Activities of mixtures of soil-applied herbicides with different molecular targets

The joint action of soil-applied herbicide mixtures with similar or different modes of action has been assessed by using the additive dose model (ADM). The herbicides chlorsulfuron, metsulfuron-methyl, pendimethalin and pretilachlor, applied either singly or in binary mixtures, were used on rice (Oryza sativa L.). The growth (shoot) response curves were described by a logistic dose-response model. The ED50 values and their corresponding standard errors obtained from the response curves were used to test statistically if the shape of the isoboles differed from the reference model (ADM). Results showed that mixtures of herbicides with similar molecular targets, i.e. chlorsulfuron and metsulfuron (acetolactate synthase (ALS) inhibitors), and with different molecular targets, i.e. pendimethalin (microtubule assembly inhibitor) and pretilachlor (very long chain fatty acids (VLCFAs) inhibitor), followed the ADM. Mixing herbicides with different molecular targets gave different results depending on whether pretilachlor or pendimethalin was involved. In general, mixtures of pretilachlor and sulfonylureas showed synergistic interactions, whereas mixtures of pendimethalin and sulfonylureas exhibited either antagonistic or additive activities. Hence, there is a large potential for both increasing the specificity of herbicides by using mixtures and lowering the total dose for weed control, while at the same time delaying the development of herbicide resistance by using mixtures with different molecular targets.     

Cultivar-Specific Response of Soybean (Glycine max L.) to Ambient and Elevated Concentrations of Ozone Under Open Top Chambers

Two cultivars of soybean (Pusa 9814 and Pusa 9712) were investigated to evaluate the impact of ambient and elevated concentrations of ozone (O₃) in a suburban site of India with and without application of 400 ppm ethylenediurea (EDU) in open top chambers having filtered air (FCs), non-filtered air (NFCs), and non-filtered plus 20 ppb O₃ (NFCs?+?20 ppb). Significant reductions were observed in various growth parameters, biomass accumulation, and yield attributes of soybean cultivars due to ambient O₃ in NFCs and elevated concentration of O₃ in NFCs?+?20 ppb. Reductions in all parameters were of lower magnitude in plants treated with EDU as compared to non-EDU treated plants. Yield (weight of seeds plant^?1) increased by 29.8% and 33% in Pusa 9712 and by 28.2% and 29.0% in Pusa 9814 due to EDU treatment in plants grown at ambient and elevated levels of O₃, respectively. The results clearly showed that (a) EDU can be effectively used to assess phytotoxicity of O₃ by providing protection against its deleterious effects, (b) EDU can be used for biomonitoring of O₃ in areas experiencing its higher concentrations, and (3) EDU is more effective against higher concentrations of O₃.     

Effects of deer browsing on the survival and growth of <Emphasis Type="Italic">Abies homolepis</Emphasis> and <Emphasis Type="Italic">Picea jezoensis</Emphasis> var. <Emphasis Type="Italic">hondoensis</Emphasis> seedlings after fencing on Mt. Ohdaigahara

We evaluated the survival and growth of Abies homolepis and Picea jezoensis var. hondoensis seedlings on Mt. Ohdaigahara, where the population of sika deer (Cervus nippon) is high and an experimental fence has been in place for 13 years. No significant differences were detected in the survival of small seedlings between fenced and unfenced plots. The growth of A. homolepis was significantly higher in the fenced plot, but growth of P. jezoensis var. hondoensis did not show significant differences between fenced and unfenced plots. Seedlings of height ≤5 cm in the forest floor vegetation of the unfenced plot were probably too small for deer to find and browse, so they survived.     

Evaluation of Different Mn Efficiency Indices and their Relation to Morphophysiological Traits in Diverse Wheat Genotypes

Wheat genotypes display differential tolerance to manganese (Mn) deficiency. Growing Mn-efficient cultivars in Mn deficient soil could be effective in improving yields. A pot experiment was conducted with eight genotypes grown in Mn deficient soil treated with 0 (no Mn fertilizer) and 50 ppm (50 mg Mn kg^?1soil applied as mangansese sulfate monohydrate (MnSO₄.H₂O) Mn. The genotypes were classified on the basis of grain yield and grain physiological efficiency as efficient and responsive (SAMNYT 410, GLUPRO 200, PBW 621, and BW 9178), efficient and nonresponsive, inefficient and responsive (HD 2967), and inefficient and nonresponsive (PDW 314, PDW 291, and PBW 636). The genotypes in different groups differed in morphophysiological characteristics; efficient and responsive genotypes recorded more leaf area, higher SPAD index, higher Fv/Fm ratio, and longer roots than inefficient and nonresponsive. Efficient and responsive genotypes are desirable by farmers, whereas inefficient and responsive genotypes in a breeding program for their Mn-responsive characteristics.     

Sex-linked AFLP marker identification in dioecious Betelvine (Piper betle L.)

This study aimed to develop sex-specific AFLP markers for dioecious Piper betle (Betelvine). A combination of ulk segregant analysis (BSA) and non-radioactive labelling led to simple, rapid and reliable PCR-based screening of sex-specific markers. A total of nine primer combinations were screened using BSA for male and female cultivars. Seven out of nine primer combinations produced bands specific to either of the sex. These seven primer combinations when used for screening DNA sample from individual male and female cultivars yielded two primer combinations which produced male sex-specific markers. Primer combinations EcoRI-CTA/MseI-CTA and EcoRI-CGT/MseI-CGT produced unique fragments of ~ 147 bp and ~ 326 bp, respectively, in bulk DNA as well as in DNA sample from individual male and female cultivars. These unique fragments were present in all the tested males and absent from all the tested female cultivars.     

Development of a RAPD marker-based classification criterion for quality semen production in Holstein crossbred bulls

In cattle production systems, an intense selection pressure for production traits has resulted in the decline of fertility traits. To optimize an efficient reproduction system, the inclusion of both male and female fertility traits in the selection process is very much essential. RAPD (Random Amplified Polymorphic DNA) was developed as a molecular biology tool and has been extensively used, to study intra- and interspecific genetic diversity. The present study was undertaken to utilize RAPD primers to investigate the association between DNA markers and semen quality traits viz. Sperm concentration, total sperm count ejaculate and initial sperm motility and thereby to identify good/poor semen producers. DNA isolated from the blood samples of healthy bulls was subjected to RAPD-PCR. The multiple regression analysis followed by independent t test was carried out to identify suitable markers. Based on the results, only 12 bands were identified as marker suitable for any of the quality trait. This includes, OPA2 ~ 760, OPA2 ~ 700, OPA6 ~ 1,200, OPA9 ~ 400, OPA9 ~ 380, OPA12 ~ 970, OPA14 ~ 715, OPA14 ~ 605, OPA16 ~ 485, OPA17 ~ 860 and OPA18 ~ 480. Multiple regression analysis selected, OPA2 ~ 760 and OPA2 ~ 1,750 for sperm concentration and OPA2 ~ 760, OPA2 ~ 700, OPA9 ~ 620, OPA4 ~ 670 and OPA18 ~ 1,015 for total sperm count/ejaculate. But the t test revealed a significant association between OPA2 ~ 760 and total sperm count. Further, discriminant function analysis also identified this marker in the first step itself. The results of the present study can be exploited as a low-cost alternative strategy for identification of good /poor semen producers in crossbred bulls at an early age.     

Guar genes to genome and meta-analysis of SSR markers in sequencing studies

Genetic Resources and Crop Evolution - Guar (Cyamopsis tetragonoloba (L.) Taub.), or cluster bean, traditionally grown for vegetable and fodder, has gained commercial importance across the globe...     

Evaluation of an Indian germplasm collection of the medicinal plant Bacopa monnieri (L.) Pennell by use of multivariate approaches

Twenty seven accessions of Bacopa monnieri collected from semi-temperate, subtropical and tropical environments at geographically distinct locations in India were examined for genetic variability carried in them at Lucknow, India in a semi-temperate environment. The accessions were grown in earthen pans, arranged in completely random block design, replicated four times, and observed for 13 qualitative and 24 quantitative characters, including bacoside-A content of herbage. On the basis of principal component and canonical variable analyses, the accessions could be grouped into seven clusters, of 2 to 6 accession sizes. The metroglyph analysis using five qualitative traits, cluster analysis and dendrogram drawn using D² data separated the clusters IV and V and cluster VII from all the others. The bacoside-A content of the herbage was found to be usually low in clusters of accessions possessing vigorous vegetative growth such as in cluster VII. It was also observed that some of the clusters included accessions having wide geographical origins. It was inferred that both the gross agroclimatic environment of a region and microenvironment in the vicinity of water bodies where a Bacopa monnieri genotype occurred must have interacted for the natural selection of the concerned genotype. This revised version was published online in July 2006 with corrections to the Cover Date.