油菜菌核病病斑扩展的动态模型

油菜菌核病主茎上病斑长度和面积的扩展与时间间的关系极相关,同一植株上、下部病斑扩展动态无明显差异,中、高两种肥力条件对主茎同一部位病斑扩展动态无明显影响,相对较低的湿度与病斑扩展相关不显著．     

“黄鳝籽”油菜植株内含物与菌核病扩展的关系

通过对中、高两种肥力下“黄鳝籽”油菜植株内含物与菌核病扩展间关系的研究,建立了12个数字模型．说明高肥田油菜病斑长、宽和面积与含水量及水溶性糖密切相关;其次是精氨酸、异亮氨酸、亮氨酸和组氨酸;中肥田油菜病斑长、宽和面积与精氨酸、天门冬氨酸密切相关;其次是水溶性糖、水溶性蛋白和硬脂酸．高、中肥田同株主茎上、下部病斑及不同株同一部位病斑扩展动态均无明显差异．     

不同播期对不同基因l型油菜产量特性的影响

研究了3个不同基因型油菜品种的产量与产量构成因素的特征及其与光温条件的生态关系,探讨了长江中游油菜区多熟种植条件下提高油菜单产的可行途径.结果表明,因播种期不同而导致油菜生育期间光温条件的不同,使各播期产量及产量构成因素产生了较大的差异.油菜单株角果数、角果皮指数、主茎产量、分枝产量均与积温和日照时数呈极显著正相关,而千粒重和SNPA与之无关.播种期对油菜产量的影响主要是通过影响分枝产生及其产量形成而实现的.因此多熟制油菜的播种期可适当提早,10月20日以后播种的油菜,其种植密度可增加至3.75×105～4.5×105株·hm-2,以主茎弥补分枝小而少的不足,实现油菜单产的提高.     

稀土积累与油菜菌核病发生的关系研究

在试验生态小区的土壤中 ,模拟长期使用稀土 ,以探讨稀土积累与油菜菌核病发生发展的关系 .结果表明 ,0 .5 %、1%、3%、5 %、7%、10 %吸附容量和 0 6kg·hm-2 的稀土以及土壤中 30kg·hm-2 和 0 6kg·hm-2 的稀土复合肥添加剂对油菜菌核病自然发生的病情指数和病株率影响无显著差异 ;对人工接种发病后的病斑绕茎度、病斑扩展速率、单株平均产量和千粒重的影响也无显著差异     

西藏与周边地区芥菜型油菜农艺性状比较研究

运用典范相关分析方法,对西藏及周边地区芥菜型油菜的产量性状、主茎性状、分枝性状、角果性状等4组性状间的典范相关关系进行了比较研究.结果表明:(1)所研究的18个性状中,西藏芥菜型油菜的平均数为周边地区芥菜型油菜的1.88倍,总体变异系数比周边省份芥菜型油菜高10.22％;(2)西藏芥菜型油菜单株产量主要取决于每株角果数和千粒重,而周边省份芥菜型油菜单株产量主要取决于每株有效角果数,中国周边国家芥菜型油菜单株产量主要取决于每株有效角果数和千粒重;(3)影响西藏芥菜型油菜产量性状最重要的因素是角果性状,其次是分枝性状和主茎性状,而影响周边省份和中国周边国家芥菜型油菜产量性状最重要的因素则是主茎性状,其次是分枝性状和角果性状.     

不同播期对不同基因型油菜产量特性的影响

研究了 3个不同基因型油菜品种的产量与产量构成因素的特征及其与光温条件的生态关系 ,探讨了长江中游油菜区多熟种植条件下提高油菜单产的可行途径 .结果表明 ,因播种期不同而导致油菜生育期间光温条件的不同 ,使各播期产量及产量构成因素产生了较大的差异 .油菜单株角果数、角果皮指数、主茎产量、分枝产量均与积温和日照时数呈极显著正相关 ,而千粒重和SNPA与之无关 .播种期对油菜产量的影响主要是通过影响分枝产生及其产量形成而实现的 .因此多熟制油菜的播种期可适当提早 ,10月 2 0日以后播种的油菜 ,其种植密度可增加至 3 75× 10 5～ 4 5× 10 5株·hm-2 ,以主茎弥补分枝小而少的不足 ,实现油菜单产的提高 .     

西藏和周边地区芥菜型油菜农艺性状比较研究

利用113份芥菜型油菜,运用典范相关分析方法,对西藏及周边地区芥菜型油菜的产量性状、主茎性状、分枝性状、角果性状等4组性状间的典范相关关系进行了比较研究。结果表明：(1)所研究的18个性状中,西藏芥菜型油菜的均值为周边地区芥菜型油菜的1.88倍,总体变异系数比周边省份芥菜型油菜高10.22%;(2)西藏芥菜型油菜单株产量主要取决于每株角果数和千粒重,而周边省份芥菜型油菜单株产量主要取决于每株有效角果数,中国周边国家芥菜型油菜单株产量主要取决于每株有效角果数、千粒重;(3)影响西藏芥菜型油菜产量性状最重要的因素是角果性状,其次是分枝性状和主茎性状,而影响周边省份和中国周边国家芥菜型油菜产量性状最重要的因素则是主茎性状,其次是分枝性状和角果性状;(4)西藏芥菜型油菜4组性状间极显著或显著相关的典型变量累计有9对性状,周边省份芥菜型油菜有8对性状,中国周边国家芥菜型油菜有5对性状,西藏与周边省份和中国周边国家芥菜型油菜生态性状间既有密切联系,亦略不同。     

陆地棉品种抗黄萎病反应规律的研究

对我国自育的108个陆地棉品种的抗黄萎病性进行了研究。在黄萎病发病期内,对黄萎病发病情况进行连续调查,测定产量、考查产量因素并检测纤维品质。利用因子分析法对陆地棉抗黄萎病反应规律进行分析,得出不同时期的黄萎病病指主要与前后3～5个阶段抗病性有关。病情发展主要由4个主因子决定,且第1、2主因子具有较大的方差贡献率。第1主因子(F1)主要与品种7月26日至8月9日的黄萎病病指有关,第2主因子(F2)主要与品种8月20日至9月4日的黄萎病病指有关。利用因子分析结果将108个品种划分为4个类型,前期抗病性较好而后期发病较快的第Ⅰ类品种,其产量较低,单株结铃数、单铃重、衣分均低于其他3类;纤维品质均较差,纤维长度、整齐度、比强度和马克隆值均较其他3类差。前期和后期病指均较低、发病缓慢的第Ⅱ类则小区产量最高,纤维品质处于平均水平。第Ⅲ类品种前期发病较慢,中期发病较快,具有较高的小区产量,单铃重最高;纤维整齐度、比强度和伸长率好于其他3类品种;前期发病较快,中期发病平缓,后期仍具有较高病指的为第Ⅳ类品种,小区产量较低,单株产量、单株结铃数和衣分较高;其他性状处于中等水平。但研究表明,某一阶段具有的抗病性并不能完全代表品种的抗病性。     

茴香薄翅野螟虫口密度与油菜产量损失关系及其防治指标的研究

在网室内人工接茴香薄翅野螟Evergestis extimalis Scopoli卵,研究结果表明,随着幼虫数量的增加,油菜产量损失增加;与对照相比,当接卵数为216、399、858、1665和3279粒时,产量损失分别达3.13%,2.08%,12.5%,25.10%和43.33%。各网室实际接虫数(x)与其相应的小区油菜产量(y)的关系为:y=-0.0007x+4.8129,表明虫口密度与油菜产量为负相关。在青海省油菜种植区内每平米幼虫或卵数超过10头或粒时,应即时防治。     

西藏野生芥菜型油菜构件种群相互关系及其与气候因素的灰色关联度分析

以生物构件理论为基础,运用灰色关联分析技术对西藏野生芥菜型油菜种群构件结构与环境因子的关系进行了研究。结果表明:1)每株角果数、每角果粒数和粒重是产量构成的重要指标,随着每株角果数、每角果粒数和粒重的增大,西藏野生芥菜型油菜的产量明显增加,它们之间的构件因子关联度较大;2)主茎系统是西藏野生芥菜型油菜植株的基础,其间的关联性显示了西藏野生芥菜型油菜植株构件组成的整合作用;3)一级分枝长度、一级分枝角果数、二级分枝数、一级分枝粗度之间有较大的关联度,但与一级分枝发生高度关联度相对较小;4)研究的7个环境因子与西藏野生芥菜型油菜种群的生长关系均较密切,且温度是影响西藏野生芥菜型油菜分布和生命活动相对重要的环境因子,而降水为次要因子。     

Assessment of resurgence of bacterial blight and its effect on cotton yield in northern Nigeria

Abstract

Cotton production in Nigeria causes fluctuating socio-economic and biotic factors. Bacterial blight induced by Xanthomonas campestris pv malvacearum causes the greatest yield loss annually. A study was therefore carried out to investigate the resurgence of the disease on 10 different cotton genotypes in Dowaya, Kem and Ngurore which are the major cotton areas of Adamawa state of Nigeria under field conditions. Other objectives were to determine the relationship between the different manifestations of bacterial blight and the yield of seed cotton and to identify resistance in the selected genotypes to the disease manifestations. Results revealed the presence of angular leaf spot, vein and boll rot manifestations of the disease in the study areas. The absence of vein blight symptoms in the Kem location did not result in higher yield because the severity of the leaf spot for this location was relatively higher than for the other two locations. Results also revealed that despite the high severity of angular leaf spot, high boll rot and vein blight incidences observed particularly on SAMCOT-11, SAMCOT-13 and ex-Benin in these locations with a high yield of seed cotton was recorded. The three multi-adversity resistant genotypes (MAR), TX-CDP37HH-1-83, TAMCOT SP-21S and TAMCOT CAMD-E recorded relatively lower severity and incidences in both cases. There was, however, a significantly negative correlation between angular leaf spot severity, boll rot incidence and yield at Kem location, significant negative correlation between angular leaf spot severity, boll rot incidence, vein blight and yield at Dowaya location, as well as significant negative correlation between angular leaf spot severity, vein blight and yield at Ngurore location. The tolerant and high yielding SAMCOT-11, SAMCOT-13 and ex-Benin should through breeding work be improved to be used for production in this area and its surroundings.     

Genetic Improvement and Crop Management Strategies to Minimize Yield Losses in Warm Non-traditional Wheat Growing Areas due to Spot Blotch Pathogen Cochliobolus sativus

Spot blotch caused by Cochliobolus sativus emerged as a major threat to wheat production in the warmer non-traditional wheat growing areas in the late 1980s. This foliar disease causes significant yield losses annually (15–20% on average in South Asia) endangering the livelihoods of millions of small farmers. Effective measures in the field are needed to mitigate the impact of spot blotch on food security in affected areas. This review summarizes the global knowledge on genetic improvement and crop management strategies to minimize yield losses based on latest field research. Recent studies have shown that spot blotch severity is highly influenced by stress factors affecting crop physiology which in turn affects host tolerance and resistance to the pathogen. Soil nutrient and water stress aggravate spot blotch-induced grain yield losses. Heat stress which is gradually increasing in Asia causes higher levels of disease damage. Genetic improvement is the cornerstone of a sustainable control of spot blotch in all affected regions. Resistance is essentially based on Chinese and South American sources and inter-specific crosses with broadly adapted semi-dwarf germplasm. A list of genotypes consistently reported in the last 10 years to harbor at least partial resistance to spot blotch, along with their inheritance of resistance, has been compiled to help breeding programmes. As the fungus is aggressive under conditions of high relative humidity and heat which in turn influences plant susceptibility, a synthesis of the different tools for scoring disease severity is given. Because resistance is incomplete, the ultimate goal is the accumulation of minor genes of resistance in adapted high yielding genotypes. This paper shows how the use of resistant varieties, timely seeding, adequate fertilization, crop rotation, and the judicious use of fungicides can be part of an integrated management strategy for controlling yield losses due to spot blotch.     

不同时期喷施多效唑对花生生理特性、产量和品质的影响

为确定高产条件下不同花生品种的最佳化控时期,以小花生品种‘花育20’(HY20)和大花生品种‘花育25’(HY25)为试验材料,研究了多效唑(PBZ)不同喷施时期对花生根系活力、叶绿素含量、叶片保护酶和碳、氮代谢酶活性,以及荚果产量和籽仁品质的影响.结果表明:不同时期喷施PBZ均提高了2个品种花生在结荚期的叶绿素含量、根系活力,以及叶片超氧化物歧化酶、过氧化物酶、过氧化氢酶、蔗糖合成酶、蔗糖磷酸合成酶和磷酸烯醇式丙酮酸羧化酶活性,降低了丙二醛(MDA)含量以及硝酸还原酶、谷氨酰胺合成酶、谷氨酸脱氢酶和谷氨酸合成酶活性,且PBZ喷施时间越早效果越明显.在饱果期,HY25的各指标以主茎高25cm时喷施PBZ的效果最好,但HY20在主茎高25 cm时喷施PBZ的保护酶活性降低,化控时间过早导致植株早衰,叶绿素含量、根系活力以及碳代谢酶活性也略低于CK,HY20的指标以主茎高30 cm时喷施PBZ效果最好.适宜时期PBZ处理提高了2个品种的荚果产量和经济系数,提高了脂肪含量和油酸相对含量以及O/L值.高产条件下,HY25和HY20的最适多效唑处理时期分别为花生主茎高25和30 cm左右.     

Nutrient deficiencies do not contribute to yield loss after waterlogging events in winter wheat (Triticum aestivum)

Frequent waterlogging increases the risk of possible harvest losses in winter wheat. The aim of this study was to analyse which developmental stage of wheat was impaired by waterlogging and whether yield losses can be explained by nutrient deficiences. A large‐scale container experiment was designed to evaluate growth, yield and nutrient status of two wheat cultivars after 14 days of waterlogging at two different developmental stages: DC 31 (first node visible) and DC 51 (beginning of ear emergence). Early waterlogging treatment impaired vegetative growth stages of winter wheat and nutrient uptake, leading to transient nutrient deficiencies, but yield was not significantly reduced. Late waterlogging at the beginning of ear emergence mainly affected generative growth stages and caused yield reductions ranging up to 61%. The main reason for yield loss was the significantly decreased thousand kernel weight in combination with a decreased number of grains per spike. Yield depressions in winter wheat depend on the timing of waterlogging. Early waterlogging transiently reduces vegetative growth through nutrient deficiencies, whereas late waterlogging results in an impaired grain development and associated therewith, yield losses.     

Forecasting yield of corn,Zea mays infested with corn leaf aphid,Rhopalosiphum maidis

Abstract: Corn leaf aphid, Rhopalosiphum maidis (Fitch) is one of the most serious corn pests in Egypt. The aim of the present study is to assess the corn yield losses and to build forecasting models of yield related with aphid infestation. Number of aphids/plant were determined during corn growth stages 10 leaves (V10); tasseling (VT); ripening 2 (R2) and ripening 4 (R4). At the end of growing season, yield losses were estimated. Results revealed that infestation with aphids through V10–VT caused 28.14% yield losses at average aphid density 818 aphid/plant. Infestation through R2–R4 caused 16.28% yield losses at average aphid density 1038 aphids/plant. Percentages of yield losses of corn ears through V10–R4 were 14.66, 22.9, 35.28 and 36.03% at average aphid density of 100, 1000, 2000 and 3000 aphids/plant. As ear yield negatively correlated with aphid density, regression analysis was used to construct forecasting yield models. Statistical analysis showed that simple linear and logarithmic models provided a good fit to the data and also indicated that the two models are similar in prediction of ear yield. These constructed models were diagnostic checked using new data. The checking revealed that the linear model is stable and valid where insignificant difference was observed between predicted and actual yield.     

Control and yield loss modelling of circular leaf spot of persimmon caused by Mycosphaerella nawae

Symptoms of circular leaf spot of persimmon (CLSP), caused by Mycosphaerella nawae, consisted of necrotic spots on leaves, chlorosis and premature defoliation. Although CLSP is a foliar disease, early fruit maturation and abscission are frequently associated with the presence of lesions on leaves and defoliation, resulting in severe economic losses. Despite their importance for the design of efficient disease management programmes, quantitative relationships between CLSP incidence and yield loss are unknown. Therefore, fungicide efficacy trials were conducted during two consecutive years in Spain to induce different levels of disease severity, defoliation and yield loss. The effects of fungicide treatments on CLSP severity were analysed by ordinal logistic regression models. Relative yield loss values were regressed against the percentage of affected leaves or defoliated obtained at different evaluation dates. The disease had high negative impact and complete yield loss was observed in the absence of effective fungicide treatments. Preventive applications of pyraclostrobin, trifloxy‐strobin and mancozeb provided the best disease control and highest yields, up to 95.77 kg tree^?1. An exponential relationship of CLSP incidence and defoliation with yield loss was found. In general, model fit and predictive ability was superior when defoliation, rather than incidence, was used as explanatory variable. The impact of defoliation on yield loss was higher in earliest evaluation dates, suggesting that early leaf abscission may be the main factor contributing to premature fruit drop and subsequent yield loss. Substantial yield losses were observed even with relatively low levels of CLSP incidence and defoliation. Therefore, it was not possible to define a critical action threshold for CLSP management based on foliar symptoms.     

中华绒螯蟹水瘪子病不同发病阶段的病理变化特点

为了解中华绒螯蟹(Eriocheir sinensis)“水瘪子”病发生发展的过程, 揭示疾病的本质, 对病蟹进行了较全面的病理特点分析研究。根据病蟹肝胰腺颜色, 将病蟹划分为浅黄、浅粉、乳白和灰白4个发病阶段。研究结果表明, 随着病情的发展, 病蟹肝胰腺与蟹重比逐渐减少, 腔液与蟹重比逐渐增加, 肝胰腺管直径逐渐缩小, 各发病阶段病蟹的这些指标都与健康蟹有极显著差异(P<0.01), 病蟹肝胰腺与蟹重比除乳白阶段与灰白阶段之间和腔液与蟹重比除浅粉阶段与乳白阶段和乳白阶段与灰白阶段之间以及肝胰腺管直径除乳白阶段与灰白阶段之间的差异均不显著(P>0.05)和浅粉阶段与乳白阶段之间的差异显著(P<0.05)外, 其他各发病阶段之间这些指标均有极显著差异(P<0.01); 4个发病阶段病蟹6种组织器官中肝胰腺、鳃、肌肉组织和心脏组织病理变化具有相似性, 浅黄阶段主要是以组织器官水肿和萎缩为主, 是一种可逆的组织病理过程, 但在浅粉阶段肝胰腺和肌肉组织出现细胞坏死, 以后发病阶段更为严重, 鳃和心脏组织在乳白阶段出现细胞坏死, 坏死是一种不可逆的组织病理过程, 神经团和肠道组织病理变化不明显。根据不同发病阶段的病理特点, 在未来确定病因后通过消除病因等方法, 只有在病理变化处于可逆状态的浅黄阶段, 病蟹才有恢复的可能, 才有防控和挽救价值, 而浅粉阶段以后的病蟹由于主要器官组织细胞崩解坏死处于不可逆的病理过程, 即使病因消除病蟹已不可能恢复, 这样的病蟹应及时清除, 减少继续养殖造成进一步的经济损失。     

冬小麦(Triticum aestivum)分蘖冗余生态学意义以及减少冗余对水分利用效率的影响

通过盆栽试验,以旱作冬小麦(Triticum aestivum)为材料,分别在拔节和抽穗期对分蘖进行人工干扰,来模拟不可预测的自然干扰,对冬小麦分蘖冗余的生态学意义以及减少这些冗余对水分利用效率影响进行研究.设置3个处理:从拔节期开始剪去所有小的分蘖,仅保留主茎和一个大的分蘖(A);在拔节期剪去主茎和两个大的分蘖,保留所有小的分蘖(B);在孕穗期剪去主茎和有效分蘖,保留无效分蘖(C).没有被干扰的植物作为对照(CK).通过花期测定叶片的叶绿素含量、叶绿素荧光参数、气孔导度和蒸腾速率等生理指标来评价植物的生理与生化活性.结果显示,在拔节期和抽穗期去除主茎和大蘖后,无效分蘖的生理活性被激活,开始执行有效分蘖的功能.到花期时,这些无效分蘖已经在生理活性上满足了补充和替代有效茎的要求.虽然株高和穗的整齐度、穗数和产量显著下降,但并没有防碍小麦的繁衍子代,因此,正是这些由早期"无效分蘖"补充而来的有效茎,避免了小麦绝种的风险.而在拔节期去除无效分蘖后,对小麦产量没有显著影响,但提高了水分利用效率,和对照相比水分利用效率提高了10%.因此,可以认为小麦在分蘖上存在着对水分利用不利的生长冗余,减少这些冗余有望节约用水、提高作物的水分利用效率.     

The impact of wintering geese on crop yields in Bulgarian Dobrudzha: implications for agri-environment schemes

Wintering wildfowl are widely perceived to damage agricultural crops, resulting in economic losses and conflict between farmers and conservationists. However, examinations of the nature and extent of the damage show very variable outcomes, ranging from no detectable impact to yield losses exceeding 50%; this makes it hard to infer losses in unstudied systems. In Bulgarian Dobrudzha, a large wintering goose population almost exclusively consumes winter wheat, but the impact on wheat yields is poorly understood. We used crop exclosures and dropping counts to manipulate and measure goose grazing intensity, and estimated crop yield and its components (grain mass, grains per stem, stem density). Crop yield was 13.2% lower in unfenced control plots than in exclosures in one winter during which goose grazing intensity was high but mainly occurred relatively early in the season, but there was no effect of goose exclusion in an earlier winter when goose grazing intensity was relatively low but occurred late in the season. A negative relationship between grazing intensity and crop yield was found, mainly driven by a lower stem density in heavily grazed plots. We use this relationship to infer total yield loss and calculate the economic impact for the study area to be in the order of €15,000–100,000. However, the generality of these results remains unclear because the impact of a given grazing intensity appears likely to vary according to factors such as timing of grazing, weather, stage of crop development and soil conditions. We discuss the results in light of a new agri-environment scheme that has been launched in the area with the aim of securing appropriate forage conditions for wintering geese whilst compensating farmers for losses and reducing conflict.     

Genetic parameters for paratuberculosis infection and effect of infection on production traits in Israeli Holsteins

Paratuberculosis (Johne's disease) is an infectious enteric disease in dairy cattle and other species that causes substantial economic loss worldwide. In this study, two recursive Gaussian-threshold models were employed in order to infer the effects of Johne's disease on milk yield, fat yield, and protein yield while simultaneously estimating genetic parameters (i.e. heritability and genetic correlation) in an Israeli Holstein population. Disease diagnosis was based on ELISA serum antibody tests. Data were available for 4694 daughters of 361 sires; 3.5% were positive; and 1.6% were suspect for the disease test. Disease status was coded either as a binary character (negative vs. positive) or as an ordered categorical trait (negative, suspect, and positive) in the two recursive models and as a binary trait in a linear model. Among sires with ≥ 50 daughters, predicted probability of Mycobacterium avium ssp. paratuberculosis (MAP) infection in future daughters ranged from <1% to 16.5%. Heritability estimates for Johne's disease were near 0.15, confirming a genetic contribution to disease susceptibility. Genetic correlation estimates for Johne's disease with the three yield traits were 0.15-0.22. Residual correlations for Johne's disease with the yield traits were between -0.01 and -0.10. For the linear regression model, yield losses associated with a positive disease diagnosis during 305 days of lactation were 300 kg milk and around 10 kg for fat and protein. Yield loss estimates from the recursive models were 25-50% less than linear model estimates. Recursive modeling has theoretical advantages over linear models for these phenotypes, but the estimated genetic parameters in this study did not differ significantly between the two types of models.