Recent research papers published by AVRDC authors
RECENT RESEARCH Identification of resistance to Bemisia tabaci Genn. in closely related wild relatives of cultivated tomato based on […]
Mulching acts to control weeds, conserves soil moisture and increases soil temperature in tropical and sub-tropical environments which has positive effects on vegetable yield and quality. Plastic mulching material is now widely available in SE Asia at a relatively low cost.
Lack of a strong and stable restorer-of-fertility (Rf) allele in sweet pepper (Capsicum annuum L.) has been a hurdle in commercial exploitation of cytoplasmic male sterility (CMS) system for cost-effective production of sweet pepper hybrid seeds.
Crop wild relatives are an inestimable source for vegetable improvement to tackle both biotic and abiotic stresses. Consequently, the major focus of this chapter is on the utilization of crop wild relatives in research and breeding of tomato and in other vegetable crops.
Among the legume family, mungbean (Vigna radiata) has become one of the important crops in Asia, showing a steady increase in global production. It provides a good source of protein and contains most notably folate and iron.
Previous studies on the legume pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a serious pest of cowpea, Vigna unguiculata (L.) Walp. (Fabales: Fabaceae), in sub-Saharan Africa have focused on sex pheromones, but the role of the host plant on sexual behavior has not been explored. We investigated this interaction in the laboratory using behavioral assays and chemical analyses. We found that the presence of cowpea seedlings and a dichloromethane extract of the leaf increased coupling in the legume pod borer by 33 and 61 %, respectively, compared to the control, suggesting the involvement of both contact and olfactory cues. We used coupled gas chromatography-electroantennographic detection (GC/EAD) and GC-mass spectrometry (GC/MS) to identify compounds from the cowpea leaf extract, detected by M. vitrata antenna. We found that the antennae of the insect consistently detected four components, with 1-octen-3-ol identified as a common and dominant component in both the volatiles released by the intact cowpea plant and leaf extract. We therefore investigated its role in the coupling of M. vitrata. In doseresponse assays, 1-octen-3-ol increased coupling in M. vitrata with increasing dose of the compound compared to the control. Our results suggest that the cowpea volatile 1-octen-3-ol contributes to M. vitrata sexual behavior.
Seed kernel extracts of China berry (Melia azedarach) against oriental fruit fly (Bactrocera dorsalis) and tomato fruit borer (Helicoverpa armigera), and commercial neem formulations containing azadirachtin (Biofree-I® and Thai neem 111®) against the legume pod borer (Maruca vitrata) were tested in Taiwan and Thailand to confirm their effects on oviposition, feeding, growth and development. Various extracts from M. azedarach seed kernels significantly reduced the oviposition of B. dorsalis and the efficacy was similar to Biofree-I®. The green drupe and dry seed kernel extracts of M. azedarach substantially increased larval mortality, and reduced successful pupation, pupal weight, adult emergence, fecundity and egg hatch of H. armigera larvae. Commercial neem formulations exhibited adverse morphogenic effects on various biological parameters of M. vitrata, but they did not reduce oviposition and egg hatch. M. azedarach extracts and commercial neem formulations can be employed together for the sustainable management of B. dorsalis, H. armigera and M. vitrata.
This study aims to identify challenges as well as entry points for governments in Southeast Asia and elsewhere to reduce the risk from agricultural pesticides by comparing levels of pesticide use, pesticide regulation, and farm-level practices in Cambodia, Laos, Thailand and Vietnam. We identified three main challenges to pesticide risk reduction: (a) the rapid expansion of pesticide tradein terms of total volume, number of products and number of selling points, combined with a weak regulatory and enforcement capacity; (b) a high level of satisfaction among farmers with pesticides combined with low levels of risk awareness, lack of technical know-how about integrated pest management (IPM), andgeneral unavailability of biocontrol agents; and (c) no regular monitoring of pesticide risk, which makes it difficult for legislators, regulators, farmers and consumers to make rational decisions. The study highlights several examples countries can emulate, including the introduction of a pesticide tax inVietnam, the pesticide registration system in Thailand, regular training of pesticide retailers in Thailand and Vietnam, and product certification.
Incidence of vector-transmitted virus diseases and the damage caused to vegetable crops by these diseases are reported to be increasing in countries with tropical and subtropical conditions. Virus-resistant crops and an integrated approach to crop management including appropriate control of plant-virus vinsect-ectors could reduce the problem. However, in developing countries, such a strategy is rarely applied effectively. We surveyed 800 growers of chili, tomato and mungbean in India, Thailand and Vietnam to understand what farmers know about plant viruses, their perceptions about yield damage, the control methods they choose to apply and the perceived effectiveness of these. Farmers regarded their economic losses from pests and diseases to be very substantial. Only a minority of them knew that certain disease symptoms were probably being caused by a plant virus and even fewer knew about the role of insect vectors in its spread. Farmers mostly relied on synthetic pesticides to manage the virus disease symptoms they observed. If farmers had better knowledge about plant viruses, their insect vectors, and cost-effective, safer means of control, then use of synthetic pesticides could be reduced substantially. Building knowledge among farmers is therefore an important way to address the diseases caused by plant viruses, while the development of virus-resistant varieties and simple and effective methods of vector control offer longer-term solutions.
Anthracnose disease caused by Colletotrichum spp. is a serious disease of chili (Capsicum annuum), particularly in tropical countries. Host plant resistance breeding is one of the most effective disease management strategies.