Characterization of wheat-Thinopyrum bessarabicum genetic stock for stripe rust and Karnal bunt resistance

Utilization of modern breeding techniques for developing high yielding and uniform plant types ultimately narrowing the genetic makeup of most crops. Narrowed genetic makeup of these crops has made them vulnerable towards disease and insect epidemics. For sustainable crop production, genetic variability of these crops must be broadened against various biotic and abiotic stresses. One of the ways to widen genetic configuration of these crops is to identify novel additional sources of durable resistance. In this regard crops wild relatives are providing valuable sources of allelic diversity towards various biotic, abiotic stress tolerance and quality components. For incorporating novel variability from wild relative’s wide hybridization technique has become a promising breeding method. For this purpose, wheat-Th. bessarabicum amphiploid, addition and translocation lines have been screened in field and screen house conditions to get novel sources of yellow rust and Karnal bunt resistant. Stripe rust screening under field conditions has revealed addition lines 4JJ and 6JJ as resistant to moderately resistant while addition lines 3JJ, 5JJ, 7JJ and translocation lines Tr-3, Tr-6 as moderately resistant wheat-Thinopyrum-bessarabicum genetic stock. Karnal bunt screening depicted addition lines 5JJ and 4JJ as highly resistant genetic stock. These genetic stocks may be used to introgression novel stripe rust and Karnal bunt resistance from the tertiary gene pool into susceptible wheat backgrounds.

Effect of meteorological parameters on Karnal bunt incidence in wheat under different agroclimatic zones of Punjab

To quantify the effect of meteorological parameters on incidence of Karnal bunt in wheat crop, an investigation was done using 9 to 12 season’s data of Bathinda and Ludhiana stations of Punjab. Maximum temperature during March in range of 25-31oC, minimum temperature of February (8.5-11.0oC), morning and evening relative humidity of March in range of 85-95 and 40-60 per cent respectively, rainfall more than 25 mm with sunshine hours 5.5-9.0 hrs/day during mid February to mid March favour Karnal bunt in wheat crop. Maximum temperature of March showed significant negative correlation with incidence of Karnal bunt whereas minimum temperature of February showed significant positive correlation with disease incidence at both locations. Morning and evening relative humidity showed significant positive correlation with disease incidence. Rain amount and rainy days during mid February to mid March significantly influenced disease incidence. Sunshine hours had negative correlation with disease incidence. Backward multiple linear regression (BMLR) analysis indicated maximum temperature, rainfall and sunshine hours play significant role in Karnal bunt incidence at Ludhiana. However, at Bathinda, maximum temperature, evening time relative humidity, rain amount and rainy days played significant role.

ARTIFICIAL FIELD INOCULATION OFBREAD WHEAT ADVANCED LINES WITH TILLETIAINDICA, CAUSAL AGENT OF KARNAL BUNT

The reaction to Tilletiaindica of one thousand and ninety twobread wheat advanced lines were evaluated in the field during the crop season 2016-2017. Sowing in beds with two rows was carried out on November 11 and 24, 2016, using 8 g of seed. Five spikes per line were inoculated by injection with 1 mL of an allantoidsporidial suspension (10,000/mL) during the boot stage, and at maturity the percentage of infection was determined by counting healthy and infected grains. The range of infection in the first date was 0-88.83 with a mean of 31.81%, while in the second date it was 0-82.65% with a mean of 24.44%.The range of infection of the two dates was 0.46-83.71% with a mean of 28.12%.Sixteenlines showed a percentage of infection equal or below 5.0% in both dates, and out of those lines, the following five showed less than 2.5%: two sister lines of MUNAL#1/FRANCOLIN#1*2/3/ATTILA*2/PBW65//MURGA(CMSS12Y00701T-099TOPM-099Y-099M-0SY-13M-0WGY), MUNAL#1/FRANCOLIN#1*2/3/ATTILA*2/PBW65//MURGA (CMSS12Y00701T-099TOPM-099Y-099M-0SY-17M-0WGY), BAJ#1/3/KIRITATI//ATTILA*2/PASTOR*2/4/MUTUS*2/TECUE#1, VILLAJUAREZF2009/6/ATTILA/3*BCN//BAV92/3/PASTOR/4/TACUPETOF2001*2/BRAMBLING/5/PAURAQ, and KACHU/BECARD//WBLL1*2/BRAMBLING/4/FRET2/TUKURU//FRET2/3/MUNAL#1. Lines with the highest percentage of infection were: BABAX/LR42//BABAX*2/3/KUKUNA/4/CROSBILL#1/5/BECARD/6/KSW/SAUAL//SAUAL/7/BABAX/LR42//BABAX*2/3/KUKUNA/4/CROSBILL#1/5/BECARD with 88.83 in the first date,MUU/KBIRD//2*KACHU/KIRITATIwith 84.77 and 82.65%in the first and second date, respectively, and TACUPETOF2001*2/BRAMBLING//WBLL1*2/BRAMBLING/6/WBLL1*2/KURUKU*2/5/REH/HARE//2*BCN/3/CROC_1/AE.SQUARROSA(213)//PGO/4/HUITES/7/BAV92//IRENA/KAUZ/3/HUITES/4/2*ROLF07 with 81.67% in the first date. The average of the three highest levels of infection of the susceptible checkwas99.7%.

Four In Silico Designed and Validated qPCR Assays to Detect and Discriminate Tilletia indica and T. walkeri, Individually or as a Complex

Several fungi classified in the genus Tilletia are well-known to infect grass species including wheat (Triticum). Tilletia indica is a highly unwanted wheat pathogen causing Karnal bunt, subject to quarantine regulations in many countries. Historically, suspected Karnal bunt infections were identified by morphology, a labour-intensive process to rule out other tuberculate-spored species that may be found as contaminants in grain shipments, and the closely-related pathogen T. walkeri on ryegrass (Lolium). Molecular biology advances have brought numerous detection tools to discriminate Tilletia congeners (PCR, qPCR, etc.). While those tests may help to identify T. indica more rapidly, they share weaknesses of targeting insufficiently variable markers or lacking sensitivity in a zero-tolerance context. A recent approach used comparative genomics to identify unique regions within target species, and qPCR assays were designed in silico. This study validated four qPCR tests based on single-copy genomic regions and with highly sensitive limits of detection (~200 fg), two to detect T. indica and T. walkeri separately, and two newly designed, targeting both species as a complex. The assays were challenged with reference DNA of the targets, their close relatives, other crop pathogens, the wheat host, and environmental specimens, ensuring a high level of specificity for accurate discrimination.

Centenary of Soil and Air Borne Wheat Karnal Bunt Disease Research: A Review

Karnal bunt (KB) of wheat (Triticum aestivum L.), known as partial bunt has its origin in Karnal, India and is caused by Tilletia indica (Ti). Its incidence had grown drastically since late 1960s from northwestern India to northern India in early 1970s. It is a seed, air and soil borne pathogen mainly affecting common wheat, durum wheat, triticale and other related species. The seeds become inedible, inviable and infertile with the precedence of trimethylamine secreted by teliospores in the infected seeds. Initially the causal pathogen was named Tilletia indica but was later renamed Neovossia indica. The black powdered smelly spores remain viable for years in soil, wheat straw and farmyard manure as primary sources of inoculum. The losses reported were as high as 40% in India and also the cumulative reduction of national farm income in USA was USD 5.3 billion due to KB. The present review utilizes information from literature of the past 100 years, since 1909, to provide a comprehensive and updated understanding of KB, its causal pathogen, biology, epidemiology, pathogenesis, etc. Next generation sequencing (NGS) is gaining popularity in revolutionizing KB genomics for understanding and improving agronomic traits like yield, disease tolerance and disease resistance. Genetic resistance is the best way to manage KB, which may be achieved through detection of genes/quantitative trait loci (QTLs). The genome-wide association studies can be applied to reveal the association mapping panel for understanding and obtaining the KB resistance locus on the wheat genome, which can be crossed with elite wheat cultivars globally for a diverse wheat breeding program. The review discusses the current NGS-based genomic studies, assembly, annotations, resistant QTLs, GWAS, technology landscape of diagnostics and management of KB. The compiled exhaustive information can be beneficial to the wheat breeders for better understanding of incidence of disease in endeavor of quality production of the crop.

Meta-Analysis Reveals Consensus Genomic Regions Associated with Multiple Disease Resistance in Wheat ( Triticum Aestivum L.)

In wheat, meta-QTLs (MQTLs), and candidate genes (CGs) were identified for multiple disease resistance (MDR). For this purpose, information was collected from 58 studies for mapping QTLs for resistance to one or more of the five diseases. As many as 493 QTLs were available from these studies, which were distributed in five diseases as follows: septoria tritici blotch (STB) 126 QTLs; septoria nodorum blotch (SNB), 103; fusarium head blight (FHB), 184; karnal bunt (KB), 66, and loose smut (LS), 14. Of these 493 QTLs, only 291 QTLs could be projected onto a consensus genetic map, giving 63 MQTLs. The CI of the MQTLs ranged from 0.04 to 15.31 cM with an average of 3.09 cM per MQTL. This is a ~ 4.39 fold reduction from the CI of initial QTLs, which ranged from 0 to 197.6 cM, with a mean of 13.57 cM. Of 63 MQTLs, 60 were anchored to the reference physical map of wheat (the physical interval of these MQTLs ranged from 0.30 to 726.01 Mb with an average of 74.09 Mb). Thirty-eight (38) of these MQTLs were verified using marker-trait associations (MTAs) derived from genome-wide association studies. As many as 874 CGs were also identified which were further investigated for differential expression using data from five transcriptome studies, resulting in 194 differentially expressed genes (DEGs). Among the DEGs, 85 genes had functions previously reported to be associated with disease resistance. These results should prove useful for fine mapping of MDR genes and marker-assisted breeding.