测DPS2可能在水稻第3轮雄蕊发育和第4轮雌蕊发育调控中发挥重要作用。     

龙眼2个品种花部特征比较研究

研究龙眼石硖和储良2个品种的花部形态、开花生物学特性、花粉形态特征及萌发率、花粉量、P/O值、柱头可授性及其黏液分泌情况。结果显示，二者花部特征相似，储良花期较石硖长；二者的花粉形态相似，储良的花粉较石硖稍大，萌发率较石硖高；P/O值说明龙眼为专性异交植物；石硖和储良花粉活力和柱头可授性是同步变化的，尤其在盛花期花粉活力趋于最大，柱头分泌黏液与柱头可授性变化也一致，都在柱头展开成水平，开花约48 h达到最大。     

二倍体马铃薯主要农艺性状及其2n花粉频率的表现

通过田间种植,比较了马铃薯二倍体与四倍体的长势、叶色、薯形、薯皮色、薯肉色、芽眼深浅、单株产量、单株块茎数、平均块茎重等植物学和农艺性状,并对二倍体马铃薯的花粉育性以及２ｎ花粉的频率进行了鉴定。根据单株产量、块茎数、薯形、２ｎ花粉频率等综合性状,筛选出ＤＹ１４－４－２５、ＤＹ４－３０以及Ｑ４９－１－９,为进一步开展马铃薯分解育种工作打下物质基础。     

Reproductive efficiency and breeding potential of East African highland (Musa AAA-EA) bananas

The East African highland banana (Musa spp. AAA) is an economically important food crop. The crop is affected by a number of diseases and pests. Genetic improvement of the crop is hindered by very low seed set and poor seed germination. The objective of this study was to compare seed set, seed quality and embryo rescue rates of hybrid seeds obtained from 20 East African highland banana cultivars crossed with a fertile diploid species, Musa acuminata spp. burmannicoides ‘Calcutta 4’, as a male parent. There was great variation in seed set, seed quality and in vitro embryo germination rates among the cultivars. Although 72% (range = 47–88%) of the seeds appeared normal externally characterized by black hard integuments, only 59% (range = 35–81%) contained embryos, of which 9% (range = 0–22%) germinated. This study demonstrated that hard-seededness alone does not signify the presence of an embryo and should not be regarded as a measure of seed fertility in East African highland bananas. Cultivars ‘Entukura’, ‘Enzirabahima’ and ‘Kabucuragye’ of the ‘Nfuuka’ clone set were superior in terms of seed set, presence of seeds with embryos and culturability of embryos. These cultivars are recommended as female parents for a crossing program in the improvement of East African highland bananas. The low embryo rescue rates suggest that hybrid seeds derived from East African highland banana possess factors that cause high embryo abortion. This may be ascribed to endosperm breakdown, which can release toxins.     

Predicting seed admixture in maize combining flowering characteristics and a Lagrangian stochastic dispersion model

The seed purity problem has received very low attention in maize coexistence studies, and has not been considered in prediction tools that simulate pollen flow and out-crossing between maize fields. To fill this gap we developed the Seed Admixture Model (SAMETH) able to predict seed admixture dispersion combining flowering characteristics (pollen shed, silks exertion) with a Lagrangian stochastic dispersion model. The model was tested with a dataset obtained from 20 fields in 2007 and in 2008, whose seeds were mixed with 1% of a homozygous blue-kernelled hybrid. The model was first calibrated with data from 6 fields and then validated with the data from the remaining 14 fields. Moreover, a sensitivity analysis was performed to test the consequences of different pollen quantities released by the admixture and the commercial hybrids. The measured seed admixture ranged from 0.7% to 6% and the model was able to simulate the seed admixture with r² = 0.83. The sensitivity analysis showed that the model was sensitive to the absolute released pollen quantities but it was still able to predict seed admixture rather accurately. Because of its reliability, the model could become a useful tool for case study scenarios that involve seed admixture and for which field implementations would be too complex and time-consuming.