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a b s t r a c tIncidence 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 insect-vectors 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.

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Use of morphological differences, between true hybrids and off types in grow out test (GOT) for genetic purity analysis, are not always apparent and cannot be recognised easily. Further, morphological traits are costly, tedious to score and environment sensitive. Alternatively, it is suggested that recent breakthrough in molecular markers can be employed in genetic purity analysis. The genetic purity of three cotton hybrids (TCHB 4510, TCHB 2310 and TCHB 213) that are widely cultivated in Tamil Nadu, India were assessed by GOT and molecular markers. A total of 400 individuals from each one of the three hybrids were raised in the field and morphological traits were recorded. Results of this GOT have shown that TCHB 2310 had lowest genetic purity (62.5%) followed by TCHB 4510 (78.2%) and TCHB 213 (95.2%). Simple sequence repeats (SSR) marker analysis of parents that were involved in the production of all the three hybrids have shown that 45 out of 150 SSRs were polymorphic among the parents. From this set of polymorphic SSRs, BNL686, BNL1679, BNL3971, BNL3955, CIR407 and CIR413 were selected to test the genetic purity of hybrid seeds since they have produced clear, scorable and unambiguous polymorphic bands among the parents. All the three hybrids were clearly distinguished from their selfed females and off types using these six SSRs. Hence, it is proposed that these SSR markers can be used in efficient analysis of hybrid seed purity since this technique is simple to use, more accurate and not affected by environment when compared with GOT.