Chapter 1 Degree and distribution of pigeonpea landrace morphological diversity in traditional cropping systems in Andhra Pradesh PJ BrameV, S Kiran2, U Reddy2, B Ford-Lloyd3 and S Chandra4 Pigeonpea (Cajanus cajan (L.) Millsp.) is a very important subsistence food crop in traditional cropping systems in peninsular India. This region is the center of origin for the domesticated species and also has the maximum diversity. The genetic diversity of this crop in the field is slowly being eroded with the introduction of improved varieties and a change in its status to that of a cash crop. This phenomenon is occurring in other pigeonpea-growing regions in the world as well. This crop, which was traditionally grown by women in gardens or on field margins, is being converted to a high value cash crop mainly grown in monoculture systems using a shorter-duration plant type. In many areas the two types of varieties - traditional landraces and improved varieties or hybrids - are grown side by side. Pigeonpeas are a partially self-pollinated or insect-pollinated species. The flower type, the abundance of insect pollinators and weather conditions during flowering can influence the degree of cross-pollination. The distribution of diversity among and within landraces is unknown and the degree of geneflow within the cultivated species or between the cultivated and wild species has not been documented. Thus, the impact of the introduction of improved varieties on traditional landraces in relation to genetic erosion is unknown. Pigeonpea is plagued by a number of pests, including insects, nematodes and diseases. These cause major economic losses for producers every year in India and attempts to control them contributes to substantial use of pesticides in the cropping system. Pigeonpea is attacked by a number of general insect feeders that also cause substantial losses on other important components of the cropping system, such as chilies and cotton. The increasing status of pigeonpea as a cash crop, its value as a legume alternative in cotton-growing regions and the complementarities of its pest with those of cotton and chilly make it a prime target for the use of transformation, especially to introduce Bt genes. The introduction and adoption of biotechnology products in pigeonpea need to be assessed to minimize possible risks to traditional cropping systems. ! Consultant, c/o Dr John Peacock, Kuwait Institute for Scientific Research, PO Box 24885,13109, Safat, Kuwait 2 Consultants, Gene Bank, ICRISAT, Patancheru, 502 324, Andhra Pradesh, India School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK 4 Principal Scientist (Biometrics) and Head, Bioinformatics, ICRISAT, Patancheru, 502 324, Andhra Pradesh, India 1