Kalinga III, bred at the Central Rice Research Institute in Cuttack, is an improved variety popular in drought-prone areas of India. It normally escapes the end-of-season drought because of its extreme earliness, but it is drought-susceptible. Sathi 34-36, an improved variety from Gujarat, India, derived from landraces, has longer and thicker roots than Kalinga III. Quantitative trait loci (QTLs) influencing root length and thickness in rice have been identified in previous studies (Price and Tomos 1996, Price et al 2000, Yadav et al 1997).
Molecular markers located near QTLs may correlate with the same trait in different varieties, and these markers could be used in marker-assisted selection (MAS) to improve drought-sensitive varieties. Restriction fragment length polymorphism (RFLP) markers on chromosomes with root QTLs were used to compare genetic variation within and between Indian landraces and improved varieties.
Sixteen rice varieties were screened with 55 RFLP probes (from chromosomes 2, 5, 7, 8, 9, and 11), 14 of which were linked to QTLs for root growth. Four varieties were landraces and six were released varieties derived from landraces, all widely grown in India (see table). Other varieties which have been used for mapping were included: Azucena (japonica), Bala (indica, an Aus variety), CO 39 (indica), and Moroberekan (japonica).