Leaf photosynthesis is enhanced in normal oil maize pollinated by high oil maize hybrids

The grain yield of normal oil maize (Zea mays L.) might increase when pollinated by high oil maize (HOM) hybrids because of heterosis. To testify that the grain yield increase might be a result of improved photosynthetic rate and related traits, the normal oil maize (NOM) hybrid, Nongda108, was cross-pollinated by three HOM hybrids, HOM202, HOM115 and HOM4515 (for short as ND108pHOM202, ND108pHOM115 and ND108pHOM4515). We found that the ND108pHOM202 and ND108pHOM115 exhibited higher net photosynthetic rate (P_n), accompanied by larger stomatal conductance (g_s) and transpiration rate (E). Moreover, delayed leaf senescence was observed in their leaves, including larger leaf area index (LAI) and higher Chl content and Chl a/b ratio. Apart from higher phosphoenolpyruvate carboxylase (PEPCase) activity, the soluble proteins were also higher in the two cross-pollinations. The higher leaf photosynthesis could explain the grain increase in ND108pHOM202 and ND108pHOM115. However, ND108pHOM4515 exhibited a decreased photosynthetic characteristic and yield performance. Significantly positive relation between grain yield and biomass (r² = 0.96, P < 0.05), P_n and biomass (r² = 0.74, P < 0.05) also suggested that the yield increase in the two cross-pollination treatments was generally owing to the higher photosynthetic rate and related photosynthetic traits.     

Characteristics of Gas Exchange and Chlorophyll Fluorescence during Senescence of Flag Leaf in Different Rice (Oryza sativa L.) Cultivars Grown under Nitrogen-Deficient Condition

Abstract

Effects of nitrogen (N) deficiency on photosynthetic gas exchange and photosystem II (PSII) photochemistry of flag leaves during grain-filling stage were investigated in six rice cultivars, Kasalath (a conventional indica), IR36 (an improved indica), Shirobeniya (a conventional japonica), Nipponbare (an improved japonica), Akenohoshi (an improved japonica-indica intermediate type) and BSI429 (an improved tropical japonica, a new plant type line) grown hydroponically in N-sufficient (NS) and N-deficient (ND) solution. From 3 to 24 days after heading (DAH), net photosynthetic rate (P_n), maximum quantum yield of photosystem II (PSII) (F_v/F_m), quantum yield of PSII electron transport ( Φ_psii), and contents of chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the flag leaves decreased, particularly under the ND condition in all six cultivars. A substantial difference was observed among the ND plants for the sustainability index (SI, the ratio of the value at 24 DAH to that at 3 DAH) of P_n, F_v/F_m, Φ_psii, Chl content and Rubisco content; SIs of those parameters of Akenohoshi, BSI429, Nipponbare and Shirobeniya were higher than those of IR36 and Kasalath. The SI of P_n showed significant positive correlations with those of F_v/F_m, Φ_psii, and the contents of Chl and Rubisco under the ND condition. It was concluded that the sustainability of photosynthesis in the flag leaves was mainly due to those of PSII photochemistry and electron transport, which was associated with the maintenance of Chl and Rubisco under the ND condition.     

不同耐密性玉米品种光合特性对弱光响应的差异

以郑单958、东单90为试材,研究不同耐密性玉米品种光合特性对弱光胁迫响应的差异。结果表明,正常光照条件下郑单958光合性能优于东单90。郑单958在弱光胁迫后与其正常光照(对照)相比表观量子效率(AQY)增大,光合速率(Pn)、最大净光合速率(P max)、光补偿点(LCP)、光饱和点(LSP)均降低,表现出对弱光的光能利用效率明显高于对照,对强光利用效率较低。东单90在弱光胁迫后与其正常光照(对照)相比AQY降低,P max、LCP、LSP均升高,表现为对强光利用效率高,对弱光利用效率与对照基本相同。叶绿素荧光参数表明,郑单958弱光胁迫后PSⅡ光化学反应中心活性降低、高光强下光能利用效率降低主要是由于叶片光合活性下降;东单90弱光胁迫后对高光强的光利用效率升高的原因是叶片经弱光胁迫后减少了光合过程中的热耗散。     

Using chlorophyll fluorometry to compare photosynthetic performance of commercial maize (Zea mays L.) hybrids in the field

The main objective of the present work was to determine if chlorophyll fluorescence techniques could be used under field conditions to detect differences in leaf photosynthetic rates among commercial maize hybrids known to differ in agronomic performance. Chlorophyll fluorometry was used to estimate thylakoid electron transport rates (J_e) in leaves of three commercial maize hybrids on 13 days between 48 days after sowing and first frost. The maximum quantum efficiency of thylakoid electron transport at low PPFD (φ), and the thylakoid electron transport rate when PPFD absorbed by leaves was equal to 1200 μmol m⁻² s⁻¹ (J_e1200) were estimated using a curve-fitting approach. Canopy absorptance of incident PPFD (α_c) and leaf absorptance of incident PPFD (α_l) were measured at regular intervals. Significant fluctuations in both φ and J_e1200 were observed over the season, and these appeared to be associated with different leaf temperatures on different measuring days. Measured values of J_e1200 declined in a linear fashion over the season, but the decline was more rapid in an older hybrid than in two more modern hybrids. All three hybrids could be differentiated from one another on the basis of J_e1200 measurements in the last part of the growing season. The two newer hybrids did not differ in their mean crop growth rates during this part of the season, however, despite the observed difference in J_e1200. Regression analyses revealed a strong relationship between mean crop growth rates and α_cJ_e1200, supporting the idea that chlorophyll fluorescence can be used to assess photosynthetic performance of maize under field conditions.     

玉米杂交种不同世代叶绿素含量变化初报

叶绿素合量是一项重要的生化指标。本试验以不同玉米杂交种的不同世代研究了玉米叶片叶绿素含量变化。结果表明，杂交种间、世代间的叶绿素含量差异显著，而不同世代内的叶片之间差异不显著．世代间的叶绿素含量变化趋势并不是随着世代增加而递减。有的杂交种F₂高于F₁，而有的杂交种F₃高于F₂，世代间的叶绿素含量变化无规律性．     

Swiss Flint maize landraces—A rich pool of variability for early vigour in cool environments

Today's modern Dent × Flint maize (Zea mays L. ssp. mays) hybrids have a high yield potential but often lack satisfying early vigour under typical low spring temperatures of temperate latitudes. Maize was introduced into Europe already in the 16th century and until the 1950s, landraces evolved and adapted well to various geographically restricted and climatically marginal regions in Europe. Therefore, the objective of this study was to assess representatives of the large pool of Swiss Flint maize landraces for their early vigour under cool conditions in the field. A set of 17 landrace accessions were tested for 2 years at sites on the Swiss plateau (450 and 550 m a.s.l.) and in the foothills of the Swiss Alps (830 and 870 m a.s.l.). Plant emergence (PE), emergence index (EI), the efficiency of the photosystem II (F_v/F_m), leaf greenness (SPAD) and plant dry weight at the three- and six-leaf stages (DW3_P, DW6_P) were measured.     

Perennial O. sativa × O. rufipogon interspecific hybrids: I. Photosynthetic characteristics and their inheritance

A survey of 24 wild Oryza accessions identified Oryza australiensis and Oryza rufipogon as potential sources of enhanced photosynthetic rate for introgression into cultivated rice. Photosynthetic capacity per unit leaf area (CER) was associated with leaf N content but not with leaf chlorophyll concentration, flag leaf area, or specific leaf area. Eight fertile, perennial F₁ hybrids between O. sativa and O. rufipogon were grown in non-flooded soil, and CER was measured at flowering under saturating light. Two F₁ hybrids had greater CER than the average of 26.1 μmol m² s⁻¹. The F₂ progeny from these hybrids were screened for CER in the field, and segregants with even greater rates of photosynthesis were selected. The basis of high photosynthetic rate in the F₂ populations was not leaf thickness or leaf chlorophyll content. One F₂ line had exceptionally high CER and stomatal conductance. Broad-sense heritability on an individual plant basis for CER in two F₂ populations was 0.44 and 0.37. A highly significant offspring-parent regression of 0.89 for CER was observed in a replicated field evaluation (four blocks, five plants per plot) of 20 vegetatively propagated F₂ selections and their F₃ seedling progeny. Broad-sense heritability for CER on a plot-mean basis was estimated as 0.74 for both selected F_2:3 families and for the selected F₂ clones. Genetic resources in the genus Oryza may represent a source of alleles to increase leaf photosynthetic rate in the cultivated species, which we have demonstrated to be a heritable, though environmentally variable, trait in an O. sativa/O. rufipogon population.     

Correlation of Chlorophyll Meter Readings with Gas exchange and Chlorophyll Fluorescence in Flag Leaves of Rice (Oryza sativa L.) Plants

Abstract

The objective of this study was to establish the correlation of the chlorophyll meter (SPAD) readings with the contents of chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the gross photosynthetic rate (P_g), and the maximum quantum yield of photosystem II (PSII) (F_v/F_m) in flag leaves of rice (Oryza sativa L.) in ripening stage. The SPAD readings significantly correlated with the Chl content, the Rubisco content, P_g and F_v/F_m (R² = 0.848, 0.648, 0.671 and 0.712, respectively), which suggests that the SPAD meter has the potential to estimate the photosynthetic capacity of the flag leaves. However, both P_g and F_v/F_m had a stronger relationship with the Rubisco content than the SPAD readings, indicating that the PSII photochemical and CO₂ assimilation capacities are strongly influenced by the Rubisco content. Therefore, accurate calibration would be indispensable to obtain the physiological information from the SPAD readings of flag leaves.     

Yield and agronomic performance of maize hybrids resistant to the maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

This study evaluated improved maize hybrids (Zea mays L.) with varying level of resistance to the maize weevil, Sitophilus zeamais Motschulsky, for yield and agronomic traits for two seasons. A total of 22 improved maize hybrids and three commercial standards were tested. Out of the 22 tested, two hybrids CKPH08035 (7.4–9.9 t ha⁻¹) and CKPH08039 (7.3–9.8 t ha⁻¹) significantly out yielded the commercial standards WH505 (8.8 t ha⁻¹) and BH140 (5.5 t ha⁻¹). In addition to yield, the improved hybrids also possess desirable traits including good plant height, good plant and ear aspects and good husk cover. The hybrid CKPH08004 had the lowest Dobie index of susceptibility and was regarded as resistant to S. zeamais. Weevils fed with the resistant hybrids produced low numbers of F₁ generation weevils, had a high median developmental time and a low percentage of grain damage and grain weight loss. An increasing number of F₁ generation resulted in an increasing grain damage and grain weight loss. We found an inverse relationship between the susceptibility index and percent mortality. However, the numbers of F₁ generation, percent grain damage and grain weight loss were positively correlated with the susceptibility index. The use of resistant maize hybrids should be promoted in managing S. zeamais in stored maize under subsistence farming conditions in Africa.     

Simultaneous selection for stem borer resistance and forage related traits in maize (Zea mays ssp. mays L.) × teosinte (Zea mays ssp. mexicana L.) derived populations

Maize spotted stalk borer (Chilo partellus Swinhoe Pyralidae) (MSSB) is a serious pest of the maize (Zea mays ssp. mays L.) crop in Pakistan. This study was conducted to introgress resistance in maize against MSSB by exploring wild sources of resistance for the development of a resistant maize variety. To achieve this, teosinte (‘PI566674’) × maize (‘Sargodha-2002’) crosses were conducted and three populations (F₁, F₂ and F₃) were established. These populations were screened at various locations and in a contrasting artificial insect infestation experiment. Teosinte species ‘PI566674’, following screening, was shown to be highly resistant to MSSB and had the ability to produce a high biomass (5 times higher than susceptible genotypes) under high temperatures (36–40 °C). The biomass of the F₁ hybrid, which was highly susceptible to MSSB, was significantly reduced (P ≤ 0.05) following infestation by MSSB in all experiments. The introgression from teosinte for genes conferring resistance to MSSB was screened in segregating F₂ and F₃ generations. Despite a susceptible F₁ population, F₂ was resistant to MSSB. Twenty new recombinant plants with resistance to MSSB and a high leaf soluble solid (16 °Brix) content were identified. They were selected to grow the F₃ population. Mean values of F₃ progenies showed similar resistance to the F₂ population but a high percentage (60%) of resistant plants was recovered.     

Physio-Biochemical Responses of Oil Palm (Elaeis guineensis Jacq.) Seedlings to Mannitol- and Polyethylene Glycol-Induced Iso-Osmotic Stresses

References

The aim of this investigation was to comparatively examine the physio-biochemical responses of oil palm seedlings to mannitol- and PEG-induced iso-osmotic stresses. The water content of osmotically stressed oil palm seedlings decreased, but the proline content and the electrolyte leakage of the seedlings increased with decreasing water potential (Ψ_w). However, the responses varied with the strength of osmotic stress and type of osmotic agent. Relative electrolyte leakage (REL) was negatively correlated to chlorophyll content in the osmotically stressed leaves. Chlorophyll a (Chl_a), chlorophyll b (Chl_b), total carotenoids (C_x+c) and total chlorophyll (TC) in the seedlings were significantly reduced by osmotic stress, subsequently reducing maximum quantum yield of PSII (F_v/F_m) and photon yield of PSII (Φ_psii), thereby lowering net-photosynthetic rate (P_n) and inhibiting growth. Physio-biochemical parameters, including REL, F_v/F_m, and Φ_psii in oil palm seedlings were reduced more greatly by PEG-induced osmotic stress than by mannitol-induced stress. A deterioration in morphological characters, including leaf chlorosis, leaf burn, and green leaf area reduction were demonstrated in oil palm seedlings under osmotic stress induced by either mannitol or PEG. However, the toxic symptoms in oil palm seedlings under PEG-induced stress were severer than in those under mannitol-induced iso-osmotic stress, especially under severe osmotic stress.     

Performance of hybrids between transgenic oilseed rape (Brassica napus) and wild Brassica juncea: An evaluation of potential for transgene escape

Understanding the potential for the evolution of herbicide tolerance in weeds following gene flow from transgenic crops is important for their management. The inter-specific hybrids formed between four Brassica juncea populations with different glyphosate-susceptibility and transgenic oilseed rape was studied, emphasizing on the possible population difference. Compared with both parents, the fitness-related components and photosynthetic capacity of hybrids decreased dramatically, but significant differences were observed among different hybrids. All F₁ hybrids exhibited highly enhanced but similar herbicide tolerance level regardless of the wild B. juncea parent, indicating that genetically engineered herbicide tolerance may over-dominate phenotype ones by wild-crop hybridization. The analysis of parental loci transmission revealed a higher transfer ratio of male-specific loci detected in F₁ hybrids, suggesting that oilseed rape genetic markers can be transferred at relatively high frequencies to the next generation. Therefore, higher transfer ratio of oilseed rape-specific loci, coupled with variation of populations in fitness-related parameters in F₁ hybrids, could complicate environmental risk assessment of transgenic oilseed rape, especially in current agroecosystems with increasing application of glyphosate.     

外源丙三醇对干旱胁迫下玉米幼苗抗逆调控作用

以郑单958幼苗为试验材料,设置空白对照(CK)、正常水分条件下1 mmol/L丙三醇(Gly)处理玉米幼苗叶片、20%聚乙二醇(PEG-6000)模拟干旱胁迫(PEG)、20%聚乙二醇模拟干旱胁迫+1 mmol/L丙三醇(PEG+Gly)处理玉米幼苗叶片4个处理展开试验。结果表明,干旱胁迫下外源施用1 mmol/L丙三醇能显著提高叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性;丙二醛(MDA)和过氧化氢(H₂O₂)积累减少;最大光量子效率(F_v/F_m)和光系统Ⅱ潜在活性(F_v/F_o)显著提高,玉米幼苗叶片的净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)、相对含水率及生长指标均显著提高,胞间CO₂浓度(C_i)降低。因此,外源施用丙三醇能通过降低叶片的氧化损伤和提高细胞保水能力来改善...     

不同生长带玉米自交系和杂交组合品质的差异分析

利用近红外光谱仪对2013年海南三亚种植收获的99份温带自交系(13份高油材料和86份普通材料)、64份热带/亚热带自交系和由这163份自交系随机组配的186份杂交组合的杂交当代F0材料进行无破损子粒品质成分鉴定,分析不同生长带玉米自交系及其不同组合的杂交种后代品质成分的差异性。结果表明,当不考虑高油材料影响时,温带材料与热带/亚热带玉米自交系之间粗蛋白、粗脂肪和粗淀粉含量差异均不显著;去除高油材料后,温带材料与热带/亚热带玉米自交系之间粗蛋白差异不显著,粗脂肪和粗淀粉含量差异极显著。对于不同生长带玉米杂交当代F0而言,考虑与不考虑高油材料影响时,粗脂肪差异都极显著,粗淀粉和粗蛋白都无明显差异;相对于粗蛋白和粗淀粉,粗脂肪表现出更高的超高亲和超中亲优势。     

利用花青素基因标记研究正反交对玉米杂交种主要性状的影响

以转花青素合成转录因子Bi和Cl基因玉米的稳定表达株系与自交系B73-329(CK)进行杂交,研究花青素基因在玉米杂种F_1植株组织、器官中表达情况。结果表明,用转基因株系作为母本的杂交种F_1植株部分存在表型分离,用自交系B73-329作为母本的杂交种F_1植株不存在表型分离。转基因杂交种F_1植株,颖紫色,苞叶、茎鞘紫色,气生根紫色,与CK差异显著;转基因杂交种F_1植株叶片为绿色,转基因株系自交分离群体株系的叶片为紫色;转基因杂交种F_1植株绝大部分花丝为黄色,个别花丝红色,子粒绝大部分为黄色。抽丝、散粉期,转基因杂交种株高、穗位高等农艺性状与对照差异不显著,但是大部分产量显著低于对照,推测其主要原因在于花青素合成途径的引入导致植株能量代谢损耗所致。研究表明,转基因玉米杂交制种应用应以转基因株系作为父本。     

Photosynthetic Recovery of a Perennial Grass Leymus chinensis after Different Periods of Soil Drought

Abstract

The effects of rewatering after different periods of soil drought stress on the photosynthetic capacity of Leymus chinensis in pots were investigated. The plants were subjected to short-term (10-d), moderate-term (20-day) and long-term (30-d) drought each followed by rewatering. Control plants were well watered during the experimental periods. The long-term water stress without rewatering decreased the chlorophyll content, Chl a/b ratio, carbonic anhydrase (CA) activity, net photosynthetic rate (A), and leaf area compared with the control. Rewatering increased the ratio of Chl a/b, CA activity and A, but decreased the leaf area and ion leakage from the cut leaf pieces. The long-term water stress without rewatering reduced the maximal efficiency of PSII (F_v/F_m), the actual quantum yield (Φ_p), and photochemical quenching (q_p), but these values were increased by rewatering to more than the control level, though non-photochemical quenching (q_N) was decreased as compared with the control. This implied that long-term drought aggravated PSII, but rewatering improved it. The net CO₂-exchange rate showed similar diurnal changes in all treatments, but the rate in the morning was lower in long-term drought (before rewatering) than in the other treatments. These results suggest the photosynthesis of Leymus chinensis may be well adapted to episodical soil drought.     

Leptines and other glycoalkaloids in tetraploidSolanum tuberosum xSolanum chacoense F2 Hybrid and Backcross Families

The leptine glycoalkaloids fromSolanum chacoense Bitter are potential resistance factors to Colorado potato beetle,Leptinotarsa decemlineata Say. A selected sample of 17 F₁ hybrids (4x) from crosses of a 4xS. chacoense clone that synthesizes leptines (8380-1) with 4xS. tuberosum L. lines were selfed to generate F₂ hybrids (4x) and were also backcrossed toS. tuberosum. Glycoalkaloid (GA) content in foliage and tubers was measured for 786 sibling genotypes from the two generations in the field at Beltsville, Maryland. Leptines were found in the foliage of all F₂ hybrids and in 98% of the backcross genotypes. Leptines were not detected in tubers from either generation. Foliage concentrations of leptines for the F₂ hybrids averaged 156 mg/100g fresh weight (FW). The proportion of the total GA content consisting of leptines averaged 42%. By backcrossing the F₁ hybrids toS. tuberosum the average concentration of leptines was reduced to 44 mg/100g FW. The proportion of leptines averaged 16%. The tuber contents of solanine plus chaconine glycoalkaloids averaged 52 mg/100g FW for the F₂ hybrids and 27 mg/100g for the backcross genotypes.     

冬前镇压和灌溉对冬小麦灌浆期旗叶光合特性和叶绿体超微结构的影响

为明确冬前镇压和灌溉对冬小麦灌浆期旗叶功能的影响,以济麦22为材料,在2016-2017小麦生长季,对其进行冬前镇压+灌溉(C+I)、灌溉(I)和镇压(C)处理,以常规种植管理为对照(CK),研究不同冬前栽培措施对冬小麦灌浆期土壤微环境、旗叶光合特性和叶绿体超微结构以及最终产量和生物量的影响。结果表明,与CK相比,C、I及C+I处理都可提高麦田土壤含水量和土壤温度,可增加花后14～28d旗叶叶绿素相对含量(SPAD)、灌浆期旗叶最大光学效率(Fv/Fm)、净光合速率(Pn)和蒸腾速率(Tr),缓解旗叶SPAD、Fv/Fm、Pn和Tr在灌浆后期的下降,其中以C+I处理的效果最佳;灌浆中后期(花后21d),CK条件下小麦植株旗叶部分叶绿体呈圆形,大部分基粒片层变形且排列紊乱,可见较多的亲锇颗粒,但C+I、C和I处理下叶绿体的破坏程度降低,较多的叶绿体呈椭圆形,单位面积内叶绿体数和叶绿体基粒数提高,基粒片层较CK清晰且排列紧密,亲锇颗粒数量减少,其中C+I和I处理对叶绿体超微结构的改善作用大于C处理。这说明在本试验条件下,冬前镇压+灌溉较单独灌溉或镇压更有利于改善小麦灌浆期旗叶光合功能,缓解灌浆后期旗叶的衰老,促进小麦产量形成。     

Resistance to Columbia root-knot nematode inSolanum ssp. and in hybrids ofS. hougasii with tetraploid cultivated potato

Several tuber-bearingSolanum species were screened for resistance to races 1 and 2 of Columbia root-knot nematode,Meloidogyne chitwoodi. Reproductive factor (R_f = P_f/P_i) was assessed and used to infer host resistance. Several clonal selections in one Plant Introduction accession ofSolanum hougasii showed high levels of resistance to both races. Crosses ofS. hougasii with tetraploid breeding clones yielded 14 vigorous F₁ hybrids. Three of these interspecific hybrids expressed non-host (R_f<0.1) responses to race 1 and poor host (0.1f<1.0) responses to race 2. Six hybrids were nonhosts to race 1 but good hosts (R_f>1.0) to race 2. Three hybrids were good hosts to both races, and one was a poor host to race 1 and non-host to race 2. The occurrence of resistance to both races in the F₁ hybrids indicates success in the first step of introducing resistance to races 1 and 2 ofM. chitwoodi to the cultivated potato gene pool.     

Physio-morphological Studies of F1 Hybrids in Rice (Oryza sativa L.): Photosynthetic ability and yield

Summary

Photosynthetic ability in terms of CO₂ exchange rate and leaf area, dry matter accumulation (dry weight) and other important growth components along with yield and yield contributing characters in two F₁ hybrids of Akebono × Chiyonishiki (A × C) and Zenith × Akebono (Z × A) were studied. The photosynthetic rate at the flowering stage was lower than that at the panicle initiation stage in all the inbred parent cultivars and F₁ hybrids. Heterosis in photosynthetic rate was higher at the panicle initiation stage than that at the flowering stage. Pre-anthesis leaf area in the F₁ hybrid was significantly larger than that in the parent cultivars. However, the post- anthesis decline in leaf area was more rapid in the F₁ hybrids than in the parent cultivars and its magnitude was the highest in the F₁ hybrid of Z × A which was tall having long and curved panicles. Pre-anthesis dry matter accumulation in both hybrids was significantly higher in the F₁ plants than the parental cultivars, but post-anthesis dry matter accumulation in the F₁ hybrid was lower than the mid-parental value in Z × A. The degree of heterosis in grain yield varied with the hybrid combination, an average heterosis being 1.03. Heterosis in grain yield was closely associated with heterosis in harvest index.