The origin of polyploids via 2n gametes in Vaccinium section Cyanococcus

Summary The production of 2n pollen (pollen with the sporophytic chromosome number) was evaluated in 4x and 6x taxa of Vaccinium section Cyanococcus. Mean frequencies of 2n pollen producers were 17.1% and 8.3% in natural 4x and 6x populations, respectively. The frequency of 2n pollen producers in the 4x species ranged from 8.6% (V. angustifolium) to 23.8% (V. pallidum). Level of 2n pollen production was genotypically variable (1% to 37.4%). The widespread occurrence of 2n pollen in 2x, 4x and 6x taxa suggests that sexual polyploidization was widespread and responsible for the origin of the polyploid species found in this genus. The frequency of 2n pollen producers was not significantly different between the 4x species and their putative 2x ancestors. These results support the origin of 4x and 6x taxa as a consequence of sexual polyploidization. Polyploids derived from sexual polyploidization would be expected to have increased fitness and flexibility due to the mode of 2n pollen formation. In blueberry species the predominant mode of 2n pollen formation is genetically equivalent to a first division restitution mechanism (FDR). FDR 2n pollen transmits a high percentage of the heterozygosity and a large fraction of the epistasis from the 2x parent to the 4x offspring.     

Genome composition of triploid lily cultivars derived from sexual polyploidization of Longiflorum × Asiatic hybrids (<Emphasis Type="Italic">Lilium</Emphasis>)

About 19 cultivars, which had originated from backcrosses between F1 LA (Longiflorum × Asiatic) hybrids (2n = 2x = 24) as female parents and Asiatic cultivars as male parents (2n = 2x = 24), were analyzed with genomic in situ hybridization. 17 of them were triploid (2n = 3x = 36), and two aneuploid (2n = 3x + 1 = 37). The triploid cultivars had resulted from the functional 2n eggs produced by the female parents (F1 hybrids) because first division restitution (FDR) occurred in their meiosis during megasporogenesis. Similarly, the aneuploid cultivars had originated from viable 2n + 1 eggs. The extra chromosome in cultivar 041555 or 041572 resulted from one univalent or one half-bivalent which might have lagged behind when the sister chromatids of the other univalents and half-bivalents were segregating during the FDR process in their LA hybrid parents, respectively. That the majority of cultivars possessed recombinant chromosomes showed that intergenomic recombination might play an important role during the selection of the cultivars directly from BC1 progenies. That five cultivars of the 15 recombinant cultivars only had reciprocal recombinant chromosomes and 10 cultivars had non-reciprocal recombinant chromosomes indicates that the latter are more important. Because 9 of the 10 non-reciprocal recombinant cultivars possessed substitutions for recombinant segments, it also indicated that such substitutions could be an important source for the genetic variation in the sexual triploid BC1 progenies. In such cases there was a potential for the expression of the recessive genes of the backcross parent in a nulliplex (aaa) condition in the substituted segments. Genetic variation resulting from such nulliplex loci might have played a role in the selection of some of the cultivars.     

Metabolite profiling of the response to high-nitrogen fertilizer during grain development of bread wheat (Triticum aestivum L.)

Wheat yield and quality are dependent largely on nitrogen (N) availability. In this study, we performed the first metabolomic analysis of the response to high-N fertilizer during wheat grain development using non-targeted gas chromatography-mass spectrometry (GC–MS). Quality parameter analyses demonstrated that high-N fertilizer application led to a significant increase in grain protein content and improvement in starch and bread-making quality. Comparative metabolomic profiling of six grain developmental stages resulted in identification of 74 metabolites, including amino acids, carbohydrates, organic acids and lipids/alcohol, which are primarily involved in carbon and N metabolism. Under high-N fertilizer treatment, numerous metabolites accumulated significantly during grain development. Principal component analysis revealed two principal components as being responsible for the variances resulting from N-fertilizer treatments. Metabolite–metabolite correlation analysis demonstrated that the high-N treatment group had a greater number of positive correlations among metabolites, suggesting that high-N fertilizer treatment induced a concerted metabolic change that resulted in improved grain development. Particularly, the high-N treatment-mediated significant accumulation of metabolites involved in the TCA cycle, starch and storage protein synthesis could be responsible for the improvement of grain yield and quality. Our results provide new insight into the molecular mechanisms of wheat grain development and yield and quality.     

Yield and tuber characteristics of 4x progeny from 2x×2x crosses

Summary Unrelated, unselected 2x haploid-species hybrids that produce 2n eggs, by second division restitution and 2n pollen due to first division restitution were intercrossed to generate 4x progeny. The 19, 4x families were compared with seven cultivars for tuber yield, tuber appearance and tuber set. The mean yield of the 4x families was 30% higher than the mean yield of the cultivars. The best five 4x families outyielded the best five cultivars by 57% and 69% at two locations. Cultivars were superior for tuber appearance and tuber set. The high yields of the 4x families are due to genetic diversity of the 2x parents and their ability to transmit that diversity to the 4x progeny utilizing 2n gametes. The potential of the 2x×2x breeding method is dependent on developing 2x hybrid clones that form 2n eggs and possess desirable tuber types; clones producing 2n pollen and good tuber quality are available.     

毛白杨杂种三倍体的2n雌配子形成途径鉴定

由于受杨树大孢子母细胞减数分裂不同步性影响,通过施加理化处理诱导杨树大孢子染色体加倍授粉杂交获得的三倍体,可能既包括来源于第一次减数分裂核复原形成的2n雌配子(FDR),也有来源于第二次减数分裂核复原形成的2n雌配子(SDR),难以进行表型鉴别,而通过分子标记分析可以实现不同类型2n雌配子的区分。本研究以通过高温诱导毛白杨大孢子染色体加倍所获得的87株三倍体及其亲本为材料,从母本杂合且与父本有差异的SSR多态性引物中,筛选出5对适宜于2n配子诱导途径来源鉴定的重组率较低的SSR分子标记。在此基础上,利用这5对低重组率SSR分子标记,开展毛白杨杂种三倍体的2n雌配子诱导途径来源分析。结果表明,不同毛白杨杂种三倍体的2n雌配子相应简单重复序列区域的等位基因配置不同,利用筛选出的5对低重组率SSR标记可以实现毛白杨杂种三倍体的2n雌配子诱导途径鉴定,其中35株三倍体来源于FDR型2n配子,另52株来源于SDR型2n配子。此外,选用5个位于高重组率位点的SSR引物进行检测分析,结果验证了随机挑选的SSR引物用于鉴别结果是不完全可靠的,只有挑选低重组率的SSR位点才可能准确鉴定2n配子来源。开展毛白杨杂种三倍体的2n配子诱导途径鉴定研究,对于FDR、SDR不同形成途径的2n配子传递亲本杂合性分析,以及毛白杨三倍体育种策略制定等具有重要意义。      

新型FDR土壤水盐一体传感器标定研究与应用

运用新型频域反射(FDR)技术和分频技术,实现传感器水盐同时测量。因土壤质地、容重等差异,土壤水盐标定是利用FDR监测土壤水盐过程中的必要环节。以东北壤土为试验对象,利用"由湿到干,由小到大"的土壤水盐运动规律,通过土柱试验,用烘干法和土壤溶液电导率法对FDR进行室内标定研究。同时,将时域反射(TDR)式水盐传感器作为对照系,进行稳定性、精准度比较。结果表明:1)经土壤水分标定曲线校正后,FDR式水盐一体传感器具有很高的测量精度,可达±1%~3%;2)在土壤里对同一水盐含量进行百次重复测定,TDR传感器水分平均值为20.07%,相对标准偏差为0.18%;盐分(电导率)平均值为0.29 m S/cm,相对标准偏差为11.06%;新型FDR传感器水分平均值为20.08%,相对标准差为0.21%;盐分(电导率)平均值为0.31m S/cm,相对标准差为8.49%。新型FDR土壤水盐一体传感器可用于农田土壤连续水盐监测,提供稳定、精确的基础数据,结合数据分析软件,指导种植生产。     

基于迁移学习的FDR土壤水分传感器自动标定模型研究

针对频域反射技术(FDR)传感器人工标定数据拟合误差大的问题,引入其他地区数据作为辅助数据,建立了基于迁移学习的自动标定模型。该模型将FDR目标使用地点采集的数据作为源域数据,结合辅助数据与少量源域数据,使用TrAdaBoost算法即可得到准确的FDR传感器标定模型。将面向分类问题的TrAdaBoost算法改进为适用于本文面向回归的TrAdaBoost算法,将TrAdaBoost算法的基学习器由AdaBoost改为XGBoost,改进了更新权重误差率的计算方法。首先使用XGBoost对辅助数据进行训练,得到初始标定模型;然后在目标地点采集少量数据,使用改进后的TrAdaBoost算法对初始标定模型进行校准,即可得到准确的FDR标定模型。将10个不同地区站点数据作为辅助数据,训练得到初始标定模型,将沈阳地区6个站点分别作为目标使用地点,取80%数据作为源域数据,进行模型校正,其余20%数据用于测试。测试结果的平均准确率为99. 1%,说明基于迁移学习的自动标定模型是有效和准确的。     

Combining ability and parental effects in 4x–2x crosses for potato breeding

Summary Nine 2x clones with different genetic backgrounds and 2n pollen production by first division restitution (FDR) were each mated with five 4x females in a linextester design. Estimates of both general combining ability (GCA) and specific combining ability (SCA) were significant for tuber yield, among female and male parents. Four FDR clones with similar genetic background (half-sibs) showed significantly different GCA for total yield, illustrating the importance of progeny testing for FDR clones before their utilization as progenitors. A stronger influence of the 2x parents, compared to that of the 4x parents, on the performance of the hybrids was observed for characters studied. The significance of male and female interactions for characters other than tuber yield reinforced the importance of careful choice of the male and female parents for improving horticultural traits of 4x–2x progenies.     

土壤水分测量原理与技术方法研究

土壤水分对作物生长和微生物活动具有重要作用,对农业领域、工程领域、生态领域等均有十分广泛的影响。土壤含水率是土壤理化特性的重要参数之一,也是制定合理灌溉制度、优化水资源管理、保障土体工程施工安全的重要指标之一。本文介绍了国内外目前应用较广泛的几种土壤水分测量方法及其测量原理,并对其优缺点进行了分析。提出了土壤水分测定方法中存在的主要问题及其发展趋势。     

不同土壤水分测定方法的比较研究

[目的]为正确使用TDR法和FDR法测定土壤水分含量提供理论依据。[方法]以铝盒烘干法为标准,通过对TDR法和FDR法进行校验,明确它们的优缺点及土壤温度对测定结果的影响。[结果]室内模拟试验结果表明：3条曲线具有相同的变化趋势;横坐标在3.0~23.0时,θT比θF更接近真实值（θv）;横坐标在18.0~23.0时,θT与θv基本一致;横坐标大于23.0时,θv、θT和θF之间的差距甚小。田间试验结果表明：除了2、3、4和8点,FDR的测定结果与θv的差距都很大;TDR的测定结果与θv的差距都很小。综合分析结果表明：FDR的曲线在最下面,与θv的曲线始终保持一段距离,它们之间只有2个交点;TDR和θv的曲线都在上面,它们距离很小,有7个交点,说明TDR的测定准确度比FDR的高。[结论]用TDR法测定土壤含水量准确、方便、快捷。