Evaluation of potato germplasm (Population A & B) for resistance to late blight in Kenya

Abstract

Resistance of potato clones of populations A and B to late blight (Phytophthora infestans (Mont) de Bary) was evaluated in field studies during 1999-2000 long and short rains cropping seasons in Kenya at two locations, Kabete (1,800 masl) and Loreto (2,400 masl). Treatments consisted of germplasm materials introduced from International Potato Centre (CIP) headquarters in Lima, Peru from two populations arranged in a completely randomised block design with three replications. At Loreto, late blight was more severe during the long rains than in the short rains while at Kabete late blight was severe during the short rains than in the long rains. The most resistant late blight genotypes among the population A at Loreto were clones 387193.21 and KP93743.6 with AUDPC values of 204.9 and 269.4, and yields of 50.6 and 46.9 t ha-1, respectively. These two clones had also acceptable agronomic characteristics. Desiree (control) was the most susceptible with AUDPC value of 2674.0 and a yield of only 9.8 t ha-1. The most resistant genotype among the population B test materials at Loreto was clone 392640.28 with an AUDPC value of 252.9 and it had the highest yield of 53.4 t ha-1. Other resistant genotypes were 392640.13 and 392640.7 with an AUDPC values of less than 600 and also high yields of 41.8 and 40.5 t ha-1, respectively. The most resistant clone at Kabete was 390013.10 with an AUDPC value of 37.6 while the most susceptible one was 387969.1 with an AUDPC value of 671.9. Clone KP90182.4 had the highest yields of 35.0 t ha-1. Dutch Robjyn (susceptible check) had also a relatively low AUDPC value of 491.3 with a yield of 27.6 t ha-1. Generally, the low levels of disease observed at the two locations were due to low rainfall and relative humidity during the growing seasons. Potato tuber moth (PTM) infestation ranged between 0.5 to 20%. The high levels of PTM experienced were due to prolonged drought during the growing season.


Key Words: Horizontal resistance, late blight, Kenya, potato tuber moth, Solanum tuberosum, Sub-Sahara Africa, yield


(African Crop Science Journal 2001 9(1): 215-224)