Reaction of Rice Germplasm to Blast and Brownspot Under Natural and Controlled Environment in Mwea, Kirinyaga County, Kenya

Abstract

Kenya has been losing tons of rice yield as a result of blast and brown spot of rice. The germplasm that farmers use is much susceptible to the two rice diseases. The rice breeders on the other hand are doing their best to come up with germplasm that can grow under normal field conditions and tolerate the attack of blast and brown spot to give a meaningful yield. After coming up with a number of blast and brown spot resistant germplasm farmers do not have information on which among them is most suitable. The objective of this project was to screen a huge number of germplasms produced by various breeders to identify which germplasm resisted blast and brown spot of rice under the local field conditions. As farmers are much interested in yields the performance of the rice germplasm would also be evaluated under field conditions. Rice crop is affected by many foliar diseases, among them rice blast, brown spot of rice and bacterial blight of rice. The rice diseases affect the productivity of the farms and the resultant profits by farmers. Farmers are forced to buy chemicals in an attempt to manage the foliar diseases of rice. Such programs are governed by research institutions but the farmers are not informed on matters concerning disease resistance. Sixty-four and 116 germplasm were planted in two separate experiments to screen for resistance against the rice foliar diseases. Each germplasm was planted in a plot 100cm by 30 cm and the whole experiment replicated three times. A path one meter wide was left between the blocks to allow accessibility to the plots. Agronomic activities like weeding and application of fertilizer were done and the disease scored on separate scoring sheet. Data was collected on number of tillers and height of the different germplasm. Diseased plant materials were collected and taken to the laboratory and the causal agent isolated to confirm the disease. It was also inoculated on the germplasms in a successive experiment and disease symptoms scored. NERICA varieties displayed high tolerance to most of the rice foliar diseases. A few were susceptible to rice blast, brown spot of rice and bacterial blight of rice. Germplasm 1, 10, 12, 14, 17, 31, 41, 48, 64, 2, 19, 47, 51, 54, 56, 57 and 61 of the BBSRC germplsm in field experiment had a brown spot incidence of less than 1 percent hence tolerant to the disease. Eighty-two of the germplasm in KAFACI experiment one, field experiment had a brown spot incidence of less than two. Fifty three of the 116 KAFACI germplsm in the field experiment had a severity blast score below five hence tolerant to blast of rice. Rice lines 7, 11, 15, 17, 44, 47, 48, 49, 53 and 58 of the BBSRC germplasm recorded no blast in the greenhouse experiment at any point of their growth hence considered resistant in experiment one. Germplasm 39 and 56 of KAFACI experiment had the highest yield of 15 tons per hectare in each of the plot in the field experiment, while 31, 48, 30, 67, 27,4, and 50 also performed well with each plot yielding over 8 tons per hectare. The germplasm also had blast and brown spot tolerance and therefore most suitable for adoption in the local environmental condition. Among the BBSRC, germplasm 63 performed better than the rest with yield of over 18 tons per hectare, while germplasm 51 had over 16 tons per hectare in the field experiment. Germplasm 54, 29,39, 59,45 and 1 also performed well yielding over 13.5 tons per hectare. The germplasm grew vigorously, taller and tillering well which supported high yields. It was found that 25 germplasm had resistance against blast and brown spot diseases of rice and can be utilized alongside other desirable production traits like high yielding to come up with superior rice seeds that can increase production of rice per unit land. Screening for resistance should continue to confirm the presence of resistance to foliar diseases of rice so that the genes can be introduced into the cultivars used by farmers. Rice breeders also need to generate local germplasm adopted to our environment and screen for several seasons for farmers to adopt.