Evaluation of Rice Genotypes for Rice Blast Resistance and its Inheritance in Mwea, Kirinyaga County, Kenya
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Date
2021
Authors
Wakaria, Njagi Mary
Journal Title
Journal ISSN
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Publisher
Kenyatta University
Abstract
Rice blast is among the challenges that affect rice production and is capable of causing 100% crop damage to susceptible genotypes. The popular aromatic genotypes grown by Mwea farmers are highly susceptible to rice blast. In this view rice genotypes were evaluated for rice blast resistance and transferring the same to susceptible genotypes grown in Mwea. Effect of rice husk ash in controlling rice blast was also evaluated. Thirty three genotypes were screened in the quarantine field in a randomized complete block design to source for resistance. For transfer of resistance, two tolerant cultivars MWUR 4 and MWUR 3 were crossed with two susceptible varieties adopted by Mwea farmers (NIMBAM 10 and NIMBAM 11) and the F1’s obtained planted to produce F2 seeds. F2 population were planted in their own experimental unit. From each experimental unit, the hills that scored up to three were referred as resistant while those above three were referred as susceptible. To test the effect of rice husk ash in controlling rice blast on both susceptible and tolerant, four levels of 120, 60, 30 and 0 and four genotypes two of which were susceptible and two which were tolerant were planted in split plot arrangement. In all experiments, rice blast infected rice straw was spread evenly in the field one month after sowing and frequent irrigation done to get high relative humidity. Disease assessment started two weeks after infection up to dough stage using IRRI 2002 standards evaluation systems and IRRI 2002 standards evaluation systems modified by Hayashi et al., 2009. Other parameters measured were; - top biomass, number of tillers, filled and unfilled spikelets, 1000 grain weight, plant height and grain yield and data obtained analyzed using SAS Version 9.4 of 2013 and means separated using Tukey HSD at P≤ 0.05. The 33 rice genotypes evaluated for rice blast resistance recorded significant difference for disease severity, leaf lesion, infected tillers, panicle lesion, panicle severity, top biomass, filled grain, unfilled grain, thousand grain weights and grain yield at P≤ 0.05. Rice genotypes had varied response to leaf blast with a mean severity range of 0.00 to 7.90. NIMBAM 11 and NIMBAM 10 had the highest leaf blast infection at P≤ 0.05. Nine cultivars; Duorado precoce, B6-144, IRAT 109, MWIR 2, NERICA 1, NERICA 10, NERICA 11, NERICA 5 and Yumenitomanochi had 0.00 score indicating high resistant. Thirteen cultivars;Vieng, Tai, Panicle 84, NERICA 4, MWUR 3, Kitumbo Nyeupe, K2-84, MWUR 4, Senso, Chao Nok, Ziada, K2-54 and Komboka scored between 0.00 to 1.00 indicating resistance. The chi square done at one degree of freedom indicated that resistance is under the influence of inter allelic interaction for 27:37 gene ratio for crosses of NIMBAM 10 and MWUR 3 (7×3), and NIMBAM 11 and MWUR 3 (3× 3) and NIMBAM 10 and MWUR 4 (7×4). For the rice husk ash, the tested rice genotypes were significantly different in terms of lesion type, disease severity, tillers at booting, panicle blast, plant height, top biomass, filled grain, unfilled grain and grain yield at P≤ 0.05. There was significant difference for rice husk rates in terms of lesion type, tillers at booting, plant height and top biomass at P≤ 0.05. Resistant genotypes were realized. The chi square done at one degree of freedom to the F2 populations evaluated for rice blast disease indicated that resistance though transferrable to susceptible genotypes was under the influence of inter allelic interaction for 27:37 gene ratio. Rice husk ash increased the number of tillers, plant height and top biomass and also reduced disease scale slightly.Resistant genotypes realized can be used in rotation between and within seasons to avoid genetic vulnerability. They can also be used to improve the already adopted susceptible genotypes like NIMBAM 10 and NIMBAM 11.
Description
A Thesis Submitted in Partial Fulfilment of the Requirement for the Award of Master’s Degree in Plant Breeding in the School of Agriculture and Enterprise Development in Kenyatta University, August, 2021
Keywords
Evaluation, Rice Genotypes, Rice Blast Resistance, Inheritance, Mwea, Kirinyaga County, Kenya