Photodegradation of hexythiazox in different solvent systems under the influence of ultraviolet light and sunlight in the presence of TiO2, H2O2, and KNO3 and identification of the photometabolites

The photodegradation of the carboxamide acaricide hexythiazox in three different solvent systems (aqueous methanolic, aqueous isopropanolic, and aqueous acetonitrilic solutions) in the presence of H(2)O(2), KNO(3), and TiO(2) under ultraviolet (UV) light (λ(max) ≥ 250 nm) and sunlight (λ(max) ≥290 nm) has been assessed in this work. The kinetics of photodecomposition of hexythiazox and the identification of photoproducts were carried out using liquid chromatography-mass spectrometry. The rate of photodecomposition of hexythiazox in different solvents followed first-order kinetics in both UV radiation and natural sunlight, and the degradation rates were faster under UV light than under sunlight. Hexythiazox was found to be more efficiently photodegraded in the presence of TiO(2) than in the presence of H(2)O(2) and KNO(3). Two major photoproducts were separated in pure form using column chromatography and identified according to IR, (1)H NMR, and mass spectral information as cyclohexylamine and 5-(4-chlorophenyl)-4-methylthiazolidin-2-one. Another nine photoproducts were identified according to LC-MS/MS spectral information. The plausible photodegradation pathways of hexythiazox were proposed according to the structures of the photoproducts.     

Molecular systematics in Chrysanthemum × grandiflorum (Ramat.) Kitamura

An attempt was made to understand the molecular systematics and genetic differences between 10 original chrysanthemum cultivars and 11 mutants. The similarity among the cultivars and mutants varied from 0.17 to 0.90 using RAPD analyses, a simple but efficient method to distinguish cultivars and to assess parentage. Two distinct groups were found. Two cultivars were present as a separate group showing differences from all other cultivars. Mutants with different flower colour could be identified at the molecular level using RAPD technique holding promise to identify unique genes as SCAR markers. A high genetic distance among the different chrysanthemums showed that there exists a possibility of introgressing new and novel genes from the chrysanthemum gene pool.     

Effects of plastic mulches on root zone temperature and on the manifestation of tomato spotted wilt symptoms and yield of tomato

Tomato spotted wilt (TSW) disease is a serious constraint to tomato production in various regions of the world. The effect of TSW on tomato yield is largely influenced by time of infection. Early infection usually results in severe stunting of the seedling and even death of the plant. Plastic film mulches affect both the incidence of TSW, and plant growth and yield of tomato. The objective of the present study was to determine the effect of root zone temperature (RZT) as affected by plastic film mulch on the manifestation of symptoms of TSW, and growth and yield of tomato plants either artificially inoculated with tomato spotted wilt virus (TSWV) or under natural TSW infection. In artificially inoculated plants as well as in plants under natural TSW infection, vegetative top fresh weight (FW) and fruit FW both increased with the length of time after transplanting that the plants remained free from TSW symptoms. The root zone temperature was highest under black mulch (seasonal mean = 27.5 °C), followed by gray (27.0 °C), silver (25.8 °C), and white (24.8 °C) mulches. The plants grown on black mulch showed the earliest appearance of TSW symptoms, and had significantly reduced vegetative growth and fruit yields compared to plants on the other mulches. In conclusion, utilization of plastic mulches that created conditions of high RZT stress resulted in reduced plant growth and yield and predisposed the plants to earlier expression of TSW symptoms compared to plants grown at RZTs more favorable to tomato plant growth (optimal RZT = 26.1 °C [Díaz-Pérez, J.C., Batal, K.D., Granberry, D., Bertrand, D., Giddings, D., Pappu, H., 2003. Vegetative top growth and yield of tomato grown on plastic film mulches as affected by the appearance of symptoms of Tomato spotted wilt virus. HortScience 38, 395–399]). Since these plant responses to TSW under heat stress occurred in artificially inoculated plants as well as in plants under natural TSW infection, high RZTs probably affected the plants directly, independently of any possible effects on the thrips vectors.     

Artificial polyploidy in medicinal plants: Advancement in the last two decades and impending prospects

Medicinal plants are in huge demand since the consumption is widespread and ever-increasing globally. The conventional breeding programs are generally environmental dependent; prone to different biotic and abiotic stresses as well as the secondary metabolite content is too low to harvest. In this context, developing polyploid individuals artificially would be a remarkable approach to increase vigor and attain this objective. Polyploids often exhibit some morphological features that are different or greater in forms than their diploid progenies. Polyploidization can be induced by quite a few antimitotic agents. The most frequently used antimitotic chemicals are colchicine, trifluralin, and oryzalin. The whole method of induced chromosome doubling consists of a series of steps, including an induction phase, regrowth phase, and a confirmation technique to evaluate the rate of achievement. The induction phase depends on different factors, such as explant types, antimitotic agents, its different concentrations, and exposure durations. To evaluate the accomplishment of polyploidization, morphological or anatomical observations are recorded as a rapid method. However, chromosome count and flow cytometry are the most eminent method for absolute confirmation. Despite significant prospects of polyploidization, there has been very little research on medicinal plants. The current review gives an overview of the different parameters of in vitro chromosome doubling, the history of the technique, and progress made over the last two decades.     

Genetics of resistance to <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> in <Emphasis Type="Italic">Cucumis sativus</Emphasis> var. <Emphasis Type="Italic">hardwickii</Emphasis> R. Alef

The genetics of resistance to Cucumber mosaic virus (CMV) in Cucumis sativus var. hardwickii R. Alef, the wild progenitor of cultivated cucumber was assessed by challenge inoculation and by natural infection of CMV. Among the 31 genotypes of C. sativus var. hardwickii collected from 21 locations in India the lowest mean percent disease intensity (PDI) was recorded in IC-277048 (6.33%) while the highest PDI was observed in IC-331631 (75.33%). All the four cultivated varieties (DC-1, DC-2, CHC-1 and CHC-2) showed very high PDI and susceptible disease reaction. Based on mean PDI, 8 genotypes were categorized as resistant, 13 as moderately resistant, 9 as moderately susceptible and one as susceptible. A chi-square test of frequency distribution based on mean PDI in F₂ progenies of six resistant × susceptible crosses revealed monogenic recessive Mendelian ratio 1(R):3(S) to be the best fit. This monogenic recessive model was further confirmed by 1(R):1(S) ratio as the best fit for back cross with resistant parent and no fit for either 3:1 or 1:1 in the back cross with the susceptible parent. The results revealed that CMV resistance in C. sativus var. hardwickii was controlled by a single recessive gene. Considering the cross compatibility between C. sativus var. hardwickii and cultivated cucumber, the resistance trait can be easily transferred to cultivated species through simple backcross breeding.     

Effect of irrigation and nitrogen application methods on input use efficiency of wheat under limited water supply in a Vertisol of Central India

Field experiments were conducted in a deep Vertisol at the Indian Institute of Soil Science, Bhopal during the years 2001–2005 to assess the effect of five different irrigation strategies through combinations of sprinkler and flood irrigation and two N application methods on yield and water use efficiency of wheat (cv WH 147). The amount of irrigation applied each year differed according to the availability of water in the water harvesting pond to simulate the actual water crisis faced by the farmers in this region during these years due to monsoon failure. Results indicated that when wheat was grown only with 8-cm irrigation at sowing or 14 cm up to the crown root initiation stage, dry sowing of wheat immediately followed by sprinkler and subsequent irrigation through flooding produced the highest yield and water and nitrogen use efficiencies. However, when 20-cm irrigation was supplied up to the flowering stage or 14-cm irrigation was supplied up to tillering stage through sprinkler in 4 and 3 splits, respectively, at critical growth stages, maximized the grain yield and water and nitrogen use efficiencies. Across the years, the crop yield and water and nitrogen use efficiencies increased with increase in water supply.     

Root biomass, crop response and water-yield relationship of mustard (Brassica juncea L.) grown under combinations of irrigation and nutrient application

A 3-year study was carried out to assess the root biomass production, crop growth rate, yield attributes, canopy temperature and water-yield relationships in Indian mustard grown under combinations of irrigation and nutrient application for revealing the dynamic relationship of crop yield (Y) and seasonal evapotranspiration (ET). Three post-sowing irrigation treatments viz. no irrigation (I ₁), one irrigation at flowering (I ₂) and two irrigations one each at rosette and flowering stage (I ₃), three nutrient treatments viz. no fertilizer or manure (F ₁), 100% recommended NPK i.e., 60 kg N, 13.1 kg P and 16.6 kg K ha⁻¹ (F ₂) and 100% recommended NPK plus farmyard manure @ 10 Mg ha⁻¹ (F ₃) were tested in a split-plot design. Root biomass was significantly greater in I ₃ than I ₂ and I ₁, and in F ₃ than F ₂ and F ₁. The I ₃ × F ₃, I ₂ × F ₃ and I ₃ × F ₂ combinations maintained significantly greater crop growth rate, plant height, yield components, ET and crop yield and better plant water status in terms of canopy temperature, canopy-air temperature difference (CATD) and relative leaf water content (RLWC). Number of siliqua plant⁻¹ and seeds siliqua⁻¹ were the major contributors to the seed yield. Marginal analysis of water production function was used to establish Y–ET relationship. The elasticity of water production (E _wp) provides a means to assess relative changes in Y and ET, and gives an indication of improvement of Y due to nutrient application. The ET–Y relationships were linear with marginal water use efficiency (WUE_m) of 3.09, 4.23 and 3.95 kg ha⁻¹ mm⁻¹ in F ₁, F ₂ and F ₃, respectively, and the corresponding E _wp were 0.63, 0.71 and 0.61. This implies that the scope for improving yield and WUE with 100% NPK was little compared with 100% NPK + farmyard manure. The crop yield was highest in I ₃ × F ₃ combination, and the similar yield was obtained in I ₂ × F ₃ and I ₃ × F ₂ combinations. Application of organic manure along with 100% NPK fertilizers maintained greater crop growth rate, better water relation in plants, yield attributes and saved one post-sowing irrigation.     

Replacing saline–sodic irrigation water with treated wastewater: effects on saturated hydraulic conductivity,slaking, and swelling

Irrigation with saline–sodic water imposes sodic conditions on the soil and reduces the soil’s productivity. We hypothesized that replacing saline–sodic irrigation water with lesser saline–sodic treated waste water (TWW), albeit with higher loads of organic matter and suspended solids, might help sodic soils regain their structure and hydraulic conductivity. We studied hydraulic conductivity (HC), aggregate stability and clay swelling of a soil from the Bet She’an Valley, Israel using samples taken from a non-cultivated field (control), and plots irrigated with TWW, saline–sodic Jordan River (JR) water, and moderately saline–sodic spring (SP) water. Soil samples were taken at the end of the irrigation season (autumn 2005) and at the end of the subsequent rainy season (spring 2006). In the HC and the aggregate stability determinations, for both sampling seasons, the TWW-irrigated samples gave significantly higher values than the SP- and JR-irrigated samples, but lower than the samples from the control plot. The autumn samples exhibited, generally, higher HC and lower swelling levels compared with the spring samples. Conversely, aggregate stability of the spring samples was higher than that of the autumn samples. These seasonal changes in the results of the three tests were associated with seasonal changes in the salinity and sodicity of the soils. Contributions from the Agricultural Research Organization, The Volcani Center, Bet-Dagan 50250, Israel. No. 601/2007 series.