Effect of Split Nitrogen Application on Growth and Yield of Wheat (T. aestivum L.) Genotypes with Different N-Assimilation Potential

A field experiment was conducted with different nitrogen regimes to assess the growth and yield performance of wheat genotypes which differ in nitrate assimilation potential. Genotypic differences in biomass accumulation were observed at different growth stages. The nitrogen treatment had little effect on biomass accumulation at early stages of growth, while at later stages of growth there was enhanced biomass accumulation when N was applied in more than two splits. On an average, genotypes with high nitrate reductase activity (the 'HNR' genotypes) accumulated 14.2 % more biomass than the genotypes with low nitrate reductase activity ('LNR' genotypes) when an extra dose (40 kg N ha⁻¹) of nitrogen was given at the time of anthesis. The application of nitrogen in more than two splits increased grain yield of both 'HNR' and 'LNR' genotypes mainly by increasing grain weight per ear. The application of an extra dose of nitrogen (40 kg N ha⁻¹) at the time of anthesis increased grain yield of 'HNR' genotypes by 38.5 % as compared to 'LNR' genotypes.     

Yield Stability of Winter Wheat (Triticum sp.) Cultivars and Lines

The purpose of this study was to compare responsiveness to environment as well as the stability of newly developed promising lines with traditional commercial cultivars. Subject research was conducted in Ankara between 1983-1989 on common and durum wheat cultivars and lines. Regression coefficient (b) was used as the criterion of genotypes' responsiveness to environment whereas deviation from regression (S²d) and coefficient of determination (r²) were used as stability parameters. Each experiment year was regarded as an environment and yield average of each year was used as the environmental index.
In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological regions.     

Relative importance of different types of inoculum to the establishment of Mycosphaerella graminicola in wheat crops in north‐west Europe

The contribution of wheat debris to the early stages of septoria leaf blotch epidemics was assessed in a 3‐year field experiment. First lesions were detected very early (December) in the case of an early sowing (mid‐October), showing that the first contamination could occur as soon as the seedlings emerge. The tested debris management options (chopped debris, removal of debris followed by tillage, or tillage in absence of debris) had a strong effect, although transient, on the epidemic dynamic: the more debris present on the soil surface, the more severe initial disease was. The magnitude of differences between treatments differed substantially between years. The relative production of pycnidiospores and ascospores was measured on the chopped debris. Peaks in pycnidiospore and ascospore production coincided in October–November. Both types of spores can be involved as primary inoculum in north‐west European conditions. The local amount of pycnidiospores available on debris in the field, estimated per square metre, was 1000‐fold the local ascospore production. Moreover, inoculum production was quantified on debris exposed to different environmental conditions. Autumnal conditions, characterized by moderate temperature with alternating wet and dry periods, were favourable for the production of both pycnidiospores and ascospores, as shown by the high inoculum production on debris exposed to field or outdoor conditions. By late autumn, the canopy became the most important source of pycnidiospores, and this period, characterized by the decreasing role of debris as a local source of inoculum compared to distant potential sources, can be considered as the end of the early epidemic stages.     

Effect of bulk density and soil water tension on denitrification in the rhizosphere of spring wheat (Triticum vulgare

Summary Pot experiments were carried out to study the influence of bulk density (D _b), soil water tension (pF) and presence of plants (spring wheat) on denitrification in a low-humus B_t-horizon of a udalf. Pots of only 5-cm depth were found to be most suitable for the experiments when using the acetylene inhibition method. Almost homogeneous soil compaction between 1.1 and 1.6g soil cm^–3 was achieved by a Proctor tamper. Water tensions were adjusted by means of ceramic plates on which negative pressure was applied. No denitrification was detected in unplanted pots. With planted pots and increasing bulk density denitrification increased more in pots with 14-day-old plants than in pots with 7-day-old plants. With 14-day-old plants N₂O emission pot^–1 increased steadily from 2 mol at D _b 1.1 to 8 mol at D _b 1.6, when soil moisture was adjusted to pF 1.5, although root growth was impaired by higher bulk density. From an experiment with different bulk densities and water tensions it could be deduced that the air-filled porosity ultimately determined the rate of denitrification. When low water tension was applied for a longer period, water tension had an overriding effect on total denitrification. Denitrification intensity, however, i.e. the amount of N₂O g^–1 root fresh weight, was highest when low water tension was accompanied by high bulk density. The results suggest that the increase in denitrification intensity at oxygen stress is partly due to higher root exudation.     

Bread-Making Quality Indices in Triticum aestivum Progenies. Implications in Breeding for Better Bread Wheat

Bread-making quality indices (dough strength and dough mixing stability) in relation to flour protein content, glutenin/gliadin ratio, and high-molecular-weight (HMW) subunits of glutenin have been investigated in Triticum aestivum progenies during a three year agronomic trial. Dough strength (W) proved to be a fairly stable characteristic, slightly but positively correlated with flour protein content. High could be associated with a high glutenin/gliadin ratio as well as with the presence of specific HMW. subunits of glutenin, while high protein content tended to favour a balanced dough tenacity-extensibility ratio (P/L = 0.4—0.6). Satisfactory values of dough-mixing stability were frequently observed in association with good expression of W showing that the two quality traits may coexist without much difficulty in the same genotype. From the plant breeding standpoint the data suggest feasible to obtain high dough strength by concentrating in a genotype the HMW subunits of glutenin known to have a beneficial effect on W. However, very high W may present unfavourable P/L ratios. This possibility is enhanced when the flour has a low protein content which often occurs in high yielding genotypes.     

不同粒重小麦品种(系)籽粒灌浆特性分析

以湖北省种植的１１个大、中、小粒品种（系）为试验材料,用Ｌｏｇｉｓｔｉｃ方程对不同小麦品种的籽粒灌浆过程进行了拟合;用ｔ测验分析了３组不同粒重品种灌浆参数差异;用相关分析和逐步回归分析研究了灌浆参数与粒重的关系。结果表明,在灌浆各阶段,不同品种类型的部分灌浆参数间有显著或极显著差异。灌浆持续期Ｔ、平均灌浆速率Ｒ、快增期灌浆速率Ｒ２和时间Ｔ２、缓增期灌浆速率Ｒ３和时间Ｔ３对粒重作用显著。除此之外,各     

The rapid and accurate determination of germ tube emergence site by Blumeria graminis conidia

The development of appressoria by germinating Blumeria graminis conidia depends on its germ tubes making contact with the host surface. Low angle, low temperature scanning electron microscopy showed that 80% or more of first-formed germ tubes of f. spp. hordei, tritici and avenae conidia emerged from close to the host leaf surface, and so made contact with it allowing them to become functional primary germ tubes. Light microscopy of f. sp.hordei confirmed this result and, in addition, showed that germ tubes frequently emerged close to, and contacted, various hydrophobic and hydrophilic artificial substrata. Geometric models of conidium-substratum interfaces were developed and a “surface point method” was derived to predict the frequency with which contact would result if germ tube emergence was a random phenomenon. However, observed contact frequencies were far higher (c. three to eight times) than predicted. Thus, the germ tube emergence site was determined as a response to substratum contact. In part, this appeared to be a non-specific response. Nevertheless, germ tube contact frequencies were greater on the curved surface of leaf epidermal cells than on planar surface, suggesting that specific recognition of leaf surface characteristics may promote directional emergence. The area of contact required to stimulate directional germ tube emergence was very small: contact with a microneedle tip or with a spiders’ suspension thread was sufficient for many conidia. Similarly, on leaves, the only contact is between the tips of a limited number of conidial wall projections and the edges of epicuticular leaf wax plates. Micromanipulation to roll conidia so that their original site of contact with a leaf was rotated away from it, led to the majority of first-formed germ tubes growing away from the leaf, i.e. emerging close to the site of original contact. The experiments indicated that the site of germ tube emergence is determined within 1 min of deposition. This implicated the release of conidial extracellular materials in recognition of the conidium-leaf surface contact site.     

Factors responsible for levels of male sterility in photoperiod-sensitive cytoplasmic male sterile (PCMS) wheat lines

A `two-line system' using photoperiod-sensitivecytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm has been proposed as a newmeans of producing hybrid wheat. The PCMS line ismaintained by self-pollination under short-dayconditions (14.5 h light period), and F<sub>1</sub> seedscan be produced by outcrossing of the PCMS line witha pollinator under long-day conditions (15 h lightperiod). As the levels of male sterility in PCMSlines under the long-day conditions is a crucialfactor in determining hybrid purity of the F<sub>1</sub>seeds, a study was conducted into the effect ofseeding rate on male sterility in PCMS lines. Threedifferent density levels were tested using analloplasmic line of Japanese wheat cultivar `Norin 26'which exhibits PCMS. Levels of male sterility of thePCMS line increased at sparse planting, because tiller(ear) number per plant increased at low seedingdensity and late-appearing ears tended to exhibithigher levels of male sterility than early-appearingears. On the other hand, male sterility levels of thePCMS lines depended on genotype, e.g., the PCMS`Fujimikomugi' was completely male sterile, whereasthe PCMS `Norin 26' showed partial male sterility. APCMS line showing complete male sterility, such as thePCMS `Fujimikomugi', should produce F<sub>1</sub> seeds withhigh purity. However, the PCMS `Fujimikomugi' showeda lower female fertility. For practical use, it isnecessary to produce PCMS lines having high malesterility with high female fertility under long-dayconditions.     

Interaction of 15N-labelled ammonium nitrate,urea and ammonium sulphate with soil N during growth of wheat (Triticum aestivum L.) under field conditions

The effects of ¹⁵N-labelled ammonium nitrate, urea and ammonium sulphate on yield and uptake of labelled and unlabelled N by wheat (Triticum aestivum L. cv. Mexi-Pak-65) were studied in a field experiment. The dry matter and N yields were significantly increased with fertilizer N application compared to those from unfertilized soil. The wheat crop used 64.0–74.8%, 61.5–64.7% and 61.7–63.4% of the N from ammonium nitrate, urea and ammonium sulphate, respectively. The fertilizer N uptake showed that ammonium nitrate was a more available source of N for wheat than urea and ammonium sulphate. The effective use of fertilizer N (ratio of fertilizer N in grain to fertilizer N in whole plant) was statistically similar for the three N fertilizers. The application of fertilizer N increased the uptake of unlabelled soil N by wheat, a result attributed to a positive added N interaction, which varied with the method of application of fertilizer N. Ammonium nitrate, urea and ammonium sulphate gave 59.3%, 42.8% and 26.3% more added N interaction, respectively, when applied by the broadcast/worked-in method than with band placement. A highly significant correlation between soil N and grain yield, dry matter and added N interaction showed that soil N was more important than fertilizer N in wheat production. A values were not significantly correlated with added N interaction (r=0.719). The observed added N interaction may have been the result of pool substitution, whereby added labelled fertilizer N stood proxy for unlabelled soil N.     

复种饲料油菜对麦茬耕层土壤酶活性的影响

采用大田试验方法,研究了不同种植密度与施氮量条件下,复种饲料油菜对麦茬耕层(0~15 cm)土壤酶活性的影响。结果表明,麦收后复种饲料油菜能显著或极显著地提高土壤过氧化氢酶(CAT)、酸性磷酸酶(APHA)、纤维素酶(CEL)和脲酶(URA)的活性,与休闲熟化地(CK)比较,最大提高幅度分别为32.15%,35.61%,78.66%和127.36%。土壤酶活性的变化与复种饲料油菜的播种量和施氮量有关,随播种量的增加土壤CAT、CEL和URA活性表现为逐渐递增态势,而土壤APHA表现为先增后减,播种量为11.5 kg/hm2时,APHA活性可达0.7888mg/g。在油菜生长的苗期,土壤APHA、CEL和URA随施氮量的增加而增加,土壤CAT则随施氮量的增加先增后降,呈单峰曲线;在生长后期(收获期),低氮量有利于土壤APHA活性的增加,中氮量有利于土壤CAT和CEL活性的增加,高氮量有利于URA活性的增加。