Adenosine cyclic monophosphate in potato tubers during storage at +10° and +2°

The levels of adenosine 3′: 5′ cyclic monophosphate in mature potato tubers (variety King Edward) stored at + 10°, for varying periods at + 2° and then after 28 days at + 2° transferred to + 10°, have been measured. The concentrations were very low (3–30 pmol/g fr. weight) and did not show marked changes with storage conditions.     

Changes in the distribution of multispecies pest assemblages affect levels of crop damage in warming tropical Andes

Climate induced species range shifts might create novel interactions among species that may outweigh direct climatic effects. In an agricultural context, climate change might alter the intensity of competition or facilitation interactions among pests with, potentially, negative consequences on the levels of damage to crop. This could threaten the productivity of agricultural systems and have negative impacts on food security, but has yet been poorly considered in studies. In this contribution, we constructed and evaluated process‐based species distribution models for three invasive potato pests in the Tropical Andean Region. These three species have been found to co‐occur and interact within the same potato tuber, causing different levels of damage to crop. Our models allowed us to predict the current and future distribution of the species and therefore, to assess how damage to crop might change in the future due to novel interactions. In general, our study revealed the main challenges related to distribution modeling of invasive pests in highly heterogeneous regions. It yielded different results for the three species, both in terms of accuracy and distribution, with one species surviving best at lower altitudes and the other two performing better at higher altitudes. As to future distributions our results suggested that the three species will show different responses to climate change, with one of them expanding to higher altitudes, another contracting its range and the other shifting its distribution to higher altitudes. These changes will result in novel areas of co‐occurrence and hence, interactions of the pests, which will cause different levels of damage to crop. Combining population dynamics and species distribution models that incorporate interspecific trade‐off relationships in different environments revealed a powerful approach to provide predictions about the response of an assemblage of interacting species to future environmental changes and their impact on process rates.     

"彩色马铃薯"块茎花色苷分子结构研究进展

“彩色马铃薯”是指块茎的“皮”和／或“肉”为红、紫、蓝或橙色的马铃薯,其块茎“皮”和“肉”变化多端的着色模式源于花色苷的积累,块茎各种颜色在根本上由花色素决定。在“彩色马铃薯”块茎中已发现6种花色素,即矮牵牛色素、花葵素、锦葵色素、芍药色素、花青素和花翠素;不同颜色块茎所含的花色素种类不同,同一颜色块茎所含花色素种类也可能不同;紫色块茎所含的花色素种类最为多样化。“彩色马铃薯”块茎的各种花色素一般在C3位经过氧一糖苷键实现1个芸香糖基取代,在苷元的C5位,要么以氧．糖苷键实现单葡萄糖基取代,要么不发生取代。“彩色马铃薯”块茎花色苷常在花色素C3位二糖取代基上或在C5位的单糖取代基上进一步发生反式单酰基取代,实现酰基取代的酚酸多为对香豆酸,其次为阿魏酸和咖啡酸。“彩色马铃薯”块茎矮牵牛素、锦葵色素、花葵素和芍药色素的对香豆酸酰化衍生物的惯用名分别为“petanin”,“malvanin”,“pelanin”和“peonanin”。本文可以为“彩色马铃薯”块茎颜色呈现的机理探索及其花色苷的分子结构鉴定提供参考。     

太子参试管微块根形成及其应用初探

太子参组培苗单茎节段插入含45g·L^-1蔗糖的MS培养基中,于60μmol·m^-2·s^-1光照强度下培养120d后,其节部位长出不定根膨大形成与太子参体内块根相似、重量约为块根1/20的微块根,平均每株可形成1.54个微块根。微块根移植入大田后,其生长特性和物候期与大田块根相似,都有低温萌芽、高温休眠的特性;开花结果、不定根膨大、块根成熟等也相似。同时,组培中的微块根还具有易培养、耐贮存、体积小、易移栽和繁殖系数高等优点,在生产中具有很大的应用潜力。     

Transgenerational maintenance of transgene body CG but not CHG and CHH methylation

In plants, RNA-directed DNA methylation (RdDM) can target both transgene promoters and coding regions/gene bodies. RdDM leads to methylation of cytosines in all sequence contexts: CG, CHG and CHH. Upon segregation of the RdDM trigger, at least CG methylation can be maintained at promoter regions in the progeny. So far, it is not clear whether coding region methylation can be also maintained. We showed that the body of Potato spindle tuber viroid (PSTVd) transgene constructs became densely de novo methylated at CG, CHG and CHH sites upon PSTVd infection. In this study, we demonstrate that in viroid-free progeny plants, asymmetric CHH and CHG methylation was completely lost. However, symmetric CG methylation was stably maintained for at least two generations. Importantly, the presence of transgene body methylation did not lead to an increase of dimethylation of histone H3 lysine 9 or a decrease of acetylation of H3. Our data supports the view that CG methylation can be maintained not only in promoters but also in the body of transgenes. They further suggest that maintenance of methylation may occur independently of tested chromatin modifications.     

影响茎用芥菜愈伤组织诱导和植株再生的因素

茎用芥菜子叶培养在MS 0.25 mg·L-1NAA 0.5 mg·L-16-BA 0.25 mg·L-12,4-D培养基上,可获得较高质量的愈伤组织.愈伤组织培养在MS 1～1 mg·L-16-BA 0.2 mg·L-1NAA培养基上分化频率为8.3%,而在加有羧苄青霉素和头孢霉素的培养基上,最高分化频率可达52.4%.将获得的再生植株转移到1/2MS 0.1 mg·L-1 NAA的生根培养基中,可获得完整植株.     

Evaluation of damage of some food commodities by larger grain borer–Prostephanus truncatus (Horn) {Coleoptera: Bostrichidae} and microbial composition of frass induced by the insect

The microbial composition of the frass from maize (Zea mays) grains and seven dried root and tuber crops (R&TC) infested by Prostephanus truncatus were evaluated. Five cubes (6 cm³) of each R&TC as well as 100 g of maize grains were separately infested with 15 pairs of 1–2 day old adult LGB in 250 cm³ sized Kilner jars and incubated for 90 days at 28 ± 1°C and 79–82% RH. At 90 days post-infestation, the microbiological assay of frass from the commodities was performed. The results indicated the presence of 10 bacterial species, namely Bacillus cereus, B. macerans, Proteus mirabilis, P. morganic, P. rettgeri, Proteus sp., Pseud geniculatum, Pseud fragii, Pseud putela, Serratia marcences and six fungal species, namely Aspergillus niger, A. tamari, A. parasiticus, A. ochraceus, Fusarium compacticum and F. oxysporum. Infested cubes of M. esculenta have the highest population of adult LGB (168.3) and frass from its damaged cubes had the highest mean bacterial count of 30.0 × 10⁷ colony forming units (CFU) and it was significantly (P < 0.05) higher than LGB infestation and bacterial infection of other R&TC. The bacterial count from the damaged commodities correlated positively and significantly (P < 0.05) with weight of frass, percentage damage and percentage weight loss. The results revealed that frass from the LGB-infested and damaged commodities were infected by bacteria and fungi. Maize grains and dried R&TC should therefore be protected from LGB infestation to avoid quantity reduction and microbial infection.     

Oxidative stress,growth factor production and budding in potato tubers during cold storage

In order to verify the role played by oxidation in the budding of potato tubers (Solanum tuberosum L. cv. Kennebec), the physiological events occurring below bud at 4°C have been studied for a period of 6 months. The low temperature storage induced an increase in the degree of unsaturation and a decrease in the ratio of saturated/unsaturated fatty acids of membrane polar lipids with a subsequent increase of lipid hydroperoxides (LOOH). Cold stress increased both enzymatic antioxidative activities (superoxide dismutase, SOD, E.C.1.15.1.1; catalase, CAT, E.C. 1.11.1.6), and α-tocopherol levels thus protecting membrane's polyunsaturated lipids. Between 0 and 15 days of storage SOD/CAT ratio, α-tocopherol, LOOH levels and the degree of lipid unsaturation showed strong variations. After 30 to 120/150 days the antioxidative system seemed to reach a homeostasis different from that of time 0, accompanied by a constant increase of indole-3-acetic acid (IAA) after 60 days. The antioxidative system, after 150 days, lost its efficiency while LOOH levels were maintained higher than time 0 and IAA concentration was sufficient to allow sprouting.     

Relationship among lipoperoxides,jasmonates and indole-3-acetic acid formation in potato tuber after wounding

Plant responses to biotic and abiotic stress can be mediated by oxidised products and in this study we analysed the relation among some of them and the growth factor indole-3-acetic acid (IAA). The plant material used was potato tuber sliced below bud and incubated for different lengths of time before analysis. Wounding in potato tuber leads, in a very short time (0–30?min), to the generation of lipid hydroperoxides (LOOH) from polyunsaturated fatty acids (PUFA). These reactive species could cause a subsequent increase of 9 and 13-lipoxygenase (LOX, E.C.1.13.12.12.), analysed by RT-PCR and spectrophotometric assay, LOOH, Jasmonates and IAA all quantified by GC–MS analysis. The activation of 9 and 13-LOX, using different timing, leads to the formation of LOOH with a subsequent generation of jasmonates and IAA as highlighted by the addition on the potato tuber slices of salicylhydroxamic acid (SHAM), an inhibitor of LOX activity. A correlation between jasmonates and IAA resulted by testing their reciprocal influence during wounding in potato tuber. The relationship occurring among each hormone analysed during wounding underlines the fact that the jasmonates level can be regulated in situ and this can suggest a role for these compounds in potato tuber which has been underestimated up to now.