Progress and challenge towards reducing wheat spot blotch threat in the Eastern Gangetic Plains of South Asia: Is climate change already taking its toll?

Spot blotch, caused by Cochliobolus sativus, is a serious constraint to wheat production (Triticum aestivum L.) in the warmer plains of South Asia. Fourteen genotypes were tested in Bangladesh, India and Nepal during 6 years (2000–2005) to determine disease severity and resistance stability over these years. We analyzed the area under the disease progress curve per day (AUDPC/day) to assess spot blotch severity, and examined grain yield, 1000-kernel weight (TKW), days to heading, and plant height. Disease severity differed in the 6 years and several genotypes showed low disease severity in all years. A few genotypes had high grain yield and low disease severity in all years. Genotype Altar-84/Ae. Sq. (224)//Yaco, with the lowest disease severity and highest 1000-kernel weight (TKW) and grain yield was also the most stable for spot blotch resistance, TKW and grain yield. Results demonstrated that wheat genotypes with improved spot blotch resistance, high grain yield, acceptable TKW, and plant height are available as a result of the regional and international collaboration in South Asia. Despite this progress, the challenge lies ahead because of an apparent tendency of increasing spot blotch overall severity in the region and decreasing TKW over 6 years (2000–2005). Higher, average night time temperature during the month of March is an indicator showing that wheat crop performance is challenged in two ways—increasing spot blotch severity and decreasing TKW causing lower yield. The results underline the possible effect of changing climatic factors on disease pressure and the continuous need to identify new resistance sources to develop more spot blotch resistant wheat for the warmer Eastern Gangetic Plains of South Asia.     

黄瓜发芽期耐冷性与赖氨酸脱羧酶基因表达

 经15℃低温诱导，采用cDNA-AFLP技术从耐冷性强的黄瓜品种长春密刺中分离到一条特异片段，该片段在耐冷性弱的北京截头中不能被诱导，命名为cctr132。将cctr132回收测序并翻译为氨基酸序列，用blastx和blsatp程序在NCBI GenBank数据库中进行同源性检索和相似性比对，结果发现cctr132与水稻推测的类赖氨酸脱羧酶蛋白同源性为88.37%，相似性为100%，并且在CCTR132中检测到了赖氨酸脱羧酶家族推测的保守结构域PGGXGTXXE，说明黄瓜发芽期耐冷性与赖氨酸脱羧酶基因表达有关。     

Effect of micronutrients on B‐N‐Oxalyl l‐α, β‐diamino propionic acid level and its biosynthesis in Lathyrus Sativus

The detoxification of L. sativus grains by spraying of 0.5 ppm cobalt (nitrate) and 20 ppm molybdehum (ammonium molybdate) salts at the maximun flowering stage ‐ a suggestion based on preliminary findings ‐ has been confirmed in this investigation. Regulatory mechanisms of these micronutrients at the enzymatic level were also studied. On the basis of these observations, the involvement of a hitherto unknown biosynthetic pathway of BOAA cannot be ruled out.     

Iron and zinc absorption characteristics and copper inhibitions in cucurbitaceae

Iron and Zn absorption, interactions, and Cu inhibitions were characterized in cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus Thunb.), and pumpkin (Cucurbita moschata Poir.) by kinetic parameters V_max and K_m. Influx and V_max values for Fe and Zn absorption decreased in each species as plant age increased. For the Michaelis constant, K_m, Fe values in cucumber and watermelon and Zn values in watermelon and pumpkin were relatively unchanged with increased plant age. K_m values for Zn absorption in cucumber and Fe absorption in pumpkin decreased as plant age increased. Among species, watermelon appeared to have a particularly effective uptake mechanism for Zn at low solution concentrations. Non‐competitive inhibition of Zn absorption by Fe (20, 50 uM) was indicated in each species. Iron uptake in pumpkin was inhibited non‐competitively by Zn (5, 10 uM), however no significant effects of Zn on Fe absorption were evident in either watermelon or cucumber. Copper (0.5, 1, 5 uM) inhibited uptake of Fe non‐competitively and Zn competitively in each species.     

Protective role of proline against salt stress is partially related to the improvement of water status and peroxidase enzyme activity in cucumber

Abstract

A salt-sensitive cucumber cultivar “Jinchun No. 2” (Cucumis sativus L.) was used to investigate the role of proline in alleviating salt stress in cucumber. Proline was applied twice (day 0 and day 4 after salt treatment) as a foliar spray, with a volume of 25?mL per plant at each time. Plant dry weight, leaf relative water content, proline, malondialdehyde (MDA), Na⁺, K⁺ and Cl^? contents, as well as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) activities in the plants were determined at day 8 after salt treatment. The results showed that 100?mmol?L^–1 NaCl stress significantly decreased plant dry weight, leaf relative water and K⁺ contents, and increased leaf MDA, Na⁺ and Cl^? contents and SOD, POD, CAT and APX activities. However, leaf proline accumulation was not affected by salinity. The exogenous application of proline significantly alleviated the growth inhibition of plants induced by NaCl, and was accompanied by higher leaf relative water content and POD activity, higher proline and Cl^? contents, and lower MDA content and SOD activity. However, there was no significant difference in Na⁺ and K⁺ contents or in CAT and APX activities between proline-treated and untreated plants under salt stress. Taken together, these results suggested that the foliar application of proline was an effective way to improve the salt tolerance of cucumber. The enhanced salt tolerance could be partially attributed to the improved water status and peroxidase enzyme activity in the leaf.     

Synthetic Iron Chelates as Substrates of Root Ferric Chelate Reductase in Green Stressed Cucumber Plants

This work studied the behavior of different iron (Fe)-chelates as substrates of ferric chelate reductase (FCR) and their ability as Fe suppliers for mildly chlorotic plants. FCR activity and Fe concentration in xylem sap were determined in green stressed cucumber plants with different stress levels using different synthetic chelates as substrates. Both reduction and Fe concentration in the xylem sap were higher for the less-stable Fe chelates, except for Fe-EDTA, which presented a relatively low Fe concentration in sap. It was concluded that a high stability of the chelate in the nutrient solution reduces the Fe reduction, but other factors, such as the complexation of the Fe(II) by the chelating agents, should be considered when the complete process of Fe uptake is studied. The use of both indexes together, i.e., FCR determination and xylem sap concentration, is useful for understanding the Fe uptake from different Fe chelates.     

甘蓝型油菜与萝卜属间杂种的获得及分子鉴定

通过蕾期重复授粉和子房培养克服甘蓝型油菜与萝卜属间杂交障碍，提高杂种获得率。从组合湘油15×萝卜、681A×萝卜和742×萝卜分别获得12、28和18粒种子，前两组合分别得到21和11株F1代植株,而从组合 742×萝卜未得到再生植株。F1植株形态有些相似于母本，有些则不同于双亲。SSR分析显示，由湘油15×萝卜所获得的21株F1植株中有10株是真杂种。     

Barley mutants with enhanced level of resistance to Swedish isolates of Bipolaris sorokiniana,casual agent of spot blotch

Spot blotch, caused by Bipolaris sorokiniana, has become an increasingly important disease on barley in Sweden. In order to enhance our knowledge of this disease, eight Swedish B. sorokiniana isolates were assessed for their virulence pathotype on 30 barley genotypes including eight lines of mutant origin, designated B. sorokiniana tolerant (bst). A leaf screen assay revealed the presence of virulence groups 1 and 7 in Sweden. Several mutant genotypes demonstrated enhanced resistance responses (P = 0.0001), of which bst1:3 had the lowest leaf scoring value to the most virulent isolate, Swe2 (virulence group 7). To evaluate the host root responses, two contrasting isolates Swe2 and Swe4 (virulence group 7 and 1) were used to inoculate a set of eight differential lines, including four promising mutant lines from the leaf screen. Mutant bst1:6 was significantly less susceptible (P = 0.001) compared with the other barley genotypes tested, independent of the two isolates used. Mutants bst1, bst1:3 and bst1:4, which displayed less or no spots, are also considered promising genotypes for further breeding attempts.     

萝卜花药愈伤组织诱导及褐变因素初探

以萝卜为试材,研究了不同激素配比、供体基因型、光照与温度以及蔗糖浓度对花药愈伤组织诱导的影响,同时比较研究了花药愈伤组织褐变过程中几种抗氧化酶活性变化。结果如下：P403在2.0mg/L 2,4-D+1.0mg/L 6-BA+2.0mg/L KT的MS培养基中愈伤组织的诱导率最高,愈伤组织开始褐化的时间晚,抗氧化酶的活性较高;同时进行低温预处理、高温预培养和初期暗培养的协同效果较任何一种单独处理好;6%的蔗糖浓度有利于愈伤组织的诱导。     

硅对盐胁迫下黄瓜幼苗根系质膜、液泡膜酶活性的影响

研究硅对盐胁迫下黄瓜幼苗生长及根细胞质膜H^＋-ATPase、液泡膜H^＋-ATPase、H^＋-PPase和Ca^2＋-ATPase活性的影响。结果表明：盐胁迫严重抑制黄瓜幼苗生长,根细胞质膜H^＋-ATPase、液泡膜H^＋-ATPase、H^＋-PPase和Ca^2＋-ATPase活性明显降低。硅处理明显提高盐胁迫黄瓜根液泡膜H^＋-ATPase、H^＋-PPase、Ca^2＋-ATPase活性,一定程度上维持了液泡膜质子泵活性,有效地防御了细胞质酸化,这可能是硅提高黄瓜耐盐性的一个重要因素。