Promising versions of a commercial pearl millet hybrid for terminal drought tolerance identified through MAS.

Extreme climatic conditions like drought are a major threat to global food production. Terminal drought stress causes severe yield losses in pearl millet. Development of climate-resilient varieties/hybrids can minimize the yield losses to the farmers caused due to climatic extremes. In the present study, marker-assisted selection (MAS) was employed with an aim to develop improved version of HHB 226 by introgression of QTLs for terminal drought stress tolerance into the male parent of the hybrid (HBL 11). HBL 11 (recurrent parent) was crossed with PRLT 2 (donor) to develop F1 and backcrossed four times to raise BC4F1 and further selfed twice to raise BC4F3. Four polymorphic SSR markers were used to track the QTL introgressed lines in each subsequent generation until BC4F2. The recurrent parent genome recovery was assessed using 25 polymorphic SSRs. Morpho-physiological analysis of BC4F3 generation at field-level under terminal drought stress conditions showed that the QTL introgressed lines showed higher, grain yield, 1000-seed weight, relative water content (%), and lower electrolyte leakage (%) than the recurrent parent. Line number 63 performed best with all the four foreground markers, 97.20% recurrent parent genome recovery, 7.27 g 1000-seed weight, 73.27% relative water content, 65.06% electrolyte leakage, 0.58 (fv/fm) chlorophyll fluorescence, and 53.25 g grain yield per plant. Finally, the Improved version of HHB 226 was developed by using the Improved HBL 11 developed through MAS. Besides this, HBL 11 is the male parent of other commercial hybrids like HHB 223 and HHB 197 as well making Improved HBL 11 an asset to improve these pearl millet hybrids.

High-Throughput Phenotyping: A Platform to Accelerate Crop Improvement.

Development of high-throughput phenotyping technologies has progressed considerably in the last 10 years. These technologies provide precise measurements of desired traits among thousands of field-grown plants under diversified environments; this is a critical step towards selection of better performing lines as to yield, disease resistance, and stress tolerance to accelerate crop improvement programs. High-throughput phenotyping techniques and platforms help unraveling the genetic basis of complex traits associated with plant growth and development and targeted traits. This review focuses on the advancements in technologies involved in high-throughput, field-based, aerial, and unmanned platforms. Development of user-friendly data management tools and softwares to better understand phenotyping will increase the use of field-based high-throughput techniques, which have potential to revolutionize breeding strategies and meet the future needs of stakeholders.

Molecular breeding of ameliorating commercial pearl millet hybrid for downy mildew resistance.

Downy mildew (DM) caused by Sclerospora graminicola is the most calamitous disease of pearl millet. Therefore, for introgression of DM resistance (DMR) in HHB 197 (MH-1302), an elite pearl millet hybrid, a marker-assisted breeding was undertaken by targeting three DMR loci on linkage groups (LGs) 1, 2 and 4. Breeding programme was initiated by crossing HBL 11 (DM susceptible), male parent of HHB 197 hybrid with ICMP 451 (DM-resistant) to produce true F1 plants. By conducting three rounds of backcrossing and selection, BC3F1 lines were generated. Foreground selection was employed using six polymorphic simple sequence repeat (SSR) markers of the 18 total selected markers. Four of these markers were linked to LG 1, five to LG 2 and nine to LG 4. Background selection was performed in BC3F1 generation using 33 polymorphic SSR markers of a total of 56 evenly spread SSR markers in the pearl millet genome to check recovery of recurrent parent genome. On the basis of genotypic selection (foreground as well as background) using selected SSR markers, agronomic performance in field and DM screening in greenhouse; 10 improved HBL 11 lines were selected and crossed with ICMA 97111 to produce DM-resistant HHB 197 hybrid versions. Six putatively improved HHB 197 hybrids were successfully tested in first year trials at Hisar and Bawal locations of Haryana and two selected versions with higher yield and zero DM incidence will be further tested in multilocation trials.

Hsp transcript induction is correlated with physiological changes under drought stress in Indian mustard.

Brassica juncea is an important oilseed crop and drought stress is major abiotic stress that limits its growth and productivity. RH0116 (drought tolerant) and RH8812 (drought sensitive) genotypes were undertaken to study some of the physiological parameters and hsp gene expression related to stress tolerance under drought stress conditions. Differential response in terms of seed germination, electrolyte leakage, RWC, osmotic potential was observed in the selected genotypes. In vitro seed germination studies using PEG stress treatments indicated reduced seed germination with increasing levels of stress treatment. Electrolyte leakage increased, whereas, relative water content and osmotic potential decreased in stressed seedlings. Expression of hsp gene was found to be upregulated during drought stress as the transcripts were present only in the stressed plants and disappeared upon rehydration. The drought tolerant variety showed higher transcript accumulation as compared to the sensitive variety. The study showed that drought induced changes in gene expression in two contrasting genotypes were consistent with the physiological response.

Genetic diversity of mungbean (Vigna radiata L.) in iron and zinc content as impacted by farmers' varietal selection in Northern India.

From the last few years a debate has been continuing over the issue of malnutrition and hunger in the developing countries. The present article investigates the importance of participatory varietal selection in the development of a suitable cultivar of mungbean along with the nutritional content and the agronomic traits of the cultivars selected by farmers in participatory varietal selection. A combination of the conventional survey strategy, participatory varietal selection, molecular markers, and chemical analysis were used to carry out the study, and results revealed that the farmers have the capacity to utilize available genetic resources to manage disease, and they can identify the disease at early stages of plant development. The genetic diversity was studied using 23 inter-simple sequence repeat marker, which shows that the extent of genetic diversity ranges from 65% to 87%, while chemical analysis of selected mungbean cultivars shows a moderate amount of iron (3.9 mg/100 g) and zinc (2.5 mg/100 g).

MYB transcription factor genes as regulators for plant responses: an overview.

Regulation of gene expression at the level of transcription controls many crucial biological processes. Transcription factors (TFs) play a great role in controlling cellular processes and MYB TF family is large and involved in controlling various processes like responses to biotic and abiotic stresses, development, differentiation, metabolism, defense etc. Here, we review MYB TFs with particular emphasis on their role in controlling different biological processes. This will provide valuable insights in understanding regulatory networks and associated functions to develop strategies for crop improvement.

Sequence related amplified polymorphism (SRAP) analysis for genetic diversity and micronutrient content among gene pools in mungbean [Vigna radiata (L.) Wilczek].

Vigna radiata (L.) Wilczek, commonly called mungbean is an important pulse crop. Commercial cultivars contain low levels of iron and zinc and it is important to assess genetic variability in the available germplasm for improving micronutrient content in commercial cultivars. The present study was undertaken to study molecular diversity using Sequence-related amplified polymorphism (SRAP) among 21 Vigna radiata genotypes. Twenty nine SRAP primer combinations produced a total of 121 amplified bands which were polymorphic with an average of 4.65 bands per primer. The size of amplified bands ranged from 70 bp to 3,000 bp and 6 out of 29 SRAP primers were most useful in fingerprinting Vigna radiata genotypes under study. The similarity coefficients between different genotypes ranged from 0.45 to 0.96 with an average similarity value of 0.71. At an arbitrary cut-off at 60 % similarity level on a dendrogram, the Vigna radiata accessions were categorized into two major clusters. ML1108 and 2KM115 were found to be genetically similar. SMH99-1A and ML776 showed high iron and zinc content while Satya was poor in iron as well as zinc content. Mapping population involving ML776 and Satya could be used for tagging gene(s) for micronutrient content. The results indicated that SRAP markers were efficient for identification of Vigna radiata genotypes and assessment of the genetic relationships among them.

Biophysical studies on the base specificity and energetics of the DNA interaction of photoactive dye thionine: spectroscopic and calorimetric approach.

In this study absorbance, fluorescence, circular dichroic spectroscopy, viscosity, thermal melting and calorimetric techniques were employed to understand the binding of the phenothiazinium dye, thionine, with deoxyribonucleic acids of varying base composition. Strong hypochromic and bathochromic effects and quenching of fluorescence were observed that showed strong binding of thionine to the DNAs. The binding parameters evaluated from Scatchard analysis through McGhee-von Hippel analysis showed that the binding was non-cooperative and affinities of the order of 10(5)M(-)(1). The results of ferrocyanide fluorescence quenching studies and viscosity experiments, taken together suggested the intercalation of thionine while thermal melting, differential scanning calorimetry and circular dichroic studies provided evidence for the thermal stabilization and conformational perturbations associated with the binding. The thermodynamic parameters elucidated through sensitive isothermal titration calorimetric studies suggested that the binding was exothermic, characterized by negative enthalpy and large positive entropy changes and that the non-electrostatic contributions play a significant role for thionine association to DNA. The heat capacity changes obtained from the temperature dependence of enthalpy changes gave negative values suggesting substantial hydrophobic contribution in the DNA binding process of thionine. Further, an observation of enthalpy-entropy compensation in the DNA binding also suggested the involvement of multiplicity of non covalent interactions in the binding process. The base specificity of the complexation and energetics of the interaction of thionine to DNA are obtained for the first time from this study.

Bacterial genes involved in type I secretion and sulfation are required to elicit the rice Xa21-mediated innate immune response.

Innate immunity to microorganisms relies on the specific sensing of pathogen-associated molecules by host recognition receptors. Whereas studies in animals have largely focused on the recognition of extracellular pathogen-associated molecules by the TLR (toll-like receptor) superfamily, few studies have been carried out in plants, and it is not understood how these molecules are secreted or modified. The rice Xa21 gene encodes a receptor-like kinase that provides immunity against strains of the bacterial pathogen Xanthomonas oryzae pv. oryzae carrying AvrXa21 activity. We identified four X. oryzae pv. oryzae genes that are required for AvrXa21 activity. raxA, raxB, and raxC encode proteins with similarity to a membrane fusion protein, an ATP-binding cassette transporter, and an outer membrane protein, respectively, of bacterial type I secretion systems. The fourth gene, raxST, encodes a sulfotransferase-like protein. Sequence analysis of three naturally occurring X. oryzae pv. oryzae strains no longer recognized by Xa21 revealed alterations in the raxST and raxA genes. The raxC gene complemented an Escherichia coli tolC mutant for secretion of a double glycine-leader peptide confirming the function of raxC in type I secretion. These results indicate that bacterial type I secretion is necessary for Xa21-mediated recognition and immunity and further suggest that type I secretion and modification of pathogen-associated molecules play an important role in triggering the innate immune response in rice.