Root lodging in sunflower. Variations in anchorage strength across genotypes,soil types,crop population densities and crop developmental stages

Root lodging is an important adversity affecting sunflower (Helianthus annuus L.) production in Argentina under current husbandry practices, and may limit progress towards the achievement of higher yields via increased plant population density. Although there are perceptions that lodging susceptibility varies across developmental stages, crop population densities, genotypes and soil types, these perceptions have not been tested for sunflower using a standardized experimental protocol. This study aimed at: (1) identifying the sources of the variation in root lodging susceptibility in response to variations in crop population density in two genotypes of reputedly different susceptibility; (2) detecting the crop developmental stages most susceptible to root lodging; and (3) examining the relationships between root failure moment, root plate diameter and soil shear strength. We mechanically induced lodging at three developmental stages in plants rooted in pre-wetted plots. The crops were grown at 5.6 plants m⁻² over 3 years on either Typic Argiudoll or Typic Hapludoll soils and at 3, 5.6, 10 and 16 plants m⁻² on a Typic Argiudoll. The force needed to induce root lodging (root failure moment) and root plate diameter varied across genotypes, plant densities and developmental stages. Root failure moment and root plate diameters were greater (p < 0.05 for both variables) in the resistant hybrid across the three development stages and almost all crop population densities. For both hybrids, the most susceptible development stage was R2, and root failure moment and root plate diameter diminished (p < 0.05) as crop population density increased. Although root failure moment did not differ between soil types, root plate diameter was greater (p < 0.0001) in the coarser soil. The relationship between root failure moment and the product of root plate diameter cubed by soil shear strength (a measure of plant anchorage strength) for both hybrids, both soil types, and all crop population densities could be described by a single linear relationship (y = 0.2382x; R² = 0.812; p < 0.025).     

华北地区不同年代玉米杂交种农艺性状的改良进展

2005年在北京和新疆两个生态区采用随机区组设计,对产量、总穗数、穗粒数、千粒重、株高、穗位高、茎倒率、倒伏率、病株率9个农艺性状和不同年代的改良进展进行比较。结果表明:产量、穗粒数、千粒重、株高、穗位高、茎倒率、倒伏率、病株率等不同年代农艺性状差异达极显著水平;北京和新疆的产量改良进展结果相似。试验结果表明玉米杂交种的农艺性状改良发生了显著的变化,穗粒数、千粒重、倒伏率、空秆率及病株率的改良提高了玉米产量。     

不同小麦品种茎秆抗倒性的研究

为了明确影响小麦抗倒伏性的主要因素,选用生产中应用较广泛的6个高产小麦品种,采用田间试验与实验室分析相结合的方法,对不同品种的抗倒伏性状进行研究。结果表明,百农矮抗58的倒伏指数较小,为0.432,与其他品种相比差异显著;百农矮抗58的茎秆机械强度大、茎秆基部第二节短粗、秆壁较厚、次生根数量较多、株高和重心高度较低。相关分析表明,倒伏指数与第二节关系密切,第二节机械强度越大、壁越厚、干重越大、地下部根量越多,倒伏指数就越小,茎秆抗倒性就越强;适当降低株高可以降低植株的重心高度,增强植株抗倒能力。逐步回归分析表明,影响茎秆抗倒性的直接因子为茎秆基部第二节机械强度、第二节干重、地下部根量及地上部鲜重,其中第二节机械强度对茎秆倒伏指数的直接作用最大,其直接通径系数为-0.775,可用第二节机械强度的大小评价品种茎秆抗倒性的强弱。     

种植密度对不同耐密夏玉米品种茎秆性状与抗倒伏能力的影响

以耐密性不同玉米品种为材料,调查吐丝期暴雨大风后玉米倒伏情况,分析增密过程中不同夏玉米群体植株形态与茎秆力学变化规律。结果表明,随密度增加,大风后根倒率和茎折率显著增加,登海618的根倒率和茎折率显著低于浚单20。随着密度增加,玉米株高和穗位高增加,基部3~7节间均表现为节间伸长、变细,茎粗系数、穿刺强度、抗折力、压碎强度显著降低,两个品种表现一致。相关分析表明,根倒率和茎折率与节间长度、株高、穗位高和穗位系数正相关,与茎粗、茎粗系数和茎秆力学负相关。站秆率与倒伏率均与基部第3节间性状的相关性达显著水平。与浚单20相比,登海618具有较低的节间长度、株高、穗位高、穗位系数和较高的茎粗、茎粗系数和茎秆力学,抗倒性能较强。     

甘蓝型油菜抗倒性评价及抗倒性与株型结构的关系

以一批抗倒伏和易倒伏的甘蓝型油菜进行田间试验，研究甘蓝型油菜抗倒性评价指标及抗倒性与株型结构关系。结果表明，成熟期田间测定抗拉力可反映出品种的抗根倒能力，成熟期根重及根颈粗与品种的抗根倒能力也有密切关系。成熟期室内测定的茎秆抗折力矩可反映出品种抗茎倒能力，茎重，尤其是茎干重/茎秆长也能反映品种茎秆的抗倒能力。株高、茎秆重心高度/株高等形态指标与品种抗倒性有密切关系。株高、分枝点高/株高适中、重心高度/株高较小、分枝数适中、角果分布均匀、株型为紧凑型的品种较抗倒伏，单株生产力也较高，是理想的抗倒株型。     

Canopy stay-green and yield in non-stressed sunflower

Delayed leaf senescence during the grain filling phase, or stay green (SG), may be functional or cosmetic; the first being considered a valuable trait in breeding of many crop species. To establish whether canopy senescence patterns exhibited by two sunflower (Helianthus annuus L.) hybrids visually selected for slow post-anthesis canopy leaf area index (LAI) loss reflected functional, rather than cosmetic, SG, LAI dynamics and total biomass increase between anthesis and physiological maturity were followed in three separate experiments in which the putative SG hybrids were compared with standard (i.e., non stay green, NSG) hybrids exhibiting normal rates of canopy senescence under non- or minimal-water stress conditions. In two experiments, pairwise (i.e., one SG vs. one NSG) comparisons were made at two crop population densities. In the third experiment, grown at a single crop population density, four NSG hybrids were contrasted with the two SG hybrids. Canopy senescence dynamics were well described by fitted bilinear functions which discriminated between an initial, slow phase of leaf area loss and a second phase of rapid canopy senescence. No differences between hybrids in the rate of senescence during the first phase were found, but the putative SG hybrids exhibited a significantly slower rate of senescence during the second phase and a significantly higher LAI at physiological maturity (as % of LAI at anthesis). One NSG hybrid showed a greater rate of second-phase senescence than the remaining three hybrids in this category. Across experiments, the anthesis-physiological maturity increment in total oil-corrected biomass and radiation use efficiency (RUE) were significantly greater in the SG hybrids. Cluster analysis based on these four attributes, using data from Exp. 3, clearly discriminated between SG and NSG hybrids. Examination of specific leaf N (SLN) dynamics suggests that the lower RUE values observed in one of the NSG hybrids could be attributable to lower SLN values, but this was not the case for the remaining NSG hybrids. It is also possible that very rapid canopy LAI loss in another NSG hybrid may underlie its lower RUE. The failure of SG hybrids to translate greater post-anthesis biomass increment into grain yield across experiments was associated with their slightly shorter times to anthesis and their significantly lower biomass at anthesis. Grain number, the component of yield most strongly associated with yield, was associated with biomass at anthesis. A further contributing factor was that the duration of grain-filling tended to be shorter in SG hybrids. In the one experiment in which this variable was measured, resistance to stalk breakage was greater in the SG hybrids than the NSG one to which they were compared. We conclude that the SG observed in the hybrids with slower canopy senescence is functional and not cosmetic, and that for this to be translated into a yield advantage all hybrids need to reach anthesis at the same time and grain-filling duration also has to be the same across hybrids. Stay green is an interesting secondary trait to select for and should lead to higher and more stable yields in environments in which stem breakage (lodging) is a problem.     

Lodging yield penalties as affected by breeding in Mediterranean wheats

Stem lodging, a permanent displacement of cereal stems which may reduce wheat yields significantly, affects wheat crops in both developed and developing countries, mainly under high-yielding conditions. Although breeding has decreased these losses by reducing the likelihood of the plant lodging through reduced height (mainly by the introgression of dwarfing genes), lodging continues to affect wheat yields. We aimed to quantify how wheat breeding has modified the sensitivity of yield to lodging, identifying physiological causes for yield reductions. Two field experiments were carried out in Mediterranean Spain during the 2006/07 and 2007/08 growing seasons. The first season two genotypes (Aragon 03 and ID-2151) and two lodging treatments (control and lodged near anthesis) were analysed. The second season four genotypes (Aragon 03, Estrella, Anza and ID-2151) and three lodging treatments (control, lodged from either jointing to maturity or anthesis to maturity) were imposed. In addition, in the 2007/08 experiment the source-sink ratios of five representative spikes of each plot were modified through hand trimming all spikelets from one side of each spike soon after anthesis. Yield losses due to early lodging were reduced by wheat breeding: yield penalties in the oldest and newest genotypes were 61% and 43% (mean values of both lodging treatments), respectively while it was 57% in intermediate cultivars (mean value of both lodging treatments and cultivars). Lodging decreased both the number of grains per m² and the average grain weight (AGW). The decrease of the number of grains per m² was associated with reductions in the crop growth, while the AGW loss seemed related to both a reduction of the availability of assimilates to fill grains and a direct effect on grain size potential. Lodged plants exhibited stronger source-limitation during grain filling than those un-lodged, while the response of the grain weight to sink-strength reductions in lodged plants was very similar to that in the un-trimmed controls, indicating that grain filling in un-lodged and in strongly lodged canopies was similarly balanced in terms of source-sink ratios.     

氮肥管理对稻虾共作模式水稻产量和抗倒伏特性的影响

通过设置不同稻作模式（水稻单作、稻虾共作）和氮肥管理（不施氮、常规施氮、减氮）两因素交互试验,研究氮肥管理对稻虾共作模式水稻产量及抗倒伏特性的影响。结果表明,稻虾共作模式下常规施氮和减氮处理的水稻产量分别为7 539 kg/hm²和7 328 kg/hm²,比水稻单作模式降低29.4%~32.3%,这主要是由于试验当年水稻移栽后连续降雨导致缓苗不利所致,也与深水淹灌下水稻有效穂数、每穗粒数和千粒重下降有关。相比水稻单作,稻虾共作模式下水稻茎秆的株高、穂颈高、重心高、弯曲力矩和倒伏指数平均增加12.9%、17.9%、8.0%、20.9%和33.5%,第2节间茎壁厚、抗折力和折断弯矩平均降低38.7%、16.8%和16.6%。在稻虾共作模式中,与常规施氮处理相比,减氮处理仅减产2.9%,水稻茎秆抗折力增加13.5%、倒伏指数降低1.8%。相关分析表明,茎壁厚度与倒伏指数呈极显著负相关（p<0.01）,株高和弯曲力矩与抗折力呈显著负相关（p<0.05）。稻虾共作模式可保证水稻稳产,氮肥减施有助于提高该模式下水稻抗倒伏能力,降低倒伏风险。     

不同机直播方式对南方优质晚籼稻产量及抗倒伏特性的影响

【目的】研究不同机直播方式对南方优质晚籼稻茎秆抗倒伏能力及产量的影响，为南方优质晚籼稻高产抗倒栽培提供参考。【方法】以籼型常规稻品种黄华占和籼型杂交稻品种泰优398为材料，设置旱直播、湿直播和淹水直播3个处理，分别测定优质晚籼稻的产量及产量构成、出苗率、干物质生产、叶面积指数和茎秆形态与力学特性。【结果】与湿直播方式或淹水直播方式相比，旱直播方式可显著提高供试晚稻品种的出苗率，增幅为6.10% ~ 22.96%，且干物质生产和叶面积指数均增加。同时，旱直播方式有利于提高供试晚稻品种产量，两品种增产幅度为6.99%~27.77%，其中泰优398产量增幅高于黄华占，从产量构成因素来看，机械旱直播方式下供试晚稻品种产量的提高主要得益于有效穗数增加。此外，旱直播方式下供试水稻株高相对较矮，基部各节间较短粗、壁厚和秆型指数与抗折力显著正相关，而与倒伏指数显著负相关；株高、穗长、弯曲力矩与抗折力显著负相关，与倒伏指数显著正相关。【结论】采用机械旱直播方式不仅有利于增加南方优质晚籼稻产量，还能显著增加茎秆强度，提高植株抗倒伏能力，降低直播生产的风险。，但茎秆粗壮，茎壁较厚，有利于提高植株茎秆抗折力和秆型指数，降低弯曲力矩与倒伏指数。相关分析表明，茎     

密度和施氮量对强筋小麦藁优2018产量和抗倒性的影响

为明确减量播种和减施氮肥对强筋小麦品种藁优2018茎秆质量和抗倒性的影响,采用双因素裂区试验,研究了种植密度(D210,210万株·hm-2;D330,330万株·hm-2;D450,450万株·hm-2)和施氮量(N0,0kg·hm-2;N120,120kg·hm-2;N240,240kg·hm-2)对小麦倒伏高发期茎秆形态的影响,以及抗倒伏指数与茎秆形态指标的相关性。结果表明,在籽粒形成期和蜡熟期,密度由D210增加至D330,小麦茎秆重心高度显著增加,基部节间充实度、秆壁厚度、茎秆机械强度和抗倒伏指数降低;茎秆重心高度以N0最小,N240最高;基部节间秆壁厚度在3个施氮量处理间差异不显著;茎秆充实度、茎秆机械强度和抗倒伏指数随施氮量增加呈降低趋势,但在乳熟期和蜡熟期N120和N240差异不显著。相关分析表明,基部第1节间抗倒伏指数与节间粗度、充实度和第1节间秆壁厚度呈极显著正相关,与第2节间秆壁厚度相关性不显著。逐步回归分析表明,种植密度对小麦抗倒性的影响大于施氮水平。籽粒产量在不同密度处理间差异性不显著,但在不同施氮量间表现为N120和N240处理显著高于N0处理。因此,210万株·hm-2至330万株·hm-2的种植密度和120kg·hm-2的氮素水平在获得较高产量的同时具有较强的抗倒伏能力,是本试验条件下小麦抗倒高产的最优组合。     

Effect of planting density on lodging-related morphology,lodging rate,and yield of tartary buckwheat (Fagopyrum tataricum)

Increase of planting density has been widely used to increase grain yield in crops. However, it may lead to higher risk of lodging hence causing significant yield loss of the crop. To investigate the effects of planting density on lodging-related morphology, lodging rate (LR), and yield of tartary buckwheat, an experiment was carried out with a split-plot randomized block design at the experimental farm of Chengdu University (Sichuan, China) in the 2012 and 2013 growing seasons. Results showed that plant density significantly affected characteristics of stem and root. In each season, with the increasing of planting density, light transmittance, main root length, number of first lateral root, root volume, internode number, and first internode diameter decreased, the plant height, first internode length, abortion rate and LR increased. Increasing density caused decreased grains number per plant, the dry matter weight and yield displayed an acceleration first and then deceleration. The correlation analysis indicated that the internode number, first internode diameter, number of first lateral roots, and root volume were significantly negatively correlated with LR, but positively correlated with stem breaking strength and lodging resistance index. The LR was significantly positively correlated with plant height and first internode length. In both years, the D2 (9 × 10⁵ plant ha^?1) and D3 (12 × 10⁵ plant ha^?1) yielded more grains than in other treatments, and the effects of density on two cultivars showed the same trend. The results suggested that planting density could alter lodging-related traits, lodging resistance, and yield of tartary buckwheat.     

新疆春小麦品种资源抗倒性评价

为了给新疆小麦抗倒育种提供参考依据,采用田间试验与实验室分析相结合的方法,比较了两种种植密度(100×104和600×104株·hm-2)下40份新疆自育春小麦品种资源的抗倒性,分析了抗倒性与其影响因素的关系。结果表明,与低密度(100×104株·hm-2)相比,高密度(基本苗为600×104株·hm-2)条件下小麦抗倒伏能力、第二节间机械强度、壁厚、茎粗、充实度及地上部鲜重极显著降低,第二节间长度及重心高度极显著增加,茎秆机械强度的降低是小麦抗倒伏能力下降的关键因素。低密度下抗倒性与第二节间长、株高、重心高及第二节间壁厚的关系密切。其中,第二节间长度与小麦抗倒性关系最密切,第二节间越短,抗倒伏能力越强。高密度下第二节间机械强度与抗倒性的关系最密切,茎秆强度越高,抗倒性越强。壁厚可作为评价茎秆机械强度的可靠指标。依据倒伏指数的大小,将40份品种分为高抗型、普抗型、中间型、风险型和易倒型5个级别。供试材料中,80.0%的品种抗倒性较好,其中新春22号为高抗型品种,是较为理想的抗倒伏育种亲本。     

甘蓝型油菜DH群体抗倒伏相关性状遗传分析

为明确油菜抗倒伏性的遗传规律，本文利用抗倒伏性差异显著的2个甘蓝型油菜品系配制杂交组合，构建含280个株系的DH群体，采用作物茎秆强度抗倒测量仪等考种工具对该群体进行连续两年的抗倒伏性鉴定，并利用植物数量性状的主基因 + 多基因混合遗传模型及偏度和峰度分析对抗倒伏性进行遗传分析。结果表明，茎秆抗折力和茎秆抗折强度都受到0对主基因 + 9对微效多基因控制，茎秆抗折力和单株生物量的基因间无互作，茎秆抗折强度的基因间有互补作用，茎秆抗折力和茎秆抗折强度两年的平均遗传率在50%左右，而茎秆直径两年的平均遗传率为69.338 %，单株生物量两年的遗传率分别为52.198%和69.284%，遗传率都较低，性状受环境影响都较大，因此对于茎秆抗折力、茎秆抗折强度、茎秆直径和单株生物量，在育种选择的早期阶段都不宜太严格。同时茎秆抗折强度相比茎秆抗折力更能说明作物的抗倒伏能力，因而在抗倒伏选择育种时应更加关注。     

不同机直播方式对南方优质晚籼稻产量及抗倒伏特性的影响

【目的】研究不同机直播方式对南方优质晚籼稻茎秆抗倒伏能力及产量的影响,为南方优质晚籼稻高产抗倒栽培提供参考。【方法】以籼型常规稻品种黄华占和籼型杂交稻品种泰优398为材料,设置旱直播、湿直播和淹水直播3个处理,分别测定优质晚籼稻的产量及产量构成、出苗率、干物质生产、叶面积指数和茎秆形态与力学特性。【结果】与湿直播方式或淹水直播方式相比,旱直播方式可显著提高供试晚稻品种的出苗率,增幅为6.10% ~ 22.96%,且干物质生产和叶面积指数均增加。同时,旱直播方式有利于提高供试晚稻品种产量,两品种增产幅度为6.99%~27.77%,其中泰优398产量增幅高于黄华占,从产量构成因素来看,机械旱直播方式下供试晚稻品种产量的提高主要得益于有效穗数增加。此外,旱直播方式下供试水稻株高相对较矮,基部各节间较短,但茎秆粗壮,茎壁较厚,有利于提高植株茎秆抗折力和秆型指数,降低弯曲力矩与倒伏指数。相关分析表明,茎粗、壁厚和秆型指数与抗折力显著正相关,而与倒伏指数显著负相关;株高、穗长、弯曲力矩与抗折力显著负相关,与倒伏指数显著正相关。【结论】采用机械旱直播方式不仅有利于增加南方优质晚籼稻产量,还能显著增加茎秆强度,提高植株抗倒伏能力,降低直播生产的风险。     

小麦倒伏的茎秆特征及对产量与品质的影响

选用6个株高不同的小麦品种，在自然倒伏条件下，研究籽粒形成期倒伏植株的茎秆性状、倒伏对产量和品质的影响。结果表明，矮秆、基部节间较短、重心高度较低、穗下节间较长且株高构成指数大的植株有利于抗倒伏。小麦在籽粒形成期倒伏对产量、品质均有较大的影响，表现为产量下降，籽粒中蛋白质含量、湿面筋含量、沉降值有所上升，但蛋白质产量下降，支链淀粉、直链淀粉和总淀粉含量亦下降。     

玉米抗倒伏性评价方法的研究

选定抗倒性不同的10个玉米品种,对现有玉米抗倒伏研究方法进行比较研究,探索玉米抗倒伏综合评价方法。相关分析结果表明,倒伏系数是株高、单茎鲜重、茎秆机械强度和根量的综合体现,倒伏系数与倒伏程度的相关性达到极显著水平。通径分析表明,茎秆机械强度和根量对玉米倒伏系数有较大负作用,单茎鲜重和株高对倒伏系数的直接和间接的效应都较小。聚类分析将10个品种划分为5个倒伏级别。以倒伏系数为评价标准,能客观准确地反映10个玉米品种的抗倒性,抗倒性强的品种倒伏系数较小,依据倒伏系数可以建立玉米抗倒等级划分标准。     

Effect of crop management on epidemics of phomopsis stem canker (Diaporthe helianthi) for susceptible and tolerant sunflower cultivars

Phomopsis stem canker (Diaporthe helianthi) is a worldwide fungal disease which is responsible for high yield losses in sunflower crop in the main regions of production. Field data on the influence of crop management on the incidence and severity of stem canker were reported by Debaeke et al. (2003) but a more thorough study was required to analyse step-by-step the spread of the fungus within the canopy from spore deposition on leaves to stem injury.In a 2-year study (2000–2001), the effects of crop management (plant density, N fertilization, and irrigation) and genotypic tolerance (susceptible vs tolerant cultivars) on the epidemics of Diaporthe helianthi were monitored under conditions of reinforced inoculum. The incidence and severity of leaf and stem symptoms were closely related to canopy development (leaf area index) and microclimatic conditions (relative humidity) resulting from different crop management options. Increasing plant density resulted in a greater proportion of girdling stem lesions, detrimental to yield, because of earlier infection under dense canopies. The number of girdling lesions per plant was maximal with high N fertilization but more leaves were infected without N fertilization.The field data were used to evaluate satisfactorily the epidemiological Asphodel model regarding the main periods of leaf infection. The relative humidity within the canopy (observed), the number of leaf infection events (simulated by Asphodel) and the final proportion of stem lesions (observed) were positively related which clearly demonstrated the key role of crop management in the development of stem canker in sunflower.     

大豆种质的倒伏性调查及其相关农艺性状分析

倒伏是大豆高产的主要限制因子之一.以60份大豆地方品种和育成品种为材料,调查和分析了大豆倒伏性及其与茎秆性状和产量性状魄关系.结果表明,不同品种间倒伏性存在显著差异,倒伏的严重程度与茎秆性状有关.大豆品种的倒伏级别与株高、主茎节数、节间长、分枝数等性状的相关系数均达1%显著水平,茎秆性状与单株籽粒产量、单株荚数和单株粒数等呈极显著正相关,但与百粒重呈负相关.不同倒伏级别组之间产量性状表现显著差异,2级倒伏组是具有轻度倒伏和高产潜力的种质资源.     

Lodging-related morphological traits of hybrid rice in a tropical irrigated ecosystem

Hybrid rice (Oryza sativa L.) has been proven to be effective in increasing yield potential, but lodging often limits its yield in high-yielding environments. This study was conducted to determine genotypic variation in lodging resistance and lodging-related morphological traits among hybrid and non-hybrid check varieties, and to identify the key morphological traits associated with lodging resistance. Lodging behavior of 16 rice genotypes, including 12 hybrids and four inbreds, was studied at the International Rice Research Institute farm during the 2004 wet season (WS) and 2005 dry season (DS). Grain yield and visual score of lodging were determined at maturity. Lodging-related morphological traits were measured at 30 days after flowering. Large genotypic differences in lodging-related morphological traits were observed. Among these traits, dry weight per unit length, breaking resistance, and lodging index (bending moment/breaking resistance × 100) of lower internodes were significantly correlated with visual score of lodging. Several hybrids demonstrated high lodging resistance although their average plant height was over 120 cm. The lodging-related morphological traits and visual score of lodging in these hybrids were comparable with those of the non-hybrid check varieties with strong lodging resistance. These results suggest that increases in dry weight per unit length and breaking resistance of lower internodes are primary targets for reducing lodging index, thus improving overall lodging resistance of hybrid rice in a breeding program.     

大豆倒伏对植株性状和产量的影响

本文探讨了大豆倒伏对植株性状和产量的影响。指出了大豆倒伏临界冠/根比和倒伏临界期植株的干物质分配状况。经对倒伏和未倒伏植株的比较研究,结果表明,倒伏可以使株高明显增高,分枝减少,并使干物质分配在营养器官中的比例明显高于繁殖器官,最终导致荚重、粒重、百粒重、经济系数显著降低,产量约减少56％。