黑龙江省大豆灰斑病生理小种监测及主栽品种抗性分析

为明确黑龙江省不同地区大豆灰斑病菌生理小种出现频率及类型,采用自行筛选的鉴别寄主对采自17个不同大豆产区的30份灰斑病菌进行生理小种监测鉴定.已鉴定出7个生理小种(1号、4号、6号、7号、8号、9号、11号)和4个未知生理小种.结果表明:1号生理小种仍是优势小种,出现频率为39%,较2006年下降了9%;其次是7号生理小种,出现频率为28%,较2006年上升了7%.对黑龙江省56份主栽品种进行抗病性鉴定,鉴定出高抗品种4个,垦丰16号、垦丰18号、绥农22号、绥农25号,抗病品种14个.     

Evaluation of fungicides to control circular leaf spot of persimmon caused by Mycosphaerella nawae

The efficacy of ten fungicides against Mycosphaerella nawae, the causal agent of circular leaf spot (CLS) of persimmon, was evaluated in vitro and in field experiments. Field trials were conducted in 2009 and 2010 to investigate the comparative efficacy of the fungicides alone or combined using alternating sequences in spray programmes based on two, three or four applications. Disease incidence was assessed by estimating the percentage of affected leaves, which included leaves showing at least one necrotic spot and defoliation. Fenpropimorph, pyraclostrobin, tebuconazole and thiophanate-methyl were the most effective fungicides in inhibiting mycelial growth of M. nawae isolates (EC₅₀ < 2 ppm). In field experiments, the most effective fungicides using two spray applications were captan, chlorothalonil, mancozeb and pyraclostrobin which significantly reduced disease incidence compared with untreated plots. Regarding the number of spray applications, two applications of captan and mancozeb were less efficient than three to control the disease. However, the percentage of affected leaves provided by three applications of captan and mancozeb alone or combined with pyraclostrobin using alternating sequences in spray programmes, was not significantly different from that provided by four applications. Experimental results demonstrated that spray programmes based on three applications of these fungicides could effectively control CLS of persimmon. The advantages of spray programmes based on alternated use of strobilurins and protective fungicides are discussed.     

New host resistances to Pseudocercosporella capsellae and implications for white leaf spot management in Brassicaceae crops

Effective host resistance is the most cost-effective long term prospect for successful management of white leaf spot disease (Pseudocercosporella capsellae) in Brassicaceae. In two separate field trials, 168 genotypes were screened. In the first trial, lines of Brassica oleracea var. capitata (59), Brassica napus (34), Brassica juncea (6) and B. juncea containing wild weedy Brassicaceae introgression(s) (14) were arranged; and in the second, Australian historic and current B. napus (45) and B. juncea (10) varieties were screened. There was wide variation in expression of resistance, from complete resistance to highly susceptible as assessed by two disease parameters, viz. (i), Area Under Disease Progress Curve (AUDPC) for percent leaves diseased (values 0–221.2) and (ii) Percent Leaf Collapse Index (%LCI) values for leaf collapse due to disease (0–38.7). Brassica oleracea var. capitata was overall the most resistant species, while B. juncea the most susceptible with the majority having AUDPC values >75 and B. napus was intermediate. Five B. oleracea var. capitata genotypes were completely resistant, with 0 AUDPC and %LCI values. Pioneer^® 45Y22 (RR) ‘Mystic’ and ‘Wahoo’ were also highly resistant, with the least %LCI (<3.7) and AUDPC (<20) of the Australian B. napus varieties. In contrast, ‘Thunder TT’ (AUDPC -133.6; %CLI – 15.6) and ‘Carbine’ (AUDPC – 73.8; %CLI – 12.5) were the most susceptible lines in first and second trials, respectively. The particularly high susceptibility of newly released B. juncea varieties such as ‘Xceed OasisCL’ highlights the risk of significant losses in such susceptible varieties when deployed in areas with high degree of pressure for white leaf spot disease. There was no association between AUDPC or % CLI with year of Australian varietal release, indicating that Australian breeding programs not made improvement for resistance to white leaf spot over the past two or more decades. Resistant varieties identified in this experiment can now not only be utilized in breeding programs to significantly improve overall crop resistance and management of white leaf spot disease, but also directly deployed to lower the severe inoculum load challenging current varieties.     

Combining ability analysis for Phaeosphaeria leaf spot resistance and grain yield in tropical advanced maize inbred lines

Phaeosphaeria leaf spot (PLS) disease (causal agent Phaeosphaeria maydis (Henn.) Rane, Payak & Renfro) of maize is increasing in importance in sub-Saharan Africa (SSA). However, there is still limited information on the combining ability for disease resistance of the germplasm that are adapted to African environments. Evaluating combining ability effects and their interactions with the environment would provide valuable information that can be used in the development of cultivars that are resistant to PLS. This study was therefore conducted to determine the combining ability, gene action and the relationship between grain yield and PLS disease severity among selected tropical advanced maize inbred lines. Forty five F₁ hybrids were generated by crossing 10 inbred lines in a half diallel mating scheme. The 45 hybrids along with the ten inbred parents were evaluated in four environments, with two replications each between 2007 and 2009. General and specific combining ability (GCA and SCA) effects were highly significant (P ≤ 0.001) for PLS, grain yield and days to anthesis. GCA effects accounted for 66–90% and SCA effects for 10–34% of the variation in the hybrids for PLS resistance, grain yield and days to anthesis. This indicated predominance of additive over non-additive gene action for the three traits in these inbred lines. The resistant inbred lines to PLS were A1220-4, N3-2-3-3, CML312, MP18 and CML488. These lines had good combining ability for PLS resistance and contributed towards resistance in their crosses. In general, resistant hybrids involved a susceptible and a resistant parent, where at least one of the parents had a negative GCA effect. In addition, lines A1220-4 and CML312 contributed towards high yield and were late maturing. Inbred line CZL00009 conferred genes for early maturity. Linear regression analysis indicated that grain yield of maize was suppressed by about 250 kg ha⁻¹ per each increase in PLS disease severity score, underscoring the need to control the disease. Significant (P < 0.01), negative correlations (r = −0.29 to −0.43) between grain yield and PLS severity were also detected. This showed the potential of PLS to reduce yield when favourable conditions for disease development are present. By and large, highly significant additive gene action implied that progress would be made through selection. Although non-additive effects were small (±10%), observation of dominance effects which were associated with reduced disease levels in some hybrids may be exploited in developing single cross maize hybrids among these inbreds when one parent is resistant.     

Assessing yield losses caused by the harvester ant Messor barbarus (L.) in winter cereals

Harvester ants from the species Messor barbarus (L.) are important seed predators in semi-arid cereal fields of NE Spain, and can contribute substantially to weed control. However, occasionally they harvest newly sown crop seeds at sowing in autumn, or ripe cereal grains close to harvest in summer, causing yield losses.A preliminary study was conducted in 34 commercial winter cereal fields to measure yield loss, and to identify factors that influence it. The area affected by ants was measured ten days prior to the anticipated harvest date. Ant colony size, nest density, crop height, weed densities and temperatures at sowing were assessed.At sowing, harvester ants did not cause yield losses (0.2% of potential yield on average). At harvest, yield losses were generally low as well (0.6%) although occasionally higher losses were recorded (max. 9.2%). Yield losses significantly increased with increasing nest density, nest size and with number of years of no-till. The results of this study show that in 2009 yield losses caused by M. barbarus were insignificant and more than offset by the benefits provided by the destruction of weed seeds.     

Yield and quality losses caused by common rust (Puccinia sorghi Schw.) in sweet corn (Zea mays) hybrids

Yield and quality of fresh ears were measured in field plots of selected hybrids of sweet corn (Zea mays L.) that were affected by rust (Puccinia sorghi Schw.) or were nearly rust-free (mancozeb-sprayed). In 1978, 28 hybrids were tested. Losses in total yield ranged from zero in the more resistant entries to nearly 50% in more susceptible entries. In 1979, three cultivars were planted. Yield losses of these cultivars were similar in ranking order to those in 1978, although the loss was greater in late-planted plots because of the greater final severity of the disease. Losses in total yield in late-planted sweet corn were 18%, 26% and 49% for cv. Sugarloaf (most resistant), cv. Jubilee (intermediate) and cv. Style Pak (most susceptible), respectively.     

Long lasting rubber tree resistance to Microcyclus ulei characterized by reduced conidial emission and absence of teleomorph

The resistance of the MDF 180 Hevea brasiliensis cultivar to South American leaf blight caused by Microcyclus ulei has been studied under both controlled conditions of inoculation, and under natural infestation in the Brazilian state of Bahia. Inoculated isolates on this cultivar in most cases developed sporulating lesions and produced conidiospores, but at a moderate level, characteristic of a race non-specific, partial resistance. The teleomorph of M. ulei has never been reported on this cultivar, either in controlled conditions or in natural infestation, whereas it is commonly observed on other susceptible cultivars. This type of resistance has seldom been described for other pathosystems. MDF 180 resistance having also endured for more than 30 years in areas very conducive to the disease can, therefore, be described as a durable resistance. Rubber productivity of this cultivar is not sufficient to allow planting on industrial scale, but its resistance characteristics make it a good progenitor candidate for rubber tree resistance breeding programs.     

Yield potential and water use efficiency of aerobic rice (Oryza sativa L.) in Japan

Intensive rice farming in aerobic soil, referred to herein as aerobic rice, can greatly reduce the water input compared to that of flooded rice cultivation. The objective of this study was to compare the potential productivity of aerobic rice and flooded rice using high-yielding varieties at two locations in Japan in two successive years. In aerobic fields, the total amount of water supplied (irrigation plus rainfall) was 800–1300 mm. The soil water potential at 20-cm depth averaged between −15 and −30 kPa each growing season, but frequently reached −60 kPa. The average yield under aerobic conditions was similar to or even higher than that achieved with flooded conditions (7.9 t ha⁻¹ in 2007 and 9.4 t ha⁻¹ in 2008 for aerobic versus 8.2 t ha⁻¹ for flooded). The average water productivity under aerobic conditions was 0.8–1.0 kg grain m⁻³ water, slightly higher than common values in the literature. The super-high-yielding cultivar Takanari achieved yields greater than 10 t ha⁻¹ with no yield penalty under aerobic conditions in 3 out of 4 experiments. The favorable agronomic characteristic of Takanari was its ample sink capacity (grain number × grain weight). In conclusion, high-productivity rice cultivation in aerobic soil is a promising technology for water conservation. With continued breeding, future aerobic rice varieties will possess large numbers of spikelets and sufficient adaptation to aerobic conditions such that they will consistently achieve yields comparable to the potential yield of flooded rice.     

Assessment of avoidable losses and economic injury levels for the sorghum head bug, Calocoris angustatus Leth. (Hemiptera:Miridae) in India

Avoidable losses and economic injury levels (EILs) were computed for the sorghum head bug, Calocoris angustatus Leth., on three cultivars during three rainy seasons (1985–1987) at ICRISAT. Grain yield in plots protected with 2–5 insecticide sprays (carbaryl at 500 g a.i./ha) between the half-anthesis and the dough stage was significantly higher than in untreated plots, with cost-benefit ratios > 1. Plots that were not protected at half-anthesis and/or complete-anthesis, and at milk and dough stages, suffered a significant loss in yield. Bug damage spoiled the grain quality in terms of germination, 1000-grain mass, grain hardness and percentage floaters. Three to four sprays between complete-anthesis and the dough stage prevented a significant reduction in grain quality. Head bug density at half-anthesis, complete-anthesis, milk and dough stages was significantly and negatively associated with grain yield. Bug density at different stages explained 43–94% of the variance in yield. Direct effects of bug numbers at the milk stage and the indirect effects of head bug density at other stages through the milk stage contributed towards maximum reduction in yield. Maximum avoidable losses were recorded in cultivar ICSV 1 (88·6%), followed by CSH 1 (69·9%), and CSH 5 (53·9% in 1986 and 55·0% in 1987). Loss in grain yield/ha due to one insect/panicle at half-anthesis and that based on natural increase, were 548 and 232 kg in CSH 5 during 1986 and 1987, respectively, 251 kg in ICSV 1, and 77 kg in CSH 1. EILs based on a cost-benefit ratio of 1:1 ranged from 1·3–1·4 insects/panicle for CSH 1, 0·4 for ICSV 1, and 0·4–0·6 and 0·2–0·4 for CSH 5 during 1986 and 1987, respectively. Simple cost estimates for insecticide sprays and the resultant saving in grain yield are a useful tool for decision-making in pest management.     

Responses of the alien leaf miners Liriomyza trifolii and Liriomyza huidobrensis (Diptera: Agromyzidae) to some pesticides scheduled for their control in the UK

Baseline responses to a range of pesticides scheduled for the statutory eradication of outbreaks of Liriomyza trifolii, a leaf miner alien to the UK, were established using a topical application bioassay against a susceptible laboratory population. Using the same technique the responses of outbreak populations of L. trifolii, and also the related species L. huidobrensis, have been investigated. Field populations of L. trifolii showed resistance to the pyrethroids tested but no evidence of resistance to organophosphates was found. There was some evidence of resistance to gamma-HCH. L. huidobrensis showed a response to pyrethroids similar to that of resistant L. trifolii, and levels of tolerance to organophosphates approximately eight times that of susceptible L. trifolii. The response to gamma-HCH was similar to that of susceptible L. trifolii.     

Yield response of okra, Abelmoschus esculentus (L.) Moench to leaf damage by the flea beetle, Podagrica uniforma Jacoby (Coleoptera: Chrysomelidae)

Yield-related response of okra plants, Abelmoschus esculentus (L.) Moench, to artificial infestation of the flea beetle (Podagrica uniforma Jac.) at different densities (0, 5, 10, 20, 30, and 40 pairs per cage) was studied in screen house and field experiments. In both experiments, increase in beetle density resulted in a significant reduction (P < 0.05) in fruit production, fruit length, fruit width, fresh fruit weight, number of seeds per fruit, 100 seed weight and fresh fruit yield. In addition, higher densities caused more dry matter accumulation in the seeds than in the husk of okra fruits. Compensation was noticed at the 5- and 10-pair levels of infestation in some of the variables measured. Fresh fruit yield reduction was more than 50% when beetle density was increased beyond 20 pairs per cage in both experiments. The lowest density of P. uniforma at which significant reduction (P < 0.05) occurred in fresh fruit yield per cage, when compared with the control, was the 20-pair level, representing the damage threshold of the beetle at which initiation of control measures would be justified. Regression analysis indicated that flea beetle density was linearly associated with fruit damage and fresh fruit yield. Also, chi-square analysis showed that the models derived from the screen house and field experiments were not significantly different (P < 0.05) from each other, and either could be used for prediction purposes.     

Variations in leaf mass per area according to N nutrition, plant age, and leaf position reflect ontogenetic plasticity in winter oilseed rape (Brassica napus L.)

Leaf mass per area (LMA) is a parameter the variability of which contributes to architectural plasticity. However its variations according to environment remain not completely understood. We hypothesise that LMA variations of winter oilseed rape (WOSR) follow an ontogenetic trajectory that can be modified by the environment. This was assessed at plant and leaf levels comparing four genotypes field-grown under different environmental conditions characterised by year and nitrogen nutrition. Leaves of the main stem of plants sampled between emergence and harvest were surfaced, oven-dried and weighed to calculate LMA of each individual leaf. At the plant level, LMA presented a common ontogenetic trajectory, which increases from seedling emergence to bolting and from then on decreases. Variations in LMA were related to the variations in plant demand, LMA decreased when demand increased. The trajectory was modified by low N nutrition that increased LMA but differently according to year and genotype, reflecting the plant plasticity. At the leaf level, variations for each individual leaf were related to the variations at the plant level. Plant plasticity and genotypic variability of the responses of LMA to N deficiency seemed to be related to differences in biomass allocation between leaves and stems.     

Variation in yield loss of oilseed rape due to grazing by mute swans Cygnus olor

Yield loss due to grazing by mute swans was measured on nine fields of autumn-sown oilseed rape located in five regions of England. Using a paired-plot design, a significant reduction in yield (total dry weight of seed) was observed on three of the fields: 18%, 23% and 24%, respectively. On the first of these fields yield reduction was not simply due to fewer seeds being produced, as the weight of individual seeds was also significantly lower on grazed plots, with a reduction in thousand seed weight of 13%. Between fields (n=9), yield loss was positively correlated with the number of swans per ha, and the number of days of swan grazing per ha. Significant levels of yield loss occurred only on fields grazed by >5 swans per ha. The density of swans grazing per ha can thus be used to predict potentially significant yield loss and provides an indicator of the level of swan grazing activity at which growers should consider deploying measures to reduce grazing.     

Transferring Translucent Endosperm Mutant Gene Wx-mq and Rice Stripe Disease Resistance Gene Stv-b by Marker-Assisted Selection in Rice (Oryza sativa)

A high-yielding japonica rice variety, Wuyunjing 7, bred in Jiangsu Province, China as a female parent was crossed with a Japanese rice variety Kantou 194, which carries a rice stripe disease resistance gene Stv-bⁱ and a translucent endosperm mutant gene Wx-mq. From F₂ generations, a sequence characterized amplified region (SCAR) marker tightly linked with Stv-bⁱ and a cleaved amplified polymorphic sequence (CAPS) marker for Wx-mq were used for marker-assisted selection. Finally, a new japonica rice line, Ning 9108, with excellent agronomic traits was obtained by multi-generational selection on stripe disease resistance and endosperm appearance. The utilization of the markers from genes related to rice quality and disease resistance was helpful not only for establishing a marker-assisted selection system of high-quality and disease resistance for rice but also for providing important intermediate materials and rapid selection method for good quality, disease resistance and high yield in rice breeding.     

Control of invasive Liriomyza leafminer species and compliance with food safety standards by small scale snow pea farmers in Kenya

The Kenyan horticultural industry faces a new challenge following invasion by the quarantine Liriomyza leafminer species Liriomyza huidobrensis, Liriomyza sativae and Liriomyza trifolii which have recently become pests of economic importance. Controlling Liriomyza leafminers poses serious difficulties due to their biology and quarantine status. This paper examines farmers’ awareness of the pests and difficulties faced in controlling them. (1) A questionnaire survey showed that snow pea farmers in Kenya rely mainly on pesticides for control of invasive Liriomyza leafminers; (2) Sixty five percent of respondents perceived pesticides to be ineffective; (3) As a result, 74% of respondents increased the frequency of pesticide applications, 61% increased dose rates and 58% used broad-spectrum insecticides to avert damage by the pests; (4) Snow pea farmers who signed contracts with exporters and whose production practices were monitored for compliance with Good Agricultural Practices (GlobalGAP) used fewer control strategies; (5) These findings imply that the pest status of Liriomyza leafminers is likely to increase and snow pea production will significantly decrease in Central areas of Kenya unless an integrated leafminer management strategy is developed and farmers educated on methods of identifying them in their early stages of attack and use appropriate chemicals and application methods.     

Grain weight response to foliar diseases control in wheat (Triticum aestivum L.)

Foliar diseases are the main biotic restriction reducing yield in wheat crops affecting both, grain number and/or grain weight, depending on developmental stage at which infection occurs (pre- or post-anthesis, respectively). Grain weight reductions due to foliar diseases were widely reported in the literature mostly associated with decreases on radiation interception during the grain filling period. However, different evidences in wheat showed variations on grain weight responses when fungicide was applied during the grain filling period, probably associated with the timing of fungicide application or with the amount of available resources per grain set when fungicides are applied. The present study was designed to determine the causes of grain weight reduction due to foliar diseases complex (including leaf rust, Septoria leaf blotch and tan spot) in wheat crops growing under contrasting agronomic and environmental conditions (i.e. different years, locations, cultivars and N supply). The experiments were carried out during 4 years under field conditions in different locations of Argentine and France. Five different commercial wheat cultivars were sown on early and late sowing dates; and two contrasting N availability and two fungicide treatments (protected and unprotected) were applied. Grain number was not affected by foliar diseases as their appeared after anthesis. Grain weight was strongly, poorly or not affected by foliar diseases and was not associated individually with both, the sink size and the source size. However, when the grain weight response due to fungicide application was plotted against the healthy area absorption per grain (HAA_G), a significant negative association (r² = 0.81; p < 0.0001) was found for the Argentine experiments. When the HAA_G was corrected by the grain weight potential (HAA_GW) all experiments conduced in Argentine and in France fit well to a common negative linear regression (r² = 0.74, p < 0.0001) for the relationship between grain weight variation and HAA_GW demonstrating that grain weight potential is an important feature to consider in diseases control programs. Foliar diseases forced the crop to use the accumulated reserved increasing the utilization rate of the water soluble carbohydrates (WSC_UR), depleting as a consequence the water soluble content at physiological maturity (WSC_PM) in all experiments. The association between WSC_UR and the healthy area absorption per grain corrected by grain weight of healthy crops (HAA_GW) suggest that foliar diseases in wheat cause source limitation, forcing to the crop to use the WSC reserve which could be insufficient to fill the grains previously formed.     

Elicitation of resistance and defense related enzymes by raw cow milk and amino acids in pearl millet against downy mildew disease caused by Sclerospora graminicola

Modulation of physiological and biochemical defensive responses against downy mildew (DM) of pearl millet induced by raw cow milk (RCM) and five amino acids is reported in this paper. In vitro conditions, none of the inducer treatments showed inhibitory action on DM pathogen. Significant enhancement of seed germination and seedling vigor was observed in RCM and amino acids treated seeds. Under greenhouse conditions, significant protection against DM was provided by l-phenylalanine (68.6%), l-isoleucine (66.5%) and l-proline (55.7%) treatments. Among the RCM treatments, the 10% dilution proved to be the best by offering disease protection of 35%. Spatio-temporal time gap studies indicated that seed treatment with l-phenylalanine increased disease resistance four days after inoculation. Seed treatments with RCM and amino acids also enhanced the vegetative and reproductive growth parameters of pearl millet when compared to the control. A similar trend in protection against DM was evident in the field trials. At the biochemical level, defense related enzymes such as phenylalanine ammonia lyase (PAL), peroxidase (POX) and β-1,3-glucanase showed an increased activity in RCM and amino acids treated seedlings than in sterile distilled water control seedlings. The highest PAL activity was recorded in RCM (10 and 20%) whereas in case of amino acids, the highest activity was observed in l-proline and l-phenylalanine treatments. The highest activity of β-1,3-glucanase was recorded in RCM (20%) and l-phenylalanine.