Heterosis in relation to genetic divergence in maize (Zea mays L.)

Summary The magnitude of heterosis was examined in relation to genetic divergence among 10 parents in a 10 × 10 diallel cross of maize. The 10 parents (varieties) were selected on the basis of multivariate analysis of quantitative characters using Mahalanobis' D²-statistic from a lot of 64 varieties of maize belonging to different geograshical regions of the world. The magnitude of heterosis for grain yield and its components was found to be higher with moderate (intermediate) parential diversity than with extreme ones. The results indicated that not only the genetic diversity but the high per se performance with respect to specific characters of interest should be taken into consideration also while selecting parents for hybridization.     

Haemato-biochemical alterations and oxidative stress associated with naturally occurring porcine circovirus2 infection in pigs

Tropical Animal Health and Production - Porcine circovirus2 (PCV2) infection in pigs is one of the major causes of economic loss to the farmers in terms of low production, slow growth and increase...     

Strategies for maximizing utilization of de-oiled rice bran (DORB) in the fish feed

De-oiled rice bran (DORB) is obtained after oil is removed from the rice bran. This is the commonly used ingredient in the feeding of Indian major carps due to its cheaper cost. DORB is used as a feed ingredient in cattle, poultry, and fish diet. Along with this, they are also used in making fiber-rich biscuits and extraction of an antioxidant compound like oryzanol and other industrial uses. Due to the increased competition, there will be a huge imbalance in the demand and supply for this ingredient in the years to come. DORB is associated with high fiber content, anti-nutrients, and non-starch polysaccharides which lead to its poor utilization resulting in a higher feed conversion ratio (FCR) in fish. Hence, the strategic utilization of this ingredient by solid-state fermentation, exogenous enzyme supplementation, and supplementing it with deficient nutrients like amino acids and fatty acids will help in improving the utilization of this ingredient.

     

Genetic diversity in common carp stocks assayed by random-amplified polymorphic DNA markers

The common carp (Cyprinus carpio L.) is one of the major aquaculture species, contributing nearly 35% to the inland fish production in Karnataka, India. Stocks collected from Hungary (2), Indonesia and Vietnam were assessed alongside two local stocks in a series of culture performance trials with the objective of setting up a base population for developing a breeding programme. The present study deals with the genetic divergence and polymorphism in these six stocks using random‐amplified polymorphic DNA (RAPD) markers. A total of 180 decamer random primers were screened for polymerase chain reaction (PCR) amplification (OPA 1‐20, OPB1‐20, OPC1‐20, OPD1‐20, OPE1‐20, OPF1‐20, OPG1‐20, OPP1‐20 and OPM1‐20). Eight primers were selected for analysis of common carp genotypes (OPA‐7, OPA‐20, OPB‐17, OPF‐10, OP F‐9, OPG‐4, OPG‐9 and OPP‐16). Out of 492 bands recorded, 57.1% were polymorphic. Stepwise regression analysis was carried out to find best combination markers affecting body weight (P<0.001). The results demonstrate major differences in the genetic structures between different stocks. Dendrogram data showed grouping of individuals according to stocks and corresponding data variables revealed the per cent homology within the stock and also found markers correlating to the body weight.     

Modifying climate change habitat models using tree species-specific assessments of model uncertainty and life history-factors

Species distribution models (SDMs) to evaluate trees’ potential responses to climate change are essential for developing appropriate forest management strategies. However, there is a great need to better understand these models’ limitations and evaluate their uncertainties. We have previously developed statistical models of suitable habitat, based on both species’ range and abundance, to better understand potential changes of 134 tree species habitats in the eastern United States (http://www.nrs.fs.fed.us/atlas). Our focus here is to build on these results via a more robust assessment framework called modification factors (ModFacs) that is made up of five components. ModFac 1 addresses nine biological characteristics (e.g., shade tolerance and seedling establishment) that quantify the influence of species life-history traits. ModFac 2 considers 12 disturbance characteristics (e.g., insect pests, drought, and fire topkill) which address the capacity of a species to tolerate and respond to climate-induced changes in habitat. ModFac 3-5 distill the tree SDM results and facilitate communication of model uncertainty; we quantified the variability in projected change for General Circulation Models (GCM) and emissions scenarios (ModFac 3), the extent to which each species’ habitat intersects novel climate conditions (ModFac4), and accounted for long-distance extrapolations beyond a species’ current range (ModFac5). The life-history components of ModFacs 1 and 2 demonstrate the marked variability among species in terms of biological and disturbance characteristics, suggesting diverse abilities to adapt to climate change. ModFacs 3-5 show that the information from the SDMs can be enhanced by quantifying the variability associated with specific GCM/emission scenarios, the emergence of novel climates for particular tree species, and the distances of species habitat shifts with climate change. The ModFacs framework has high interpretive value when considered in conjunction with the outputs of species habitat models for this century. Importantly, the intention of this assessment was not to create a static scoring system, but to broadly assess species characteristics that likely will play an important role in adaptation to climate change. We believe these scores based on biological, disturbance, and model synthesis factors provide an important expansion of interpretive and practical value to habitat model projections.     

Rapid detection of propiconazole and tebuconazole in wood by solid phase desorption: ion mobility spectrometry

The durability of wood is improved by wood preservatives. Due to new environmental legislation, commonly used active ingredients such as chromium and arsenate are being replaced by alternative and more environmentally friendly preservatives. However, the alternative wood preservatives are more difficult to detect in the wood. Detection of the preservatives is necessary in order to monitor millwork production for qualitative assessment of the wood preservative uptake. The aim of this study is to examine the use of solid phase desorption-ion mobility spectrometry (SPD-IMS) can be used for rapid detection of the wood preservatives propiconazole and tebuconazole in Scots pine (Pinus sylvestris). The findings proved that SPD-IMS is capable of detecting and distinguishing wood preservatives directly from treated wood shavings. SPD-IMS requires no additional sample preparation or extraction of the wood sample. The findings show that SPD-IMS is a fast and easily applied method for direct detection of propiconazole and tebuconazole in small wood samples.     

Intergenotypic competition in mixed stands of spring wheat genotypes

Summary Grain yield and yield components were studied in the three spring wheat genotypes HD 2160 (dwarf), Kalyansona (semi-dwarf) and C 306 (tall) in pure stands as well as in their binary mixed stands during two years. The grain yields of the three genotypes in pure stands ranked as follows: HD 2160 > Kalyansona > C 306. Four mixed stands, 3:1 HD:K, 1:1 HD:C in the first year and 1:1 K:C, 1:3 K:C in the second year out-yielded the pure stand of the better component genotype by 4.4, 2.7, 3.3 and 0.8 percent, respectively. Out of the nine mixed stands four in the first year and seven in the second year out-yielded the midmonoculture yields and the increases ranged from 1 to 7.6 percent. Mixed stands were more stable than pure stands.The yield and yield components of the dwarf genotype HD 2160 scored less and those of the taller genotype C 306 scored higher in mixed stands. The semi-dwarf genotype Kalyansona yielded more with HD 2160 and less with C 306. Plant height but not high yielding ability conferred high competitive ability. With respect to competitive ability the three genotypes ranked as follows: C 306 > Kalyansona > HD 2160.The results illustrate the importance of intergenotypic competition in increasing crop production and reducing genotype-environment interactions. Such studies are important to agronomists as genotypes with high competitive ability can be useful to combat the weed problem. They are also important to plant breeders for predicting the fate of genotypes with low competitive ability in heterogeneous populations.     

Applications of reduced tillage in hills of central Nepal

Conventional tillage practices on steep and fragile landscape of Himalayan hills result in significant loss of topsoil during rainy season. Soil erosion in Nepal mid-hills is the most critical during pre-monsoon season. Many reviews argue that reduced tillage could be an option to tackle this problem. However, very few field experiments to evaluate reduced tillage systems have to date been conducted in this region. Thus, a field experiment was initiated in factorial randomized complete block design on acidic sandy loam soil (Lithic Dystochrept) during the summer season of 2001 at Kathmandu University (1500 masl) to assess the effects of tillage and cropping patterns on soil and nutrient losses, crop yield and soil fertility. Two main treatments viz. conventional and reduced till, and two sub-treatments viz. sole maize (Zea mays) and maize + soybean (Glycine max) were considered. Soil organic carbon (OC), total nitrogen (N), plant available phosphorus (P) and exchangeable potassium (K) were determined for the original soil and eroded sediment using standard methods. Two years of data indicated annual soil and nutrient losses to be significantly lowered by reduced till as compared to conventional till. Total annual soil loss from conventional and reduced till was 16.6 and 11.1 Mg/ha, respectively. Similarly, annual nutrient losses associated with the eroded sediment were 188 kg OC/ha, 18.8 kg N/ha, <1 kg P/ha and 3.8 kg K/ha for conventional till and 126 kg OC/ha, 11.8 kg N/ha, <1 kg P/ha and 2.4 kg K/ha for reduced till. Soil OC and N losses were significantly higher in conventional till and this may be one of the major causes of fertility depletion in the Nepalese hills. Soil chemical properties did not differ due to tillage and cropping systems; however, over years pH, N and P were increased irrespective of treatments. Although treatments were at par for maize grain yield, conventional till + soybean produced highest grain yield (4.0 Mg/ha) followed by reduced till + soybean (3.9 Mg/ha) and conventional till sole maize (3.8 Mg/ha). Mixed cropping of legumes and maize do not help conserve soil and nutrient loss in hills of central Nepal. Thus, reduced till could be a viable option for minimizing soil and nutrient losses without sacrificing economic yields in central hills of Nepal.