酸枣根系导管结构的可塑性对自然梯度干旱生境的适应机制

根系导管是植物吸收和输送水分的主要通道,导管的结构将最终决定其导水功能和效率,研究导管结构的可塑性是理解植物对干旱梯度适应机制的关键。以采自烟台-石家庄-银川-吐鲁番形成的自然梯度干旱生境中生长的酸枣植株为试验材料,采用离析法和植物显微技术,探究酸枣根次生木质部导管对梯度干旱生境适应的结构特征和机制。结果表明:酸枣根系次生木质部导管有6种类型,不同生境中同种导管的数量和形态差异较大。根据管尾情况可将导管分为三类:无尾型、一端有尾型和两端有尾型导管,且在结构上表现出特定的适应特征及规律。从烟台至吐鲁番随干旱加剧,根系中网纹导管管壁加厚,管尾变短;孔纹导管长度、宽度、直径减小,壁厚增加,管尾变长;螺纹导管长度变小,管壁变薄,管尾变短;梯纹导管长度、宽度和直径均降低,从无尾型向有尾型转变;木纤维长度、宽度变小,管壁变薄,管尾加长。与烟台样地的导管相比,石家庄、银川和吐鲁番样地的孔纹导管长度分别减小了17.63%、11.23%和7.67%;螺纹导管的管壁分别减小了20.2%、11.4%和14.6%;梯纹导管的长度和宽度分别减小了29.1%、37.6%、31.4%和20.7%、48.5%、28.6%;木纤维的长度分别减小了0.7%、1.5%和2.6%,宽度减小了2.2%、4.7%和5.4%,管壁厚度减小了33.2%、29.3%和22.1%。说明酸枣植株根系导管的可塑性较大,导管形态和结构的变化利于水分和养分的高效吸收和转运。导管长度、管壁和管尾的变化增强了根系的韧性和伸展能力,利于根系深扎、吸收深层土壤中的水分并快速补充植株在干旱环境中的蒸腾散失,从而适应干旱生境,保证植株的正常生长和代谢。     

Geographical distribution of traits and diversity in the world collection of pearl millet [<Emphasis Type="Italic">Pennisetum glaucum</Emphasis> (L.) R. Br., synonym: <Emphasis Type="Italic">Cenchrus americanus</Emphasis> (L.) Morrone] landraces conserved at the ICRISAT genebank

The genebank at ICRISAT conserves the largest collection of 23,092 pearl millet germplasm accessions originating in 52 countries. A total of 15,979 landraces originating in 34 countries and having geographic coordinates of the collection sites were selected to investigate the geographical distribution of pearl millet traits and diversity in the collection. Results revealed adaptation of pearl millet to latitudes ranging between 33.00°S and 36.91°N. Landraces with early flowering (33–40 days) were predominant in Pakistan, Ghana, Togo and India; with very late flowering (121–159 days) in Sierra Leone and the Central African Republic; with short plant height (80–100 cm) in India, Zambia and Sudan; with tallness (401–490 cm) in Chad, Burkina Faso, Nigeria and the Central African Republic; with high tillering (11–35) in India and Yemen; with high panicle exsertion (11–29 cm) in Ghana, Chad, India and Yemen; with long panicles (75–135 cm) in Nigeria and Niger; with thick panicles (41–58 mm) in Namibia, Togo and Zimbabwe and those with large seeds (16–19 g 1000 seeds^?1) were predominant in Togo, Benin, Ghana and Burkina Faso. Collections from Ghana for flowering (36–150 days), Burkina Faso for plant height (80–490), India and Yemen for total (1–35) and productive (1–19) tillers per plant, Niger for panicle exsertion (?45 to 21.0), panicle length (9–135 cm) and thickness (12–55 mm) and Zimbabwe for 1000 seed weight (3.5–19.3 g), were found as important sources for trait diversity. Launching collection missions for trait-specific germplasm is suggested to enrich the world collection of pearl millet at ICRISAT genebank for diversity.     

Molecular characterization of Desmodium species — An important ingredient of ‘Dashmoola’ by RAPD analysis

Identification of medicinal plants by their molecular signature is a fast growing tool. The identification of Desmodium gangeticum (L.) DC. (Shalparni, a constituent of Ayurvedic formulation “Dashmoolarishtha”) was carried out using genomic approach. Authentic samples of D. gangeticum(L.) DC., D. velutinum (Willd.) DC. and D. triflorum (L.) DC. were analyzed and compared to commercial samples of various origin. Within twenty primers used, eleven gave 223 RAPD fragments. RAPD profiles of three species showed very low similarity index (0.21–0.39), whereas market samples showed high similarity of 0.82–0.89 with authenticated D. gangeticum.     

Resistance to foliage feeding aphid in wheat

Experimental trials were conducted at Integrated Pest Management Programme, National Agriculture Research Centre Islamabad, to evaluate the resistance of host plants (cereals) against Rhopalosiphum padi (L.). For evaluation of susceptibility, twenty varieties/-advanced lines of National Uniform Wheat Yield Trails (NUWYT) Normal (N) of year 2004-2005 were used. In seedling bulk tests varieties/advanced lines were grouped into three categories resistant, moderately resistant and susceptible. Data from seedling bulk tests showed that DN-47 and PR 87 lines of wheat were resistant to aphid as compared to the other varieties/-advanced lines. In antixenosis tests varieties/-advanced lines were grouped into three categories, least preferred, moderately preferred, highly preferred. Lines V-01180, DN-47 and PR-84 were least preferred, sixteen varieties/-advanced lines were moderately preferred and only one variety V-9021 was found to be highly preferred.     

Effects of uniconazole with or without micronutrient on the lignin biosynthesis,lodging resistance,and winter wheat production in semiarid regions

Lodging stress results in grain yield and quality reduction in wheat. Uniconazole, a potential plant growth regulator significantly enhances lignin biosynthesis and thus provides mechanical strength to plants in order to cope with lodging stress. A field study was conducted during the 2015–2016 and 2016–2017 growing seasons, to investigate the effects of uniconazole sole application or with micronutrient on the lignin biosynthesis, lodging resistance, and production of winter wheat. In the first experiment, uniconazole at concentrations of 0(CK), 15(US1), 30(US2), and 45(US3) mg L~(-1)was applied as sole seed soaking, while in the second experiment with manganese(Mn) at concentration of 0.06 g L~(-1)Mn, 0.06 g L~(-1)Mn+ 15 mg L~(-1)uniconazole(UMS1), 0.06 g L~(-1)Mn+30 mg L~(-1)uniconazole(UMS2), and 0.06 g L~(-1)Mn+45 mg L~(-1)uniconazole(UMS3), respectively. Uniconazole sole application or with micronutrient significantly increased the lignin content by improving the lignin-related enzyme activities of phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase, tyrosine ammonialyase, and peroxidase, ameliorating basal internode characteristics, and breaking strength. The spike length, spike diameter, spikes/plant, weight/spike, yield/spike, and grain yield increased and then decreased with uniconazole application at a higher concentration, where their maximum values were recorded with UMS2 and US2 treatments. The lignin accumulation was positively correlated with lignin-related enzyme activities and breaking strength while, negatively correlated with lodging rate. Uniconazole significantly improved the lignin biosynthesis, lodging resistance, and grain yield of winter wheat and the treatments which showed the greatest effects were uniconazole seed soaking with micronutrient at a concentration of 30 mg L~(-1)and 0.06 g L~(-1), and uniconazole sole seed soaking at a concentration of 30 mg L~(-1).     

Comparison of three dielectric moisture sensors for measurement of water in saline sandy soil

The number of sensor types available for measuring soil water content has increased but investigations to compare their performance in saline soils needs clarification. In this study the performance of commercially available, low-cost soil moisture sensors [time domain reflectometry (TDR), PR1 and WET], all measuring changes in the dielectric constant of the soil water, was evaluated under laboratory conditions in a saline sandy soil. The three sensors were also tested in the same sandy soil growing drip irrigated sorghum ( Sorghum bicolor L. cv. Moench) in a greenhouse. Plants were irrigated daily with either saline water (ECw: 9.4 dS/m) or fresh water (0.11 dS/m). The volume of irrigation was equivalent to 100% of the pan evaporation. The results showed that measurement accuracy was strongly dependent on the salinity of the soil. The PR1 sensor overestimated volumetric water content ( θ ) when the salinity level exceeded 4 dS/m [root mean square of the standard error (RMSE) = 0.009 cm³/cm³]. The WET sensor significantly overestimated θ irrespective of the salinity level (RMSE = 0.014 cm³/cm³). The TDR sensor estimated θ with more accuracy (RMSE = 0.007   cm³/cm³) and thus can be considered as more reliable than the other two sensors. The calibrations were strongly affected by the salinity level of the water, so we recommend that calibration equations are modified to take account of salinity.     

Immunoprotective role of LaSota vaccine under immunosuppressive conditions in chicken challenged with velogenic avian avulavirus-1

The first objective of the present study was to evaluate if the antibodies induced by the live LaSota and killed Newcastle disease (sub-genotype VIIi) vaccines protect the chickens against exposure with pathogenic avian avulavirus-1 (AAvV-1) of chicken and/or pigeon origins. The second objective was to study the effect of vaccines on stressed birds (dexamethasone, aflatoxin, and heat stressed) with respect to antibody production and protection against pathogenic AAvV-1 challenge. Sixty-one-day-old Hubbard chickens were divided into six groups (gA–gF) with ten animals each. All the groups received LaSota (10⁵ EID₅₀, 0.1 ml per chick) on days 7 and 27 via eye drop and one intramuscular injection of a killed vaccine (sub-genotype VIIi) (10^7.5 EID₅₀, 1 ml) on day 18, except the control birds received the PBS only. Moreover, group gC-DEX received dexamethasone intramuscularly at a dose rate of 1-mg/kg body weight daily; gD-AFLA had received aflatoxin as oral gavage at a dose rate of 30 ppb daily, and gE-HEAT was kept under heat stressed (38 °C) till challenged. All the groups were challenged with AAvV-1 strain of chicken origin of sub-genotype VIIi, except the group gA-pigeon was challenged with pigeon-origin strain (sub-genotype VIm). The result showed that the gA-pigeon and gB-chicken vaccinate showed 100% and 80% protection. The immunosuppressive birds produced low pre-challenge HI titer, and protection was observed at 40%, 50%, and 70% in gC-DEX, gD-AFLA, and gE-HEAT, respectively. Our findings suggest the stress factors such as aflatoxin in the feed and dexamethasone are immunosuppressive in nature and suppress the immune response and its associated protective role during infection.

     

Evaluation of Sustainable Cropping Sequences for Ameliorating Saline-Sodic Soil with Amendments and Water Having Different EC to SAR Ratios

A pot experiment was conducted on saline-sodic soil following sorghum-oat and rice-wheat crop rotations and amending with gypsum (G), farm manure (FM), and mulch (M). Water of different qualities viz. electrical conductivity (EC) 0.6 + sodium adsorption ration (SAR) 6, EC 1.0 + SAR 12 and EC 2.0 + SAR 18 was used for irrigation. The results showed that one pore volume (PV) of brackish water with higher EC and SAR ratio may be used beneficially, if proper amendments are applied. For rice and oat crops, the order of effective amendments was G>FM>M>control (C). With sorghum and wheat, the order was FM>G > M > C. Salt removal from soils was the lowest when leaching fraction (LF) was 0.20 and was the highest when LF was 0.32, i.e. a direct positive relationship. This proposes that irrigation water and the salt accumulated in the profile should be measured after short intervals to avoid reoccurrence of salinity.     

Geographical patterns of diversity in pearl millet germplasm from Yemen

Yemen differs considerably from many other countries in its extreme variation in elevation. A set of 229 pearl millet germplasm accessions collected from diverse elevations of Yemen was characterized for 12 morpho-agronomic characteristics at ICRISAT, Patancheru, India. Analysis of variance revealed highly significant differences (P < 0.001) among elevational zones for flowering, plant height and seed weight when evaluated in the post-rainy season and for panicle length and thickness when evaluated in the rainy season. The differential performance of accessions for flowering and plant height during the rainy and post-rainy seasons at ICRISAT, Patancheru reflected the photoperiod and temperature sensitivity of the accessions. Shannon-Weaver diversity indices indicated high diversity from low elevations for flowering and plant height. The results of the present study imply that environmental factors such as elevation, temperature and rainfall are the important determinants of variation patterns of pearl millet in Yemen and pearl millet germplasm from high elevations of Yemen is a good source for early maturity, cold tolerance, short plant height and large seeds.