Productivity and water use efficiency of sweet sorghum as affected by soil water deficit occurring at different vegetative growth stages

The growth and production of sweet sorghum [Sorghum bicolor (L.) Moench] crops under semi-arid conditions in the Mediterranean environment of southern Italy are constrained by water stress. The effects of temporary water stress on growth and productivity of sweet sorghum were studied during three seasons at Rutigliano (Bari, Italy). The aim of this research was to evaluate the sensitivity of phenological stages subjected to the same water deficit. In a preliminary study it was observed that stomata closed when pre-dawn leaf water potential (Ψ_b) became lower than −0.4 MPa. This criterion was used in monitoring plant water status in three different plots: one never stressed and two stressed at different phenological stages (‘leaf’ and ‘stem’) when mainly leaves or stems were growing, respectively. An evaluation of the sensitivity of phenological stages subjected to identical water stress was obtained by comparing the above-ground biomass and WUE of drought crops with those of the well-irrigated crop (up to 32.5 t ha⁻¹ of dry matter and 5.7 g kg⁻¹). The sensitivity was greatest at the early stage (‘leaf’), when a temporary soil water stress reduced the biomass production by up to 30% with respect to the control and WUE was 4.8 g kg⁻¹ (average of three seasons). These results help quantify the effects of water constraints on sweet sorghum productivity. An irrigation strategy based on phenological stage sensitivity is suggested.     

A cross disciplinary framework for linking farms with regional groundwater and salinity management targets

Irrigation delivers major benefits in food security and human development. Irrigation also leads to waterlogging and salinity which threaten the sustainability of irrigated agriculture and pose major socioeconomic and environmental risks. The issue can be addressed by limiting net recharge to groundwater such that the water and salt keep natural equilibria. Often the information on net recharge within catchments is unavailable, particularly at lower spatial scales such as the farm or paddock; this offers little guidance for on-farm land and water management decisions—basic decisions that ultimately impact regional net recharge and waterlogging and salinity dynamics. This paper develops a cross disciplinary framework based on the concept of net recharge for setting paddock scale targets and to link these to the regional targets and community's goals for sustainable irrigation management. A management model, cast in a dynamic programming format to integrate a detailed hydrological model with an economic model was applied to estimate the productivity, profitability and sustainability of irrigated agriculture in a region of the Murray Darling Basin in Australia. SWAGMAN^® Farm model was used to determine paddock scale net recharge. This interactive model enables an individual farmer to choose a profit optimizing crop mix while lowering net recharge; this in turn leads to a win-win outcome for all farmers. The net recharge metric can be used for the conversion of diffuse source groundwater recharge to a point source recharge at paddock scale, enabling the definition of private property rights to a common pool problem and assigning individual responsibilities for its management—a vexing issue and a new concept for the commons literature. Net recharge shows significant spatial and temporal variation which warrants a targeted/zonal approach to address the issue. Regional and targeted strategies and actions to address the issue are identified. Apart from its applied and action research orientation, the development of paddock scale net recharge metric is perhaps the most significant conceptual contribution of this research which can lead to shared management of groundwater aquifers.     

Analysis of the effect of ozone on soybean in the Mediterranean region: I. The consequences on crop-water status

This study was carried out over three successive years (2003–2004–2005) in the southern Mediterranean region of Europe. Soybean plants were subjected to well-watered and water-stress conditions, and three levels of ozone (zero, low and high) in open top chambers (OTC) during the growing seasons.

The paper has four objectives: (i) to reproduce in OTCs the ozone concentrations actually observed in the field; (ii) to analyze the effect of ozone on well-watered crops by comparing a “control” (OTC ozone filtered treatment) with two ozone levels (at the end of the soybean growing seasons accumulated AOT40 values were 3400 and 9000 ppb h for low and high ozone treatments, respectively); observations were carried out both at leaf scale (stomatal conductance) and at canopy scale (determination of daily evapotranspiration, AET); (iii) to take into consideration the effect of drought, where the leaf and canopy scale observations were also implemented on water-stressed crops; and (iv) to analyze and verify the reliability of the ozone exposure–plant response relationship.

In well-watered conditions, an increase in ozone concentration levels reduced stomatal conductance and AET. Reductions in AET were 14% and 28% at low and high ozone levels, respectively, as compared to the control treatment. Hence, the results of daily AET were consistent with stomatal conductance results.

In water stress conditions, on the contrary, an increase in ozone had no effect on stomatal conductance and AET.

During the 3-year study, significant relationships were found between AOT40 and relative (low or high to control ozone treatment) values of stomatal conductance and AET in well-watered conditions. The reliability observed for these relationships suggest that they will be useful in soybean growth and yield-prediction models.     

Dietary choline, betaine and lecithin mitigates endosulfan-induced stress in Labeo rohita fingerlings

A five-week experiment was conducted to delineate stress-mitigating effects of three different methyl donors in Labeo rohita fingerlings subjected to endosulfan toxicity. Four iso-nitrogenous and iso-caloric feed were prepared with and without supplementation of methyl donors. The feed were basal or control diet (i.e., without methyl donor supplementation), feed supplemented with choline, feed supplemented with betaine and feed supplemented with lecithin. Two hundred and twenty-five fishes were distributed randomly in five treatment groups each with three replicates. The experimental setup were normal water (without endosulfan) and fed with control diet (control group), endosulfan-treated water and fed with control diet (T?), endosulfan-treated water and fed with choline supplemented feed (T?), endosulfan-treated water and fed with betaine supplemented feed (T?) and endosulfan-treated water and fed with lecithin-supplemented feed (T?). The level of endosulfan in endosulfan treated water was maintained at the level of 1/10 of LC??, that is, 0.2 ppb. During the experiment, growth performances, metabolic enzyme activity and histological examination were done to assess the effect of treatments. The growth performance (percentage weight gain, feed conversion ratio, specific growth rate and protein efficiency ratio) and nutrient digestibility were significantly different (P<0.01) in lecithin, betaine and choline fed group when compared to endosulfan-exposed group fed with basal diet. The liver LDH and MDH activity were significantly (P<0.01) improved in the groups fed with methyl donor supplemented diet. The liver AST and ALT, brain AChE and muscle ALT did not change with supplementation in the diet, but muscle ALT and G6PDH significantly (P<0.01) changed with supplementation. The gill and liver ATPase and intestinal ALP were significantly (P<0.01) noticeably changed in supplemented group. After endosulfan exposure, histopathology alter like slight large vacuolation in hepatocyte and lipoid vacuole were observed and with supplementation normal appearance of liver were observed. The chromosome aberration (karyotype) was observed in endosulfan-exposed group. The result obtained in present study concluded that inclusion of methyl donors, particularly lecithin and betaine, in feed as nutritional supplements has a potential stress-mitigating effect in L. rohita fingerlings.     

Occurrence of Prunus necrotic ringspot virus on nectarine (Prunus persica) in India

This paper presents the results of the first survey for Prunus necrotic ringspot virus (PNRSV) on nectarine ( Prunus persica ) in India, where stone fruits are grown on a commercial scale. Using basic diagnostic techniques such as ELISA and RT-PCR, the occurrence of Prunus necrotic ringspot virus is reported for the first time on nectarine ( Prunus persica ) in India.     

Molecular analyses of genetic variability in soap nut (Sapindus mukorossi Gaertn.)

Sapindus mukorossi Gaertn. (Sapindaceae) is commercially an important plant much valued for its fruits commonly known as soap nut as well as for the seed oil used as a feed-stock for biodiesel production. Molecular polymorphism, determined, using three single primer amplification reaction (SPAR) methods (RAPD, DAMD and ISSR) is used to assess the genetic variability in 69 accessions of S. mukorossi Gaertn., encompassing different geographical regions in India. Cumulative band data generated using the three SPAR methods resulted in 82.49% polymorphism across all genotypes of S. mukorossi Gaertn. UPGMA tree showed two major clusters that were in accordance with the geographical diversity. The intra-population genetic diversity (0.16), Shannon information index (0.24) and polymorphic loci (45.62%) were highest in AS population, while the corresponding lowest values were recorded in HP population. The inter-population average distance ranged from 0.05 (GA and HP) to 0.26 (AP and HP). Based on these distances, the UPGMA tree for the populations was computed, which showed the presence of two major clusters. Cluster I contained all the populations from Himachal Pradesh (HP) and Uttarakhand (GA and KU) and cluster II grouped the populations from North Eastern region (AS, AP, MG). The present study showed that SPAR methods are informative and useful to unravel the diversity among different populations of the soap nut plants and is a prelude for further utilization of promising and genetically divergent materials in the breeding programmes.     

Acute and chronic effects of aqueous ammonia on marbled spinefoot rabbitfish,Siganus rivulatus (Forsskål 1775)

Ammonia is a metabolite of aquatic organisms which might reach deleterious levels in intensive fish farms. The aim of the present study was to determine median lethal concentrations (96‐h LC₅₀) of total ammonia nitrogen (TA‐N) on marbled spinefoot rabbitfish (Siganus rivulatus) and chronic effects of TA‐N on survival, growth and behaviour of juvenile rabbitfish over a 50 day period. In the first experiment, fish were exposed to 0, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 mg L^?1 TA‐N for 96 h and survival evaluated. In the second experiment, 12 fish were stocked per 50‐L tank and treated with one of 0, 2, 4, 6, 8, 10 and 12 mg L^?1 TA‐N with three replicate tanks per treatment. Survival and growth were determined and histopathological alterations of gills due to chronic ammonia exposure were studied by light and electron microscopy. The 96‐h LC₅₀ values were 16–18 mg L^?1 TA‐N. In the chronic exposure experiment, fish reared in water with 0 mg L^?1 TA‐N had 100% survival and had 50% weight increase in 50 days. Fish at 2 and 4 mg L^?1 TA‐N all died whilst fish in 6, 8, 10 and 12 mg L^?1 TA‐N survived and grew albeit less than in treatment 0 mg L^?1. Gills from ammonia treated fish displayed severe histological and ultrastructural alterations including hyperplasia, hypertrophy and fusion of secondary lamellae, aneurysms and presence of pleomorphic altered cells. Chronic exposure to ammonia is deleterious to marbled spinefoot rabbitfish and low concentrations of ammonia appear to kill the fish in <50 days whilst fish can survive for more than 50 days at concentrations between 6 and 12 mg L^?1 TA‐N.     

Prevalence of Ocular Disorders in an Indian Population of Horses

The objective of this clinical study was to report the prevalence of ocular disorders in a large population of horses from the Indian army. Both eyes of 500 horses were examined using a direct ophthalmoscope and by a transillumination procedure. Intraocular pressures were measured in several study horses. Fluorescein dye, Schirmer tear test, and menace testing were performed when indicated. Corneal culture swabs were collected from horses affected with corneal ulcers found on ophthalmoscopic examination. A total of 100 horses were found to be affected with some form of ocular disorder. The eye problems recorded were congenital eye lid disorders (2%) and included a subcutaneous cyst in the lower eye lid and slit in upper eye lid; conjunctivitis (12%); chronic interstitial keratitis (30%); a parasite in the anterior chamber (1%), which was however not removed for genus and species identification; phthisis bulbi (1%); uveitis (24%); glaucoma (13%); cataracts (3%); unilateral retinal hemorrhage (1%); luxation of cataractous lens (3%); posterior synechia (2%); and corneal ulceration (8%). Pseudomonas spp was the most common bacteria identified in horses affected with corneal ulceration. Vision-threatening ocular disorders are high in Indian army horses; this is a cause of major concern for the rider and the horse and, therefore, it is important to include ocular examination in horses as part of a routine and complete physical examination.