High Phytomass Producing Oats for Cultivation in Northern Growing Conditions

It has been argued that the breeding of cultivars with higher weight per panicle but constant phytomass (i.e., improved harvest index) is unlikely to improve grain yield of cereals in the future. To examine this question in oats, this study observed relationships between above-ground phytomass production and grain yield as well as 18 morphological and physiological traits representing maturity class and architecture of oat stand. The study was conducted in two dissimilar growing seasons. Material consisted of 29 Finnish and Scandinavian oat cultivars and breeding lines. Correlations between phytomass and other traits were evaluated by linear regression analysis. The study revealed that there has already been a trend toward improving the above-ground phytomass production in cereal breeding in Finland. The phytomass elevation can be attributed to both higher panicle weight as well as increased above-ground vegetative phytomass. Thus, improved grain yield of oats is not merely a consequence of increased harvest index, as is often mentioned, but is also a result of higher phytomass as such. The weight of the above-ground phytomass did not correlate with undesirable traits such as plant height or susceptibility to lodging, but it did have a positive relationship with days to yellow ripening. The applicability of phytomass weight in indirect yield breeding of oats in the northern growing conditions is discussed.     

陕西省不同年代玉米品种产量和氮效率性状的变化

明确陕西省不同年代玉米产量和氮效率性状响应氮肥的变化趋势,对西北旱区玉米高产氮高效品种选育具有重要的实践意义。本文以1981—2010年间陕西省12个玉米主栽品种为材料,于2011年和2012年在典型旱区陕西长武进行3个氮水平(0、120和240 kg hm–2)的田间试验,分析了不同年代玉米品种农艺和氮效率性状变化趋势。结果显示,不同年代玉米品种籽粒产量随氮水平增加而提高,在施氮0、120和240 kg hm–2处理下籽粒产量增益分别为每年46、65和83 kg hm–2。所有氮水平下2000—2010年间品种产量和生物量显著高于1980—1989年间品种,而秸秆产量变化不明显;现代玉米品种(2000—2010年)产量的增加归因于穗粒数、千粒重和生物量的提高。不同年代玉米品种消光系数随氮水平增加而降低,说明现代玉米品种(2000—2010年)较老品种(1980—1989年)叶片直立,截获更多的光能,致使产量和生物量高。随着年代的递进,玉米品种氮肥农学利用率呈递增趋势,在低氮水平下现代品种氮肥利用效率最高,且显著高于老品种。氮肥农学利用率与氮吸收效率(NUpE)和花后氮素积累量呈显著相关(r=0.75;r=0.72),而与氮生理效率(NUtE)和花前氮素积累量相关性不显著(r=0.42;r=0.39)。说明现代玉米品种氮肥农学利用率提高主要来自氮肥吸收效率和花后氮素积累量的增加。上述结果表明,陕西玉米育种应注重穗粒数、千粒重、氮吸收效率性状和株型结构改良,低氮环境压力选择将有助于旱区玉米高产氮高效新品种培育。     

Progress since the 1930s in Breeding for Yield, its Components, and Quality Traits of Spring Wheat in Finland

The contribution of improvements in morphophysiological traits to increased gram yield in spring wheat (Triticum aestivum L.) and the achievements of breeding for high bread-making quality in Finland since the 1930s were assessed. Ten wheat cultivars released in Finland between 1939 and 1990 were evaluated in Held experiments at the Viikki Experimental Farm, University of Helsinki, Finland (60°13′N) in 1991 and 1992. Twenty-two traits representing maturity, plant architecture, plant stand structure and N accumulation, and nine quality traits, including protein concentration and protein quality, were assessed. A 20 % increase in grain yield arising from cultivar improvement was associated with a 7 % reduction in height, an 80 % improvement in lodging resistance, and a 15 % higher harvest index (HI). Ear weight was 30 % higher in the modern cultivars. The higher ear weight of the modern cultivars was a result of more grains per ear and a higher spikelet weight. No decrease in vegetative phytomass in modern cultivars was recorded in this study. Grain yield and total N accumulation increased simultaneously and a positive correlation between year of cultivar release and nitrogen index was established. Although use of high N fertilizer application rates resulted in significantly improved baking quality of the flour, no trend between baking quality and year of cultivar release was recorded. The relatively low HI recorded in this study suggests that further yield increases art-likely to be achieved by selecting for higher HI.     

Productive oat ideotype for northern growing conditions

Summary Yield formation of four Finnish and three Nordic oat varieties and 12 breeding lines developed at the Hankkija Plant Breeding Institute was studied during four different growing seasons (1986–1989). Seventeen characteristics were measured, including traits representing the date of maturity and architecture of the oat stand. The variation between genotypes in the examined traits was studied by means of two-way analysis of variance. The relationship between grain yield and morpho-physiological traits was studied by means of simple correlation analysis and stepwise regression analysis.The present study, carried out in highly dissimilar growing seasons, showed that ideotype breeding in the northern growing areas is likely to be successful only in moderate to optimal growing conditions. Based on the findings of this study, a productive oat ideotype for northern cultivation is composed of traits such as early maturation, high phytomass production with a high panicle weight resulting from a large number of grains. short straw length (high resistance to lodging), and reduced tillering. The importance of other factors influencing oat breeding in northern growing conditions is discussed.     

Leaf Area Duration of Oat at High Latitudes

Contribution of leaf area duration (LAD) to grain yield during the short growing season characteristic of northern latitudes may differ from the marked impact it has at lower latitudes. Three experiments (exps) were carried out at Viikki Experimental Farm, University of Helsinki, Finland (60° 13′N) to compare associations between main shoot and tiller LAD with grain yield, yield components and morpho-physiological traits characterizing plant stand structure. This was done using correlation analysis and principal component analysis (PCA) for data from trials conducted during 1993–1995. Exp I included three N fertilizer rates (80, 120, 160 kg N ha^?1), three seeding rates (250, 500, and 750 seeds m^?2), and tall, moderate, semi-dwarf, and dwarf oat lines. Exp II incorporated two N fertilizer rates (80 and 120 kg ha^?1), three seeding rates (400, 600, and 800 seeds m^?2), and naked and hulled oat lines, and exp III, foliar applications of plant growth regulators [control, chlormequat chloride (CCC), and ethephon], and dwarf, naked, and conventional oat lines. LAD for main shoots and tillers [calculated as ∫ LAI d T, where T is cumulated degree days from seedling emergence to yellow ripening (dd °C)] and 12 morpho-physiological traits were measured. Oat was not able to benefit from high main shoot LAD if drought occurred at grain-fill, but in the absence of severe drought or if it occurred at pre-anthesis, high LAD favoured yield formation. Tiller LAD had a negative impact, if any, on grain yield in cases of an inverse relationship between tiller LAD and yield components on main shoots was recorded. Use of low seeding rates resulted in improved ability of total LAD to contribute to dry-matter production, but was not associated with grain yield. Low seeding rates enhanced formation of high tiller LAD, which was not able to compensate for grain yield reduction caused by fewer main shoots. Foliar application of CCC and ethephon tended to increase the proportion of LAD production by tillers at the expense of grain yield, which can be attributed to lower post-anthesis precipitation. Oat types differed in main shoot and tiller LAD. Disadvantageous characteristics of naked oat, such as low single groat weight, were not associated with insufficient main shoot LAD. High tiller LAD in naked lines and the Minnesota-adapted dwarf line that was not associated with high tiller grain yield in naked lines, in particular, indicates that tiller growth was enhanced at the expense of grain yield production. Application of N fertilizer at various rates did not have any effect on LAD.     

Effects of root systems of tomato genotypes on growth and earliness,studied in grafting experiments at low temperature

Summary The contribution of the roots to growth and earliness of 29 genotypes of tomato cultivated under low energy conditions, was analysed in two grafting experiments.There were significant effects of the rootstocks on the vegetative growth, earliness and fruit production of the different scions, but not on plant length or number of leaves or trusses. There was hardly any interaction between rootstock and scion.The commercial rootstock KNVF and a commercial breeding line especially promoted vegetative growth of all scions, but the former delayed flowering of the scion by 6–7 days. The breeding line also stimulated early flowering. Most of the IVT breeding lines selected for growth and early production under low energy conditions scored very poorly as rootstock.Implications for breeding tomatoes with efficient root systems are discussed.     

Growth rate inheritance and associations with other traits in backcross populations of Avena sativa x A. sterilis

Summary Improved grain yields in lines of oats from matings of Avena sativa x A. sterilis were found to be due to increased plant growth rate. Growth rates of oats were quantitatively inherited, with the minimum number of effective factor pairs segregating in the interspecific matings ranging from 3 to 9. Heritability values for this trait averaged 0.4. Growth rate was highly and positively correlated with bundle weight, straw yield, grain yield, and unit straw weight, but it was uncorrelated with heading date and harvest index. Correlations with plant height were low. Thus, it should be possible for oat breeders to combine the high growth rates from A. sterilis with any combination of agronomic traits.Journal Paper No. J-8608 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011. Project 1752. Supported in part by a grant from the Graduate College.Hirosaki University, Hirosaki, Japan (formerly Visiting Scientist at Iowa State University).     

Increasing grain yield of oats by independent culling for harvest index and vegetative growth index or unit straw weight

Summary Most variation in grain yield of oats is due to variation in harvest index and vegetative growth index, but the latter traits are negatively associated. Therefore we used independent culling levels to select oat genotypes with high levels of vigor traits and a desirable level of harvest index in an attempts to maximize grain yield. Harvest index and vegetative growth index or harvest index and unit straw weight were selected at various culling levels. Intensive selection for harvest index resulted in high harvest index but no grain yield improvement, because the selected lines had poor vigor. Intensive selection for vegetative growth index or unit straw weight resulted in high biomass but low harvest index.The most effective combination of culling levels was to select 25% of the original population for harvest index and, subsequently, to select for vegetative growth index or unit straw weight at an 8% intensity in the remnant population.Journal Paper No. J-11272 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA 50011. Project 2447. This work was supported in part by the World Food Institute, Iowa State Univ., in the form of a Senior Fellowship for the senior author.     

公顷产10000kg小麦氮素和干物质积累与分配特性

以泰山23和济麦22为试验品种,通过连续2年的田间试验,对单产高达10 000 kg hm^-2的小麦进行了施氮量和氮素吸收转运和分配特性的研究。在2006-2007年生长季,随着施氮量的增加,小麦籽粒产量先增加后降低,施纯氮240 kg hm^-2 (N240)和270 kg hm^-2(N270)处理的产量分别达9 954.73 kg hm^-2和10 647.02 kg hm^-2,比不施氮肥处理(N0)分别增加11.20%和18.93%。与N0处理相比,施氮处理显著增加了小麦植株氮素积累量、籽粒氮素积累量和开花后营养器官氮素向籽粒的转运量;随着施氮量的增加,成熟期小麦植株氮素积累量呈先增后降趋势,以N270处理最高;开花后营养器官氮素向小麦籽粒转运量和转运率先升后降,转运量以N270处理最大,为213.78 kg hm^-2;而转运率以N240处理最高,为67.98%。随施氮量的增加,小麦成熟期各器官干物质积累量、花后营养器官干物质再分配量和再分配率先增后降,均以N270处理最高;开花后干物质积累对籽粒的贡献率亦呈先增后降的趋势,以N240处理最高。2005-2006年的试验结果呈相同变化趋势。在本试验条件下,小麦产量水平达10 000 kg hm^-2时的适宜施氮量为240~270 kg hm^-2,可供生产中参考。     

公顷产10000kg小麦氮素和干物质积累与分配特性

以泰山23和济麦22为试验品种,通过连续2年的田间试验,对单产高达10 000 kg hm^-2的小麦进行了施氮量和氮素吸收转运和分配特性的研究。在2006—2007年生长季,随着施氮量的增加,小麦籽粒产量先增加后降低,施纯氮240 kg hm^-2 (N240)和270 kg hm^-2(N270)处理的产量分别达9 954.73 kg hm^-2和10 647.02 kg hm^-2,比不施氮肥处理(N0)分别增加11.20%和18.93%。与N0处理相比,施氮处理显著增加了小麦植株氮素积累量、籽粒氮素积累量和开花后营养器官氮素向籽粒的转运量;随着施氮量的增加,成熟期小麦植株氮素积累量呈先增后降趋势,以N270处理最高;开花后营养器官氮素向小麦籽粒转运量和转运率先升后降,转运量以N270处理最大,为213.78 kg hm^-2;而转运率以N240处理最高,为67.98%。随施氮量的增加,小麦成熟期各器官干物质积累量、花后营养器官干物质再分配量和再分配率先增后降,均以N270处理最高;开花后干物质积累对籽粒的贡献率亦呈先增后降的趋势,以N240处理最高。2005—2006年的试验结果呈相同变化趋势。在本试验条件下,小麦产量水平达10 000 kg hm^-2时的适宜施氮量为240~270 kg hm^-2,可供生产中参考。     

Correlated Response to Selection for Protein Yield in Oats After Three Cycles of Recurrent Selection

Three oat (Avena saliva L.) populations (i.e., lines of descent), high grain yield (HG), high protein content (HP), and high protein yield per se (HGP), each developed by three cycles of S, recurrent selection, were evaluated for the effect of selection for groat-protein yield upon other agronomic traits. Selections making up the HG line of descent had high protein yield primarily due to high grain yield, and those selected for HP had high protein yield due to both high protein content and high grain yield. Selection in HGP was on the basis of protein yield per se. Selection caused increases in bundle weight, harvest index, vegetative growth rate, and seed number in all lines of descent. Heading date, plant height, and seed weight were unaffected, whereas groat percentage and test weight were decreased in HP and HGP. Heritabilities were high for heading date, plant height, test weight, and seed weight, moderate for harvest index and bundle weight, and low for groat percentage. Genetic variability generally declined from CO to C3 for all traits. Groat-protein yield and amount of protein per groat increased in all lines of descent. In HG, the increase in groat weight was due primarily to increases in the nonprotein fraction, with groat-protein content actually decreasing. In HGP, groat weight increased due to increases in protein and nonprotein fractions, and groat protein content remained constant. In HP, groat weight and amount of nonprotein per groat decreased, thus increasing groat-protein content. Three cycles of recurrent selection resulted in oat lines with groat-protein yields significantly higher than the highest lines from CO. Utilization of index selection may be desirable to obtain populations of greater breeding value.     

Combining ability and patterns of inheritance for plant and fruit traits in Japanese quince (Chaenomeles japonica)

Phenotypic variation and pattern ofinheritance was investigated for plant andfruit traits in Japanese quince (Chaenomeles japonica, Maloideae). Japanesequince is a minor fruit crop in Latvia andLithuania, and is presently being developedfor production of juice, aroma and fruitfibre in Sweden and Finland. General andspecific combining ability was estimatedfor five plant vegetative traits, eightfruit yield and morphology traits, and fivefruit biochemistry traits in a studypopulation consisting of 14 hybridfamilies. Thorniness seems to be controlledprimarily by a single locus. All othertraits studied appear to be governedprimarily by additive genes, as judged fromgeneral combining ability estimates.Significant specific combining ability(SCA) was detected for yield, plant heightand some fruit traits. However, therelative contribution of SCA to the overallgenetic variance was in general low. Anefficient breeding strategy for Japanesequince could therefore be based onrecurrent selection.     

内蒙古农牧交错区施氮量对燕麦饲草产量和饲用品质的影响

对比施氮量对饲草产量、品质的影响,为内蒙古农牧交错地区燕麦饲草增产提质提供理论依据。在旱作条件下对2个燕麦品种‘蒙燕1号’和‘8202’分别设低氮(30 kg/hm²)、中氮(90 kg/hm²)和高氮 (150 kg/hm²)3处理,比较其产量和品质。结果表明：施氮量显著影响2个燕麦品种饲草产量,‘蒙燕1号’在高氮处理下鲜、干产分别较其他处理增加8.42%~10.73%、9.30%~13.38%,显著高于低氮处理(P<0.05),且分别较‘8202’高氮处理下增产17.58%、19.28%。2品种粗蛋白、粗脂肪含量随施氮量的增加而提高。‘8202’粗蛋白含量在高氮处理下较其他处理提高4.24%~14.14%,较高氮处理下‘蒙燕1号’提高29.85%;‘8202’高氮处理下粗脂肪产量较其他处理提高0.44%~6.43%,较‘蒙燕1号’提高6.94%,2品种粗蛋白、粗脂肪含量在高氮、中氮处理下差异不显著,却与低氮处理差异显著(P<0.05)。施氮后品种间草产量和品质有差异,若以草产量为目标,应选‘蒙燕1号’,施高氮,可获鲜草40891 kg/hm²,可获干草7801 kg/hm²;若以品质为目标,应选‘8202’,施中氮,整株粗蛋白、粗脂肪含量分别可达17.66%,2.88%,可获粗蛋白1080 kg/hm²,粗脂肪166 kg/hm²。     

氮素对燕麦冠层结构及光合特性的影响

为了研究氮素对燕麦坝莜1号的冠层结构、光合特性及产量的影响,用红外气体分析仪和冠层分析仪测定不同氮肥处理下群体的冠层结构和光合特性,同时分析了不同氮素水平下产量性状指标之间的差异性。结果表明:随着施氮量的增加,单株叶面积和叶绿素含量均显著增加,单株叶面积在整个生育期呈"M"型变化,叶绿素含量在抽穗期达到最大值。施氮量对叶面积指数和透光率的影响呈相反的变化趋势,随着施氮量的增加,叶面积指数变大,而透光率变小。随着施氮量的增加,燕麦坝莜1号旗叶净光合速率、气孔导度和蒸腾速率显著提高,胞间CO2浓度则降低。产量以N2处理(144.0 kg/hm2)最高。因此认为,合理的氮肥用量能显著改善燕麦群体的冠层结构,提高光合效率,是燕麦增产的重要农艺措施。     

Effects of Seeding Rate on Growth Duration and Accumulation and Partitioning of Dry matter in Oats

Crop management influences considerably the three components of grain yield, growth duration, growth rate, and harvest index (HI). Effects of seeding rate on these yield components in oats ( Avena sativa L.) was assessed in field experiments at the Viikki Experimental Farm, University of Helsinki, Finland (60°13'N) in 1991 and 1992. Three Finnish oat genotypes were evaluated; a long-strawed landrace cultivar, a moderately long-strawed modern cultivar, and a semi-dwarf breeding line. The following traits were measured: grain yield, days from sowing to yellow ripeness, number of tillers on main shoot, phytomass, vegetative phytomass, and their growth rates (PGR and VGR, respectively), panicle weight and its filling rate (PFR), HI, leaf area index (LAI), and at intervals, dry-matter accumulation in leaves and straw.
Increases in seeding rate significantly decreased growth duration and PGR of individual plants but increased PGR on a ground area basis. Seeding rate did not, however, affect HI. When seeding rate was increased from 200 seeds m⁻² to 500 seeds m⁻², reductions in vegetative phytomass, panicle weight, VGR, and PFR for individual plants ranged between 20 and 40 %, depending on genotype. At ≥600 seeds m⁻² differences in these components between seeding rates were modest. However, PGR, VGR, and PFR per unit ground area increased with increasing seeding rates up to 600–700 seeds m⁻². Moreover, the higher the seeding rate, the higher the peak LAI (2.7 maximum) and the earlier the canopy closure. Hence, our results showed that a seeding rate of 600–700 seeds m⁻², which resulted in uniculm growth habit, is advantageous in terms of grain yield at high latitudes due to higher biomass accumulation and subsequently greater interception of PAR.     

The relationship of propagule pressure to invasion potential in plants

Summary The invasive potential of a species can be assessed by propagule pressure, which measures the chances for propagules of a species to find a suitable habitat for establishment and reproduction. Seeds, fruits, and vegetative structures that contribute to the propagule pressure are morphologically, physiologically and genetically different from one another, thus each kind should have a specific way of contributing to a successful invasion. In this paper we review plant traits that contribute to the propagule pressure. Seed production provides an estimate of the potential multiplication rate of the weed. However, it is gap-sensing mechanisms of seeds based on dormancy termination and germination requirements, which significantly contribute to the naturalization and invasion processes assuring a successful seedling establishment in environments of high competition. Dispersal of propagules reduces competition, mating with a sibling, and subsequent inbreeding depression, and increases colonization opportunities and range of expansion. Some of those benefits can be achieved in a population by existence of dormancy mechanisms and thus, the existence of a seed bank. Finally, vegetative propagation may ensure expansion of local populations when seedling establishment is low. Broadening the scope of traits that are considered in the breeding programs aimed at commercial production of plant propagules, to include those related to propagule pressure, is essential for adequate evaluation of invasive potential.     

辽宁不同年代水稻品种生产力和氮肥效率对施氮水平的响应差异

阐明水稻品种演进过程中植株生产力和资源利用效率的变化特征,对高产高效协调的水稻品种选育和稻作技术改进具有重要的理论参考意义。本研究以1950-2010年间辽宁省的12个水稻主栽品种为材料,探讨氮肥施用对不同年代水稻品种植株生产力和氮肥利用效率的影响。结果表明,1990s及之后品种的最高生物学产量和籽粒产量均显著高于1980s及以前的品种,1990s及之后品种产量的递增主要归功于穗粒数的增加。其最高产量的施氮量显著高于1980s及以前的品种,低氮条件下不同年代品种间的生产力差异不显著。随年代的递进,水稻品种的氮肥农学利用率、偏生产力呈现递增趋势,但生理利用率和吸收利用率的变化趋势不明显;茎叶氮含量变化不明显,但籽粒氮含量呈下降趋势。随施氮量的递增,各年代品种植株含氮量均呈现递增趋势,但农学利用率、偏生产力、生理利用率、吸收利用率均呈下降趋势。在低氮条件下1990s及之后品种的氮肥利用效率与1980s及以前品种的差异不明显,但高氮下前者的氮肥利用效率显著高于后者。上述结果表明,虽然辽宁水稻植株生产力提升是品种改良和施肥水平提高的双重作用的结果,但在今后品种选育和栽培技术改进中要进一步协调好高产与资源高效的关系。     

Inheritance of characters determining growth and development of tomato (Lycopersicon esculentum Mill.) under low energy conditions

Summary Diallel crosses were made between 15 tomato genotypes with varying performance under a low energy regime. It appeared that differences between genotypes for 11 vegetative and generative plant characters are determined mainly by additive genetic variation. For breeding cultivars adapted to low energy conditions, crossing genotypes with a high GCA for weight of trusses and fruits (WTF) and genotypes with a high GCA for weight of vegetative plant parts (WVP) seems most promising. Complications may arise from the negative correlation between GCA values for WTF and WVP, and the strong positive correlation between GCA values for fruit number and WTF, causing small fruits.     

氮肥水平对不同育种时代粳稻产量、氮素吸收利用差异的影响

以选育时期不同(两个选育时代)的12个水稻品种为材料,于施氮量为0,225,300 kg/hm~2纯氮大田条件下,研究了不同氮肥水平下两选育时代的水稻品种产量、物质生产积累量及氮素吸收、利用效率的差异.结果表明,水稻产量随着选育时代的更替有所提高,并随施氮量的增加两时代产量表现不同,早期品种中有83.3%的水稻基因型的产量随施氮量增加呈增加趋势,当代品种产量则有一半基因型在225 kg/hm~2氮肥水平下产量达最大,说明早期品种对氮肥反应较当代品种敏感.农艺性状中的株高和穗长随着育种时代的更替有矮化和减小的趋势,着粒密度有所增加.干物质和氮素平均积累量在生育时期各阶段均表现为当代品种大于早期品种,氮素利用效率亦表现相同的规律.相关分析表明,水稻产量与抽穗、成熟期物质积累量和氮素吸收量均呈显著或极显著正相关关系,与拔节期关系不密切.氮素利用效率与产量呈显著正相关,与株高和穗长呈显著负相关.说明随着选育时代的更替,水稻产量、吸氮量及氮素利用效率有所提高,株型趋于矮化,穗型由散穗向密穗型演变.     

Genotypic variation and relationships between seedling and adult plant traits in maize (Zea mays L.) inbred lines grown under contrasting nitrogen levels

Genotypes with better root development have good nutrient acquisition capacity and may yield better under limited nitrogen (N) conditions and consequently can help reduce the N fertilization rate and hence mitigate some economic and ecological problems. This study focused on the genotypic variation among diverse maize inbred lines for seedling and adult plant traits under contrasting N levels. Seventy-four lines were screened under high and low N levels in a climate chamber and in the field. High phenotypic diversity was observed for seedling and adult plant traits together with moderate to high broad-sense heritability estimates. Seedling total root length and root dry weight were significantly correlated with other root traits in maize. Of the adult plant traits evaluated in the field, the anthesis-silking interval and the leaf chlorophyll contents were significantly correlated with grain yield under both low and high N levels. In one location, the seminal root length was correlated with grain yield both under low and high N levels and the root dry weight was correlated with grain yield under high N. Selection indices based on secondary root traits along with grain yield could lead to an increase in selection efficiency for grain yield under N stress condition. By identifying lines with better root development, particularly lines with longer SRL, it may be possible to select inbred lines with higher grain yield particularly under low N condition.