Browsing by Author "R.C. Sharma"

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Associations of environments in South Asia based on spot blotch disease of wheat caused by Cochliobolus sativus
(2007) A.K. Joshi; G. Ortiz-Ferrara; J. Crossa; G. Singh; G. Alvarado; M.R. Bhatta; E. Duveiller; R.C. Sharma; D.B. Pandit; A.B. Siddique; S.Y. Das; R.N. Sharma; R. Chand
Spot blotch is an important disease of wheat (Triticum aestivum L.) in South Asia. Division of test sites for this disease into homogenous subregions is expected to contribute to more efficient evaluation and better differentiation of cultivars. Data from a collaborative regional program of South Asia conducted by CIMMYT were analyzed to group testing sites into relatively homogenous subregions for spot blotch area under the disease progress curve (AUDPC). Five-year data of eight locations from Eastern Gangetic Plains Nursery (EGPSN) and five locations of the Eastern Gangetic Plains Yield Trial (EGPYT) conducted in three countries (India, Nepal, and Bangladesh) of South Asia were used. A hierarchical cluster analysis was used to group locations on the basis of genotype x location interaction effects for spot blotch AUDPC. Cluster analysis divided South Asia into two broad regions and four subregions. This classification was not entirely consistent with the geographic distribution of locations, but clusters mostly followed general geographic-climatic locations. The locations Varanasi (India) and Bhairahawa (Nepal) were identified as the most suitable sites for evaluation of spot blotch, followed by Rampur (Nepal). The major determinant for the clustering was mean temperature. The results suggest that the major wheat region of South Asia can be divided into subregions, which may reduce the cost of resistance evaluation and aid in developing wheat with resistance to this disease. © Crop Science Society of America.
Combining superior agronomic performance and terminal heat tolerance with resistance to spot blotch (Bipolaris sorokiniana) of wheat in the warm humid Gangetic Plains of South Asia
(2007) A.K. Joshi; G. Ortiz-Ferrara; J. Crossa; G. Singh; R.C. Sharma; R. Chand; Rajender Parsad
Seven hundred twenty-nine lines of diverse wheat germplasm lines were evaluated in eight locations of three countries (India, Nepal and Bangladesh) of South Asia for 5 years (1999-2000 to 2003-2004) through Eastern Gangetic Plains Screening Nursery (EGPSN) organized by CIMMYT South Asia, Nepal, for agronomic performance and tolerance to spot blotch of wheat. Each year, the number of lines represented a new set of 150 lines that included six common checks and a different local check at each of the eight locations. One hundred and five lines, 21 in each year, advanced from EGPSN were also tested for 5 years (2000-2001 to 2004-2005) in five locations of South Asia through Eastern Gangetic Plains Yield Trials (EGPYT) to verify spot blotch tolerance and superior yield performance of the selected germplasm. Many lines yielded significantly more than the best check and possessed high levels of spot blotch resistance under warm humid environments of South Asia. The most promising 25 lines have been listed as sources of strong resistance, with 9 lines better yielding than the best resistant check PBW 343 in fewer days to maturity. Most of these superior lines represented elite CIMMYT germplasm and around half were derived from Kauz and Veery. The line EGPYT 67, Kauz//Kauz/Star/3/Prinia/4/Milan/Kauz, was the best for spot blotch resistance, yield, days to maturity, and 1000 grain weight (TKW). The next two lines in the order of merit were EGPYT 84 (Mrng/Buc//Blo/Pvn/3/Pjb 81) and EGPYT 69 (Chirya3/Pastor). The results demonstrate that additional spot blotch resistant wheat genotypes with high grain yield and TKW, and early maturity, have become available as a result of the regional and international collaboration in South Asia. © 2007 Elsevier B.V. All rights reserved.
Helminthosporium leaf blight resistance and agronomic performance of wheat genotypes across warm regions of South Asia
(2004) R.C. Sharma; E. Duveiller; F. Ahmed; B. Arun; D. Bhandari; M.R. Bhatta; R. Chand; P.C.P. Chaurasiya; D.B. Gharti; M.H. Hossain; A.K. Joshi; B.N. Mahto; P.K. Malaker; M.A. Reza; M. Rahman; M.A. Samad; M.A. Shaheed; A.B. Siddique; A.K. Singh; K.P. Singh; R.N. Singh; S.P. Singh
Helminthosporium leaf blight (HLB) is the most important disease constraint to wheat (Triticum aestivum L.) cultivation in the eastern Gangetic Plains of South Asia. A Helminthosporium Monitoring Nursery (HMN) including potential adapted and exotic sources of HLB resistance was developed in Bangladesh, India and Nepal to assess the stability of genetic resistance across locations. The 8th, 9th and 10th HMN assessed the HLB resistance and agronomic traits of 17 wheat genotypes across 20 environments of Bangladesh, India and Nepal in the 1999-2000, 2000-2001 and 2001-2002 cropping seasons, respectively. The area under the disease progress curve (AUDPC) for HLB, grain yield, thousand-kernel weight (TKW), days to heading, days to maturity, and plant height were examined. The 17 genotypes showed a range of variability for disease and agronomic characters. Disease severity (AUDPC) differed in the 3 years and showed the highest values in 2002. The increase in AUDPC in 2002 caused the lowest grain yield, with an average 18% reduction due to HLB. A few genotypes (SW 89-5422, Yangmai-6 and Ning 8201) appeared to have stable HLB resistance across environments. However, most of the higher-yielding genotypes, except BL 1883, were unstable. The results suggest that careful selection of HLB resistance with acceptable grain yield, TKW and plant height may be possible using the wheat genotypes included in the HMN.
Laser optogalvanic spectroscopy of argon in the wavelength region 605-740 nm
(Indian Academy of Sciences, 1998) R.C. Sharma; T. Kundu; S.N. Thakur
Two-photon optogalvanic transitions in Ar glow discharge with Nd: YAG laser pumped dye laser excitation in the frequency range 13520-16520 cm-1 has been studied using linear and circular polarization. The intensities of two-photon optogalvanic transitions are very sensitive to changes in the incident laser power which is not the case with one-photon transitions. Intensity ratio for circular and linear polarized light for two photon transitions 6s′[1/2]°1 ← 4s[3/2]°2, 6s′[1/2]°0 ← 4s[3/2]°2, and 5d[1/2]°0 ← 4s[3/2]°2, 5d[1/2]°1 ← 4s[3/2]°2 are quite different from the other two-photon transitions. This has been explained as due to near one photon resonance of 4p′[3/2]1 level for the first pair and 4p′[1/2]1 for the second pair of transitions. The ratio of optogalvanic intensity for circular to linear polarized light has been theoretically estimated and compared with the observed results.
Partnering with farmers to accelerate adoption of new technologies in South Asia to improve wheat productivity
(2007) G. Ortiz-Ferrara; A.K. Joshi; R. Chand; M.R. Bhatta; A. Mudwari; D.B. Thapa; M.A. Sufian; T.P. Saikia; R. Chatrath; J.R. Witcombe; D.S. Virk; R.C. Sharma
There are many socioeconomic and technological constraints that affect the production of wheat and other staple cereals in South Asia. Wheat production is one of the economic mainstays in South Asia, but the yield gap between farmers' fields and experimental yields is wide across the region. For the last 3 years, CIMMYT and the CAZS-NR have been collaborating with farmers, NARS, and other South Asian partners to promote improved wheat varieties and new resource conservation technologies (RCTs) in farmers' fields. Participation fostered among farmers, scientists, extension specialists, NGOs and the private sector included variety selection (PVS), and evaluation of agronomic practices. Through PVS, several farmer-preferred technologies have been identified including wheat varieties for adverse conditions in eastern Uttar Pradesh (India) and for boron deficiency in parts of Nepal. There has been considerable improvement in the access of farmers to new varieties and technologies in the rural areas. Yield increases (15-70%) have been achieved by resource-poor farmers over the existing varieties through the adoption of new varieties and RCTs. The farmers have also made substantial cost savings and achieved higher yields through resource-conserving agronomic techniques such as zero till. Seed of the new farmer-selected cultivars has been multiplied by groups of collaborating farmers and widely distributed. © 2007 Springer Science+Business Media B.V.