World Vegetable Center

About: World Vegetable Center is a nonprofit organization based out in Tainan City, Taiwan. It is known for research contribution in the topics: Population & Agriculture. The organization has 294 authors who have published 364 publications receiving 8785 citations. The organization is also known as: AVRDC, Asian Vegetable Research and Development Center.

Cowpea Cultivar Mixtures for Stable and Optimal Leaf and Seed Yields in a Maize Intercropping System

Abstract: Cowpea [Vigna unguiculata (L.) Walp.] is an important crop in many African countries, though its use as a leafy vegetable has not received adequate research attention. Leaf and grain yields are low and unstable, especially in highly variable climates in marginal areas. A study was conducted to evaluate the impact of cowpea cultivar mixtures on leaf and seed yield and stability in a cowpea–maize (Zea mays L.) intercropping system. Four cowpea cultivars and a local landrace check were used in monoculture or in different mixture levels. When leaves were harvested, seed yield was reduced on average by 57% and 59%, on-station and on-farm, respectively, with large variation among treatments. The local landrace check had the highest leaf yields on-farm where it produced a mean of 25 g/plant/2-weekly harvesting interval. It also conveyed positive mixture effects; however, yield stability across successive harvests was lowest, indicating its capacity to react to positive environmental changes. Some mixtures of mor...

First report of the A2 mating type of Phytophthora capsici infecting peppers (Capsicum annuum) in Taiwan.

Abstract: Phytophthora capsici Leonion was first identified on pepper (Capsicum annuum L) in Taiwan in 1976. At that time, only the A1 mating type was present (2). In 2007, the A2 mating type of P. capsici was identified on tomato and eggplant in the central part of the country (1). During an excessively rainy period in mid-2008, many chili and sweet pepper fields in Taiwan suffered severe losses due to P. capsici. Symptoms included a foliar blight and stem, root, and fruit rot. Plants eventually wilted and died. Symptomatic plants were collected from chili- and sweet pepper-production areas in central, southern, and eastern Taiwan. Fifty-three isolates from single zoospores were identified by PCR using species-specific primers CAPFW/CAPRV2 (4). Mating type was determined by co-inoculating rape seed agar plates (3) with mycelial plugs of the tester and a known isolate. Pc134, maintained by the mycology unit at The World Vegetable Center, and 27220, provided by P. J. Ann at the Taiwan Agricultural Research Institute, were used as reference isolates of A1 and A2 mating types, respectively. Plates were examined microscopically for oospores after 5 to 7 days of incubation at 24°C in the dark. Of the 53 isolates, 15 were identified as the A2 mating type and the remaining 38 isolates were identified as A1. The A2 mating type was found in the central and southern regions while the A1 mating type was widely distributed across all three regions. The sporangia of the A2 mating type were 60.4 to 73.4 × 40.9 to 51.8 μm (average 69.2 × 44.7 μm), whereas sporangia of the A1 mating type were 50.1 to 73.9 × 37.9 to 48.1 μm (average 61.4 × 44.1 μm). In general, the A2 mating type produced longer sporangia and only a few isolates produced chlamydospores in V8 broth and on agar. To our knowledge, this is the first report of the A2 mating type of P. capsici infecting peppers in Taiwan. The presence of both mating types in the same field has been observed. References: (1) P. J. Ann et al. Plant Pathol. Bull. 17:69, 2008. (2) L. S. Leu and C. W. Kao. Plant Prot. Bull. (Taiwan) 23:59, 1981. (3) M. M. Sautor. Mycologia 59:161, 1967. (4) C. Silvar et al. Eur. J. Plant Pathol. 112:43, 2005.

Molecular Characterization of Begomoviruses Infecting Sauropus androgynus in Thailand

Abstract: Begomoviruses were detected in leaf samples of Sauropus androgynus (L.) Merr. plants showing leaf curling with or without yellowing symptoms in Kamphaeng Saen, Nakhon Pathom, Thailand in 2009 and 2010. From eight plants with symptoms, 17 complete begomoviral DNA-As were amplified by polymerase chain reaction and sequenced. No DNA-B was detected in any of the plants. All the DNA-As had the characteristic begomovirus genome organization of six open reading frames, two in the virion-sense orientation and four in the complementary orientation. Sequence comparison of these virus isolates indicated that one isolate belongs to Tomato leaf curl New Delhi virus, 12 isolates belong to Ageratum yellow vein virus and four isolates belong to a novel species with the tentative name Sauropus leaf curl virus. Five of the eight samples were found to be co-infected by isolates of two different begomovirus species. Recombination analysis indicated that all but one of the isolates were probably the product of one or more recombination events. The results indicated that S. androgynus plants act as natural hosts as well as potential nurseries for genetic recombination between begomovirus species and strains.

Virulence Diversity of Phakopsora pachyrhizi Isolates From East Africa Compared to a Geographically Diverse Collection

Abstract: Soybean rust, caused by the biotrophic pathogen Phakopsora pachyrhizi, is a highly destructive disease causing substantial yield losses in many soybean producing regions throughout the world. Knowledge about P. pachyrhizi virulence is needed to guide development and deployment of soybean germplasm with durable resistance against all pathogen populations. To assess the virulence diversity of P. pachyrhizi, 25 isolates from eight countries, including 17 isolates from Africa, were characterized on 11 soybean genotypes serving as differentials. All the isolates induced tan lesions with abundant sporulation on genotypes without any known resistance genes and on soybean genotypes with resistance genes Rpp4 and Rpp5b. The most durable gene was Rpp2, where 96% of the isolates induced reddish brown lesions with little or no sporulation. Of the African isolates tested, the South African isolate was the most virulent, whereas those from Kenya, Malawi, and some of the isolates from Tanzania had the lowest virulence. An Argentinian isolate was virulent on most host differentials, including two cultivars carrying multiple resistance genes. Ten distinct pathotypes were identified, four of which comprised the African isolates representing considerable P. pachyrhizi virulence. Soybean genotypes carrying Rpp1b, Rpp2, Rpp3, and Rpp5 resistance genes and cultivars Hyuuga and UG5 were observed to be resistant against most of the African isolates and therefore may be useful for soybean-breeding programs in Africa or elsewhere.

Mungbean in Southeast Asia and East Africa: varieties, practices and constraints

Abstract: Improving the productivity of grain legumes is important to address global challenges of food security and soil degradation. This study’s objective was to quantify the adoption of improved mungbean (Vigna radiata L.) varieties and agricultural practices and to identify production constraints for six countries in Southeast Asia and three countries in East Africa. A Delphi method using expert elicitation was applied at subnational levels and then aggregated to national levels. Each panel employed repetitive and independent questioning of experts. The study organized 31 expert panels involving 387 experts across 9 countries. The share of improved varieties in the planted area, as estimated by the expert panels, was 92% for the Philippines, 91% for Vietnam, 99% for Thailand, 84% for Cambodia, 60% for Indonesia, 35% for Laos, 91% for Kenya, 30% for Uganda and 25% for Tanzania. The average age of improved varieties was 19 years in Asia and 12 years in East Africa. Of the mungbean area in Southeast Asia, 61% was planted to varieties developed by the World Vegetable Center, but this was only 2% in East Africa. Production constraints generally included insect pests and plant diseases, unstable markets with low price and low market demand, and the lack of quality seed of suitable varieties. There are ample opportunities to improve mungbean productivity through wider use of improved varieties and practices, which is important to meet the contemporary challenges of improving human nutrition and agricultural sustainability.