Selection and evaluation of pigeonpea (cajanu5 cajan (l) millsp.) genotypes for resistance to fusariuh wilt pathogen (fusariuh oxysporuh f.sp. udum) and other agronomic traits.

Abstract

Fusarium wilt caused by Fusarium udum Butler has been identified as an important factor in YIeld reduction of pigeonpea in maJor growing areas of Kenya. Studies to develop varieties resistant to the Fusarium wilt were initiated in 1983 by the University of Nairobi pIgeonpea improvement programme using crosses between susceptible and resistant varieties from both local and exotic germplasm selections, while maintaining desirable agronomic traits. Disease screening was initiated at the Makueni sick plot and finally at both the Makueni and Katumani sick plots and in the glass house (Kabete) during the 1989/90 and 1990/91 seasons. Objectives were to compare glass house and field screening and to select genotypes from the initial crosses that were high yielding, early maturing and resistant/tolerant to Fusarium wilt. Selection was done in each season since 1983 on the populations derived from the crosses. 1989 season, 111 lines had been selected to constitute a population. Ten (10) lines that were resistant/tolerant to the disease and that were also early maturing, short in height and high yielding were finally selected in the 1990/91 season. The selection intensity in the 1990 season at Katumani and Makueni sick plots was 23.7% and 21.0% respectively, with a selection response of 4.2 and 8.3 for percent wilt mortality. Results also showed a high and significant correlation coefficient (r = 0.79) between the glass house and Makueni field ratings and a low and non significant correlation coefficient (r 0.22) between the glass house and Katumani field ratings implying that glass house reaction indicates field disease reaction as long as the strain being used is similar in both cases. A high significant correlation coefficient (r = 0.77) was observed between the the field sick plots and a significant correlation coefficient (r = 0.57) between the Qlasshouse and field wilt mean ratings at both locations.