RESUMEN
Leymus secalinus (Blue wild rye) is a perennial grass species distributed in Leh-Ladakh region of India. Culms are usually solitary, 20-100 cm tall, 2-5-noded, smooth and glabrous. It is found on mountain slopes, rocky, stony and pebbled soils, grassy places, river banks, sandy and alkaline soils. It is one of the dominant species of the region and is mostly used for forage and grazing. L. secalinus plants with blackish-brown powdery spore mass/sori on the culm was observed in Leh region of Jammu and Kashmir, India during a wheat germplasm exploration (to collect wild relatives, land races, cultivars etc. of cultivated wheat) in September, 2018. Initially, sori were covered by the leaf sheath and at later stage more or less exposed with the absence of peridium. Infected culms and leaves are stunted, while inflorescences are abortive. Spores are globose, sub-globose to ovoid, blackish-brown in color, 3-5 x 4-4.5 µm in size, wall 0.5 µm thick and smooth. The fungus was identified as Tranzscheliella hypodytes (Schltdl.) Vanky & McKenzie based on morphological characteristics (Li et al. 2017; Vanky 2012, 2003; Vanky and McKenzie 2002). The ustilospore germination was not observed on potato dextrose agar during the lab experiment. In some cases, ustilospore germination is recorded in other smut fungi which shows considerable variation according to media and conditions used (Ingold, 1983). Moreover, there is no report available for the artificial culture of T. hypodytes. Identity was confirmed using the internal transcribed spacer (ITS) region of ribosomal DNA, amplified with universal primers ITS1 which was then sequenced. NCBI-BLAST showed 99.28% similarity with the ITS sequences of Tranzscheliella hypodytes (GenBank accession no. MH855460.1). The sequence was deposited in NCBI GenBank with accession number (MN108147). Pathogenecity test was conducted in glasshouse wherein smut infected samples of L. secalinus collected from Leh were made into small pieces and mixed with the sterilized soil filled in three pots before sowing. In addition, seeds were also mixed with smut spores before sowing. Inoculated pots after sowing were kept at 16±20C temperature and a relative humidity of 70% in a glass house. Control pots were maintained without inoculum. Inoculated and control pots were placed in separate chambers of the same glasshouse. Seventy days after sowing, inoculated plants were symptomatic, matching those described above and produced no seed. Pathogen reisolated from infected plants was identical in all respects to the isolate used to inoculate the plants, which confirmed the Koch's postulates. Control plants remained healthy and produced seed. Leh region is covered by sparse vegetation due to its topography and cold desert climate (cold, dry winter and warm, dry summer with very low precipitation, occuring in temperate region). Stem smut in L. secalinus can have significant negative impact on the fodder and grazing situation of the region. To our knowledge, this is the first report of stem smut caused by T. hypodytes on L. secalinus in India. A voucher specimen of the fungus was deposited at Herbarium Cryptogamae Indiae Orientialis (HCIO) (52182), ICAR-Indian Agricultural Research Institute, New Delhi.
RESUMEN
[This corrects the article DOI: 10.1371/journal.pone.0167702.].
RESUMEN
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.
