A number of exotic wheat (Triticum aestivum) genotypes resistant to spot blotch caused by Cochliobolus sativus are being used to improve the resistance of commercial cultivars in the warm regions of ...South Asia. The objective of the present study was to determine the inheritance of field resistance to spot blotch in two resistant (R) wheat genotypes, ‘Chirya.3’ and ‘Milan/ Shanghai #7’ (MS#7), which were crossed to a susceptible (S) commercial cultivar, ‘BL1473.’ The two resistant genotypes also were crossed to determine allelic relationships for resistance between them. Spot blotch severity was recorded on the parents and on F1, F2, and F3 progenies. The F1 plants from the two crosses between susceptible and resistant genotypes had low disease severity like the resistant parents, indicating that resistance in Chirya.3 and MS#7 is conditioned by dominant gene action. The F2 plants segregated in 3R:1S ratios, and the F2:3 families showed the ratio of 1R:1S:2S, segregating for R and S, suggesting that resistance in the two resistant parents is conditioned by a single, dominant gene. The F1 plants from the cross between the two resistant genotypes were resistant, whereas their F2 progenies segregated in 15R:1S, suggesting that the resistance genes in MS#7 and Chirya.3 are nonallelic. These simply inherited sources of resistance could be useful for improving spot blotch resistance in the warm regions of South Asia and also may offer useful diversity to breeding programs for developing spot-blotch-resistant wheat cultivars in other regions.
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 fi ve 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 × location interaction effects for spot blotch AUDPC. Cluster analysis divided South Asia into two broad regions and four subregions. This classifi cation was not entirely consistent with the geographic distribution of locations, but clusters mostly followed general geographicclimatic locations. The locations Varanasi (India) and Bhairahawa (Nepal) were identifi ed 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.
Improving the level and stability of grain yield is the primary objective of wheat breeding programs in the Eastern Gangetic Plains (EGP) of South Asia. A regional wheat trial, the Eastern Gangetic ...Plains Yield Trial (EGPYT), was initiated by CIMMYT in collaboration with national wheat research programs in Bangladesh, Nepal, and India in 1999–2000 to identify wheat genotypes with high and stable grain yield, disease resistance, and superior agronomic traits for the EGP region. A set of 21 wheat experimental genotypes selected from a regional wheat screening nursery in South Asia, three improved widely grown cultivars (Kanchan, PBW343 and Bhrikuti), and one long-term cultivar (Sonalika) were tested at 9–11 sites in six wheat growing seasons (2000–2005) in the EGP. The 21 experimental genotypes were different in each year, whereas the four check cultivars were common. In each year, one or more of the experimental genotypes showed high and stable grain yield and acceptable maturity, plant height, and disease resistance compared to the check cultivars. Three improved cultivars have already been commercially released in the region through EGPYT and many germplasm lines have been used in the breeding programs as parents. Identification of wheat genotypes with high-grain yield in individual sites and high and stable yield across the EGP region underlines their value for regional wheat breeding programs attempting to improve grain yield and agronomic performance.
Five DNA probes (RC8, 754, XJ 1-1, pert 87.8, and L1.28) from the short arm of the human X chromosome were investigated in samples from five populations (English, Nigerian, Chinese, Muslim, and Hindu ...from India). The variation in the allele frequencies of several probes between different groups was significant. The average heterozygosity in females of the five populations ranged from 32% to 51%. The genetic distance between the five groups was compatible with that using traditional polymorphic systems. There is an interesting suggestion of longitudinal cline for allele *2 (9 kb) detected with probe L1.28. The X-linked RFLPs are useful genetic markers for anthropological studies.
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.
Maldivian atolls are known for their beautiful coral structures, fish abundance, white sandy beaches, coastal vegetation and mangroves. This paper provides an economic valuation of the recreational ...uses of atoll-based marine resources in the Republic of the Maldives. We use a travel demand model to estimate the benefits of atoll-based marine tourism. We contribute to the literature by estimating two separate travel demand models-one without and one with endogenous costs. Our results suggest a large disparity between the amount of economic value generated from nature-based tourism and the amount going into atoll conservation. Currently, more than half the Maldivian government's annual environmental protection expenditure comes from unstable international aid, which makes it imperative that more stable financing sources be found. Our study shows that transferring four percent of the total annual recreational benefits from visitors as a one-time conservation fee would generate enough resources to cover government and foreign donor contributions towards environmental protection. The additional per tourist tax or user fee necessary to raise funds at the current level of conservation funding (domestic and overseas) is USD 41. This amount constitutes only a small percentage of what an average tourist spends on each trip (1.25 percent) and the economic surplus (benefit) s/he derives from each trip (3.98 percent). The paper concludes with a discussion of the policy implications of sustainable user-based financing mechanisms.
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