小麦旗叶光呼吸对光强和CO2浓度的响应

为给C₃作物光呼吸等光合参数以及光响应模型和CO₂响应模型的研究提供参考,定量研究了小麦花期旗叶光呼吸速率对光强和CO₂浓度的响应。结果表明,在21%和2%O₂下小麦旗叶光饱和点分别为1 960.629和2 030.120 μmol·m^-2·s^-1。在较弱光强(小于800 μmol·m^-2·s^-1)下,小麦的总光呼吸速率(R_pt)与表观光呼吸(R_pa)均随着光强的升高而增大;当光强大于800 μmol·m^-2·s^-1时,R_pt和R_pa趋于稳定;整体上,不同光强下R_pt与R_pa之间差异较小(P>0.05),这主要是由于在380 μmol·mol^-1 CO₂下,光呼吸的CO₂回收利用率较低。饱和光强下,R_pa随着CO₂浓度的增加呈先上升后下降的趋势,R_pa最大值(Rpmax)所对应的外界CO₂浓度为600 μmol·mol^-1,而R_pt则随着CO₂浓度的升高而降低;在低浓度CO₂(小于380 μmol·mol^-1)条件下,R_pt与R_pa之间差异显著(P<0.05)。R_pt与羧化速率的比值(R_pt /Vc)随着胞间CO₂浓度的升高而呈下降的趋势,而不同光强下R_pt /Vc相对稳定,整体上未达到显著水平(P>0.05)。     

壳寡糖对小麦早期生长生理的影响

为了阐明壳寡糖调节小麦早期生长发育的机理,以室内培养的方法研究了四种浓度的壳寡糖对小麦幼苗早期生长的影响,同时利用组化染色和分光光度计法分别检测了其对根尖和叶片中H₂O₂和O₂^-含量的影响。结果表明,1 μg·mL^-1壳寡糖可以显著促进小麦根和幼苗的生长,而10 μg·mL^-1壳寡糖则抑制其生长;壳寡糖对小麦幼苗叶片和根尖中的H₂O₂和O₂^-含量影响不同,在根尖中1 μg·mL^-1壳寡糖可以增加H₂O₂和O₂^-含量,10 μg·mL^-1壳寡糖可以增加H₂O₂含量而降低了O₂^-含量;在叶片中1 μg·mL^-1壳寡糖对H₂O₂和O₂^-无明显影响,10 μg·mL^-1壳寡糖可以降低H₂O₂含量而不改变O₂^-含量。壳寡糖对小麦幼苗叶片中的丙二醛和可溶性蛋白质含量影响不大。     

灌水和施肥对垄作沟灌啤酒大麦产量及水分利用效率的影响

为给甘肃河西绿洲灌区啤酒大麦垄作沟灌栽培的水肥管理提供参考,通过裂区试验,设置4个不同灌溉定额(1 500 m·hm^-2、2 100 m·hm^-2、2 700 m·hm^-2和3 300 m·hm^-2)和3个不同施肥水平（N 75 kg·hm^-2+P₂O₅56.25 kg·hm^-2、 N 150 kg·hm^-2+P₂O₅112.5 kg·hm^-2、N 225 kg·hm^-2+P₂O₅168.75 kg·hm^-2）,研究了灌水和施肥对垄作沟灌栽培啤酒大麦产量及水分利用效率的影响。结果表明,灌溉定额、施肥量及水肥互作对啤酒大麦的产量和水分利用效率均有明显影响。当灌溉定额从1 500 m·hm^-2增大到2 700 m·hm^-2时,啤酒大麦千粒重提高5.36 g,成穗数增加1.16×10⁶·hm^-2,增产57.99%,水分利用效率提高24.12%;灌水量超过2 700 m·hm^-2时,增产效果不明显。在N 75～150 kg·hm^-2、P₂O₅56.25～112.5 kg·hm^-2范围内,增施肥料有利于啤酒大麦千粒重和穗粒数增加,并显著提高产量和水分利用效率。在灌溉定额2 700 m·hm^-2、纯N 150 kg·hm^-2、P₂O₅ 112.5 kg·hm^-2条件下,垄作沟灌栽培啤酒大麦的产量和水分利用效率分别为6 239.84 kg·hm^-2和13.33 kg·mm^-1·hm^-2,水肥利用效果和经济效益相对较优。     

玉米回交后代群体中供体基因组成分分析

以郑58为受体亲本,昌7-2为供体亲本,通过杂交、回交和79对亲本间有多态的SSR标记,分析BC₂F₁和BC₃F₁世代供体的基因组成分。结果表明：BC₂F₁世代单株内的供体染色体片段数平均为11.4个,BC₃F₁世代为4.8个,从BC₂F₁到BC₃F₁单株内的供体染色体片段数减少了57.6%;BC₂F₁世代单株内的供体染色体片段长度平均为99.3 cM,BC₃F₁世代为87.1 cM,BC₃F₁较BC₂F₁减少了12.3%;BC₂F₁世代单株内的供体基因组大小平均为1 132.8 cM,BC3F1世代为421.4 cM,BC₃F₁较BC₂F₁减少了62.8%。     

密度对不同株型玉米光合特性及产量的影响

对不同密度条件下3个不同株型春玉米的光合特性及产量进行了研究。结果表明,随密度增加叶面积指数(LAI)、初始荧光(F₀)上升,单株功能叶片光合速率(P_n)、PSⅡ的潜在活性(F_v /F₀)、PSⅡ最大光化学量子产量(F_v /F_m)下降;产量构成因素表现为单位面积有效穗数先上升后下降,穗粒数下降,百粒重变化因品种而异。先玉335、金玉4号和吉农大302最高产量分别为9 638.45、8 523.94、8 330.92 kg/hm²;先玉335最适播种密度为75 000株/hm²,吉农大302为60 000～67 500株/hm²,金玉4号为45 000株/hm²。先玉335群体产量与LAI、单株F₀呈正相关,与单株P_n、F_v /F_m、F_v /F₀呈负相关;吉农大302与金玉4号群体产量与LAI、单株F₀呈负相关,与单株P_n、F_v /F_m、F_v /F₀呈正相关,且金玉4号的相关程度要高于吉农大302。     

缓释肥配比与密度互作对冬小麦产量及品质的影响

为了探究不同缓释肥配比与基本苗互作对冬小麦生产的影响,以中筋小麦扬麦25为材料,于2019-2020年在江苏省仪征市进行田间试验,设置100%普通尿素（S₁）、50%缓释肥与50%尿素配施（S₂）、100%缓释肥（S₃）3种施肥处理及4种氮密模式［施氮（纯N）量225 kg·hm^-2、密度225×10株·hm^-2（A₁）;施氮量191.25 kg·hm^-2、密度258.75×10株·hm^-2（A₂）;施氮量157.5 kg·hm^-2、密度292.5×10株·hm^-2（A₃）;施氮量123.75 kg·hm^-2、密度326.25×10株·hm^-2（A₄）］,研究不同处理对冬小麦产量及其构成因素、品质的影响。结果表明,氮肥类型和氮密模式均对产量有极显著效应;与 A₁处理比较,A₂处理的穗数和穗粒数较高,千粒重下降,继续增加种植密度、减少施氮量后,穗数与穗粒数显著下降;产量以S₂A₂与 S₃A₂组合处理较高。S₂与S₃处理的氮肥利用率与氮素农学效率均优于S₁处理,A₄模式的氮素农学效率最高,不同氮密模式处理间的氮肥利用率差异不显著。氮肥类型与氮密模式对出粉率、容重与硬度影响不显著,对湿面筋含量、沉降值、面团形成时间、面团稳定时间与吸水率有极显著影响, A₁和 A₂处理的品质表现较好,S₂与S₃处理的小麦二次加工品质优于S₁处理;氮肥类型与氮密模式互作对籽粒蛋白质含量与产量有极显著影响。本试验条件下,50%缓释肥与50%尿素配施或100%缓释肥处理下,施氮量191.25  kg·hm^-2、密度258.75×10株·hm^-2（A₂）,施用基肥与返青肥,有利于小麦减氮稳产、改善品质、提高氮肥利用率。     

长期定位施氮条件下种植密度对冬小麦石4366品质和氮肥利用的影响

为探究长期施氮条件下种植密度对冬小麦品质特性和氮肥利用的调控作用,在长期定位试验的基础上,2020-2021年度采用裂区试验设计,主区为施氮量,设75 kg·hm^-2（N75）、150 kg·hm^-2（N150）、225 kg·hm^-2（N225）和300 kg·hm^-2（N300） 4个水平;副区为种植密度,设225×10⁴ 株·hm^-2（D225）、300×10⁴株·hm^-2（D300）、375×10⁴株·hm^-2（D375）、450×10⁴株·hm^-2（D450）和525×10⁴株·hm^-2（D525）5个水平;分析了不同施氮条件下种植密度对石4366产量、粉质特性、RVA特性、拉伸特性及氮肥利用率的影响。结果表明,不同施氮量和密度组合下籽粒产量和品质相关指标有较大差异,施氮量对氮肥农学效率和氮肥偏生产力有显著影响。小麦产量随着施氮量的升高而增加,施氮量225 kg·hm^-2、密度范围375×10⁴~525×10⁴株·hm^-2和施氮量300 kg·hm^-2、密度范围225×10⁴~450×10⁴株·hm^-2组合下均能获得较高产量。蛋白质含量、容重和湿面筋含量随着施氮量增加呈升高趋势;稳定时间和粉质质量指数随着施氮量增加呈先升高后降低的趋势,N225下粉质参数最高。小麦籽粒品质和面粉粉质指标均随种植密度的增加而增加。施氮量225 kg·hm^-2、密度525×10⁴株·hm^-2组合是小麦粉质指标最优组合。淀粉RVA参数在施氮量225 kg·hm^-2、密度225×10⁴株·hm^-2处理下最好。拉伸特性在施氮量225 kg·hm^-2、密度450×10⁴~525×10⁴株·hm^-2组合和施氮量300 kg·hm^-2、密度225×10⁴株·hm^-2组合下较好。氮肥农学效率和氮肥偏生产力在施氮量225 kg·hm^-2、密度375×10⁴~525×10⁴株·hm^-2组合下较高。综合籽粒产量、品质相关指标和氮肥利用效率的结果,本试验条件下,施氮量225 kg·hm^-2、种植密度450×10⁴~525×10⁴株·hm^-2可作为石4366高产、优质的较佳肥密组合。     

小麦玉米一体化群体配置对小麦冠层结构和产量影响

为探索冬小麦-夏玉米一体化种植中小麦的适宜群体配置模式,设置20 cm-20 cm（R₁）、12 cm-12 cm-12 cm-24 cm（R₂）及13 cm-20 cm（R₃）三种行距处理方式和120 kg·hm^-2（S₁）、157.5 kg·hm^-2（S₂）及195 kg·hm^-2（S₃）三种播量,研究了行距和播量对小麦冠层结构特征和光合特性及产量的影响。结果表明,不同处理对各指标的影响因小麦生育时期的变化而不同。在孕穗至开花期, R₁S₁处理的小麦叶片SPAD值、净光合速率（P_n）及气孔导度（G_s）高于其他处理,开花期后R₂S₂处理表现出明显的光合优势。其中,R₂S₂处理的小麦LAI、叶倾角（MTA）在开花期后高于其他处理,在花后10 d之后其SPAD、P_n值最高。在不同处理中,R₂S₂处理产量最高,这主要归因于其有较高的穗数和千粒重。因此,在本试验条件下小麦高产的最佳群体配置是行距12 cm-12 cm-12 cm-24 cm和播量157.5 kg·hm^-2。     

球孢白僵菌CXJ-1与吡虫啉防治棉蚜配方筛选和田间防治效果

 为了明确球孢白僵菌与吡虫啉复配防治棉蚜的效果,提出抗吡虫啉棉蚜的治理策略,采用浸渍法测定了球孢白僵菌CXJ-1菌株对棉蚜的致死中浓度和致死中时间,并以对棉蚜致死率较高的1×10⁹ mL^-1、1×10⁸ mL^-1和1×10⁷ mL^-1  3个浓度的孢子悬浮液分别与0、0.03 g·L^-1和0.04 g·L^-1的吡虫啉复配后,采用大田喷雾施药法测定对棉蚜的防治效果。结果表明：1×10⁸ mL^-1  CXJ-1孢子悬浮液与0.03 g·L^-1吡虫啉混用是最佳配比;施用3 d后对棉蚜的校正防效为85.18%,第11天为60.33%,显著高于单用0.03 g·L^-1吡虫啉,且对天敌瓢虫和草蛉种群数量影响最小。球孢白僵菌孢子悬浮液与吡虫啉复配后对棉蚜的持效期长,可减少吡虫啉的施用量,从而减轻其对棉蚜的选择压力。     

秋播冬麦区矮秆基因 RhtB1b、 RhtD1b和 Rht8的分布频率及其与产量性状的关系

为给小麦株高和产量的遗传改良提供参考依据,利用 Rht-B1b、 Rht-D1b基因的STS分子标记BF/MR1和BF/WR1、DF1/MR2和DF2/WR2,以及 Rht8基因的微卫星标记Xgwm261,对237份不同生态区秋播小麦材料进行分子标记检测,并分析 Rht-B1b、 Rht-D1b和 Rht8对株高及产量相关性状的影响。结果表明：（1）在分布频率方面, Rht-B1b、 Rht-D1b和 Rht8在秋播冬小麦中的频率较高,其中携带 Rht-B1b、 Rht-D1b和 Rht8的小麦材料分别占比16.5%、47.9%和44.1%;聚合两个矮秆基因（ Rht-D1b+Rht8、 Rht-B1b+Rht8和 Rht-B1b+ Rht-D1b）的小麦材料占比25.4%;聚合三个矮秆基因（Rht-B1b+Rht-D1b+Rht8）的小麦材料占比2.1%;（2）在分布特点方面,不同冬麦区存在一定偏好性：北部冬麦区、黄淮冬麦区、长江中下游冬麦区均以 Rht-D1b、 Rht8和 Rht-D1b+Rht8为主;西南冬麦区以 Rht-B1b、 Rht-D1b和 Rht8为主,西南冬麦区以 Rht-B1b、Rht-D1b和Rht8为主;（3）在降秆效应方面,降秆效果从强到弱依次为（ Rht-B1b+Rht-D1b+Rht8）>（ Rht-D1b+Rht8）> （ Rht-B1b+Rht8）> Rht-D1b> Rht-B1b> Rht8;(4)在产量结构特点方面, 携带 Rht-D1b和 Rht8的材料总体上具有较高的千粒重和单位面积穗数,携带 Rht-B1b的材料具有较高的穗粒数,但矮秆基因本身与产量因子间无显著的遗传相关性。     

Improvement of growth and gymnemic acid production by altering the macro elements concentration and nitrogen source supply in cell suspension cultures of Gymnema sylvestre R. Br

Gymnema sylvestre is an important medicinal plant which bears bioactive compound namely gymnemic acids. The present work deals with optimization of cell suspension culture system of G. sylvestre for the production of biomass and gymnemic acid and we investigated effects of macro elements (NH₄NO₃, KNO₃, CaCl₂, MgSO₄ and KH₂PO₄ - 0.0, 0.5, 1.0, 1.5 and 2.0× strength) and nitrogen source [NH₄⁺/NO₃⁻ ratio of: 0.00/18.80, 7.19/18.80, 14.38/18.80, 21.57/18.80, 28.75/18.80, 14.38/0.00, 14.38/9.40, 14.38/18.80, 14.38/28.20 and 14.38/37.60 (mM)] of Murashige and Skoog medium on accumulation of biomass and gymnemic acid content. The highest accumulation of biomass (165.00 g l⁻¹ FW and 15.42 g l⁻¹ DW) was recorded in the medium with 0.5× concentration of NH₄NO₃ and the highest production of gymnemic acid content was recorded in the medium with 2.0× KH₂PO₄ (11.32 mg g⁻¹ DW). The NH₄⁺/NO₃⁻ ratio also influenced cell growth and gymnemic acid production; both parameters were greater when the NO₃⁻ concentration was higher than that of NH₄⁺. Maximum biomass growth (159.72 g l⁻¹ of FW and 14.95 g l⁻¹ of DW) was achieved at an NH₄⁺/NO₃⁻ ratio of 7.19/18.80, and gymnemic acid production was also greatest at the same concentration of NH₄⁺/NO₃⁻ ratio (11.35 mg g⁻¹ DW).     

Efficacy and effects on yield of different fungicides for control of wet bubble disease of mushroom caused by the mycoparasite Mycogone perniciosa

Carbendazim, iprodione, prochloraz-Mn, thiabendazole and thiophanate-methyl were tested in vitro and in vivo for their effect on Mycogone perniciosa, the mycoparasite that causes wet bubble disease of white button mushroom. In vitro experiments showed that prochloraz-Mn (ED₅₀ = 0.006–0.064 μg ml⁻¹) and carbendazim (ED₅₀ = 0.031–0.097 μg ml⁻¹) were the most effective fungicides for inhibiting the mycelial growth of M. perniciosa, while iprodione (ED₅₀ = 1.90–3.80 μg ml⁻¹) was the least effective. The resistance factors calculated for the five fungicides were between 1.4 and 2. The results obtained suggest that there is very little risk that M. perniciosa will develop resistance to the fungicides assayed. The in vivo efficacy of fungicides for control of wet bubble was studied in two mushroom cropping experiments, which were artificially infected with two doses of M. perniciosa, 10⁶ and 10⁷ spores m⁻², respectively. There was, in the low dose inoculum experiment, a very high degree of effectiveness (96.5–100.0%) with all the fungicides assayed. However, iprodione performed poorly (20.5–24.4%) compared with the other fungicides (88.7–100.0%) in the high concentration inoculum experiment. The most effective treatments for controlling wet bubble did not improve the biological efficiency of Agaricus bisporus.     

Combination of On-Line Solid-Phase Extraction with LC-MS for the Determination of Potentially Hazardous Glycoalkaloids in Potato Products

A simple and rapid method for the determination of naturally occurring, potentially hazardous glycoalkaloids (GAs) in potatoes and their products has been developed. The procedure is based on the on-line solid-phase extraction of the acetic acid extracts from potato products and combined with liquid chromatography (LC)-mass spectrometry (MS) in a fully automated system (Symbiosis™, Spark Holland Instruments, Emmen, The Netherlands). As sorbent material HySphere™ 18HD was used for alkaloid enrichment. GAs were eluted with the LC gradient and directly analysed by MS. Detection of the analytes was achieved in the sensitive multiple reaction monitoring mode using two characteristic ions (m/z 98 as a qualifier for GAs and m/z 868.3 as a quantifier for α-solanine or m/z 852.4 for α-chaconine). Typical validation data for method precision (v _k α-solanine = 5.3–6.5, v _k α-chaconine = 3.4–15.4), accuracy (average recovery of α-solanine = 84%, average recovery of α-chaconine = 87%) and linearity over the range from 1 to 1,000 ng ml⁻¹ (R ² = 0.9915 for α-solanine, R ² = 0.9939 for α-chaconine) with detection limits of 0.3 ng ml⁻¹ for α-chaconine and 0.5 ng ml⁻¹ for α-solanine were obtained. GA contents of commercial potato products were determined by the new on-line method and afterwards compared with those obtained with an established high-performance LC routine procedure. Better performance of the on-line procedure was obvious from the standard deviations of both methods. Other advantages included a strong reduction of overall analysis time, human intervention and solvent consumption as well as waste production. The time required for the on-line analysis was 5 min, which would allow processing of almost 100 samples in 8 h.     

Inclination Angle Affects Ozone Injury in the Flag Leaf of Rice

Abstract

To evaluate the effect of inclination angle of the leaf on the leaf injury of rice by O₃, we examined the effect of a 5-hr exposure to 0, 0.1, 0.3 cm³ m-³ O₃, abbreviated as O⁰, O^0.1 and O^0.3, respectively, of the flag leaf using natural-light gas-exposure chambers. The middle portion of the flag leaf was set horizontally using lead weights (H plant) and it was compared with a non-treated, erect leaf (E plant). Gas exchange and chlorophyll fluorescence were measured immediately before, immediately after, and 1 and 3 d after the start of the exposure. The net photosynthetic rate, stomatal conductance and operating quantum efficiency of photosystem II (F_q’/F_m’) were decreased by the exposure to O₃. Furthermore, the inhibitory effects of O^0.1 and O^0.3 on the H plants were severer than those on the E plants. The maximum quantum efficiency of photosystem II (F_v/F_m) in the leaf of H plants decreased immediately after exposure to O₃. These results indicate that the weaker inhibitory effect of O₃ on the erect leaf depends on the lower light intensity at the leaf surface, rather than the horizontal leaf position.

Key words: Ascorbic acid, Chlorophyll fluorescence, Gas exchange, Leaf inclination angle, Oryza sativa, O₃, Quantum efficiency.     

Rubisco small subunits of C4 plants,Napier grass and guinea grass confer C4-like catalytic properties on Rubisco in rice

ABSTRACT

Overexpression of Rubisco small subunit (RbcS) of C₄ plant, sorghum (sorghum bicolor) was shown to enhance the catalytic turnover rate (k _cat) of Rubisco in rice (Oryza sativa). In this study, the effects of other Rubisco small subunits of C₄ plants, Napier grass (Pennisetum purpureum) and guinea grass (Megathyrsus maximus) on kinetic properties of Rubisco in rice were studied. The expression levels of Napier grass RbcS (NgRbcS) and guinea grass RbcS (GgRbcS) proteins accounted for 41% and 45% of total RbcS, respectively in homozygous overexpression lines. The k _cat and K _m for CO₂ (Kc) of Rubisco were increased in all transgenic lines. Interestingly, the k _cat was markedly higher in NgRbcS homozygous line, whereas K _c was notably higher in GgRbcS homozygous line. Although its effects depend on species, these results suggest that the introduction of C₄ RbcS are effective approaches to alter the catalytic properties of Rubisco in rice.     

Effects of crude seed extracts of Annona atemoya and Annona squamosa L. against the cabbage looper, Trichoplusia ni in the laboratory and greenhouse

Antifeedant, growth inhibitory and toxic effects of crude seed extracts of Annona squamosa and Annona atemoya from Fazenda Viveiro Bona, Parasisópolis – Minas Gerais, Brazil, were evaluated against the cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) using different bioassays. Crude methanolic seed extracts deterred feeding of third instar T. ni larvae in a leaf disc choice bioassay. A. squamosa was ∼10 times more active as a feeding deterrent than A. atemoya (DC₅₀ = 2.3 mg/ml vs. 20.1 mg/ml). A. squamosa was ∼three times more active as a growth inhibitor than A. atemoya (EC₅₀ = 38.0 ppm vs. 117.0 ppm). Methanolic seed extracts of A. squamosa and A. atemoya were toxic to third instar T. ni larvae both through topical and oral application. A. squamosa was more toxic through feeding (LC₅₀ = 167.5 ppm vs. 382.4 ppm) whereas, A. atemoya exerted greater toxicity via topical application (LC₅₀ = 301.3 μg/larva vs. 197.7 μg/larva). Both A. squamosa and A. atemoya extracts reduced leaf area consumption and larval growth in a greenhouse experiment. Our results indicate that both A. squamosa and A. atemoya have potential for development as botanical insecticides, especially for local use in Brazil.     

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.     

Genetic gains in grain yield, net photosynthesis and stomatal conductance achieved in Henan Province of China between 1981 and 2008

Knowledge of the changes in agronomic and photosynthetic traits associated with genetic gains in grain yield potential is essential for an improved understanding of yield-limiting factors and for determining future breeding strategies. The objectives of this study were to identify agronomic and photosynthetic traits associated with genetic gains in grain yield of facultative wheat (Triticum aestivum L.) between 1981 and 2008 in Henan Province, the most important wheat producing area in China. During the 2006-2007 and 2007-2008 crop seasons, a yield potential trial comprising 18 leading and new cultivars released between 1981 and 2008 was conducted at two locations, using a completely randomised block design of three replicates. Results showed that average annual genetic gain in grain yield was 0.60% or 51.30 kg ha⁻¹ yr⁻¹, and the significant genetic improvement in grain yield was directly attributed to increased thousand grain weight which also contributed to the significant increase in harvest index. The genetic gains in rates of net photosynthesis at 10, 20 and 30 days after anthesis were 1.10% (R² = 0.46, P < 0.01), 0.68% (R² = 0.31, P < 0.05) and 6.77% (R² = 0.34, P < 0.05), respectively. The rates of net photosynthesis at 10 (r = 0.58, P < 0.05), 20 (r = 0.59, P < 0.05) and 30 (r = 0.65, P < 0.01) days after anthesis were closely and positively correlated with grain yield. A slight decrease in leaf temperature and an increase in stomatal conductance after anthesis were also observed. Grain yield was closely and positively associated with stomatal conductance (r = 0.69, P < 0.01) and transpiration rate (r = 0.63, P < 0.01) at 30 days after anthesis. Therefore, improvement of those traits was the likely basis of increasing grain yield in Henan Province between 1981 and 2008. The genetic improvement in yield was primarily attributed to the utilization of two elite parents Yumai 2 and Zhou 8425B. The future challenge of wheat breeding in this region is to maintain the genetic gain in grain yield and to improve grain quality, without increasing inputs for the wheat-maize double cropping system.