Bacterial wilt is a problematic disease affecting potato production in Kenya and the available management methods are not efficient. Field, semi-field and laboratory experiments were conducted to evaluate the effect of canola green manure and compound fertilizer on bacterial wilt management. Laboratory experiment was conducted at Egerton university biological laboratory to evaluate the effect of canola extract on R. solanacearum population density in-vitro. Four levels of canola extract quantities were used; 0, 100, 200, 300microlitres, and enrich immunomodulator (Di-bromo Di-nitro propane 1-3-diol) (DDD) was used as a positive control. Inoculum was prepared from infested soil and Selective Medium South Africa (SMSA) (Casamino acids, Bacto-Peptone, Glycerol, and Bacto-Agar) was used as growth medium in a completely randomized design. Field experiment was carried out in two sites (Elburgon site is in Upper high land zone two (UH2) and Mau-Narok is in Upper high land zone one UH1). Two levels of canola green manure (with and without green manure application), four levels of fertilizer (NPK+Ca+Mg+ micronutrients) applied at 0(F1), 250(F2), 575(F3), 900 (F4) kg ha-1 and diammonium phosphate (DAP500 kg ha-1) +Calcium ammonium nitrate (CAN300 kg ha-1) (F5) as a positive control. The experiment was carried out in randomized complete block design (RCBD) spilt plot replicated three times, canola green manure as main plot and fertilizer and varieties combination as sub plots. Semi-field experiment (in pots) was conducted at Egerton university farm, five levels of canola green manure (100, 75, 50 and 0 g kg-1 soil) and four levels of the compound fertilizer as used in the field experiment were used in a completely randomized design (CRD) with three replicates. The data shows that canola extract did not have a significant (Pr <0.05) effect on bacterial population density (CFU), where chemical treatment (DDD) restricted the growth of R. solanacearum under laboratory experiment. Under field and semi-filed experiments, canola green manure and fertilizer treatments had no significant (Pr <0.05) effect on bacterial population density in the soil nor bacterial wilt incidence. Kenya karibu variety it did not show any wilting symptoms of bacterial wilt across the sites and semi-field experiment. Canola did not suppress the growth of R. solanacearum; further investigation should be done on other brassica family plants.
Stem rust (Puccinia graminis f. sp tritici) is a destructive disease of wheat (Triticum aestivum L.) making it a major challenge to wheat production in Kenya as well as other wheat growing countries. Due to this, mutation breeding has been as a source of increasing variability and confers specific improvement to the Kenyan varieties without significantly altering its phenotype. The objective of this study was to determine adult plant resistance of wheat mutant lines to stem rust across three different locations. The study area was in three locations, Nakuru County (Njoro and Mau Narok) and Meru County (Timau) during 2015-2016 cropping season. Sixty three mutant lines and six checks (NJBWII, Duma and Kwale, Kingbird, Robin and Cacuke) were evaluated under field conditions with three replications in an alpha lattice (23 rows by 3 columns) design. Mean for area under disease progress curve and coefficient of infection revealed that Duma200gry (1026), Duma200gry (1124) were best disease performers. The calculated variance (Si) distinguished stable genotypes in terms of disease and yield which included Duma100gry (995) and Kwale100gry (1483), respectively. There was positive effect of dosage 400gry on the mutant lines in terms of disease, yield and 1000 kernel weight, mostly with the Duma mutant lines. The mean grain yield for the genotypes ranged from 5.5 to 14.1 t ha -1 . Genotype, location and genotype by location interaction for the area under disease progress curve, coefficient of infection and yield were significant at P< 0.01 and P<0.001. There was a negative correlation displayed between yield and disease components. R-Square values revealed 0.1508 and 0.3911 of the variation in yield was contributed by the disease severity and area under disease progress curve, respectively. Considering the best lines both in disease and yield can be taken for further screening in breeding programmes.
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