M. S. Saharan

Evaluation of 19,460 Wheat Accessions Conserved in the Indian National Genebank to Identify New Sources of Resistance to Rust and Spot Blotch Diseases

A comprehensive germplasm evaluation study of wheat accessions conserved in the Indian National Genebank was conducted to identify sources of rust and spot blotch resistance. Genebank accessions comprising three species of wheat–Triticum aestivum, T. durum and T. dicoccum were screened sequentially at multiple disease hotspots, during the 2011–14 crop seasons, carrying only resistant accessions to the next step of evaluation. Wheat accessions which were found to be resistant in the field were then assayed for seedling resistance and profiled using molecular markers. In the primary evaluation, 19,460 accessions were screened at Wellington (Tamil Nadu), a hotspot for wheat rusts. We identified 4925 accessions to be resistant and these were further evaluated at Gurdaspur (Punjab), a hotspot for stripe rust and at Cooch Behar (West Bengal), a hotspot for spot blotch. The second round evaluation identified 498 accessions potentially resistant to multiple rusts and 868 accessions potentially resistant to spot blotch. Evaluation of rust resistant accessions for seedling resistance against seven virulent pathotypes of three rusts under artificial epiphytotic conditions identified 137 accessions potentially resistant to multiple rusts. Molecular analysis to identify different combinations of genetic loci imparting resistance to leaf rust, stem rust, stripe rust and spot blotch using linked molecular markers, identified 45 wheat accessions containing known resistance genes against all three rusts as well as a QTL for spot blotch resistance. The resistant germplasm accessions, particularly against stripe rust, identified in this study can be excellent potential candidates to be employed for breeding resistance into the background of high yielding wheat cultivars through conventional or molecular breeding approaches, and are expected to contribute toward food security at national and global levels.

Draft Genome Sequence of Two Monosporidial Lines of the Karnal Bunt Fungus Tilletia indica Mitra (PSWKBGH-1 and PSWKBGH-2)

ABSTRACT Karnal bunt disease caused by the fungus Tilletia indica Mitra is a serious concern due to strict quarantines affecting international trade of wheat. We announce here the first draft assembly of two monosporidial lines, PSWKBGH-1 and -2, of this fungus, having approximate sizes of 37.46 and 37.21 Mbp, respectively.

Efficacy of botanicals and biopesticides against foliage feeding aphids in wheat

A field study was carried out during rabi 2013–14 to 2014–15 at the Experimental farm of Indian Institute of Wheat and Barley Research, Karnal, Haryana to determine the efficacy of promising entomopathogenic fungi and botanicals against wheat aphid. The entomopathogenic fungi, Metarhizium anisopliae 1.15% WP @ 4g/l was found to be the most effective with the least opulation of 18.03, 13.13, 5.93 and 11.00 aphids/shoot/plant at 1, 2, 7 and 15 days after spraying, respectively. The next effective was of Verticillium lecanii 1.15% WP @ 4 g/l with population of 14.20, 8.67 and 11.33 aphids/shoot/plant after 2, 7 and 15 days after spraying, respectively. There was no significant difference as regards yield, however the highest yield of 47.79q/ha was obtained with Metarhizium anisopliae 1.15% WP @ 4g/l followed by Verticillium lecanii 1.15% WP @ 4g/l (46.62q/ha).

Evaluation of new insecticides against wheat foliar aphid complex

An insecticide efficacy trial was carried out during 2013–14 at four locations viz., Karnal, Ludhiana, Niphad and Pantnagar for evaluation of six new insecticides against foliar aphid complex in wheat. Aphid counts were made on five randomly selected plants, one day before spray and then after 1, 2, 7 and 15 days after spray. After one day of spraying, flubendamide 480 SC @20g a.i./ha resulted in the least number of aphids at Karnal (4.33/shoot) and Ludhiana (1.06/shoot). However, thiamethoxam 25WG @12.5g a.i./ha and chlorantranilipride 18.5 SC @20g a.i./ha were observed as the best at Niphad (1.50/shoot) and Pantnagar (17.53/shoot), respectively. The maximum yield of 45.42 q/h and 58.31 q/ha at Karnal and Ludhiana was obtained with acetamiprid 20SP @20 g a.i./ha, respectively, whereas at Niphad and Pantnager, highest yield was obtained with clothianidin 50 WDG @15g a.i./ha and imidacloprid 17.8 SL@20g a.i./ha.

Determination of genetic and pathological variance among Tilletia indica isolates and monosporidial lines using PCR based markers and host differentials

Karnal bunt of wheat caused by Tilletia indica is an important international quarantine disease in many countries. In this investigation, genetic and pathological variation among the 10 isolates and 15 monosporidial (Ms) lines belonged to different locations of North-West India was studied. Depending upon the pathogenic potential, most virulent and least aggressive isolate was found from Chaksu (Rajasthan) and Tarau (HP), which scored coefficients of infection 70.98 and 6.22, respectively, on susceptible host genotype HD 2009 under artificially inoculated conditions. Fifteen Ms lines were inoculated in 20 combinations. Most virulent compatible combination was found KB2MsD × KB6MsA, which scored co-efficient of infection 74.91%. Out of 32 Inter Simple Sequence Repeats based molecular markers, 28 were polymorphic generating 192 reproducible bands for all the T. indica isolates and Ms lines in this study. A grouping analysis using the unrooted neighbour – joining method was consistent with DARwin software and winboot analysis and combination approach suggested that self-paired Ms lines exhibit narrow genetic diversity. This result will be useful for developing integrated strategies for disease management and breeding programmes for improvement of the varieties.