Person: Joshi, A.K.
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Joshi
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A.K.
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Joshi, A.K.
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0000-0003-4205-9329 6 results
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- Wheat stripe rust virulence and varietal resistance in the foot hill Himalayas of Nepal(David Publishing, 2015) Sharma, S; Duveiller, E.; Chandra Bahadur Karki; Thapa, D.B.; Sharma, R.; Joshi, A.K.
Publication - First Report of Wheat Blast Caused by Magnaporthe oryzae Pathotype triticum in Bangladesh(American Phytopathological Society (APS), 2016) Malaker, P.K.; Barma, N.C.D.; Tiwari, T.P.; Collis, W.J.; Duveiller, E.; Singh, K.; Joshi, A.K.; Singh, R.P.; Braun, H.J.; Peterson, G.L.; Pedley, K.F.; Farman, M.; Valent, B.Wheat blast or ‘brusone,’ caused by the ascomycetous fungus Magnaporthe oryzae B.C. Couch (syn. Pyricularia oryzae Cavara), was first identified in 1985 in Brazil. M. oryzae is composed of a range of morphologically identical but genetically different host-specific pathotypes that are specialized for infecting rice (Oryza pathotype), wheat (Triticum pathotype - MoT), perennial and annual ryegrass (Lolium pathotype), foxtail millet (Setaria pathotype), and many other graminaceous hosts. Isolates from different hosts are genetically distinct, although cross infection occurs to some extent. Wheat blast has become a serious biotic constraint to wheat (Triticum aestivum L.) production in parts of the warmer wheat growing areas of the Southern Cone region of South America, causing yield losses of 10 to 100% in recent years (Duveiller et al. 2016). Wheat blast was observed for the first time outside of South America during the 2015-16 cropping season in the districts of Kushtia, Meherpur, Chuadanga, Jhenaidah, Jessore, Barisal, Bhola, and several other districts in the south of Bangladesh. Infected plants showed the typical wheat blast symptoms with the spike becoming partially or completely bleached with the blackening of the rachis in a short span of time. Examination of diseased plants showed the presence of elliptical, grayish to tan necrotic lesions with dark borders on the leaf often mixed with spot blotch disease lesions. Additionally, in some fields, blackening of lower nodes was observed. Grains from blast-infected heads were small, shriveled, deformed, and had low test-weight leading to serious yield losses. Diseased plants were collected and brought to the Wheat Research Centre, Bangladesh Agricultural Research Institute, Dinajpur, for further investigation. Grayish mycelium of the fungus taken from the infection point on the rachis of several independent spikes was observed. Incubation of several infected spikes/leaves in a 3-layered moist blotter at room temperature less than 12 h light/darkness cycle for 5 days led to the production of pyriform conidia. Morphobiometrical characteristics of the typical pyriform (pear-shaped) and 2-septate hyaline conidia were in agreement with the identification of the fungus as M. oryzae (Subramanian 1968). The air-dried spike samples have been kept in cold storage and several infected spikes were sent to the USDA-ARS, FDWSRU laboratory in the United States for characterization of the pathogen. There, the presence of M. oryzae in the infected samples was confirmed based on morphobiometrical analysis, and strains were preserved in the FDWSRU permanent wheat blast strain collection. Molecular analysis with MoT-specific markers and comparative genome analysis of isolates (BdBar16-1, GenBank accession no. LXON01000000; BdJes16-1, LXOO01000000; BdMeh16-1, LXOP01000000) confirmed that the wheat blast observed in Bangladesh is caused by MoT pathotype and has strong genetic identity to a strain from South America (B71, LXOQ01000000). This first incidence of wheat blast was significantly widespread accounting for approximately 15% of Bangladesh’s total wheat area. This large scale incidence of wheat blast has underscored a concern about the potential spread of wheat blast to other wheat producing areas in Bangladesh, South Asia, and beyond.
Publication - Resistance to spot blotch in two mapping populations of common wheat is controlled by multiple QTL of minor effects(MDPI, 2018) Singh, P.K.; Xinyao He; Sansaloni, C.; Juliana, P.; Dreisigacker, S.; Duveiller, E.; Kumar, U.; Joshi, A.K.; Singh, R.P.Spot blotch (SB) is an important fungal disease of wheat in South Asia and South America. Host resistance is regarded as an economical and environmentally friendly approach of controlling SB, and the inheritance of resistance is mostly quantitative. In order to gain a better understanding on the SB resistance echanism in CIMMYT germplasm, two bi-parental mapping populations were generated, both comprising 232 F2:7 progenies. Elite CIMMYT breeding lines, BARTAI and WUYA, were used as resistant parents, whereas CIANO T79 was used as susceptible parent in both populations. The two populations were evaluated for field SB resistance at CIMMYT’s Agua Fria station for three consecutive years, from the 2012–2013 to 2014–2015 cropping seasons. Phenological traits like plant height (PH) and days to heading (DH) were also determined. Genotyping was performed using the DArTSeq genotyping-by-sequencing (GBS) platform, and a few D-genome specific SNPs and those for phenological traits were integrated for analysis. The most prominent quantitative trait locus (QTL) in both populations was found on chromosome 5AL at the Vrn-A1 locus, explaining phenotypic variations of 7–27%. Minor QTL were found on chromosomes 1B, 3A, 3B, 4B, 4D, 5B and 6D in BARTAI and on chromosomes 1B, 2A, 2D and 4B in WUYA, whereas minor QTL contributed by CIANO T79 were identified on chromosome 1B, 1D, 3A, 4B and 7A. In summary, resistance to SB in the two mapping populations was controlled by multiple minor QTL, with strong influence from Vrn-A1.
Publication - An integrated approach to maintaining cereal productivity under climate change(Elsevier, 2016) Reynolds, M.P.; Quilligan, E.; Bansal, K.C.; Cavalieri, A.J.; Chapman, S.; Chapotin, S.M.; Datta, S.; Duveiller, E.; Gill, K.S.; Jagadish, K.S.V.; Joshi, A.K.; Koehler, A.K.; Kosina, P.; Krishnan, S.; Lafitte, H.R.; Mahala, R.S.; Raveendran, M.; Paterson, A.H.; Prasanna, B.M.; Rakshit, S.; Rosegrant, M.W.; Sharma, I.; Singh, R.P.; Sivasankar, S.; Vadez, V.; Valluru, R.; Prasad, P.V.V.; Yadav, O.P.; Aggarwal, P.K.Wheat, rice, maize, pearl millet, and sorghum provide over half of the world's food calories. To maintain global food security, with the added challenge of climate change, there is an increasing need to exploit existing genetic variability and develop cultivars with superior genetic yield potential and stress adaptation. The opportunity to share knowledge between crops and identify priority traits for future research can be exploited to increase breeding impacts and assist in identifying the genetic loci that control adaptation. A more internationally coordinated approach to crop phenotyping and modeling, combined with effective sharing of knowledge, facilities, and data, will boost the cost effectiveness and facilitate genetic gains of all staple crops, with likely spill over to more neglected crops.
Publication - Introduction and exchange of improved bread wheat germplasm in the eastern gangetic plains of South Asia(Global Science Books, 2008) Ortiz-Ferrara, G.; Sharma, R.; Bhatta, M.R.; Gyanendra Singh; Pandit, D.B.; Joshi, A.K.; Siddique, A.B.; Duveiller, E.; Ortiz, R.Wheat (Triticum aestivum L.) yield must be increased in the Eastern Gangetic Plains (EGP) of South Asia to improve the livelihoods of poor farmers. The International Maize and Wheat Improvement Center (CIMMYT) and its partners in South Asia initiated a regional yield trial, the Eastern Gangetic Plains Wheat Yield Trial (EGPYT) in 2000 to identify wheat cultivars with high and stable grain yield, superior agronomic traits and disease resistance. Advanced breeding lines from CIMMYT, Mexico and wheat programs in the region were assembled each year and tested at key sites in Bangladesh, India and Nepal. A total of 168 experimental genotypes and four checks were tested over eight years (2000–2007). The wheat genotypes showed arrays of genetic variation in grain yield, days to heading, plant height, 1000-kernel weight (TKW), and spot blotch severity in the eight years. Several experimental genotypes were superior to checks in yield, TKW, spot blotch resistance in individual country and across the region. We identified two sets of superior lines across the region that could be used as parents (Parent 1 = ‘BL1804’, ‘BL1968’, ‘BL2324’, ‘G162/BL1316//NL297’, ‘NL750’, ‘NL835’ and ‘Shatabdi’; Parent 2 = ‘BL2966’, ‘Milan/Shanghai#7’, ‘NL966’, ‘PBW373’, ‘BL3122’, ‘BL3124’, ‘BL3191’ and ‘SW89.5124*2/Fasan’) to develop new improved lines with high grain yield and TKW, spot blotch resistance, early maturity and acceptable plant height. New cultivars have been developed through this effort, and many outstanding lines selected by wheat breeders in the region are being used as parents in the breeding programs of different centers. This regional effort has helped in the introduction and exchange of superior wheat genotypes, thus enriching the germplasm base in the region. The findings underline the importance of region-focused varietal testing approach in developing and disseminating high yielding wheat germplasm.
Publication - Physiological and morphological aspects of bipolaris sorokiniana conidia surviving on wheat straw(Korean Society of Plant Pathology, 2002) Chand, R.; Singh, H.V.; Joshi, A.K.; Duveiller, E.Wheat samples showing typical spot blotch symptoms on stems and sheaths were collected from the field after physiological maturity, and were sealed in paper bags and stored in the laboratory at room temperature to study the survival of Bipolaris sorokiniana conidia on wheat straw. The materials were observed at monthly intervals to assess the conidia viability during storage. After 4 months, the frequency of individual conidia already present on wheat straw at the time of sampling was reduced and appeared to be progressively replaced by the formation of round structures consist-ing of conidia aggregates. After 5 months, distinct, individual conidia were no longer detected, and only 'clumps of conidia' were observed. These dark black aggregates or 'clumps of conidia’measured 157-170 μm in diameter and were grouped into boat-shaped olivacious conidia showing thick wall and measuring 50-82 × 20-30 μm. The germination was unipolar and below 0.5%, suggesting the occurrence of dormancy, In contrast, individual conidium produced on wheat during the growing season were 96-130 × 16-20 μm, slightly curved, hyaline to light pale, and euseptate with a bipolar germination reaching 98-100%. Bipolaris sorokiniana conidia produced on PDA were 55-82 × 20-27 μm, tapered at both ends, dark brown to olivacious, distoseptate, showed up to 1% germination, and were predominantly unipolar. Results of the present study suggest that B. sorokiniana conidia belonged to two different physiological categories corresponding to the pathogen's infection phase and its survival, respectively. The infection phase is characterized by a high germination percentage as opposed to the survival phase harboring apparent dormancy
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