RELATIONSHIP BETWEEN INHERITANCE AND LINKAGE FOR DROUGHT TOLERANCE INUPLAND RICE (ORYZA-SATIVA) VARIETIES

At Kanke 13 landraces of rice (Oryza sativa L.) showing high degree of drought tolerance were taken and crossed with drought-susceptible var ieties. The F-1 generations of 10 crosses showed high degree of drough t tolerance, indicating that drought tolerance was dominant to drought susceptibility, whereas in 3 other crosses drought susceptibility was dominant to drought tolerance. The drought tolerance in 'Brown Gora', 'Dular', 'Karanga Gora', 'Saraya Gora', 'Chirikata', 'N 22' and 'Dhud hi Gora' was found governed by a single dominant gene, whereas that in 'Nanhi Gora', 'Chain Gora' and 'Nawakani Gora' was conditioned by a s ingle recessive gene. Drought tolerance was also found controlled by d ominant duplicate genes in 'Black Gora', 'Pidi Gora' and 'Jaranga Gora '. The allelic relationships of genes governing drought tolerance in d ifferent varieties was worked out. The gene for drought tolerance in ' Brown Gora' was designated Drt-1 and was allelic to those found in 'Du lar', 'Karanga Gora', 'Black Gora', 'Pidi Gora' and 'Jaranga Gora'. Th e gene for drought tolerance in 'Dhudhi Gora','Nanhi Gora', 'Chain Gor a', 'Nawakani Gora', 'Saraya Gora' 'Chirikata' and 'N 22' was differen t from that in 'Brown Gora'. The drought-tolerant gene(s) had pleiotro pic effects on the root-systems and other characters involved in droug ht-escape mechanism. The linkage relationship of Drt-1 gene with plant height, pigmentation, hull colour, awning and kernel colour in 'TN 1' x 'Brown Gora' was calculated. The gene for drought tolerance in 'Bro wn Gora' was found associated with red kernel colour and plant height with 35 and 36.7% recombination frequency respectively.