Molecular markers for late blight resistance breeding of potato: an update

Late blight is the most devastating disease of the potato crop that can be effectively managed by growing resistant cultivars. Introgression of resistance (R) genes/quantitative trait loci (QTLs) from the Solanum germplasm into common potato is one of the plausible approaches to breed resistant cultivars. Although the conventional method of breeding will continue to play a primary role in potato improvement, molecular marker technology is becoming one of its integral components. To achieve rapid success, from the past to recent years, several R genes/QTLs that originated from wild/cultivated Solanum species were mapped on the potato genome and a few genes were cloned using molecular approaches. As a result, molecular markers closely linked to resistance genes or QTLs offer a quicker potato breeding option through marker‐assisted selection (MAS). However, limited progress has been achieved so far through MAS in potato breeding. In near future, new resistance genes/QTLs are expected to be discovered from wild Solanum gene pools and linked molecular markers would be available for MAS. This article presents an update on the development of molecular markers linked to late blight resistance genes or QTLs by utilization of Solanum species for MAS in potato.     

Regeneration of tree species in the sub-tropical forest of Alaknanda Valley, Garhwal Himalaya, India

We studied the regeneration of tree species in the sub-tropical forest of Alaknanda Valley in Garhwal Himalaya, India. The overall regeneration status was fairly good in the study area. Seedling density ranged between 520 and 1,240 seedlings per ha while the density of saplings varied between 400 and 800 saplings per ha. Out of eight sites studied, five sites, viz., A1 , A2 , B1 , B2and C2contained the highest number of seedlings (280-480 per ha) and saplings (200-440 per ha) for Pinus roxburghii and remaining three sites viz., C1, D1and D2represented the highest number of seedlings (240-400 per ha) and saplings (200-240 per ha) for Anogeissus latifolius. The DBH class distribution of the tree species revealed that the highest number of individuals was concentrated in the lower diameter classes while smallest numbers were found in the higher diameter classes. Species such as Acacia catechu, Anogeissus latifolius, Dalbergia sissoo, Engelhardtia spicata, Lannea coromandelica, Mallotus philippensis and Pinus roxburghii have the largest number of saplings and seedlings in the lower DBH classes, suggesting that they have good regeneration potential. Other species such as Aegle marmelos, Bauhinia variegata, Bombax ceiba, Cassia fistula, Erythrina variegata, Haldinia cordifolia, Mangifera indica, Ougeinia oojeinensis, Phyllanthus emblica, Syzygium cumini, Terminalia alata and Toona hexandra have either no or very small number of saplings in the lower DBH classes, which indicates that the status of these species implies poor regeneration.     

Identification of bovine viral diarrhea virus type 1 in yaks (Bos poephagus grunniens) in the Himalayan region

Since cattle are widely infected by bovine viral diarrhea virus (BVDV) in India, we searched for pestivirus infection in yaks. Of 71 pure and crossbred yaks from Himalayan region, pestivirus antigen was detected by Ag-ELISA in three animals. Pestivirus in leukocyte and cell culture isolated virus samples originating from positive yaks was also confirmed by RT-PCR using panpestivirus specific primers selected from 5'-untranslated region (5' UTR). The 5' UTR, N(pro) and E2 regions were sequenced and used for genetic typing. Phylogenetic analysis revealed that pestiviruses detected in three Himalayan yaks were similar genetically, belonging to BVDV-1. Antigenic characterisation of yak pestivirus also confirmed the typing as BVDV-1. This is the first report on the identification of BVDV type 1 in yaks.     

Se18.9, an anti-phagocytic factor H binding protein of Streptococcus equi

Evasion of phagocytosis is an important virulence determinant of Streptococcus equi (S. equi subsp. equi), the cause of equine strangles and distinguishes it from the closely related but much less virulent S. zooepidemicus (S. equi subsp. zooepidemicus). We describe Se18.9, a novel H factor binding protein secreted by S. equi but not by S. zooepidemicus that reduces deposition of C3 on the bacterial surface and significantly reduces the bactericidal activity of equine neutrophils suspended in normal serum for both S. equi and S. zooepidemicus. Se18.9 is secreted abundantly by actively dividing cells and is also bound to the bacterial surface. Strong serum and mucosal antibody responses are elicited in S. equi infected horses. Although a gene identical to se18.9 was not detected in S. zooepidemicus, sequences encoding proteins of similar size with similar signal peptide sequences were found in 3 of 12 randomly selected strains. Since Se18.9 is unique to S. equi, and immunoreactive with convalescent sera and mucosal IgA, it has potential for immunodiagnosis and for study of mucosal antibody response to S. equi.     

Environmental behaviour and translocation of imidacloprid in eggplant,cabbage and mustard

The recently registered insecticide, imidacloprid, was applied to three vegetable crops at 20 and 40 g AI ha⁻¹. The persistence of the parent insecticide and its translocation, along with the quantification of the metabolites formed on these crops are presented. The parent insecticide dissipated with a half‐life of 3–5 days and persisted longest on mustard leaves. The detectable limit of the HPLC method was 0.01 µg g⁻¹. The metabolites 1‐(6‐chloropyridin‐3‐yl‐methyl)imidazolidin‐2‐one and 6‐chloronicotinic acid were found to be translocated by day 10 in eggplant, cabbage leaves and mustard leaves but not in cabbage curd. The MRL of imidacloprid is not documented by the FAO/WHO on these crops and comparison of the MPI with the TMRC, calculated on the residue data generated in this study, establishes the safety of the schedule. © 2000 Society of Chemical Industry     

Thraustochytrids of Mangrove Habitats from Andaman Islands: Species Diversity,PUFA Profiles and Biotechnological Potential

Thraustochytrids are the most promising microbial source for the commercial production of docosahexaenoic acid (DHA) for its application in the human health, aquaculture, and nutraceutical sectors. The present study isolated 127 thraustochytrid strains from mangrove habitats of the south Andaman Islands, India to study their diversity, polyunsaturated fatty acids (PUFAs), and biotechnological potential. The predominant strains were identified as belonging to two major genera (Thraustochytrium, Aurantiochytrium) based on morphological and molecular characteristics. The strain ANVKK-06 produced the maximum biomass of 5.42 g·L⁻¹, while ANVKK-03 exhibited the maximum total lipid (71.03%). Omega-3 PUFAs such as eicosapentaenoic acid (EPA) accumulated up to 11.03% in ANVKK-04, docosapentaenoic acid (DPA) up to 8.65% in ANVKK-07, and DHA up to 47.19% in ANVKK-06. ANVKK-06 showed the maximum scavenging activity (84.79 ± 2.30%) while ANVKK-03 and ANVKK-10 displayed the highest antibacterial activity against human and fish pathogens, S. aureus (18.69 ± 1.2 mm) and V. parahaemolyticus (18.31 ± 1.0 mm), respectively. All strains were non-toxic as evident by negative blood agar hemolysis, thus, the thraustochytrids are suggested to be a potential source of DHA for application in the health care of human and fish.     

Evaluation of housekeeping genes as references for quantitative real-time PCR analysis of gene expression in the murrel <Emphasis Type="Italic">Channa striatus</Emphasis> under high-temperature stress

Quantitative real-time polymerase chain reaction is the most advanced method of quantifying gene expression studies; however, the significance of the obtained results strongly depends on the normalization of the data to compensate for differences between the samples. In the present study, expression analysis of six different constitutively expressed genes viz. 18S ribosomal RNA, glyceraldehyde-3-phosphate dehydrogenase (gapdh), beta actin (βactin), ribosomal binding protein L13, tubulin and TATA-box-binding protein (tbp) were carried out to test their efficacy as reference genes in three different tissues, namely liver, gill and muscle of murrel Channa striatus exposed to high temperature for variable time periods. The stability and suitability of the genes were determined by using bioinformatic tools: GeNorm, NormFinder and BestKeeper. Based on the results, tub/βactin could be used as the reference genes for liver and gill tissues and βactin/gapdh could be the reference genes for muscle tissues in Channa striatus under both short- and long-term thermal stress.     

Effect of molybdenum stress on growth,yield and seed quality in black gram

Black gram (Vigna mungo L.) var. Shyam plants were raised in refined sand at four levels of molybdenum (Mo), i.e., low (0.002 µM) to excess (2 µM) for 70 days. The molybdenum deficiency symptoms appeared as interveinal chlorosis of young and middle leaves. Compared to control (0.2 µM Mo), total dry matter, seed yield and seed protein decreased at low and excess Mo. The concentration of Mo in leaves and seed as well as activity of nitrate reductase increased with an increase in Mo supply. Low and excess Mo deteriorated the quality of seeds by lowering the content of starch, sugars, protein, and nitrogen and increasing electrical conductivity of seed leachate. Molybdenum deficiency and excess both resulted in production of lightweight immature seeds, poor in vigor and germination potential. The values of sufficiency and threshold of toxicity in leaves were 0.078 and 2.15 µg Mo g^?1 dry matter of black gram.     

Evaluation and utilization of <Emphasis Type="Italic">Aegilops</Emphasis> and wild <Emphasis Type="Italic">Triticum</Emphasis> species for enhancing iron and zinc content in wheat

Grains of 80 accessions of nine species of wild Triticum and Aegilops along with 15 semi-dwarf cultivars of bread and durum wheat grown over 2 years at Indian Institute of Technology, Roorkee, were analyzed for grain iron and zinc content. The bread and durum cultivars had very low content and little variability for both of these micronutrients. The related non-progenitor wild species with S, U and M genomes showed up to 3–4 folds higher iron and zinc content in their grains as compared to bread and durum wheat. For confirmation, two Ae. kotschyi Boiss. accessions were analyzed after ashing and were found to have more than 30% higher grain ash content than the wheat cultivars containing more than 75% higher iron and 60% higher zinc than that of wheat. There were highly significant differences for iron and zinc contents among various cultivars and wild relatives over both the years with very high broad sense heritability. There was a significantly high positive correlation between flag leaf iron and grain iron (r = 0.82) and flag leaf zinc and grain zinc (r = 0.92) content of the selected donors suggesting that the leaf analysis could be used for early selection for high iron and zinc content. ‘Chinese Spring’ (Ph ^I ) was used for inducing homoeologous chromosome pairing between Aegilops and wheat genomes and transferring these useful traits from the wild species to the elite wheat cultivars. A majority of the interspecific hybrids had higher leaf iron and zinc content than their wheat parents and equivalent or higher content than their Aegilops parents suggesting that the parental Aegilops donors possess a more efficient system for uptake and translocation of the micronutrients which could ultimately be utilized for wheat grain biofortification. Partially fertile to sterile BC₁ derivatives with variable chromosomes of Aegilops species had also higher leaf iron and zinc content confirming the possibility of transfer of required variability. Some of the fertile BC₁F₃ and BC₂F₂ derivatives had as high grain ash and grain ash iron and zinc content as that of the donor Aegilops parent. Further work on backcrossing, selfing, selection of fertile derivatives, leaf and grain analyses for iron and zinc for developing biofortified bread and durum wheat cultivars is in progress. Nidhi Rawat, Vijay K. Tiwari, and Neelam Singh have contributed equally to the work.