Population suppression of Bemisia tabaci (Hemiptera: Aleyrodidae) using yellow sticky traps and Eretmocerus nr. rajasthanicus (Hymenoptera: Aphelinidae) on tomato plants in greenhouses

We conducted three experiments for management of Bemisia tabaci (Gennadius) biotype ‘B’ on tomatoes under greenhouse conditions: (i) vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3‐m row; (ii) releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m² in the high whitefly density greenhouses (> 10 adults/plant), or twice at 15 adults/m² at a 5‐day interval in the low whitefly density greenhouses (< 10 adults/plant); and (iii) using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m² in high whitefly density greenhouses or twice at 15/m² at a 5‐day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m² in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m² in low whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs of B. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m² in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m² at a 5‐day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.     

Evaluating the potential of the extract of Perilla sp. as a natural insecticide for Bemisia tabaci (Hemiptera: Aleyrodidae) on sweet peppers

The sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is a major pest on greenhouse crops including sweet pepper (Capsicum annuum L.), which is one of the leading greenhouse crops in South Korea. Synthetic insecticides, especially the neonicotinoids, have been used to conventionally control this pest. There have been continuous efforts to develop plant‐derived compounds as insecticides, deterrents, and repellents to reduce spraying synthetic insecticides. To develop new plant‐extract insecticides, we investigated the insecticidal effects of Perilla sp. (Perilla frutescens var. crispa) extract on B. tabaci in laboratory conditions. The Perilla sp. extract induced 90 % mortality within one hour, but phytotoxicity symptoms on sweet pepper leaves were also observed. We monitored the population change and spatial distribution of adult B. tabaci in an experimental sweet pepper greenhouse using yellow sticky traps, and analyzed distribution patterns by spatial analysis with distance indices (SADIE). Based on monitoring data and SADIE analysis, we concluded that B. tabaci aggregated near the greenhouse entrances, and it showed aggregation and association pattern as time passed. Therefore, we recommend spraying Perilla sp. extract near the entrances or wild host before the pest population penetrates. It will be one of the alternative pest management strategies to reduce B. tabaci population with fewer negative effects from chemical insecticide. Further study is required to reduce the phytotoxicity symptoms from Perilla sp. extract spray and insecticidal effect should be evaluated under field conditions.     

The effect of replicate number and image analysis method on sweetpotato [Ipomoea batatas (L.) Lam.] cDNA microarray results

Microarray analysis makes it possible to determine the relative expression of thousands of genes simultaneously. It has gained popularity at a rapid rate, but many caveats remain. In an effort to establish reliable microarray protocols for sweetpotato [Ipomoea batatas (L.) Lam.], we compared the effect of replication number and image analysis software with results obtained by quantitative rela-time PCR (Q-RT-PCR). Sweetpotato storage root development is the most economically important process in sweetpotato. In order to identify genes that may play a role in this process, RNA for microarray analysis was extracted from sweetpotato fibrous and storage roots. Four data sets, Spot4, Spot6, Finder4 and Finder6, were created using 4 or 6 replications, and the image analysis software of UCSF Spot or TIGR Spotfinder were used for spot detection and quantification. The ability of these methods to identify significant differential expression between treatments was investigated. The data sets with 6 replications were better at identifying genes with significant differential expression than the ones of 4 replications. Furthermore when using 6 replicates, UCSF Spot was superior to TIGR Spotfinder in identifying genes differentially expressed (18 out of 19) based on Q-RT-PCR. Our study shows the importance of proper replication number and image analysis for microarray studies.     

Cultivar‐specific effects of pathogen testing on storage root yield of sweetpotato,Ipomoea batatas

The accumulation and perpetuation of viral pathogens over generations of clonal propagation in crop species such as sweetpotato, Ipomoea batatas, inevitably result in a reduction in crop yield and quality. This study was conducted at Bundaberg, Australia to compare the productivity of field‐derived and pathogen‐tested (PT) clones of 14 sweetpotato cultivars and the yield benefits of using healthy planting materials. The field‐derived clonal materials were exposed to the endemic viruses, while the PT clones were subjected to thermotherapy and meristem‐tip culture to eliminate viral pathogens. The plants were indexed for viruses using nitrocellulose membrane‐enzyme‐linked immunosorbent assay and graft‐inoculations onto Ipomoea setosa. A net benefit of 38% in storage root yield was realised from using PT materials in this study. Conversely, in a similar study previously conducted at Kerevat, Papua New Guinea (PNG), a net deficit of 36% was realised. This reinforced our finding that the response to pathogen testing was cultivar dependent and that the PNG cultivars in these studies generally exhibited increased tolerance to the endemic viruses present at the respective trial sites as manifested in their lack of response from the use of PT clones. They may be useful sources for future resistance breeding efforts. Nonetheless, the potential economic gain from using PT stocks necessitates the use of pathogen testing on virus‐susceptible commercial cultivars.     

黄河三角洲盐碱地条件下不同甘薯品种耐盐性

利用北方薯区当前生产上广泛种植的甘薯新品种,在黄河三角洲盐碱地上开展种植试验,以期选育耐盐甘薯品种。对每个测试品种的重要农艺性状及盐离子含量进行分析。结果表明不同甘薯品种的耐盐性存在差异。除叶片数、分枝数、分枝长度无显著性差异外,其他农艺性状如总鲜重、鲜薯产量、薯块干率、薯干产量、薯块数等都在不同品种中达到显著水平,建议耐盐性的评价指标应以鲜薯和薯干产量为主。对甘薯新生叶片、成熟叶片、须根、块根等不同器官进行Cl-、Ca2＋、Na＋和K＋的含量分析,结果表明不同品种其不同器官中各种盐离子含量差异显著,暗示不同基因型耐盐机制存在差异。基于对鲜薯和薯干产量的比较,筛选出耐盐碱的品种,主要有‘泰中9号’、‘苏薯7号’、‘龙薯1号’、‘徐薯18’等。同时,对甘薯种植前后的土壤总盐分和营养成分的分析显示：甘薯收获后,土壤中的含盐量显著降低。本研究为沿海滩涂培育和种植耐盐碱甘薯新品种进行了有益的尝试,同时也为盐碱地改良和生物质能原材料种植提供了思路。     

浙江省甘薯种质资源的品质鉴定与聚类分析

开展甘薯种质资源的品质鉴定评价,可以系统地了解种质的营养价值、食用品质和加工性能,为甘薯生产的品种选择和种质资源的育种利用提供依据.对2017-2019年浙江省第三次全国农作物种质资源普查与收集行动中征集的62份甘薯种质进行了干物率、胡萝卜素含量、生薯和熟薯可溶性糖含量以及食味的测定,并进行了品质性状的主成分和系统聚类...     

秸秆还田配施化肥对土壤肥力及鲜食甘薯产量和品质的影响

通过2017和2018两年的田间试验研究了小麦秸秆还田和施肥对土壤肥力、酶活性以及鲜食甘薯产量和品质的影响。试验设5个处理:秸秆不还田+常规施肥(CK)、小麦秸秆半量还田+常规施肥(50%S)、小麦秸秆全量还田+不施肥(100%S-F)、小麦秸秆全量还田+常规施肥(100%S)、小麦秸秆全量还田+常规施肥+150 kg·hm^-2氮肥(100%S+N)。结果表明:秸秆还田施肥处理显著提高了土壤中的有效磷、碱解氮、总氮和有机质含量,显著提高了土壤过氧化氢酶、碱性磷酸酶、脲酶和蔗糖酶活性。秸秆还田施肥处理均显著提高了薯块产量、单薯鲜重和商品薯率,其中50%S处理下薯块产量最低。2年的秸秆还田处理下,薯块产量和商品薯率均在100%S处理下最高。2年的秸秆还田施肥处理总体上提高了甘薯的淀粉和蛋白质含量,但100%S和100%S+N处理均降低了甘薯还原糖和可溶性糖含量。可见,小麦秸秆全量还田的效果优于半量还田,与常规施肥配合下薯块产量和商品薯率最高,但影响食用口感,实际生产中可适当减少氮肥用量。     

菜用和观赏甘薯种质资源遗传多样性分析

为了发掘菜用和观赏甘薯优异种质资源,通过对国家种质徐州甘薯试管苗库中1000余份资源材料进行鉴定,筛选了96份优异种质。利用30对SSR引物对入选材料进行了遗传多样性和群体结构分析,明确了这些材料遗传差异;并对入选材料12个表型质量性状进行主成分和聚类分析。结果表明:扩增的总条带数为275条,其中多态性条带为269条,多态率97.8%;利用DPS软件计算入选材料间的Nei72遗传距离为0.15~0.76,平均遗传距离0.66;群体结构分为3个组群,与分子标记聚类结果相似,表明入选材料有较大的遗传差异性;表型质量性状主成分分析得到5个主要成分,其累计贡献率达到80.50%;利用表型质量性状,可聚为8个组群。本研究通过分子标记与表型质量性状分析为下一步杂交选育菜用和观赏甘薯新品种提供了亲本选择信息。