Evaluation of rice (Oryza sativa l.) genotypes for yield and resistance to blast disease (Magnaporthe oryzae) in Kenya

Abstract

Rice (Oryza sativa L) is a staple food for approximately 3.5 billion people of the world. Kenya is insufficient of rice by 75%. This is with an annual production of approximately 150,000 metric tonnes against demand of 620,304 metric tonnes as of 2018. . Rice blast Magnaporthe oryzae is one of the limiting factors of rice production across the world and in Kenya it affects rice production up to 70-80% in disease favorable weather conditions. The objective of this study was to identify well adapted high yielding varieties that are resistant/tolerant to rice blast in major rice growing areas. Twenty five lowland and upland rice genotypes were evaluated for two seasons in Ahero National irrigation board scheme and Kenya Agricultural and Livestock Research Organization (KARLO), Industrial Crops Research Institute (ICRI), Mwea.The experiment was laid out in a partially balanced lattice design (5 x 5) and replicated three times. Data collected was on plant height, yield, biomass, 1,000 grain weight, days to flowering, booting and panicle initiation. Rice leaf blast disease was scored using the 0-9 visual subjective scoring scale from the Institute of plant molecular biology, IRRI. Data was subjected to analysis of variance using statistical analysis software version 9.1 and means separated using Duncan’s multiple range test at ?=0.05. Genotypes were significantly different for yield, agronomic traits and blast disease.  In Mwea high yielding genotypes were ARIZETEJGOLD, KOMBOKA and 08FAN10 with an average of 5.11, 4.45 and 4.02 tonnes/hectare respectively. In Ahero 08FAN10, KOMBOKA and ARIZETEJGOLD with 9.37, 9.00, 8.82 tonnes/hectare. Blast disease scores in both Mwea and Ahero, indicate that genotypes 08FAN10, IR2793 and CHINA HYBRID were the most resistant/tolerant with a disease score of 0.08, 0.58 and 0.50 respectively while BASMATI 217 was the moderately susceptible, followed by SARO 5 and KOMBOKA with a disease score of 5.33, 3.00 and 2.41 respectively across the two sites and this affected their production. The April-June season was not suitable due to the cold stress in Mwea and it reduced the yield by 25% and blast disease. Therefore this study recommends that genotypes 08FAN10, KOMBOKA and ARIZETEJGOLD be evaluated in other rice growing areas and for other traits. The released varieties such as KOMBOKA should be promoted for production by the farmers.