Endophytic colonization of entomopathogenic fungi increases plant disease resistance by changing the endophytic bacterial community

Various mechanisms are involved in plant disease resistance mediated by entomopathogenic fungi; however, the role of plant endophytic microbes in disease resistance is unknown. In the present study, we showed that the disease incidence of northern corn leaf blight caused by Exserohilum turcicum (Et) on maize was reduced significantly by soil inoculation with Beauveria bassiana (Bb). Meanwhile, B. bassiana colonization and E. turcicum infection increased the diversity and abundance and diversity of endophytic bacteria and fungi, respectively, while the abundance of endophytic bacterial of the Bb + Et treatment decreased significantly compared with that of Et treatment alone. However, Bb + Et treatment increased the relative abundance of plant beneficial bacteria significantly, for example, Burkholderia and Pseudomonas. Network analyses showed that the microbiome complexity increased after soil inoculation with B. bassiana. Taken together, these results revealed the potential mechanism by which entomopathogenic fungi exert biological control of maize leaf spot disease.     

Quantitative Modeling of Climate Change Impacts on Mycotoxins in Cereals: A Review

Our climate is projected to change gradually over time. Mycotoxin occurrence in cereal grains is both directly and indirectly related to local weather and to climate changes. Direct routes are via the effects of precipitation, relative humidity, and temperatures on both fungal infection of the grain and mycotoxin formation. Indirect routes are via the effects of the wind dispersal of spores, insect attacks, and shifts in cereal grain phenology. This review aimed to investigate available modeling studies for climate change impacts on mycotoxins in cereal grains, and to identify how they can be used to safeguard food safety with future climate change. Using a systematic review approach, in total, 53 relevant papers from the period of 2005–2020 were retrieved. Only six of them focused on quantitative modeling of climate change impacts on mycotoxins, all in pre-harvest cereal grains. Although regional differences exist, the model results generally show an increase in mycotoxins in a changing climate. The models do not give an indication on how to adapt to climate change impacts. If available models were linked with land use and crop models, scenario analyses could be used for analyzing adaptation strategies to avoid high mycotoxin presence in cereal grains and to safeguard the safety of our feed and food.     

Functional Properties,Nutritional and Sensory Qualities of Maize-Based Snack (Kokoro) Supplemented with Protein Hydrolysate Prepared from Pigeon Pea (Cajanus Cajan) Seed

Kokoro is a popular maize-based snack in Nigeria, which is consumed by adults and children but characterized by low protein content. The snacks were produced from blends of maize flour supplemented with protein hydrolysate from pigeon pea at 100:0 (control), 95:5, 90:10, 85:15, and 80:20. Flour blends were evaluated for functional and pasting properties, while snacks were analyzed for proximate composition and sensory qualities. Proximate analysis results showed significant (p < 0.05) increase in protein (9.64–11.12%), fat (13.40–20.17%), ash (1.83–2.38%) content, and energy value (431.84–468.97 kcal/100 g), while fiber (1.19–0.96%) and carbohydrate (68.17–60.74%) content decreased with inclusion of protein hydrolysate. No significant difference (p < 0.05) occurred in the sensory qualities of products from 100% maize and 80:20 flour blend. Hence, acceptable Kokoro snacks from an 80:20 (maize: protein hydrolysate) blend have been formulated, which could enhance the nutritional wellness of the target consumers.     

Chemical composition and starch digestibility of tortillas prepared with non-conventional commercial nixtamalized maize flours

Non-conventional nixtamalized maize flours elaborated by a factory in Mexico were used for tortilla preparation. Tortillas were stored at 4°C for up to 72 h and the total starch, available starch, resistant starch and retrograded resistant starch were assessed. The traditional white tortilla, used as a control, showed higher protein and fat contents than blue maize tortilla, whereas a maize–bean mixed tortilla had the highest protein, ash and fat contents. Lower total starch was obtained in the maize–bean tortilla than in white and blue maize tortillas. The available starch content in all tortillas decreased with the cold-storage, although the change was more marked for blue-maize tortillas. The maize–bean mixed tortillas exhibited the lowest in vitro digestibility, which is consistent with the relatively high resistant starch levels in the bean. Differences in resistant starch content were found between the two maize tortillas, which might be related to the softer texture of blue-maize tortilla. The starch digestibility features of these new types of nixtamalized maize flours open up the possibility of producing tortillas with variable nutritional properties.     

Sequence composition and genome organization of maize

Zea mays L. ssp. mays, or corn, one of the most important crops and a model for plant genetics, has a genome approximately 80% the size of the human genome. To gain global insight into the organization of its genome, we have sequenced the ends of large insert clones, yielding a cumulative length of one-eighth of the genome with a DNA sequence read every 6.2 kb, thereby describing a large percentage of the genes and transposable elements of maize in an unbiased approach. Based on the accumulative 307 Mb of sequence, repeat sequences occupy 58% and genic regions occupy 7.5%. A conservative estimate predicts approximately 59,000 genes, which is higher than in any other organism sequenced so far. Because the sequences are derived from bacterial artificial chromosome clones, which are ordered in overlapping bins, tagged genes are also ordered along continuous chromosomal segments. Based on this positional information, roughly one-third of the genes appear to consist of tandemly arrayed gene families. Although the ancestor of maize arose by tetraploidization, fewer than half of the genes appear to be present in two orthologous copies, indicating that the maize genome has undergone significant gene loss since the duplication event.     

The maize disease resistance gene Htn1 against northern corn leaf blight encodes a wall-associated receptor-like kinase

Northern corn leaf blight (NCLB) caused by the hemibiotrophic fungus Exserohilum turcicum is an important foliar disease of maize that is mainly controlled by growing resistant maize cultivars. The Htn1 locus confers quantitative and partial NCLB resistance by delaying the onset of lesion formation. Htn1 represents an important source of genetic resistance that was originally introduced from a Mexican landrace into modern maize breeding lines in the 1970s. Using a high-resolution map-based cloning approach, we delimited Htn1 to a 131.7-kb physical interval on chromosome 8 that contained three candidate genes encoding two wall-associated receptor-like kinases (ZmWAK-RLK1 and ZmWAK-RLK2) and one wall-associated receptor-like protein (ZmWAK-RLP1). TILLING (targeting induced local lesions in genomes) mutants in ZmWAK-RLK1 were more susceptible to NCLB than wild-type plants, both in greenhouse experiments and in the field. ZmWAK-RLK1 contains a nonarginine-aspartate (non-RD) kinase domain, typically found in plant innate immune receptors. Sequence comparison showed that the extracellular domain of ZmWAK-RLK1 is highly diverse between different maize genotypes. Furthermore, an alternative splice variant resulting in a truncated protein was present at higher frequency in the susceptible parents of the mapping populations compared with in the resistant parents. Hence, the quantitative Htn1 disease resistance in maize is encoded by an unusual innate immune receptor with an extracellular wall-associated kinase domain. These results further highlight the importance of this protein family in resistance to adapted pathogens.Plants are constantly attacked by potential pathogenic microbes, specifically, viruses, bacteria, and fungi. Although lacking an adaptive immune system comparable to the one found in vertebrates, plants have evolved a plethora of strategies to fend off microbial pathogens. The first tier of defense is formed by plasma membrane-anchored pattern recognition receptors (PRRs). These receptor proteins monitor the extracellular space for the presence of microbial- or host-derived elicitors, also called pathogen-associated molecular patterns (PAMP) or danger-associated molecular patterns (DAMP), respectively. Perception of PAMPs and DAMPs triggers a signaling cascade that activates numerous defense responses, called PAMP-triggered immunity and DAMP-triggered immunity, respectively. PAMPs are often highly conserved microbial structures that are characteristic for entire pathogen classes (1, 2). Examples are the fungal cell wall component chitin or bacterial flagellin. Perception of highly conserved PAMPs therefore results in broad-spectrum resistance against whole groups of nonadapted microbes, also referred to as nonhost resistance. To avoid PAMP-triggered immunity and DAMP-triggered immunity, pathogens are equipped with specific effectors that are tailored to suppress the plant’s immune response. These virulence effectors are injected into the host cytoplasm, where they can then, in turn, be recognized by cytoplasmic receptor proteins, which results in effector-triggered immunity (ETI) (3). The intracellular recognition of effector molecules is mediated by structurally related proteins belonging to the nucleotide-binding site-leucine-rich repeat (NBS-LRR) family (4). ETI forms the second tier of the plant immune response. In contrast to nonhost resistance, the ETI response against adapted pathogens is much stronger and often results in the death of the infected cell through hypersensitive reaction. Hence, there is a strong selective pressure on the pathogen to avoid ETI by evolving new virulence effectors that escape recognition by NBS-LRR immune receptors. This coevolutionary arms race is the major reason for rapid breakdown of NBS-LRR-based disease resistance in crop plants, which often occurs within only a few years (5, 6).Cell surface PRRs are encoded by receptor-like kinase (RLK) and receptor-like protein (RLP) genes. Both RLKs and RLPs contain an extracellular elicitor-binding domain and a transmembrane domain. In contrast to RLKs, RLPs lack a cytoplasmic serine/threonine kinase domain (7). The best-studied PRR is the leucine-rich repeat (LRR) receptor-like kinase flagellin-sensitive-2 (FLS2) of Arabidopsis, which binds an epitope of bacterial flagellin. On flagellin perception, this kinase initiates a signaling cascade that results in nonhost resistance (8). Most PRRs described until today contain such an extracellular LRR domain. Not all PRRs, however, are involved in nonhost resistance. The rice LRR-RLK Xa21, for example, confers race-specific resistance against the bacterial rice blast pathogen Xanthomonas oryzae pv. oryzae (9). The effector recognized by Xa21 is still unknown. In addition, plants have evolved the ability to perceive endogenous molecules through PRRs that are produced during pathogen infection. For example, the Arabidopsis wall-associated kinase 1 (WAK1) binds cell wall-derived oligogalacturonides that are released during pathogen infection and serve as DAMPs (10). AtDORN1, an Arabidopsis lectin-RLK, binds plant-derived extracellular ATP likely produced during pathogen infection or wounding (11).Maize (Zea mays L.) is the most widely grown crop in the world and represents an important source of food, feed, biofuel, and industrial products. Fungal diseases are a major threat to maize production and can result in severe crop losses. Northern corn leaf blight (NCLB) is the most devastating foliar disease of maize. It is caused by the hemibiotrophic ascomycete fungus Exserohilum turcicum (teleomorph Setosphaeria turcica) (12). The fungus spreads biotrophically during the initial infection process before switching to a necrotrophic lifestyle. Infections manifest as local lesions and necrosis, which lead to reduced photosynthetically active leaf area and yield losses. The disease occurs prevalently under conditions of high humidity and moderate temperatures and can be found in most regions where maize is grown (13–15). The Htn1 locus confers quantitative and partial resistance against NCLB by delaying lesion formation. Htn1 was originally introgressed into modern maize cultivars from the Mexican landrace Pepitilla in the 1970s (16). The Htn1 resistance reaction is different from the other known major NCLB resistance genes Ht1, Ht2, and Ht3, which confer qualitative resistance, resulting in chlorotic-necrotic lesions. In contrast, Htn1 leads to a delay of sporulation without chlorotic lesions (17, 18). The dominant and race-specific Htn1 gene is effective against the most prevalent NCLB races, but virulent isolates have been found (18). The strength of the Htn1 resistance depends on environmental conditions and maize genotype (19). Htn1 has been mapped to maize chromosome 8 ∼10 cM distal to the NCLB resistance gene Ht2 (20–23).Here, we describe the map-based isolation of the Htn1 gene, which encodes for a pattern recognition receptor with a putative extracellular, wall-associated domain.     

近50年河南省夏玉米生产潜力及产量差时空变化特征--测试文章

利用河南省96个县1961—2010年气象资料和夏玉米实际产量,采用逐步订正模型,计算了近50年河南省夏玉米光温生产潜力和气候生产潜力,分析了光温生产潜力与气候生产潜力、光温生产潜力与实际产量两种产量差的时空变化特征。结果表明：(1) 光温生产潜力由北向南、由东向西递减,近50年呈极显著下降趋势,全省平均每10 a减少696.8 kg·hm^-2,北、中大部分站点和南部的部分站点下降幅度较大。(2) 气候生产潜力南部高于北部、东部高于西部,近50年变化趋势不明显。光温生产潜力与气候生产潜力之间的产量差呈极显著下降趋势,平均每10 a减少958.7 kg·hm^-2。(3) 夏玉米实际产量极显著增加,光温生产潜力与实际产量之间的产量差极显著下降,平均每10 a减少1 718.0 kg·hm^-2,但71.9%的站点产量差大于24 000 kg·hm^-2,产量潜力仍有较大提升空间。降水是制约河南省西部夏玉米产量的主要因素,可通过灌溉提高产量;后期热量不足影响北部玉米产量进一步提高,选用中早熟品种和改进栽培技术是提高产量的途径;东部可通过增加灌溉面积、选用优良品种和科学施肥等措施缩小产量差。     

转基因玉米Bt-799对Wistar大鼠仔代发育的影响

目的 研究转基因玉米Bt-799对Wistar大鼠体格发育、生理发育和神经反射发育的影响. 方法 不同剂量转基因玉米对Wistar大鼠进行干预,干预到12周龄时进行交配.母鼠分娩后,观察仔鼠体格发育情况,检测仔鼠生理发育指标和神经反射发育指标达标情况.连续进行两代. 结果 F1仔鼠出生后体重稳步增长,不同时间点各组体重差异无统计学意义;F2仔鼠出生后随着日龄增加体重逐渐增加;TH组和N组4、7、14 d仔鼠体重高于BC组,TH组、GTH组、N组21 d仔鼠体重均高于BC组,差异均有统计学意义;F1仔鼠各组耳廓分离、门齿萌出、睁眼、雄性睾丸下降和雌性阴道开放达标时间比较,差异无统计学意义;F2仔鼠TH组和N组睁眼达标时间较BC组提前,TH组和N组差异无统计学意义.各组F1、F2仔鼠神经反射发育达标时间差异无统计学意义.F2仔鼠生理发育指标和神经反射发育指标达标时间较F1仔鼠提前. 结论 本研究未发现转基因玉米Bt-799对Wistar大鼠仔代发育产生毒性影响的证据.     

ESI-Mass spectrometric and HPLC elucidation of a new ergot alkaloid from perennial ryegrass hay silage associated with bovine reproductive problems

This case report involves four dairies in the Willamette Valley, Oregon, which experienced reproductive problems associated with the presence of a large, previously unidentified, peak eluting at 5?min in a standard ergovaline high-performance liquid chromatography assay of perennial ryegrass silage fed to those animals. Mycotoxin analysis of the silage was negative, as was serological screening of the herds for infectious bovine rhinotracheitis, bovine diarrhea virus and Leptospirosis, including culturing of urine for Leptospira hardjo hardjobovis. Prolactin concentrations were low in most cattle, consistent with ingestion of ergot alkaloids. We believe that this peak represents a novel ergot alkaloid-related compound due to its extractability with Ergosil, its detectability due to fluorescence, and its chromatographic retention between ergovaline (mw?=?533) and ergotamine (mw?=?581). Its molecular weight was calculated as 570 owing to the predominance of a m/z 593.5 ion in the full scan ESI(+)MS and its deduced tendency to complex with Na⁺ (as m/z 593) or K⁺ (as m/z 609) ions. We offer rationales for elucidation of the structure of this compound, with the closest starting point comprising an m.w. of 566—a fructofuranosyl-(2-1)-O-beta-D-fructofuranoside derivative of 6,7-secoergoline from Claviceps fusiformis. This m.w. requires modifications, such as reduction of two double bonds in the secoergoline component to give the target 570 m.w. Despite the lack of a definitive structure, the analysis herein provides a starting point for eventual elucidation of this apparently new ergot alkaloid, and to guide and encourage further investigation as to its association with endophyte toxicosis in livestock.