Physiological factors determining yield in bread wheat. Effects of introducing dwarfism genes

Summary Improvements in bread wheat productivity have been related to changes in plant morphology and function associated with a large increase in the harvest index for a more or less constant biological yield. The appearance of short genotypes possessing dwarfism genes may modify markedly the objectives of breeding as the upper limits of the harvest index are approached. The aim of the investigations presented here was to identify some contrasts between short and tall genotypes in terms of the physiological characteristics associated with grain yield, so as to orientate more efficiently the selection of genotypes, with or without dwarfism genes, for productivity. Various parameters of flag leaf functioning (photosynthesis rate, chlorophyll fluorescence index, leaf area duration) were related to the biological and economic yields and the harvest index for two groups of genotypes that were differentiated by their height. For all genotypes, the relationships between the various traits and the grain yield were difficult to ascertain. For the tall genotypes without dwarfism genes, the classical relationships between grain yield, harvest index, flag leaf area duration and net photosynthesis rate were confirmed. Moreover, the rate of chlorophyll fluorescence decrease (Rfd) during the slow Kautsky kinetics phase, which is representative of the leaf photosynthesis at low light, was found to be an excellent marker of economic yield. Chlorophyll fluorescence decrease was closely related to grain yield and also with other factors that are known to be important in its expression (harvest index, flag leaf area duration). In very short genotypes, the biological yield and directly related factors (leaf area, plant height) were the main parameters associated with economic yield, since the harvest index had approached its upper limit. The selection of short genotypes must therefore maintain the biological yield through an increase in the size of the aerial organs to counterbalance the decrease in height.     

Effects of Thiourea, Thiamine and Ascorbic Acid on Growth and Yield of Maize (Zea mays L.)

Three chemicals, viz., thiourea, thiamine and ascorbic acid capable of potentiating-SH turnover, were tested with the objective to improve growth and productivity of maize. Thiourea was tested as seed-soaking and foliar-applied treatments as also in combination. Thiamine and ascorbic acid were tested as foliar sprays alone. Foliar treatments were applied at vegetative stage (30 and 45 days after sowing).
The results of the field experiment showed that seed soaking with thiourea (500 ppm) tended to improve grain yield (13.4 per cent over control), but improvement in biological yield was significant. However, seed soaking plus foliar treatment of thiourea significantly increased both biological and grain yields, besides causing significant improvement in leaf area index and number of green leaves plant^-1. The increase in grain yield ha^-1 was of the order of 34.6 per cent over control.
It was further noted that foliar sprays of thiourea (1000 ppm), thiamine (100 ppm) and ascorbic acid (100 ppm) significantly increased leaf area index, number of green leaves plant^-1 and biological yield ha^-1. These treatments also significantly increased grain yield ha^-1 by 40.6, 20.2 and 26.3 per cent, respectively over control. Improvement in maize yield with thiourea, thiamine and ascorbic acid treatments appeared to have resulted from increased photosynthetic efficiency and canopy photosynthesis on account of the biological activity of -SH group. It was also apparent that leaf senescence was delayed under the influence of these chemicals. It is therefore suggested that thiourea, thiamine and ascorbic acid are the potential bioregulators for improving photosynthetic efficiency and grain yield of maize and possibly other cereals, and that thiourea, a sulphydryl compound, holds considerable promise in this context.     

我国玉米自交系叶片保绿性及其与产量的关系

选用我国75个常用不同基因型玉米自交系,对其叶片保绿性参数进行了定点动态测定。结果表明,不同自交系抽丝后叶片保绿度的变化均符合方程y = ae^b-cx/ (1+e^b-cx),成熟期的绿叶数、成熟期叶绿素含量和相对绿叶面积平均衰减速率(V_m)可作为区分玉米保绿型与非保绿型的关键指标。按照Hiechical聚类分析方法,筛选出12个保绿型自交系,其成熟期相对绿叶面积在60%以上,其V_m平均值为0.687% d^-1,在生长季内相对绿叶面积无大幅度衰减,成熟期绿叶数多,叶绿素含量较高;其余63个为非保绿型自交系,还可分为植株叶片衰老较快型与植株叶片衰老较慢型两个亚类。不同自交系抽丝后叶片保绿性与叶面积持续期、单株产量均呈正相关。保绿型的叶面积持续期和单株产量比非保绿型分别高20.02%~23.87%和50.44%~59.38%;与非保绿型自交系相比,保绿型在籽粒灌浆期绿叶面积大,叶绿素含量高,群体光合速率高,光合作用时间长,因而生物产量较高。     

不结球白菜组合农艺性状与产量表现

为选育出适合绿洲农区种植的不结球白菜新品种,通过对参试组合的各农艺性状进行变异性分析、方差分析、相关性分析和外观性状比较。结果表明,在变异性分析中,单产变异最大,其次是小区产量;通过对参试组合单产方差分析及PLSD多重比较,单产均呈极显著性,单产排在前三的组合是：K-14:34666.85kg/hm2; K-5:34400.18kg/hm2; 和K-12:32000.16kg/hm2。相关分析表明,单株产量与单产呈极显著相关,r=1**。外观性状比较结果表明,K-14直立紧凑叶色绿色,叶柄色为淡绿且鼓有挺性,K-5的株型直立,叶色为深绿,叶柄颜色为绿色且鼓,K-12虽然是不紧凑型的,叶色为绿色、叶柄为淡绿色,且鼓有挺性;综合参试组合的各性状,结论是K-14、K-5和K-12比较适合新疆绿洲农区种植。     

不同年代中籼水稻品种的叶片光合性状

旨在探明中熟籼稻在品种改良过程中籽粒产量和叶片光合性能的变化特点。以江苏省近70年来不同年代在生产上应用的12个代表性中籼水稻品种(含杂交稻组合)为材料,依据应用年代将其分为20世纪50-60年代、60-70年代、80-90年代和21世纪00-10年代(超级稻) 4种类型,研究其产量、冠层结构及叶片光合特性的变化。结果表明,随品种的改良,中籼水稻品种的产量不断提高。群体总颖花量、面积指数和粒叶比显著增加,叶基角减小,群体透光率、光合势(绿叶面积持续期)、抽穗期剑叶光合速率、气孔导度、蒸腾速率和PSII最大和实际光化学效率以及荧光与非荧光淬灭系数增加。最大叶面积指数和全生育期总光合势与籽粒产量呈极显著正相关。灌浆期剑叶光合速率、气孔导度、PSII最大和实际光化学量子效率以及荧光和非荧光淬灭系数与结实率或粒重呈显著相关。表明在品种改良过程中,株型和叶片光合性能的改善是中籼水稻产量提高的重要原因。     

Growth analysis in a reduced leaf mutant of common bean (Phaseolus vulgaris L.)

Summary A comparison between the Royal Red bean variety and a reduced leaf mutant on the basis of growth indices is reported. The mutants has lower leaf area index (LAI) and leaf area duration (LAD) (–43.7%), higher specific leaf weight (SLW) (on the mean +33.3%) and accumulates less dry matter (–7.7%) than the normal genotype. When the net assimilation rate (NAR) is considered, the mutant is superior to the normal (+62.3%). It is concluded that the unit area of the mutant leaves accumulates dry matter more efficiently than that of the corresponding normal variety.     

Growth Analysis Using Classical and Functional Techniques in Relation to Soil Moisture in Mustard

A Reid experiment was conducted to study the effect of soil moisture on growth of two mustard cultivars using classical and functional techniques of growth analysis. Two soil moisture levels were irrigated at 10-day intervals and a rainfed control was included. Total dry matter (TDM), leaf area index (LAI) and leaf area duration (LAD) were significantly increased by irrigation at most of stages of growth. Starting from a lower value, LAI and LAD reached a peak and then gradually declined. Among the growth attributes, crop growth rate (CGR), leaf area ratio (LAR) and leaf weight ratio (LWR) increased significantly under irrigation. Net assimilation rate (NAR) decreased more in the irrigated plants than the rainfed plants at the later stages of growth. LAR and LWR declined throughout with increasing time and plant weight. Seed yield of the irrigated plants was positively correlated with the pre-flowering LAI and the post-flowering CGR and NAR. In the rainfed plants, seed yield was positively correlated with LAI and CGR at the post-flowering stage and negatively with the post-flowering NAR and pre-flowering LAR.     

Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages

The effects of water stress on physiological attributes of drought‐sensitive (Kalyansona) and drought‐tolerant (C‐306) wheat cultivars were studied in a pot experiment. Water stress was imposed by withholding irrigation at boot and anthesis stages. Leaf water potential, leaf osmotic potential and leaf turgor potential (measured with pressure chamber and osmometer), as well as leaf diffusive resistance, leaf transpiration rate and leaf‐to‐air transpiration gradient (measured with a steady‐state porometer) were measured diurnally. Growth and yield parameters were recorded after harvesting of the crop. Triplicate data were analysed using a completely randomized design and correlations amongst these parameters were computed. Water stress was found to reduce diurnal leaf water potential and leaf osmotic potential in both the genotypes but leaf osmotic potential was significantly higher in the drought‐tolerant cultivar C‐306 than in the drought‐sensitive cultivar Kalyansona. Positive turgor was recorded in both the genotypes under water stress and non‐stress conditions. Water‐stressed plants showed significantly lower turgor potential than control plants. In diurnal observations, water‐stressed plants exhibited significantly higher leaf diffusive resistance in both genotypes at both stages. The diffusive resistance of C‐306 was predominantly higher than that of Kalyansona. Water stress decreased leaf transpiration rate at both stages but the reduction was higher at the anthesis stage. The leaf‐to‐air temperature gradient was much higher in C‐306 than in Kalyansona at the boot stage but at the anthesis stage genotypic variation was non‐significant. The capacity to maintain cooler foliage was lower at the anthesis stage than at the boot stage in both the cultivars. Shoot dry weight, number of grains, test weight, grain yield, biological yield and harvest index decreased to a greater extent when water stress was imposed at the anthesis stage, while imposition of water stress at the boot stage caused a greater reduction in plant height and number of tillers. Similarly, water stress caused a smaller reduction in growth, yield and yield attributes in C‐306 than in Kalyansona. In general, the correlation coefficient of grain and biological yield with water potential and its components was positive and highly significant. Similarly, turgor potential was also correlated positively and significantly with grain yield at both the stages, but with biological yield it was significant only at the anthesis stage. A negative and significant correlation was obtained for diffusive resistance and leaf‐to‐air temperature gradient with grain yield at the boot and anthesis stages. The rate of transpiration was also positively and significantly correlated to grain and biological yields at both the stages. Amongst the yield attributes, number of leaves and number of tillers were positively correlated at the anthesis stage, whereas leaf area and shoot dry weight were significantly correlated with grain and biological yields at both the stages.     

不同库容量类型籼稻品种源库相关参数的基本特点

在群体水培条件下,以国内、外不同年代育成的常规籼稻代表品种(2001年为88个、2002年为122个)为材料,测定叶面积、干物质重(包括根系)、产量及其构成因素、氮素含量等,采用组内最小平方和的动态聚类方法将供试品种按库容量从低到高依次分为A、B、C、D、E、F 6类,研究各类品种源、库主要性状的基本特点。结果表明：(1)供试品种间库容量的差异很大(426%和817%)。A、B、C、D、E、F类品种的平均库容量,2001年分别为426.37、642.53、770.96、903.73、1 064.32、1 213.90 g m^-2,2002年分别为359.36、574.11、764.98、962.43、1 200.11、1 455.59 g m^-2;(2)大库容量品种全生育期天数、每日形成的库容量较大,库容量显著受到全生育期天数、每日形成库容量的影响,后者对库容量的作用大于前者对库容量的作用;(3)大库容量类型品种抽穗期叶面积、成熟期叶面积、抽穗期绿叶重、成熟期绿叶重、比叶重较大,但结实期叶面积下降比例小;(4)大库容量类型品种结实期净同化率、单位叶面积籽粒产量、单位叶面积库容量、单位干物质库容量、单位氮素库容量大于小库容量类型品种;（5）多元逐步回归分析表明,抽穗期绿叶重、单位叶面积库容量、单位氮素库容量、单位干物质库容量、净同化率、比叶重是影响库容量的主要源库性状(R²= 0.953~0.963)。通径分析表明,抽穗期绿叶重、单位叶面积库容量对库容量的作用要显著大于单位氮素库容量、单位干物质库容量、净同化率、比叶重等对库容量的作用。     

北京地区冬小麦品种冠层结构的研究

1983～85年对本地区22个冬小麦品种的产量及其构成因素与上部三个节的茎、叶和穗部性状的关系进行了研究。结果表明,在产量水平为5～6吨/公顷时,决定产量的主导因素是穗粒重,其中千粒重和穗粒数的贡献大体相同。上部三个叶片性状有较大的一致性,旗叶宽、面积、绿色面积持续期对穗粒数、粒重、穗粒重有中度正相关,其中叶宽影响较大;但与穗数/米~2呈中度负相关,因而与产量表现为一定程度的正相关。茎、鞘直径与产量构成因素关系比长度密切,上部茎节直径影响也比下部大。逐步回归分析表明决定产量的还是产量构成因素本身,旗叶性状居从属地位,其中开张角、基角和叶宽对千粒重的影响较大。将产量居前五名品种的主要性状平均值与由曲线回归方程计算而得的“最优值”相比较,二者基本一致。据此提出选育产量潜力为6吨/公顷上下品种时可加考虑的冠层性状指标。     

Effects of an Early Application of Sulphur or Etephon as Foliar Spray on the Growth and Yield of Spring Barley in a Mediterranean Environment

Leaf area development, biomass production and yield of four spring barley varieties grown in a Mediterranean environment (southern Spain) in response to an early application of foliar sulphur or etephon have been studied. Both sulphur and etephon produced similar results compared to the control. Thus, whereas the maximum leaf area index on untreated plots was reached at the beginning of shooting, the growth of foliar area in the treated ones was extended until anthesis and its decline during maturity was similarly retarded. This led to a significant improvement in the biomass at anthesis (which was closely correlated with grain yield) as well as in the leaf area duration during grain filling. These effects were principally due to variations in the number of leaves per plant, caused by a higher tiller production in the treated plants and not by an increase in the number of leaves per tiller or by leaf size.
An application of sulphur or etephon at tillering increases grain yield by raising both the number of ears per plant and per plot, without modifying the number of grains per ear or 1000-grain weight. The similarity between the effects of sulphur and etephon may be due to the fact that sulphur absorbed by the leaves results in an increase in methyonine, the biological precursor or ethylene. The positive correlation between biomass at anthesis and number of ears over grain yield suggests that sink capacity and source activity are closely related and both simultaneously limited by the environment.     

高产旱作玉米品种的光合性能及物质生产力研究

通过对 6个玉米品种在旱作条件下的试验研究 ,结果表明 ,高产旱作玉米品种叶面积指数 (LAI)大 ,衰退慢 ,成熟时LAI仍在 2 0以上。吐丝后光合势明显提高 ,较低产品种平均增加4 6 8%。总光合与产量呈极显著正相关 (r =0 8867 )。叶片光合速率增强 ,干物质积累增多 ,向外转移减少。群体穗数与产量无明显相关 ,但单株穗粒数与群体产量呈显著正相关 (r =0 874 7)。     

籼、粳超级稻光合物质生产与转运特征的差异研究

为阐明籼、粳超级稻干物质积累及光合生产特征的差异,以江苏地区大面积推广种植的5个超级杂交籼稻组合和5个常规粳型超级稻品种为试验材料,对稻麦两熟制条件下籼、粳超级稻干物质积累、分配、运转及叶面积、光合势、群体生长率、净同化率、秧苗素质、叶型等方面进行了系统的比较研究。结果表明,粳稻生育前期(移栽至拔节期)干物质积累量、光合势、群体生长率、净同化率及上三叶叶长、叶基角、叶开角、披垂度和叶面积衰减率、收获指数均小于籼稻,而生育中后期(拔节至成熟期)干物质积累量、光合势、群体生长率、净同化率及有效叶面积率、高效叶面积率、粒叶比(颖花/叶、实粒/叶、粒重/叶)、最大叶面积指数、总充实量、实收产量、生物产量、茎鞘最大输出量和表观输出量及比率均大于籼稻,差异显著或极显著。虽然粳稻主要生育期单茎干物重均不及籼稻,但群体数量优势保证粳稻具有较高的群体干物质积累量和叶面积,且随着生长发育的持续,群体光合物质生产优势不断加大,群体干物质积累量于抽穗后25 d前后超过籼稻。粳稻灌浆后期(乳熟至成熟期)仍保持强劲生长优势,而灌浆初期(抽穗至乳熟期)茎鞘贮存物质合理输出,有效保障了高效光合层的安全支撑及高积累产量库的流畅充实。高生物学产量的稳定形成和叶面积“稳升缓降”态势以及拔节至成熟期较强的高效光合物质生产,是粳稻光合系统高效持续产出、灌浆充实多及高产形成的重要特征和原因。     

中黄35超高产群体的生理参数

为探索新疆绿洲农田生态条件下大豆超高产(≥5 625 kg hm^-2)栽培的产量形成机理,在2006和2007年超高产栽培试验中测定了中黄35的群体生理指标和生态参数,分析了品种群体结构。结果表明,中黄35和新大豆1号(对照)的最大叶面积指数(LAI_max)分别为4.31和3.64,LAI＞3的天数分别持续50 d和36 d;全生育期的总光合势(LAD)分别为2 766 375 m² d和2 385 645 m² d;中黄35生育前期(出苗后第16~58天群体的光合生产率为3.3~5.2 g m^-2 d^-1,而后期(出苗后第72~114天)则为2.52~5.0 g m^-2 d^-1,对照分别为3.8~6.0和0.6~3.5 g m^-2 d^-1;中黄35的生物产量、籽粒产量和经济系数为13 943.2 kg hm^-2、5 521.5 kg hm^-2和39.6%,对照则为13 108.1 kg hm^-2、4 666.5 kg hm^-2和35.63%。和对照相比,中黄35最大叶面积指数持续时间长,全生育期的总光合势高,后期群体的光合生产率大,经济系数高是达到超高产目标的基础。中黄35在新疆绿洲农田栽培,具有良好的适应性。     

中黄35超高产群体的生理参数

为探索新疆绿洲农田生态条件下大豆超高产(≥5 625 kg hm^-2)栽培的产量形成机理,在2006和2007年超高产栽培试验中测定了中黄35的群体生理指标和生态参数,分析了品种群体结构。结果表明,中黄35和新大豆1号(对照)的最大叶面积指数(LAI_max)分别为4.31和3.64,LAI＞3的天数分别持续50 d和36 d;全生育期的总光合势(LAD)分别为2 766 375 m² d和2 385 645 m² d;中黄35生育前期(出苗后第16~58天群体的光合生产率为3.3~5.2 g m^-2 d^-1,而后期(出苗后第72~114天)则为2.52~5.0 g m^-2 d^-1,对照分别为3.8~6.0和0.6~3.5 g m^-2 d^-1;中黄35的生物产量、籽粒产量和经济系数为13 943.2 kg hm^-2、5 521.5 kg hm^-2和39.6%,对照则为13 108.1 kg hm^-2、4 666.5 kg hm^-2和35.63%。和对照相比,中黄35最大叶面积指数持续时间长,全生育期的总光合势高,后期群体的光合生产率大,经济系数高是达到超高产目标的基础。中黄35在新疆绿洲农田栽培,具有良好的适应性。     

不同水分条件下小麦持绿表型性状评价及其与产量相关性研究

找出适宜在多个环境条件下评价小麦持绿性状的表型指标,为快速筛选小麦持绿品系,加速抗旱、高光效育种进程提供数据支撑。以包含306个家系的RIL群体（旱选10号×鲁麦14）为材料,分析了不同水分条件下灌浆不同时期旗叶叶绿素SPAD值、功能绿叶面积持续期（GLAD）以及衰老参数变化特征,并对其与产量性状的相关性进行了研究。结果表明：RIL群体SPAD值、GLAD在整个灌浆期的变化动态复杂,衰老相关参数无法反映其动态变化过程。2种水分条件下,在灌浆后期（花后20、25和30d）SPAD值与粒宽、粒厚、千粒重以及单株产量呈显著或极显著正相关。在灌溉条件下花后10、13、16、19和22d的GLAD与单株产量呈极显著正相关;而在干旱胁迫条件下GLAD与单株产量相关性则未达到显著水平。不同环境条件下,旗叶SPAD值在灌浆后期（花后20、25和30d）相比于GLAD和衰老特征参数与产量性状具有更好的相关性,且测定相对简单,更适宜于持绿品系的快速筛选。     

Foliar diseases affect the eco-physiological attributes linked with yield and biomass in wheat (Triticum aestivum L.)

Foliar diseases are the main biotic cause of yield loss in wheat crops (Triticum aestivum L.) in Argentina and other regions around the world. Most of the studies on foliar diseases take a phytopathological perspective, but few studies have analyzed the problem with an eco-physiological approach aimed at the understanding of which crop traits are affected by foliar diseases. The present study was designed to determine the effects of a foliar disease complex (including leaf rust, Septoria leaf blotch and tan spot), on (i) grain yield and (ii) the physiological components of biomass production; intercepted radiation (RI) and radiation use efficiency (RUE), in bread wheat crops growing under contrasting agronomic and environmental conditions (i.e. different cultivars, years, location and nitrogen supply). The experiments were carried out during 4 years in different locations (three in the rolling pampas of Argentina and one in northern of France). Five different commercial wheat cultivars were sown on early (E) and late (L) sowing dates (SD); and two contrasting nitrogen availability and two fungicide treatments (protected and unprotected) were applied. Foliar diseases appeared during the grain filling period and affected both, leaf area duration (LAD) and healthy area duration (HAD) during that period. Foliar diseases reduced both, above-ground biomass at harvest (1533 and 1703 g m⁻² for unprotected and protected treatments, respectively) and grain yield (646 and 748 g m⁻² for unprotected and protected treatments, respectively) without important effects on harvest index. Biomass reductions after anthesis, due to the effects of foliar diseases, were associated with a reduced capacity of the canopy to absorb solar radiation more than any effect on RUE. However, RUE was consistently lower—when leaf rust was the predominant disease in the crop, suggesting that this biotrophic pathogen could affect the photosynthetic activity at the leaf or canopy level.     

带状套作荫蔽及复光对不同大豆品种(系)生长及产量的影响

选取我国南方套作模式下20个不同产量水平的大豆品种(系),于2013—2014年采用净作和遮阴(遮阳网或玉米)对比分析了高产和低产大豆品种在荫蔽期及复光期的生长特点。结果表明,荫蔽期间,茎叶干物重显著低于净作,分配规律表现为"茎多叶少",分别为58.4%和41.6%;与高产类型大豆相比,低产类型茎叶干重下降比例、茎长、茎长/茎粗、茎长/地上部干物质、茎长/叶面积显著增加;荫蔽期地上部干物质与产量呈显著正相关,茎干物质比例与产量呈显著负相关。光照恢复后,地上部干物质迅速增加,分配规律表现为"茎少叶多",复光后30 d分别为47.7%和52.3%;高产类型地上部干物质、叶面积、叶干重比例、茎粗均显著大于低产类型,茎长/茎粗、茎长/地上部干物质、茎长/叶面积均显著小于低产类型;地上部干物质、叶面积、茎粗、叶干物质比例与产量呈显著正相关,茎长/茎粗、茎长/地上部干物质、茎长/叶面积与产量呈极显著负相关。通过复光前后生长性状与产量的回归分析,复光后30 d的叶干物质比例、茎长/地上部干物质、茎粗可作为预测套作大豆产量的主要指标。上述结果表明,选择荫蔽期茎长较短、地上部干物质较大、叶面积更大,光照恢复期茎粗较大、叶干物质比例较大、茎长/地上部干物质较小的大豆品种可以在套作下获得高产。     

Components of resistance to late leaf spot and rust among interspecific derivatives and their significance in a foliar disease resistance breeding in groundnut (Arachis hypogaea L.)

Late leaf spot (LLS) and rust cause substantial yield losses and reduce the fodder and seed quality in groundnut (Arachis hypogaea L.). Adoption of resistant cultivars by the semi-arid tropic farmers is the best option to overcome yield losses. Knowledge on components of resistance to these diseases should facilitate the development of groundnut cultivars with enhanced resistance to LLS and rust. The objectives of the experiments were to study the genetic variability and relationships among components of resistance to LLS and rust, and assess their significance in disease resistance breeding. Fifteen interspecific derivatives for LLS and 14 for rust and a susceptible control, TMV 2, were evaluated in a randomised complete block design with two or three replications under greenhouse conditions. The experiments were repeated twice. Genotypic differences were highly significant for all the traits studied. Resistance to LLS is due to longer incubation and latent periods, lesser lesions per leaf, smaller lesion diameter, lower sporulation index, and lesser leaf area damage and disease score. Selection based on components of resistance to LLS may not lead to plants with higher retained green leaf area. The remaining green leaf area on the plant should, therefore, be the major selection criteria for resistance to LLS in breeding programs. Resistance to rust is due to longer incubation and latent periods, fewer pustules per leaf, smaller pustule diameter, lower sporulation index, and lesser leaf area damage and disease score. Rust resistant components appear to work additively, therefore, selection based on resistance components together with green leaf area retained on the plant should be the basis of selecting for resistance to rust in breeding programs. ICGV 99005, 99003, 99012, and 99015 for rust and ICGV 99006, 99013, 99004, 99003, and 99001 for LLS are the better parents for use in resistance breeding programs. This revised version was published online in July 2006 with corrections to the Cover Date.     

抽穗后冬小麦旗叶光合特性的变化对产量的影响

为了探讨不同小麦品种之间的光合特性的差异及光合作用与经济产量的关系,本研究选取4个不同冬小麦品种分别在6个生育时期进行了光合特性的测定。结果表明：小麦旗叶6项光合特性指标随发育进程变化的趋势、变化程度基本相同,但不同品种在不同发育时期内光合特性指标的数值、变化程度不同;6项光合特性指标均与籽粒产量正相关;相关程度表现为绿叶面积>气孔导度>胞间CO₂浓度>净光合速率>叶绿素含量>蒸腾速率;不同时期光合特性与籽粒产量的相关性顺序为灌浆中期>灌浆前期>灌浆后期>开花期>抽穗期>灌浆末期;在开花期至灌浆后期,维持和提高旗叶的绿叶面积、叶绿素含量、净光合速率、气孔导度、胞间CO₂是提高小麦产量的基础。因此,在开展小麦高光效育种时,对种质资源材料进行光合特性测定和比较对育种工作具有非常重要的参考价值和指导意义。