Inheritance of resistance to Pyricularia grisea in GULU-E finger millet blast resistant variety
Gene action and heritability of blast resistance in GULU-E was determined from crosses between GULU-E as female parent mated to four susceptible genotypes using North Carolina 1 crossing design to determine nature of resistance. Inoculation was done using one potentially most virulent local pathogen isolate (NGR1) identified from Ngora in Odwarat parish, one of the pathogen hotspots of eastern agro-ecology of Uganda. It was identified following isolate screening trial for virulence in Makerere University during 2012 B. The F1, F2 and backcrosses were evaluated under controlled conditions and disease reaction indicated that resistance is partially dominant and additive based on mid parent values from crosses. Segregating ratios and chi-square tests of F2 populations fitted 13R:3S genetic model, indicating presence of duplicate dominant epistasis at probability level of 0.05. Broad-sense heritability estimated by variance components method was high at about 88.8% on entry mean basis. Selection for resistant progeny derived from crosses between GULU-E and DR21 would be most effective in early generations followed by modified backcrossing at F3 to the adapted recurrent resistant parent leading to diversification of a population and derivation of materials for selection for disease resistance. From the study it is possible to accumulate genes for race specific resistance in host cultivars that might reduce development of disease epidemics in some areas. The genetic control of components of resistance and mechanisms of resistance in the host which affect the rate of development of a disease epidemic need to be determined, since they are important variables for durable resistance.
Key words: Broad sense heritability, durable resistance, gene action, modified backcrossing, virulence