WO3/g-C3N4复合催化剂的制备及其可见光 光催化性能分析

在盐酸质子化条件下,采用超声微波协助法成功制备了可见光型复合催化剂WO₃/g-C₃N₄。利用X射线多晶粉末衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见漫反射(UV-Vis)和BET比表面测试仪对样品进行了表征,并以罗丹明B(RhB)为目标降解物对其光催化性能进行研究。结果表明:复合催化剂样品是由片状的WO₃纳米片负载在g-C₃N₄表面组成的。当WO₃负载的质量分数为40%时,前驱物在500℃条件下煅烧2 h后所得样品的光催化性能明显好于同条件下制得的单一相WO₃和g-C₃N₄,在可见光(波长大于420 nm)照射下,5 h内对100 mL浓度为10^-5 mol/L罗丹明B橙溶液的降解高达98%。     

棉花黄萎病生防芽孢杆菌 Z-5 菌株发酵培养基的优 化简

 在农用微生物菌剂中芽孢杆菌菌剂产品多采用芽孢作为有效成分,因此产芽孢条件的优化对棉花黄萎病生防细菌的工业生产有着重要意义。本文通过单因素试验分析了8种碳源、8种氮源和6种无机盐对Bacillus malacitensis Z-5菌株芽孢产量的影响,采用Plackett-Burman试验设计确定了影响芽孢产量的主要因素,用最陡爬坡路径逼近最大响应区域,利用Box-Behnken试验设计及响应面分析法确定主要影响因素的最佳条件。结果表明,单因素试验筛选出3种碳源（玉米粉、麸皮、葡萄糖）、3种氮源（豆饼粉、花生饼粉、酵母粉）和2种无机盐（MnSO₄·H₂O、CaCl₂）;Plackett-Burman试验确定Z-5菌株生产芽孢最适碳源、无机盐和氮源分别为玉米粉、MnSO₄·H₂O和豆饼粉,最陡爬坡路径法获得此3种因子的最适浓度范围为：玉米粉1.0%~2.0%、MnSO4·H2O 0.05%~0.09%、豆饼粉为1.0%~2.0%。响应面法得到芽孢产量与玉米粉、MnSO4·H2O和豆饼粉含量的回归方程。最终确定优化培养基组合为玉米粉1.66%、豆饼粉1.30%、MnSO₄·H₂O 0.07%、NaH₂PO₄·2H₂O 0.2%、Na₂HPO₄·2H₂O 0.4%,优化后芽孢产量达到1.9⁷×10⁹ mL^-1,与理论值基本相符。     

盐胁迫条件下外源Ca2+对蚕豆气孔运动及质膜K+通道的调控

研究了Ca²⁺ 对NaCl胁迫下蚕豆气孔运动及质膜K+通道的影响。结果表明,100 mmol L^-1 NaCl可明显诱导气孔开放,该现象可被10 mmol L^-1 CaCl₂ 显著抑制。为探讨盐胁迫下Ca²⁺对K⁺和Na⁺跨膜运输的调控机制,我们利用膜片钳技术记录全细胞K⁺ 电流发现,在100 mmol L^-1 NaCl胁迫下,加入10 mmol L^-1 CaCl₂胞外处理,显著抑制质膜K+内向及外向通道电流,这种抑制可被1 mmol L^-1 La³⁺ (Ca²⁺通道抑制剂)缓解。非盐胁迫下,10 mmol L^-1 CaCl₂ 胞外处理也能显著抑制质膜内向K⁺通道,但明显激活其外向通道,加入1 mmol L^-1 La³⁺并不能被缓解。用H₂O₂专一的荧光探针二氯荧光素二乙酸酯(H2DCF-DA)单细胞分析保卫细胞内H₂O₂含量变化显示,在100 mmol L^-1 NaCl盐胁迫下,10 mmol L^-1 CaCl₂ 处理明显诱导H₂O₂在保卫细胞中积累;100 mmol L^-1 NaCl和10 mmol L^-1 CaCl₂单独处理并不能诱导H₂O₂积累。推测Ca²⁺在盐胁迫下可能先诱导H₂O₂在胞内积累,进而激活质膜Ca²⁺通道,迅速提高胞内Ca²⁺浓度以抑制Na⁺通过质膜K⁺通道跨膜内流,同时调节Na⁺外流,两种效应共同作用促使气孔关闭,减少盐胁迫下水分的过度散失。上述结果将为Ca²⁺调控作物抗盐机制研究提供新的思路。     

Q235钢表面环氧复合涂层在变电站环境中的腐蚀行为分析

以Q235钢表面涂覆的环氧富锌底漆,水性聚氨酯中间漆,银灰环氧磁漆构成的环氧复合涂层为对象,研究变电站环境中涂层自然暴露18个月后的腐蚀行为,并将其与用5% NaCl溶液浸泡250天处理的涂层的腐蚀行为做对比。采用电化学阻抗谱（EIS）研究环氧复合涂层试样的电化学腐蚀行为,评价环氧复合涂层的耐候性与耐盐性,并通过FT-IR表征涂层浸泡和自然暴露过程的结构变化。结果表明,环氧复合涂层试样在5% NaCl溶液中浸泡250 d后,涂层阻抗从3.967×10⁹ Ω·cm²降至9.780×10² Ω·cm²,其失效机制为腐蚀介质通过涂层微孔逐渐渗入涂层中形成微观电通路,导致涂层孔隙率逐渐增大,基底材料腐蚀加速;自然暴露试验18个月的试样,其涂层阻抗为2.708×10⁶ Ω·cm²,防护性良好。     

转2-Cys Prx基因烟草抗氧化酶和PSII电子传递对盐和光胁迫的响应

以转2-Cys Peroxiredoxins (2-Cys Prx)基因的烟草(Nicotiana tabacum)为材料,非转基因烟草为对照,调查盐和光胁迫对转基因烟草幼苗叶片抗氧化酶和叶绿素荧光特性的影响,揭示2-Cys Prx基因在植物抗逆方面的功能。结果表明,弱光(200 μmol m^–2 s^–1)下,随着盐浓度增大,转基因烟草和对照的SOD活性皆增加,APX活性变化不大,H₂O₂含量稍有升高;强光(1000 μmol m^–2 s^–1)下,随着盐浓度增大,转基因烟草SOD活性增强,APX活性下降,H₂O₂含量增加缓慢,而对照的H₂O₂含量迅速升高,转基因烟草叶片的PSII电子传递速率(ETR)、最大光化学效率(F_v/F_m)和实际光化学效率(Ф_PSII)均高于对照,而且PSII电子受体侧的受抑制程度明显低于对照。结果暗示在强光和盐胁迫使APX活性降低的情况下,2-Cys Prx可有效清除细胞中过量H₂O₂,增强光合电子传递链的稳定性,特别是PSII电子受体侧的电子传递,有效减轻盐和高光胁迫引起的PSII光抑制。     

非线性Mohr-Coulomb破坏准则下边坡可靠度上限

传统边坡可靠度分析往往在岩土参数服从线性Mohr-Coulomb（简称线性M-C）破坏准则的假设条件下进行,并且常常采用极限平衡法或有限元法计算安全系数。然而,岩土介质破坏准则具有一定的非线性。为能更加实际地描述岩土破坏机理和得到严格精确的解,基于非线性Mohr-Coulomb（简称非线性M-C）破坏准则,结合极限分析上限法和蒙特卡洛法,进行边坡可靠度上限分析。当非线性参数m=1时,与等效的线性M-C破坏准则进行对比计算,验证了方法的可行性。同时,将初始粘聚力、内摩擦角arctan（c₀/σ_t）和非线性参数作为随机变量且服从截断正态分布,进行了参数变异性和敏感性影响分析。研究表明：非线性M-C破坏准则下,边坡可靠度随初始粘聚力、内摩擦角arctan（c₀/σ_t）和非线性参数变异性的增大而减小;边坡可靠度随初始粘聚力和内摩擦角arctan（c₀/σ_t）的增大而增大,随非线性参数的增大而减小。     

山药块茎发育中物质积累及相关代谢酶变化

以桂淮5号和桂淮16两个不同山药品种为材料,根据块茎生长发育特性,在山药发育进程中测定块茎的有关生理生化指标。结果表明,随着块茎发育进程的推进,块茎长度及干物质积累持续增加,淀粉酶(AMY)活性降低;多数碳水化合物、功能性物质及过氧化物酶(POD)、酸性转化酶(AI)和蔗糖磷酸合酶(SPS)活性先持续增加,达到峰值后下降,但峰期不同;2个品种的还原糖、ADPG焦磷酸化酶(AGPase)变化不一致。t检验表明,在块茎发育全过程中,品种间的干物质(P=0.011)、淀粉(P=0.031)、皂苷(P=0.019)差异显著。可溶性糖(r₅=0.97^**,r₁₆=1.00^**)、AGPase (r₅= –0.85^*)、还原糖(r₁₆=0.87^*)与蔗糖显著相关;多糖(r₅=0.95^**)、Vc(r₅=0.83^*)、皂苷(r₁₆=0.88^**)与淀粉显著相关;干物质(r₅=0.97^**,r₁₆=0.87^*)、AMY(r₁₆= –0.95^**)、AGPase (r₁₆=–0.90^**)、蛋白质(r₁₆=0.83^*)与块茎伸长膨大显著相关。由此表明,蔗糖积累、SPS和AI活性在山药块茎发育中起关键调控作用,主要功能性物质彼此间密切相关。     

油菜不同氮素籽粒生产效率品种氮素积累与分配特征

2007—2008年度以98个甘蓝型常规油菜品种(系)为材料, 在不施氮肥(N₀)和纯氮150 kg hm^–2 (N₁) 2个处理下, 通过测定成熟期不同器官干重、氮素含量, 采用组内最小平方和动态聚类方法对供试品种的氮素籽粒生产效率(NUEg)聚类并分析其氮素积累与分配差异。结果表明, 不同品种氮素籽粒生产效率差异较大, 类型间差异极显著。不同类型品种随着氮素籽粒生产效率增加, 产量增加。相关分析表明, 氮素籽粒生产效率与成熟期氮素吸收总量之间相关不显著(r_N0= –0.0245, r_N1= –0.1131), 与成熟期茎秆氮素分配比例(r_N0= –0.5941^**, r_N1= –0.4141^**)和果壳氮素分配比例(r_N0= –0.6007^**, r_N1= –0.5374^**)呈极显著负相关, 与籽粒氮素分配比例(r_N0= 0.7954^**, r_N1= 0.7239^**)呈极显著正相关;与成熟期总籽粒数呈极显著正相关(r_N0= 0.5945^**, r_N1= 0.5412^**)。氮素籽粒生产效率和氮素吸收总量对产量都有显著影响, 油菜品种的选育应在一定氮素吸收总量基础上, 促进后期氮素从营养器官向籽粒中输送, 提高氮素籽粒生产效率, 从而达到高产和高氮素利用效率的统一。     

长江流域油菜氮磷钾肥料利用率现状研究

总结近年来在长江流域冬油菜主产区进行的74个田间试验结果,分析目前条件下油菜氮磷钾肥的偏生产力、农学效率、肥料表观利用率、生理效率及肥料对油菜产量的贡献率。结果表明,油菜农学效率分别为6.2 kg kg^–1 N、6.3 kg kg^–1 P₂O₅和2.6 kg kg^–1 K₂O;表观利用率为N 34.0%、P₂O₅ 17.4%和K₂O 36.9%,生理利用率为18.5 kg kg^–1 N、35.5 kg kg^–1 P₂O₅和9.1 kg kg^–1 K₂O,氮磷钾肥对油菜籽产量的贡献率分别为41.9%、21.4%和11.5%。研究结果显示,试验条件下长江流域油菜的肥料利用率较低,生产上需同时解决油菜高产及肥料利用效率提高的问题。     

甜菜-甜菜坏死黄脉病毒互作过程中过氧化氢的积累与分布

以甜菜抗、感丛根病品种与甜菜坏死黄脉病毒互作体系为研究对象,检测不同体系间H₂O₂的产生和积累,并利用电镜细胞化学标记技术在亚细胞水平上对H₂O₂的空间分布定位,探讨H₂O₂积累和分布与甜菜抗丛根病性的关系。结果表明, 甜菜抗、感丛根病体系均出现大量H₂O₂,其中抗病体系的H₂O₂产生量明显高于感病体系。H₂O₂在抗病和感病体系中的分布位置基本相似,多分布在块根、叶脉细胞的液泡膜和质膜上,叶脉细胞间隙也有H₂O₂的分布,但不同体系间H₂O₂含量有着明显差异,感病体系H₂O₂沉积量明显弱于抗病体系。研究结果说明,H₂O₂产生量和分布与甜菜抗丛根病性有密切联系,H₂O₂参与了甜菜对病毒侵染的防御反应。     

Inheritance of foliar zingiberene contents and their relationship to trichome densities and whitefly resistance in tomatoes

The sesquiterpene zingiberene, present in leaf glandular trichomes, is reportedly responsible for the high level of arthropod resistance found in Lycopersicon hirsutum var. hirsutum. This paper reports on the inheritance of zingiberene contents and of the various types of glandular trichomes in the interspecific cross L. esculentum × Lycopersicon hirsutum var. hirsutum. Plants of L. esculentum ‘TOM-556’ (= P₁), L. hirsutum var. hirsutum ‘PI-127826’(= P₂), F₁ (P₁ × P₂) and F₂ (P₁ ×P₂) were evaluated for zingiberene contents and densitities of and glandular (types I, IV, VI and VII) trichomes. Broad sense heritabilities were high for all traits studied (0.678, 0.831, 0.996, 0.799 and 0.717 respectively for zingiberene and trichome types I, IV, VI, VII). There were significant positive genetic correlations between zingiberene contents and densities of trichomes types IV, VI and VII. Inheritance of zingiberenecontents can be explained mostly by the action of a single major locus, inwhich the allele from L. hirsutum that conditions high content is incompletely recessive over the allele from L. esculentum. Action of an incompleteley recessive allele in one major locus appears to be evident for densities of trichome types IV, VI and VII, but there is also evidence of the action of other epistatic loci for types IV and VI. F₂ genotypes selected for high zingiberene levels showed higher levels of resistance to the silverleaf whitefly Bemisia argentifolii than L. esculentum ‘TOM-556’, levels that were comparable those found in L. hirsutum var. hirsutum ‘PI-127826’ and other whitefly resistant accessions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Identification of QTLs for BYDV tolerance in bread wheat

We searched for QTLs involved in tolerance to barley yellow dwarf (BYD), a serious viral disease of small grain cereals in two wheat populations, Opata × Synthetic (ITMI)and Frontana × INIA66 (F × I), for which marker data had previously been generated. The populations were evaluated in replicated field trials under artificial inoculation with a BYDV-PAV-Mex isolate and under disease-free conditions. Disease symptoms (yellowing, dwarfism and biomass reduction) were visually recorded and agronomic traits (number of tillers,height, biomass, yield and thousand-kernel weight) were measured on five plants per plot. Phenotypic data on all evaluated traits showed normal distribution with high correlation between visual estimates and measured values. Heritabilities were mostly moderate to high in the 114 lines of the ITMI population, and from low to moderate in the 117 lines of the F × I population. QTL analyses were based on genetic maps containing 443 loci for the ITMI population and 317 loci for the F × I population. Using composite interval mapping, 22 QTLs in the ITMI population and seven in the F × I population were detected, explaining9.8–43.3% of total phenotypic variation (σ² _P)per agronomic trait in the first population, and 4.1–13.7% in the second. Individual QTLs explained less than 15.8%of σ² _P. In the F × I population a minor QTL explaining 7% of σ² _P for yellowing was detected on the short arm of 7D, linked to leaf tip necrosis, a morphological marker for linked genes Bdv1, Yr18 andLr34. A QTL consistently detected for several traits on 2D in the ITMI population and on the short arm of group 6 chromosome(6S) in F × I explained 10–15% of σ² _P. The large number of QTLs having mostly small effects and the continuous distribution of all evaluated traits confirmed the polygenic nature and complexity of BYD tolerance in wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Interspecific cross of Brassica oleracea var. alboglabra and B. napus : effects of growth condition and silique age on the efficiency of hybrid production, and inheritance of erucic acid in the self-pollinated backcross generation

Interspecific hybrids were produced from reciprocal crosses between Brassica napus (2n = 38, AACC) and B. oleracea var. alboglabra (2n = 18, CC) to introgress the zero-erucic acid alleles from B. napus into B. oleracea. The ovule culture embryo rescue technique was applied for production of F₁ plants. The effects of silique age, as measured by days after pollination (DAP), and growth condition (temperature) on the efficiency of this technique was investigated. The greatest numbers of hybrids per pollination were produced under 20°/15°C (day/night) at 16 DAP for B. oleracea (♀) × B. napus crosses, while under 15°/10°C at 14 DAP for B. napus (♀) × B. oleracea crosses. Application of the ovule culture technique also increased the efficiency of BC₁ (F₁ × B. oleracea) hybrid production by 10-fold over in vivo seed set. The segregation of erucic acid alleles in the self-pollinated backcross generation, i.e. in BC₁S₁ seeds, revealed that the gametes of the F₁ and BC₁ plants carrying a greater number of A-genome chromosomes were more viable. This resulted in a significantly greater number of intermediate and a smaller number of high-erucic acid BC₁S₁ seeds.     

Heritabilities and Minimum Gene Number Estimates of Carrot Carotenoids

Summary Broad sense heritabilities and gene numbers were estimated for the production of total carotenoids and the major component carotenoids of carrot storage roots: phytoene, ζ-carotene, β-carotene, α-carotene, and lycopene. Two crosses with different backgrounds were evaluated: orange B493 × white QAL and orange Brasilia × dark orange HCM. The HCM (high carotene mass selection), Brasilia and B493 parents had both α-carotene and β-carotene, but HCM had proportionally more α-carotene. Carotene content in F ₂ populations ranged from 522 ppm to 1714 ppm in Brasilia × HCM and from 0 to 695 ppm in B493 × QAL progeny. F ₂ plants segregating for absence of α-carotene were identified in B493 × QAL. Broad-sense heritabilities ranged from 28% to 48% for all carotenes except lycopene and phytoene where estimates were 44% to 89% in the Brasilia × HCM cross, All heritability values exceeded 88% for the B493 × QAL cross, except one estimate for lycopene. The estimated number of genes was 4 conditioning α-carotene, 2 to 3 each for β-carotene and total carotenes and one each for ζ-carotene, lycopene and phytoene in the orange × dark orange cross. In the orange × white cross, the estimates were 4 genes for α-carotene, 1 to 2 each for lycopene and total carotenes and 1 for each of the other carotenes. These results are in general agreement with QTL studies and they provided evidence for continuous inheritance of α-carotene, β-carotene and total carotenoids in the orange × dark orange cross and discrete inheritance for β-carotene and total carotenoids in the orange × white cross.Part of thesis “Biometrical studies and quantitative trait loci associated with major products of the carotenoids pathway of carrot (Daucus carota L.)” presented by the first author as partial fulfillment of the requirement of the PhD degree in Plant Breeding and Plant Genetics, UW-Madison, USA, 2001.     

尿素及秸秆添加对华中地区茶园土壤CO_2和N_2O排放的影响

为了明确尿素和秸秆添加对茶园土壤CO_2和N2O排放的影响,为茶园合理施肥提供理论依据,本研究在室内培养条件下,以华中地区红壤丘陵区茶园土壤为对象,运用静态培养系统研究方法,研究该土壤在尿素输入和作物秸秆添加后CO_2和N_2O的排放特征。培养试验共设置对照、尿素、作物秸秆和尿素+作物秸秆4种处理。结果表明:不同处理下华中地区茶园土壤CO_2和N_2O排放呈显著差异。作物秸秆添加显著提高茶园土壤CO_2的排放,作物秸秆和作物秸秆+尿素处理分别是对照的5.57和4.99倍。尿素输入显著促进茶园土壤N_2O的排放,而秸秆添加却降低N_2O的排放。对照和添加尿素处理土壤N_2O排放通量与铵态氮含量呈显著正相关关系。无秸秆添加处理土壤N_2O排放通量与硝态氮含量呈显著的相关性,而添加秸秆处理二者无显著相关关系。土壤可溶性有机碳含量对CO_2排放有显著影响,二者之间呈极显著线性正相关关系。     

Heritability estimates of spot blotch resistance and its association with other traits in spring wheat crosses

Summary Spot blotch caused by Cochliobolus sativusis considered a major disease problem of wheat(Triticum aestivumL.) in the warm areas of South Asia. This study estimated heritability (h ²) of resistance to spot blotch and its correlation with days to heading DH) and maturity (DM), one-hundred-kernel weight (HKW), and plant height (PHT) in 14 crosses involving four resistant (‘Attila’, ‘Chirya 7’, ‘G 162’, and ‘SW89.5422’) and two susceptible (‘Sonalika’ and ‘HD2329’) wheat genotypes. Data were recorded on F₅and F₆lines in fields under natural epidemics of spot blotch in 2003 and 2004, respectively. Heritability was estimated for area under disease progress curve (AUDPC), AUDPC/day, and the highest disease score (HDS) using offspring-parent regression (h _op ²) and realized heritability (h ² _R) procedures. Heritability estimates were low to high in terms of AUDPC (0.21 < h _op ²< 0.64; 0.32 < h _R ²< 0.70), AUDPC/day (0.40 < h _op ²< 0.96; 0.42 < h _R ²< 0.99), and HDS (0.29 < h _op ²< 0.92; 0.32 < h _R ²< 0.95). The h ²estimates for AUDPC/day were higher than for AUDPC and HDS. Estimates of h _R ²were by and large higher than h _op ²in the same cross. A weak negative or nonsignificant correlation of spot blotch score with HKW, DH, DM, and PHT indicated that independent selection for resistance and these agronomic traits is possible.     

Improving ovary and embryo culture techniques for efficient resynthesis of <Emphasis Type="Italic">Brassica napus</Emphasis> from reciprocal crosses between yellow-seeded diploids <Emphasis Type="Italic">B. rapa</Emphasis> and <Emphasis Type="Italic">B. oleracea</Emphasis>

The primary aim of this study was to optimize in vitro culture protocols to establish an efficient reproducible culture system for different Brassica interspecific crosses, and to synthesize yellow-seeded Brassica napus (AACC) for breeding and genetical studies. Reciprocal crosses were carried out between three B. rapa L. ssp. oleifera varieties (AA) and five accessions of B. oleracea var. acephala (CC). All the parental lines were yellow-seeded except one accession of B. oleracea. Hybrids were obtained through either ovary culture from crosses B. rapa × B. oleracea, or embryo culture from crosses B. oleracea × B. rapa. A higher rate of hybrid production was recorded when ovaries were cultured at 4–7 days after pollination (DAP). Of different culture media, medium E (MS with half strength macronutrients) showed good response for ovaries from all the crosses, the highest rate of hybrid production reaching 45% in B. rapa (1151) × B. oleracea (T₂). In embryo culture, the hybrid rate was significantly enhanced at 16–18 DAP, up to 48.1% in B. oleracea (T₃) × B. rapa (JB₂). The combinations of optimal DAP for excision and media components increased recovery of hybrids for ovary and embryo culture, and constituted an improved technique for B. rapa × B. oleracea crosses. In addition, yellow seeds were obtained from progenies of two crosses, indicating the feasibility of developing yellow-seeded B. napus through the hybridization between yellow-seeded diploids B. rapa and B. oleracea var. acephala.     

Establishment of a long-term storage method for soft X-ray irradiated pollen in watermelon

A new method for preserving viable soft X-ray irradiated pollen for the production of seedless watermelons (Citrullus lanatus L.) from diploid plants was established by storing the pollen under N₂ at −25°C for 1 year. Pollen stored at 4°C had the ability to germinate until 28 days under all atmospheres tested except O₂. However, after storage at this temperature for 3 months it did not germinate in any treatment conditions. Pollen stored at −25°C for 1 year under N₂, CO₂ or under a vacuum had a germination rate of about 50%. Pollen stored in O₂ or in air had a much lower germination rate, less than 20% and 10%, respectively. Thus, it is important to store watermelon pollen at a low temperature when it is being stored for a long time. Nitrogen and CO₂ were effective in extending the life of watermelon pollen. On the other hand, it has been demonstrated that the viability of pollen was reduced by storage under O₂. The N₂ and CO₂ are thought to be effective because they are essentially inert to the living pollen. Also, a lot of pollen tubes were observed in a middle portion of an ovary pollinated with pollen stored at −25°C under N₂; however, pollen tubes were not observed in ovaries pollinated with pollen stored under a vacuum. It was revealed in 1 year storage experiments that viability of pollen stored under N₂ was higher than that stored under a vacuum. Seedless fruits produced with pollen stored at −25°C under N₂ had the same characteristics as the control fruit. Authors did this research in ‘Research and Development Program for New Bio-Industry Initiatives’.     

Heterosis and heritability in crosses among Asian and Ethiopian parents of hot pepper genotypes

Hot pepper is the most important worldwide grown and consumed spice and vegetable crop. Though hybrid breeding has been proposed for genetic improvement in the crop, but there is lack of information on heterosis in crosses among crop genotypes in Ethiopia. Twelve genotypes (nine Asian and three Ethiopian parents) of hot pepper were crossed in 2003 cropping season in a half-diallel fashion to fit Griffing’s fixed effect model analysis. An open field experiment was conducted in 2004/2005 to investigate heterosis for fourteen traits in 66 F₁ hybrids grown together with their 12 selfed parents. Highly significant genotypic differences were observed for all the traits except for leaf area. Variance component due to specific combining ability (dominance) were larger than that due to general combining ability (additive) for each of the studied traits with few exceptions. Broad sense heritability (H _b²) for fruit traits were more than 60% and with wide gap from narrow sense heritability (h _n²) for most of the important traits like number of fruit per plant (H _b² = 88.3% and h _n² = 46.0%), days to maturity (H _b² = 87.2% and h _n² = 23.1%) and dry fruit yield per plant (H _b² = 72.6% and h _n² = 14.6%). Maximum heterosis over mid-parent and better-parent, and economic superiority of hybrid over standard check were recorded, respectively for dry fruit yield per plant (163.8, 161.8 and 92.1%), number of fruits per plant (104.4, 79.6 and 136.4%) and days to maturity (−29.8, −31.5 and −23.6%). These observations suggested a possibility of utilizing dominance genetic potentiality available in diverse genotypes of the crop by heterosis breeding for improving hot pepper to the extent of better economic return compared to the current commercial cultivar under production in the country. Low narrow sense versus very high broad sense heritability for days to maturity and dry fruit yield per plant could be a sign for achievability of earliness and high fruit yield using heterosis in hot pepper. The maximum heterobeltiosis were recorded either from F₁s obtained from Ethiopian and Asian crosses or from within Asian crosses, suggesting the possibility of maximizing heterosis by considering genetically diverse parental genotypes. The manifestation of highest heterosis in hybrids from among Asian lines indicated existence of genetic diversity among Asian genotypes and the potentiality for improvement of hot pepper using genotypes from different regions of the world along with elite inbred lines from local cultivars.