Stratified distribution of Fusarium and Bipolaris on wheat and barley with dryland root rot in South Australia

Dryland root rot of wheat and barley in South Australia is a syndrome from which the associated fungi Fusarium equiseti, F. acuminatum, F. oxysporum and Bipolaris sorokiniana were isolated consistently. Fusarium infections were concentrated on the subcrown internodes, crown roots and culm bases, and occurred with equal frequency on wheat and barley. Bipolaris infections were more numerous on barley than on wheat, and were concentrated on culm bases and subcrown internodes. Recoveries of each of the four fungi showed a pattern of infection that was neither randomly nor evenly distributed. Each fungus had preferences for certain sites which resulted in a stratified distribution over the roots and crown. When two barley cultivars were compared, the patterns of infection were different; the subcrown internode was attacked more severely, and there was a substantial increase in the amount of infection by all four fungi on one of the cultivars. Pathogenicity tests on barley and oats showed that all four species of fungi were capable of causing damage to roots, but there were differences between isolates of each fungus and differences in their ability to damage barley and oats.     

A comparative assessment of potential components of partial disease resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight using a detached leaf assay of wheat,barley and oats

The relative resistance of 15 winter barley, three winter wheat and three winter oat cultivars on the UK recommended list 2003 and two spring wheat cultivars on the Irish 2003 recommended list were evaluated using Microdochium nivale in detached leaf assays to further understand components of partial disease resistance (PDR) and Fusarium head blight (FHB) resistance across cereal species. Barley cultivars showed incubation periods comparable to, and latent periods longer than the most FHB resistant Irish and UK wheat cultivars evaluated. In addition, lesions on barley differed from those on wheat as they were not visibly chlorotic when placed over a light box until sporulation occurred, in contrast to wheat cultivars where chlorosis of the infected area occurred when lesions first developed. The pattern of delayed chlorosis of the infected leaf tissue and longer latent periods indicate that resistances are expressed in barley after the incubation period is observed, and that these temporarily arrest the development of mycelium and sporulation. Incubation periods were longer for oats compared to barley or wheat cultivars. However, oat cultivars differed from both wheat and barley in that mycelial growth was observed before obvious tissue damage was detected under macroscopic examination, indicating tolerance of infection rather than inhibition of pathogen development, and morphology of sporodochia differed, appearing less well developed and being much less abundant. Longer latent periods have previously been related to greater FHB resistance in wheat. The present results suggest the longer latent periods of barley and oat cultivars, than wheat, are likely to play a role in overall FHB resistance if under the same genetic control as PDR components expressed in the head. However the limited range of incubation and latent periods observed within barley and oat cultivars evaluated was in contrast with wheat where incubation and latent periods were shorter and more variable among genotypes. The significance of the various combinations of PDR components detected in the detached leaf assay as components of FHB resistance in each crop requires further investigation, particularly with regard to the apparent tolerance of infection in oats and necrosis in barley, after the incubation period is observed, associated with retardation of mycelial growth and sporulation.     

A comparison of controlled environment and field trials for detection of resistance in cereal cultivars to root rot caused by Rhizoctonia solani

A screening test was developed to study the effect of different quantities of inoculum of Rhizoctonia solani on root rot and growth of cultivars of wheat, barley, oats, rye and triticale in a controlled environment and the field in two seasons. The ranking of relative susceptibility to disease of cultivars within a cereal differed between the controlled environment and field experiments, and between seasons in the field. The ranking of relative susceptibility between cereals also differed between experiments. In the controlled-environment experiment, wheat had the highest disease rating, followed by oats, barley, triticale and rye, but in the field barley had the highest rating followed by wheat and then oats. The overall differences between the cereals were small.     

Influence of soil moisture on the competitive ability and seed dormancy of Sinapis arvensis in spring wheat

Two experiments were carried out, one in 1995 and one in 1997, to investigate the competitive abilities of two spring wheat cultivars with Sinapis arvensis L. The spring wheat cultivars (Baldus and Canon) of contrasting growth habit were grown with and without S. arvensis under two different moisture regimes (10% and 70% of field capacity). In 1995, S. arvensis was found to be less competitive when subjected to moisture stress, resulting in smaller wheat yield losses in dry soil than in moist soil. In both years, seed production of S. arvensis was reduced by competition and moisture stress, and the seeds produced by plants that had been grown in drier soil were small and had negligible dormancy. Hence, in dry conditions, the competitiveness of S. arvensis and its potential to produce persistent seed may be reduced. Some differences between the two wheat cultivars were evident: cv. Baldus was more competitive against S. arvensis than cv. Canon. This could be attributed to differences in canopy structure.     

小麦禾谷胞囊线虫致病型研究

 玉米弯抱霉叶斑病菌(Cuvrularia luanat(walk) Bode),近年来在河南对玉米的为害日趋严重,常导致叶片枯焦。     

Studies on the Australian Pathotype of Heterodera avenae1

Australian studies on populations of Heterodera avenae have been conducted in Victoria, Western Australia. South Australia, and New South Wales. Only one pathotype has been identified so far, and it is distinct from those recorded elsewhere. Few recognised sources of resistance in barley and oats are useable in Australian breeding programmes. The first commercially acceptable cultivars of wheat, barley, and oats resistant to cereal cyst nematode will be released in Victoria within the next year or two. Their resistances are derived from spring wheat(AUS 10894), Marocaine 079 (CI 8334), and Arena sterilis (Cc 4658) respectively.     

Effect of invasion by cereal cyst nematode (Heterodera avenue) on the growth and development of the seminal roots of oats and barley

The effect of juvenile cereal cyst nematodes (Heterodera avenae) on the root growth of oat and barley seedlings was tested in three pot experiments. Invasion by juveniles hindered the extension of the seminal root axes of both cereals; after invasion, axes took 2–3 days to attain normal rates of extension. This response was found in susceptible and resistant cultivars. When oats and barley were exposed to continued invasion over 9 days, barley produced a larger root system than oats and was less stunted by nematode invasion. The density of nematodes per unit of root was less in barley than in oats. The effects on root growth were similar to reported responses of roots to mechanical damage.     

Effects of winter wheat cultivars and seed rate on the biological characteristics of naturally occurring weed flora

Summary Differential competitive ability of six winter wheat cultivars and traits that confer such attributes were investigated for a range of seed rates in the presence or absence of weeds for a naturally occurring weed flora in two successive years in split-plot field experiments. Crop height and tillering capacity were considered suitable attributes for weed suppression, although competitiveness is a relative rather than an absolute characteristic. Maris Huntsman and Maris Widgeon were the most competitive cultivars whereas Fresco was the least competitive. Manipulation of seed rate was a more reliable factor than cultivar selection for enhancement of weed suppression, although competitiveness of cultivars Buster, Riband and Maris Widgeon was not enhanced by increased seed rate. Crop densities ranging between 125 and 270 plants m⁻² were found to offer adequate weed suppression. Linear relationships were observed between individual and total weed species dry weight and reproductive structures per unit area.     

A review of the potential for competitive cereal cultivars as a tool in integrated weed management

Competitive crop cultivars offer a potentially cheap option to include in integrated weed management strategies (IWM). Although cultivars with high competitive potential have been identified amongst cereal crops, competitiveness has not traditionally been considered a priority for breeding or farmer cultivar choice. The challenge of managing herbicide‐resistant weed populations has, however, renewed interest in cultural weed control options, including competitive cultivars. We evaluated the current understanding of the traits that explain variability in competitive ability between cultivars, the relationship between suppression of weed neighbours and tolerance of their presence and the existence of trade‐offs between competitive ability and yield in weed‐free scenarios. A large number of relationships between competitive ability and plant traits have been reported in the literature, including plant height, speed of development, canopy architecture and partitioning of resources. There is uncertainty over the relationship between suppressive ability and tolerance, although tolerance is a less stable trait over seasons and locations. To realise the potential of competitive crop cultivars as a tool in IWM, a quick and simple‐to‐use protocol for assessing the competitive potential of new cultivars is required; it is likely that this will not be based on a single trait, but will need to capture the combined effect of multiple traits. A way needs to be found to make this information accessible to farmers, so that competitive cultivars can be better integrated into their weed control programmes.     

Susceptibility of winter and summer crops to root and crown infection by Bipolaris sorokiniana

The susceptibility of 24 winter and 17 summer crops to infection by Bipolaris sorokiniana was tested in a glasshouse experiment by growing them in soil amended with wheat-barley grain colonized by B. sorokiniana (0.2 g per 100 g soil). At anthesis, infection of both lesioned and randomly selected segments of roots and of crowns was determined by plating them on modified Czapek-Dox Agar. Incidence of infection in winter crops was higher than in summer crops. Guar, mung bean, soybean and sunflower were the least infected of the summer crops while chickpeas and safflower were the least infected of the winter crops. Amongst the taxonomic groups tested, the highest incidence of infection occurred in the gramineous species and the lowest in the leguminous species.
Five summer crops growing in the field were sampled and infection by B. sorokiniana confirmed. Cultivars of wheat, barley, triticale and oats were also screened in a field experiment. Amongst these winter cereals, oats was the least susceptible in both field and glasshouse experiments. Differences between cultivars in susceptibility to common root rot, measured by the degree of lesion development in the subcrown internode, were identified in wheat, triticale and oats but not in barley.     

Behaviour of alkyl oleates following foliar application in relation to their influence on the penetration of phenmedipham and quizalofop-P-ethyl

The foliar penetration of four alkyl oleates (methyl to butyl) and their influence on the penetration of phenmedipham and quizalofop-P-ethyl was studied in barley ( Hordeum vulgare L.), cleavers ( Galium aparine L.) and pea ( Pisum sativum L.). Loss of alkyl oleates from glass and plant surfaces was inversely related to the length of the alkyl chains and was assumed to be due to volatilization. All four alkyl oleates after application alone, readily penetrated into pea and barley leaves but much less into G. aparine . Penetration of methyl oleate appeared to be faster than that of butyl oleate. Both alkyl oleates were completely metabolized in barley and pea in 27 h, but not in G. aparine . The penetration of herbicides was from 2% to 10% in the absence of alkyl oleates. The penetration of phenmedipham was increased in the presence of all four aikyl oleates: to the greatest extent into pea (55-80% after 27 h), to the lowest into G. aparine (20-45%). In all three species, the effect of butyl oleate was higher than that of methyl oleate. The penetration of quizalofop-P-ethyl was increased to 10%, 30-35% and 50% on G. aparine , pea and barley respectively. The length of the alkyl chains did not influence the effects of the alkyl oleates on the foliar penetration of quizalofop-P-ethyl.     

Mapping rhizoctonia patch in consecutive cereal crops in Western Australia

Rhizoctonia patches in a field were mapped during consecutive seasons of cropping with wheat, oats or barley sown directly without tillage into the previous season's stubble. Distribution, size, shape and number of patches varied considerably between seasons. Less than a quarter of patches were circular and the others tended to be elongated parallel to seed-rows. Barley was most severely affected, followed by wheat and then oats.
It is proposed that changes in patch distribution, configuration and number between seasons is due to shifts in a balance of suppressive or conducive soil factors interacting with Rhizoctonia solani inoculum.     

Losses in grain yield of winter crops from Lolium rigidum competition depend on crop species, cultivar and season

The competitive abilities of eight winter crops were compared against Lolium rigidum Gaud, (annual ryegrass), an important weed of southern Australia, as a potential strategy to suppress weeds and reduce dependence on herbicides. Two cultivars of each species were chosen to represent the range of competitive ability within each crop and grown in field experiments in 1992 and 1993. The order of decreasing competitive ability (with the ranges of percentage yield reduction from L. rigidum at 300 plants m^?2 in parenthesis) was as follows: oats (Avena sativa L.), 2–14%; cereal rye (Secale cereale L.), 14–20%; and triticale (×Triticosecale), 5–24%; followed by oilseed rape, (Brassica napus L.), 9–30%; spring wheat (Triticum aestivum L.), 22–40%; spring barley (Hordeum vulgare L.), 10–55%; and, lastly, field pea (Pisum sativum L.), 100%, and lupin (Lupinus angustifolius L.), 100%. Differences in competitive ability of cultivars within each species were identified, but competition was strongly influenced by seasonal conditions. Competition for nutrients (N, P and K) and light was demonstrated. L. rigidum dry matter and seed production were negatively correlated with grain yield of the weedy crops. More competitive crops offer the potential to suppress grass weeds while maintaining acceptable grain yields. Ways of improving the competitive abilities of grain legume crops are discussed.     

江苏省镇江市麦田杂草发生情况调查

为了摸清江苏省镇江市麦田杂草种类、分布状况、出草规律、草相变化、防除情况等,通过倒"W"形九点取样法对镇江市麦田杂草进行了调查。调查结果显示镇江市麦田杂草有29科99种,日本看麦娘、菵草、猪殃殃、看麦娘、稻槎菜、硬草、繁缕、大巢菜、荠菜、涩荠、野老鹳草、牛繁缕、早熟禾为该地区主要危害性杂草,其中菵草、日本看麦娘、猪殃殃为麦田杂草群落优势种。不同地形区域杂草种类和优势种不同。镇江市麦田杂草由20世纪90年代初以看麦娘、日本看麦娘和猪殃殃等为主演变为以菵草、日本看麦娘、猪殃殃为主,稻槎菜、硬草、繁缕等发生较重。出草高峰集中在小麦播后15 d左右,具体到镇江来说11月底至12月上旬为杂草发生高峰期。针对镇江本地杂草发生情况,制定了以土壤封闭和茎叶处理相结合的防控技术方案。     

UNTERSUCHUNGEN ZUR KONKURRENZWIRKUNG VON KULTURPFLANZEN UND UNKRAUTERN AUFEINANDER

Summary. Pot experiments on the competitive effects of charlock (Sinapis arvensis L.) on oats and wild oat (Avena fatua L.) on barley had the following results:
(1) During the period up to tillering there was an appreciable effect of the weeds on crop growth with depression in plant weight of 10–15% from that in the absence of weeds.
(2) The greatest competitive effect occurred up to the middle of shooting of the cereals, when there were depressions in plant weight of 25–32%.
(3) After this stage, the competitive effects of the weeds were much less in pots with a high nutrient level, and at low nutrient level there was almost no competitive effect.
(4) The reduction in growth at the time of weeding was somewhat less at the low nutrient level than at the high nutrient level, and it is concluded that at the high level the competitive ability of the weeds was favoured more than that of the cereal crops.
(5) The cereals were not able to overcome the initial damage caused by the weeds even when the weeds were removed at the beginning of tillering. A partial recovery did how ever occur at the high but not at the low nutrient level.
(6) Both combinations, oats with charlock and barley with wild oat, behaved similarly, but some differences could be observed.
Compétition entre plantes cultivées et mauvaises herbes II. Action des mauvaises herbes annuelles sur les céréales     

Population Dynamics and Control of Heterodera avenae -A Review with some Original Results1

Control of Heterodera avenae should largely aim to keep densities below tolerance limits at sowing-time (in spring oats < 1 egg/g soil, in susceptible barley < 3 eggs/g soil; spring wheat is only slightly less sensitive than oats, autumn-sown cereals are more tolerant than spring-sown ones). To obtain this, knowledge of population dynamics is important. Essential items in population dynamics are the host properties of different plants (characterized by two factors which do not always covary: maximum rate of multiplication and equilibrium density of the nematode), population decline of the nematode under fallow and non-hosts and the external factors influencing these characteristics. For cereals the following host efficiency order is found: winter oats (best), spring oats, spring wheat, spring barley, winter wheat, rye. Winter barley may be close to spring barley, and maize is a bad host. Grasses are generally less good hosts than cereals and usually cause high and moderate densities of H. avenae to decline. However, especially in first-year leys, rather high equilibrium densities may sometimes be maintained. Host properties of plants vary between sites and years and also relations between hosts may change. Populations decline under fallow, non-hosts and resistant cereals, usually in the order of 70–85 96 annually. H. avenae populations are favoured by lighter soils and heavier soils with a proper structure and also by good plant nutrient conditions. Soil moisture in interaction with temperature influences population dynamics in a complex way, in which natural enemies of the nematodes may also be involved, not least certain fungi. In many fields these may keep nematode populations at harmless levels. Traditional control measures like proper crop rotations can only be used to a limited extent. The most promising approach for controlling H. avenae is an appropriate use of resistant cultivars, of which barley cultivars are also tolerant, while oat cultivars are usually very sensitive. Biological control has hitherto not been used actively. Chemical control is profitable in Australia but not under European conditions. Farmers should check the need for control through soil sample investigations or by other means.     

小麦叶内杀菌剂含量对条锈病组分的定量影响

来源于澳大利亚的２５份麦类作物抗笥材料及中国８个省市的２２个小麦品种对禾谷胞囊线虫太谷群体的抗病性测定表明,６个由硬粒小麦的品种“Ｌａｎｇｄｏｎ”与节节麦的抗性材料为亲本合成的异源六倍体小麦均表现高抗;一些含有抗病基因Ｃｃｎ－１的品种,如Ｆｅｓｔｉｇｕａｙ和Ａｕｓ１０８９４等表现感病;其它来源于澳大利亚的６份燕麦及５份大麦材料也均高抗。     

Responses of cucumber cultivars to induction of systemic resistance against anthracnose by plant growth promoting fungi

Initial experiment on the reactions of five Japanese cultivars of cucumber toColletotrichum orbiculare infection in the greenhouse revealed that cv Suyo and Gibai were susceptible and moderately susceptible, respectively, while cv Shogoin fushinari and Sagami hanjiro were resistant to infection byC. orbiculare; cv Ochiai fushinari was moderately resistant. The ability of 16 plant growth promoting fungi (some isolates belonged to species ofPhoma and some non-sporulating isolates) isolated from zoysiagrass rhizospheres to induce systemic resistance in the above five cucumber cultivars was tested by growing plants in potting medium infested with barley grain inocula of PGPF in the greenhouse. The second true leaves of 21-day-old plants were challenge inoculated withC. orbiculare and disease assessed. Nine, out of 16 isolates, caused significant reduction of disease caused byC. orbiculare in at least two cultivars.Phoma isolates (GS8-1 and GS8-2) and non-sporulating isolates (GU21-2, GU23-3, and GU24-3) significantly reduced the disease in all the five cultivars. The disease suppression in cucumber was due to the induction of systemic resistance, since the inducer(s) and the pathogen were separated spatially and that the inducer did not colonize aerial portions. The resistance induced by certain isolates in a susceptible cultivar was less than that in a resistant cultivar. Disease suppression caused by isolate GU21-2 was similar to theC. orbiculare induced control in certain cultivars. The average rate of expansion of lesion diameter on leaves due toC. orbiculare was slower due to induction with the selected plant growth promoting fungi compared to the uninduced control plants. Roots of four cultivars were colonized by only three isolates, however, roots of one cultivar (Suyo) was colonized by five isolates suggesting the cultivar-specific root colonization ability.Abbreviations cv cultivar(s) - PGPF plant growth promoting fungal isolates - PGPR plant growth promoting rhizobacteria     

A second survey of cereal weeds in central southern England

A survey of grass weeds of cereals in central southern England made in 1981 was repeated in 1982 between 28 June and 23 July. Dicotyledonous weeds were also assessed in 1982. A total of 1021 fields were surveyed, 702 in winter wheat. 198 in winter barley and 121 in spring barley. A total of twenty-four grass weeds were found and their levels of infestation were scored. The most frequently found grass weeds were the same as in 1981. In all cereals combined, these were Elymus (Agropyron) repens in 35% of fields, Avena fatua in 32%, Alopecurus myosuroides in 26% and Poa trivialis in 24%. Sixty-three species of dicotyledonous weeds were recorded and of these, eighteen species occurred in 2% or more of fields. The eight most frequent were Viola arvensis, Galium aparine, Stellaria media, Myosotis arvensis, Polygonum aviculare, Convolvulus arvensis, Bilderdykia (Polygonum) convolvulus and Lamium purpureum. Most species were fairly uniform in distribution, but Galium aparine, Convolvulus arvensis and Cirsium arvense were most frequent in the east while Viola arvensis was least frequent there. The cereals varied in weediness, 32% of winter barley, 23% of spring barley and only 7% of winter wheat fields had no weeds recorded.