Evaluation of physiological traits as indirect selection criteria for drought tolerance in sugar beet

Drought is the most important limitation to sugar beet (Beta vulgaris L.) production in the UK and other areas dependent on usually insufficient summer rainfall. As increased irrigation is not a viable answer to the problem, an economically and environmentally desirable solution is new varieties with decreased sensitivity to water deficits. However, there is little genotypic information on drought tolerance in sugar beet, and breeders are not equipped to make these selections. The objectives of this study were to assess the degree of genotypic diversity for drought-related morpho-physiological traits and to measure the strength of association between these traits and indicators of crop performance. 46 sugar beet genotypes with diverse genetic backgrounds were tested in three field experiments from 1999 to 2001. Drought was imposed by covering plots with large polythene tunnels, allowing the crop to grow solely on stored soil moisture. Agronomic characters and drought tolerance indices are described in a companion paper [Ober et al., Assessing the genetic resources to improve drought tolerance in sugar beet. Agronomic traits of diverse genotypes under droughted and irrigated conditions. Field Crops Res., in press]. In this report, we show that there were significant genotypic differences for stomatal conductance, succulence index, specific leaf weight, and osmotic adjustment, but not for photosynthetic rate, relative water content or total water use. Patterns of water use within the soil profile differed between genotypes; some extracted more water from deep soil layers. The maintenance of green foliage cover during drought was positively correlated with drought tolerance index, which was negatively correlated with succulence index and scores for wilting and leaf senescence. Droughted sugar yield was positively correlated with soil water extraction and negatively correlated with relative leaf expansion rate measured in late summer. Under irrigated conditions, there was high positive correlation between transpiration rate and sugar yield. Genotype × trait biplots showed superior genotypes with relatively greater expression of combinations of favourable traits. The results suggest that succulence index and wilting score could be used to cull inferior plants in early stages of breeding programs, and green foliage cover and patterns of water use could help identify superior genotypes in elite germplasm. These data should enable tools to be developed for indirect selection of genotypes suited to drought-prone environments.     

不同株型玉米叶片形态结构的研究

紧凑型玉米与平展型玉米叶片形态结构有一定差别。主要表现在紧凑型玉米叶表皮气孔数目多于平展型。上表皮多17.0%，下表皮多11.5%。紧凑型玉米叶片上、下表皮气孔密度差别比平展型小。紧凑型玉米下表皮比上表皮气孔多44%，而平展型多50%。两种株型玉米叶片维管束鞘中的叶绿体均位于细胞外方，呈半圆形排列。紧凑型玉米比平展型玉米叶片维管束鞘中叶绿体含量较多。两种株型玉米叶片中脉有一定差异，紧凑型玉米叶片中脉较宽且向叶正面凹陷较深。     

Assessing the genetic resources to improve drought tolerance in sugar beet: agronomic traits of diverse genotypes under droughted and irrigated conditions

Drought is the major cause of sugar beet (Beta vulgaris L.) yield losses in the UK and many other regions where the crop is not normally irrigated. However, drought tolerance has not been a breeding target partly because the extent of the problem was not understood, it is difficult to design effective selection screens, and because of the suspicion that few varietal differences existed. The aim of this study was to evaluate the genetic resources necessary to improve drought tolerance. Specific objectives were to assess the degree of genotypic diversity for drought tolerance, characterise genotypic differences in response to drought, and identify sources of germplasm with greater drought tolerance than current commercial varieties. Over 3 years, 46 beet genotypes representing diverse genetic backgrounds were tested in the field under large polythene covers to impose a drought beginning approximately 40 days after emergence until harvest. Sugar, root and total dry matter yields were measured under drought and irrigated conditions. The percentage green crop cover was measured at regular intervals and used in the calculation of radiation use efficiencies for each genotype. Drought tolerance index (DTI) was computed as the fraction of irrigated yield maintained under drought, normalised by the mean yield across all genotypes in the trial. Seven genotypes were tested in all years, and the data on these were used to calculate yield stability statistics and to estimate broad-sense heritability. There were more than two-fold differences in droughted and irrigated yields between genotypes, and nearly a two-fold difference in DTI. According to an index that combines yield potential and drought tolerance, some genotypes performed better than the three locally adapted commercial varieties included in the test. There were significant effects for genotype, treatment and G×E interactions for yield components and radiation use efficiency. There were also significant genotype differences in harvest index but few significant G×E interactions. Droughted and irrigated yields were positively associated, but there was no close relation between yield potential and DTI. The seven genotypes common to all years differed in yield stability and in sensitivity to water availability. Thus, the genetic resources exist for germplasm improvement. Both yield potential and DTI (which may ensure better yield stability) should be considered simultaneously as breeding targets for drought-prone areas.     

肉饼兜兰叶片生长模型与解剖结构研究

以2种肉饼兜兰为试材,研究其叶片生长发育规律和解剖结构。结果表明:兜兰叶片生长动态呈现S型生长曲线,生长周期长,叶片寿命长。兜兰的叶片长度、宽度和叶面积随苗龄增大而增大,萌发新叶的间隔时间随苗龄增大而增长,新叶的发育周期随苗龄增大而增长。兜兰的表皮细胞厚,而叶肉细胞厚度低,叶片组织结构紧密度低,可能是导致兜兰虽为C_3植物但是营养生长速度慢的原因。兜兰的叶片厚、上表皮细胞巨大、角质层较厚、气孔下生型和龙骨状主叶脉发达,具有明显的旱生特点。     

Foliar micromorphology of Felicia muricata Thunb., A South African medicinal plant

The foliar micromorphology of Felicia muricata (Thunb.) Nees (Asteraceae) was observed with the JEOL (JSM-6390LV) Scanning Electron Microscope (SEM). Both the abaxial and adaxial surfaces were characterized by anisocytic stomata which were more prevalent on the abaxial surface than the adaxial surface. The leaves have only one type of multicellular non-glandular trichomes that are long and cylindrical, tapering to a sharp point and running parallel to the leaf surface in the direction of the apices. Crystal deposits were also observed on the surfaces of the leaves near the stomata. Energy dispersive X-ray spectroscopy-SEM shows that Na, Al, Si, and K were the major constituents of the crystal analyzed. Since no glandular trichomes were present on the leaves of this herb, the bioactive components present in this plant may be produced in some other tissues in the leaf other than the trichomes.     

Differences in lamina joint anatomy cause cultivar differences in leaf inclination angle of rice

ABSTRACT

Leaf erectness is an important agronomic trait for improving canopy photosynthesis in rice. It is well known that leaf inclination angle (LIA) decreases after expansion during ripening. However, the high-yielding indica cultivar ‘Takanari’ retains a greater LIA during ripening than the high-quality japonica cultivar ‘Koshihikari’. To clarify the cause of the cultivar difference in LIA, we investigated anatomical characteristics of the lamina joint of a flag leaf. We found a close linear correlation between LIA at the centre and at the base of the leaf blade in both cultivars during ripening. The length of the lamina joint increased significantly more on the adaxial side of a leaf (the margin of the collar) than on the abaxial side (the abaxial side of the central part of the collar) in ‘Koshihikari’ after leaf expansion, but there was no clear difference in ‘Takanari’. We found a close linear correlation between the ratio of lamina joint length on the adaxial to abaxial sides and LIA in ‘Koshihikari’ and ‘Takanari’ during ripening. In ‘Koshihikari’, the average length of cells on the adaxial side increased significantly after leaf expansion, with no significant increase in that on the abaxial side and no significant change in cell number on either side. In ‘Takanari’, cell length and cell number showed no significant changes on either side of the lamina joint. We conclude that the cultivar difference in LIA during ripening is caused mainly by cell elongation on the adaxial side of the lamina joint.

List of Abbreviations: k: light extinction coefficient; LIA: leaf inclination angle; QTL: quantitative trait locus     

Nitrogen compounds in organs of two sugar beet genotypes (Beta vulgaris L.) during the season

A major aim in sugar beet breeding is to decrease the concentration of soluble N compounds in the beet to avoid negative impacts during beet processing. Due to its importance and analytical limitations the only selection criterion is amino N analyzed in the beet at harvest. It is thus not clear when genotypic differences are established during the season. Furthermore, it is not known whether selection for low amino N affects other N compounds in the beet and the N composition of other plant organs. Therefore, the concentrations of total N and soluble N compounds (protein, amino N, glutamine, betaine, nitrate) were investigated during the season in different organs (leaf blades, petioles, crown, beet) of two sugar beet genotypes differing in the amino N concentration of the beet. Field trials were carried out at three sites in 2002 and in 2003 with harvests at three times from 100 to 170 days after sowing.     

谈甜菜的节水灌溉与技术

论述了甜菜的耐旱性与需水规律及节水灌溉的必要性;总结了我国甜菜节水灌溉的试验研究;介绍了节水灌溉的多项技术.     

Influence of the soil physical environment on rice (Oryza sativa L.) response to drought stress and its implications for drought research

Plant performance under drought stress is not solely defined by an inadequate water supply but by an interaction among many factors, including climatic, edaphic, and biological factors. An important interacting factor affecting root growth, and therefore the ability of a plant to access and take up water, is the soil physical environment. Soil penetration resistance can restrict, or even halt, root system growth. For rice, a soil penetration resistance of 1.4 MPa is sufficient to inhibit root system expansion. This review describes the effects of the soil physical environment on root growth and its interaction with drought stress. A large variation in soil penetration resistance exists among rainfed rice-growing areas of South and Southeast Asia and within experimental stations used for managed-drought field phenotyping. This variability may influence genotypic performance across experimental sites/countries and the response of crop genotypes to drought stress. A case study is presented in which differences in the soil physical environment may partially elucidate differences in experimental results between two field studies conducted at different locations. These results highlight the need for increased knowledge of environmental interactions to allow the outputs of genomics to increase drought tolerance at the field level.     

Alterations of Panicle Antioxidant Metabolism and Carbohydrate Content and Pistil Water Potential Involved in Spikelet Sterility in Rice under Water-Deficit Stress

Two rice genotypes with different drought tolerance,namely Jin 23B(drought tolerant)and Zhenshan 97B(drought sensitive),were used to study the antioxidant enzyme activities,soluble sugar and starch contents in spikelets,pistil water potential and pollen number on a stigma under water-deficit stress at the flowering stage,which were involved in the spikelet sterility.Compared with respective controls,drought stress induced more serious decreases of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)ac...     

Dispersion and evaporation of droplets amended with adjuvants on soybeans

Quantification of the effects of adjuvants on droplet behaviour on plant surfaces is needed to improve pesticide spray application efficiency for soybeans. Dispersion and evaporation of single 300-μm diameter droplets amended with each of four spray adjuvants at five concentrations were investigated for four soybean plant surfaces (abaxial and adaxial leaflet surfaces, petiole, basal stem). The four adjuvants were a crop oil concentrate (COC), a modified seed oil (MSO), a non-ionic surfactant (NIS) and an oil surfactant blend (OSB). A single-droplet generator was used to produce and deposit 300-μm diameter droplets on target surfaces under controlled environmental conditions. Adjuvants significantly increased the dispersion (or wetted area) of droplets on plant surfaces. Droplet-wetted areas increased with increased adjuvant concentrations but not in direct proportion. The average increases of wetted areas across the four soybean plant surfaces were 443, 462, 416, or 343% when the spray mixture was amended with COC, MSO, NIS or OSB at the manufacturer-recommended concentrations, respectively. Among the four surfaces, the largest wetted area was on the abaxial surface, followed by the adaxial surface, the petiole and then the basal stem. Droplet evaporation times were inversely proportional to the wetted areas. The evaporation time of 300-μm diameter droplets ranged from 36 to 142 s on the four surfaces when the spray mixture was amended with an adjuvant, whereas the water-only droplets ranged from 161 to 190 s. The results demonstrated that use of adjuvants offers great potential to improve the homogeneity of sprayed pesticides, to increase spray coverage and to reduce pesticide application rates on soybean plants. These effects could benefit farmers economically and reduce environmental contamination by pesticides.     

干旱胁迫对燕麦叶片气孔和叶肉细胞超微结构的影响

为了解干旱后燕麦解剖结构的变化,以燕麦品种白燕2号为材料,通过盆栽控水试验,设置正常供水、轻度干旱和重度干旱三个不同水分处理(土壤含水量分别为田间持水量的75%、60%和45%),研究了干旱胁迫对燕麦叶片渗透调节物质含量、气孔和叶肉细胞超微结构的影响。结果表明,正常水分条件(对照)下,燕麦叶片脯氨酸和可溶性糖含量较低,表皮细胞皱褶,气孔关闭或微张,叶肉细胞内细胞器形状规则,结构清晰。与对照相比,轻度干旱胁迫下,燕麦叶片脯氨酸和可溶性糖含量增加,叶片表皮细胞饱满,气孔开启度较大,叶绿体形状变圆,近球状,线粒体外被膜膨胀,但结构未见明显损伤;重度干旱胁迫下,叶片脯氨酸和可溶性糖含量极显著增加,表皮细胞干瘪,气孔保卫细胞膨胀,气孔关闭,气孔器下陷。重度干旱胁迫下,燕麦叶绿体和线粒体受到的损伤较大,叶绿体内基粒、基质类囊体降解,出现较大的空腔;线粒体外被膜断裂,内含物流失;细胞核染色质凝聚,叶绿体之间出现嵌合现象。因此,干旱胁迫能诱导燕麦叶片渗透调节物质的积累和细胞超微结构的改变,渗透调节物质增幅和细胞超微结构的破坏程度随着土壤有效水分含量的降低而上升,但在细胞超微结构上也出现抗性反应,表明燕麦具有较强的抗旱性。     

江淮大豆育种种质苗期耐旱性鉴定

江淮地区是我国大豆重要产区,季节性干旱时有发生,发掘适合本地区种植的耐旱新材料十分必要。选用210份江淮大豆育成新品种(系)及其部分亲本为材料,于2015和2016两年进行旱棚盆栽试验,以地上部干重、株高、主根长和根干重4个性状的耐旱系数为指标,通过主成分分析、隶属函数值法和聚类分析对其苗期耐旱性进行综合评价。结果表明:与正常供水相比,干旱胁迫下4个性状均显著降低,其中地上部干重、根干重、株高和主根长平均分别减小54%、42%、39%和15%;方差分析显示各性状在水分处理间和材料间均存在极显著差异,而株高和根干重性状上基因型、水分处理和年份三因子间一级互作和二级互作效应均为极显著。地上部干重与株高、根干重间以及主根长与根干重间的耐旱系数存在显著正相关,反映指标间有内在联系;主成分分析提取的前3个相互独立的主成分的累积贡献率达83.61%,能较好地替代原有4个信息部分重叠的性状;进一步获得耐旱性综合评价D值,结合聚类分析将所有材料分为强耐旱、耐旱、中度耐旱、干旱敏感、干旱强敏感5类。共鉴定出强耐旱材料5份(包括IA2077、YC4H/NN88-31//NN73-935、蒙8108、NN88-48/NN86-4和NN88-48/D76-1609)、耐旱材料57份。来自淮南和淮北地区的强耐旱或耐旱材料分别为27份(占该地区83份材料的32.53%)和19份(占该地区76份材料的25.00%)。所得结果可为大豆耐旱遗传育种提供材料。     

甜菜不同生长期叶柄锤度的变化与主要性状问的相关分析

通过对甜菜不同生长期叶柄锤度与产质量性状间的相关分析看出,在营养生长期甜菜叶柄锤度与根产量、产糖量二性状的相关不密切,而同褐斑病病情呈负相关,同块根含糖率呈正相关,且到生育后期达显著或极显著水平.通过对甜菜营养生长期叶柄锤度的测试,进行育种材料的高糖性状的预选,具有一定的实际意义。     

Molecular aspects of drought tolerance in bread wheat (T. aestivum)

In order to evaluate molecular indices of drought tolerance and selection of drought tolerance genotypes in bread wheat a randomized complete block design was carried out with three replications in the field of research station of Sararood, Kermanshah, Iran. Positive significant correlation coefficient was observed between grain yield and proline, soluble sugar and total protein under rainfed condition. Based on the grain yield, proline content, soluble sugar and total protein the genotypes were classified into four clusters using cluster analysis and UPGMA method. Genotypes numbers 4, 9, 10, 11, 18 and 19 in the first clusters indicated the highest performance.     

添加蚯蚓粪对盐胁迫下玉米气孔特征和光合特性的影响

以玉米为试验材料,设置5个处理,盐胁迫下添加蚯蚓粪比例分别为0、10%、20%、40%,以不添加蚯蚓粪和NaCl溶液的处理为空白对照,分析盐胁迫下添加蚯蚓粪对玉米气孔特征和光合特性的影响。结果表明,添加蚯蚓粪能够显著增加盐胁迫下玉米叶片近轴面的气孔长度、气孔面积和气孔周长,远轴面气孔长度和气孔周长也随着蚯蚓粪的添加显著增加,玉米叶片近轴面和远轴面气孔空间分布在添加蚯蚓粪处理变得更加规则。添加蚯蚓粪处理后玉米幼苗的净光合速率、胞间二氧化碳浓度和气孔导度与盐胁迫处理相比显著升高,同时玉米幼苗的水分利用效率显著升高。添加蚯蚓粪能有效增大盐胁迫下玉米幼苗叶片的最大光化学转化效率,降低相对电导率,缓解盐胁迫对玉米的伤害。     

转TaNHX2基因大豆的抗旱性鉴定

本研究利用转TaNHX2基因大豆T3代株系,研究其在干旱胁迫情况下表型、生理特性、生物量与光合作用等方面的变化。结果表明:随着干旱时间的不断延长,对照表现出明显的萎蔫,且转基因植株能够持续地保持绿色状态。转基因植株叶片中含水量高于对照,但株系间叶绿素和可溶性糖含量差异不大,转基因植株中的脯氨酸和丙二醛含量明显低于对照,SOD的活性高于对照。综合评价表明转TaNHX2基因大豆T3代株系比对照具有更强的耐旱性。     

Maize genotype susceptibility to Rhizoctonia solani and its effect on sugar beet crop rotations

Root and crown rot is the major soil-borne fungal disease in sugar beet. In Europe, the disease is mainly caused by the anastomosis group (AG) 2-2IIIB of the basidiomycete Rhizoctonia solani (Kühn). No chemical fungicide to control the disease has been registered in Europe. Therefore, agronomic measures must be optimized to keep the disease severity below an economic damage threshold and to minimize white sugar yield losses. R. solani AG 2-2IIIB infects many other crops besides sugar beet, including maize, where it causes root rot. Sugar beet and maize are frequently grown in the same crop rotation. The proportion of cultivated maize in several European sugar beet growing areas is expected to rise due to a projected increase in demand for renewable resources over the next few years. Although the susceptibility to and tolerance of the disease varies among cultivars in both crops, little is known about the effects of cultivar susceptibility in the pre-crop on a subsequent susceptible crop. The cultivation of R. solani-resistant maize genotypes in rotation with resistant sugar beet might therefore be a useful tool in an integrated control strategy against R. solani, eliminating the need to restrict the desired crop rotation for phytosanitary reasons. A crop rotation experiment with artificially inoculated R. solani was conducted in the field to investigate the pre-crop effects of maize cultivars which differed in their susceptibility to R. solani on a susceptible sugar beet cultivar. We hypothesized that the maize genotype would influence the inoculum potential and performance of a susceptible sugar beet genotype grown after a maize pre-crop, and that this would correlate with the susceptibility of the maize genotype. The results demonstrate that the susceptibility of maize genotypes is consistent over a period of years and that cultivated maize genotypes influenced the inoculum potential measured as disease severity in sugar beet. However, disease severity in sugar beet did not correlate with the disease susceptibility of the genotype of the maize pre-crop. Possible reasons for this missing relationship might be differences in the quality of maize residues for the saprophytic survival of the pathogen or a genotype-specific alteration of the antagonistic microbial community. However, our findings showed that in the presence of maize- and sugar beet-pathogenic R. solani, the most favourable maize cultivar for a crop rotation cannot be determined solely on the basis of its resistance level against Rhizoctonia root rot.     

干旱胁迫下不同苎麻品种的形态解剖特征研究

抗旱性强的苎麻品种,在正常水分条件下叶面茸毛多、叶着生角度小、比叶重大,而在干旱胁迫下叶片衰老慢,根冠比大、根活跃吸收面积大、萝卜根数量多且直径大,纤维细胞直径和胞壁厚度降低幅度小。抗旱性强的苎麻品种正常水分及干旱条件下叶片气孔密度以及茎导管和根系维管束均较大。