LEVELS OF SEED AND SOIL BORNE

Transcription

1 Multi-Purpose Legume project LEVELS OF SEED AND SOIL BORNE INOCULUM IN NANDI SOUTH AND BEAN ROOT ROT MANAGEMENT BY SEED DRESSING Anne Kadaari Kivisi MSc. Crop protection University of Nairobi Supervisor: Prof. James Muthomi

2 OBJECTIVES Determine bean disease inoculum levels in soils and seed in diverse agro-eological zones in Nandi south To evaluate the efficacy of seed dressing in management of root rot disease complex

3 MATERIALS AND METHODS STUDY AREA AND SAMPLE COLLECTION The study was carried out in different agro ecological zones Upper midland zones 1, 2, 3 (UM1, UM2, UM3) and Lower highlands zone 1 (LH1) in Nandi East, Nandi Central and Nandi South 10 bean farms sampled in each AEZ From each farm 5 soil samples collected in X pattern and combined to make a composite sample. 1kg bean seed sample collected collected from each farm.

4 PURITY TEST Done following the procedures described by (ISTA 2010) Three replicates of 100 g each of the seed samples separated into pure seed of the stated variety, discoloured/ shriveled seed, other bean varieties, other crop seed, inert materials and weed seeds The different fractions individually weighed and the percentage of each proportion calculated as follows: component(%) = weight of individual fractions Total test sample

5 DETERMINATION OF GERMINATION AND SEED INFECTION Done following ISTA (2010) procedures Three replicates of 50 seeds taken at random from each seed sample and placed on wet absorbent paper towel, folded and incubated under moist conditions Data collected - number on number of germinated seeds, normal seeds, abnormal seeds, mouldy seeds, dead seeds and seedlings showing infection

6 DETERMINATION OF BACTERIAL CONTAMINATION OF SEED Used plating technique described by (ISTA, 2007). 50g of seed sample taken from each sample and soaked overnight in 50 ml 8.5% sterile saline with 0.2 ml Tween 20 Extract was subjected to 10-fold dilution series up to 10 2 and 1 ml of the 10 1 and 10 2 dilutions were plated in molten nutrient agar & incubated in an inverted position at 28 C ± 2 C for 2-3 days Number of yellow and cream colonies determined; the number of colony forming units per seed for each bacteria was calculated Bacterial pathogen was identified based on cultural and pathogenicity tests

7 Shriveled and discoloured seed Germination test on paper towel Germination test - rolled paper towel Germinated seeds

8 Germinated seedlings showing infection Mouldy seed Dead seeds Infected seedling

9 EVALUATION OF EFFICACY OF SEED DRESSING IN MANAGEMENT OF BEAN ROOT ROT COMPLEX Field trials conducted at Koibem (high soil fertility, higher rainfall area) and Kapkerer (Low soil fertility, lower rainfall area). Six seed treatments evaluated: 1. Seed plus (10% Imidacloprid, 10% Metalaxyl, 10% Carbendazim) - fungicide and insecticide active ingredients 2. Murtano super (20% Lindane, 26% Thiram) - fungicide and insecticide active ingredients.

10 3. Rootgard (Trichoderma spp., Bacillus spp., Pseudomonas spp., Aspergillus spp., Chaetomium spp., Esherichia spp., Azorobacter spp.) - biological product with insecticidal and fungicidal properties 4. Funguran OH 50WP (50g/l Copper hydroxide); fungicide active against Bacterial and fungal disease i.e. late blights, leaf spots 5. Click 20SL (imidacloprid 200g/l); an insecticide and used in control of soil borne pests 6. Monceren 125 DS -Imidacloprid 233g/l, Pencycuron 50g/l, Thiram107g/l.); a fungicide active against root rots, damping off 7 Untreated seeds (control).

11 Data collected from the field experiments: o Plant emergence, o Plant stand, o Nodulation, o Root rot incidence and severity, o Plant biomass at harvest and seed yield STATISTICAL DATA ANALYSIS Collected data subjected to analysis of variance (ANOVA) Differences among the treatment means determined at 5% probability level using genstat statistical software version 15.

12 RESULTS Major root rot pathogens isolated from soils included Rhizoctonia, Fusarium solani, F. oxysporum, and Pythium Soil borne inoculum levels of up to 40,000 CFU/g soil detected in most of the agro-ecological zones Seed samples showed symptoms of infection shrivelling and discolouration, mouldiness and infection on incubation between paper towels Agro-ecological zones significantly differed in levels of shrivelled seed, and seedling infection Most seed samples had less than 95% recommended germination percentage Seed dressing chemicals signficantly differed in efficacy; chemicals containing imidachloroprid (Click 20SL and Moncerene were the most effective in reducing root and increasing yields

13 CFU/g soil CFU/g soil CFU/g soil CFU/g soil 8,000 7,000 6,000 5,000 Rhizoctonia 6,000 5,000 4,000 Fusarium oxysporum 4,000 3,000 3,000 2,000 1,000 2,000 1,000 - LH1 LM1 UM1 UM1-2 UM2-3 - LH1 LM1 UM1 UM1-2 UM2-3 Agro-ecological zone Agro-ecological zone 6,000 Pythium 6,000 Fusarium solani 5,000 5,000 4,000 4,000 3,000 3,000 2,000 2,000 1,000 1,000 - LH1 LM1 UM1 UM1-2 UM2-3 - LH1 LM1 UM1 UM1-2 UM2-3 Agro-ecological zone Agro-ecological zone Fig 1. Soil borne inoculum levels (CFU/g soil) of the major bean root rot pathogens isolated from soil samples from different agro-ecological zones in Nandi

14 Table 1. Quality parameters of seed samples collected from different agro-ecological zones in Nandi Shriveled Mouldy Dead seeds Infected seedlings LH ab 4.0 a 3.9 a 8.2 b LM ab 5.0 ab 4.2 a 5.1 a UM1 9.2 a 6.8 b 6.1 a 7.3 b UM b 4.7 ab 4.6 a 7.9 b UM a 5.0 ab 5.2 a 6.9 b CV LSD Normal seeds Pure seed Germinated seeds Other bean LH a 76.5 a 95.2 a 11.0 a LM a 79.3 a 94.3 a 8.4 a UM a 77.2 a 93.0 a 11.1 a UM a 84.0 a 94.1 a 10.3 a UM a 76.0 a 94.5 a 11.9 a CV LSD

15 CFU/seed X.c.p P.s.p High levels of seed borne bacterial infection of up to 100 cfu/ seed was detected in samples; Samples from Nandi south had higher infection levels 0.0 Nandi central Nandi East Nandi South Region Fig. 2. Seed borne inoculum levels of bean common bacterial blight (Xanthomonas campestris pv phaseoli X.c.p) and halo blight (Pseudomonas savastanoi pv phaseolicola P.s.p) isolated from seed samples from different region of Nandi

16 Number of plant per plot Nodules per plant 30.0 Koibem Kapkarer Seed plus Murtano Rootgard Funguran Click 20SL Monceren Untreated Seed treatment Koibem Kapkarer 0 Seed plus Murtano Rootgard Funguran Click 20SL Monceren Untreated Seed treatment Fig. 3. Number of nodules per plant and number plants per plot in field experiment plots planted with bean seed dressed with different chemical ingredients

17 Root rot severity (%) Root rot severity (%) Non-symptomatic Symptomatic 0.0 Seed plus Murtano Rootgard Funguran Click 20SL Monceren Untreated Seed treatment Non-symptomatic Symptomatic 0.0 Seed plus Murtano Rootgard Funguran Click 20SL Monceren Untreated Seed treatment Fig. 4. Percent root rot severity on bean plant without and with symptoms of infection after dressing of the seeds with different chemicals before planting

18 Yield (kg/ha) Root rot incidence (%) Koibem Kapkarer Seed plus Murtano Rootgard Funguran Click 20SL Monceren Untreated Seed treatment Seed yield Biomass Seed plus Murtano Rootgard Funguran Click 20SL Monceren Untreated Seed treatment Fig. 5. Percent incidence of root rot and corresponding biomass and seed yields on field experimental plots plated with seeds dressed with different chemicals

19 CONCLUSIONS AND RECOMMENDATIONS 1. Soils in Nandi have high levels of root rot pathogen inoculum 2. The farmer produced seed in Nandi is contaminated with other bean varieties and mostly contaminated with bacterial blight pathogens 3. Seed dressing of the farmer-saved seed would help reduced incidence and severity of root rots and lead to improved yields Following is recommended: Advice to farmers on seed selection selecting healthy plants and collect only good looking pods to obtain seed for the next season Thorough sorting of the seeds to remove discoloured and shriveled seed to reduce disease inoculum in the subsequent season Train farmers on seed dressing to reduce the losses due to root rots and maintain good yield; seed dressing is cheap option

20 ACKNOWLEDGEMENT 1. McKnight Foundation CCRP 2. Multi-purpose legume project Researchers & technical staff 3. All who contributed in any small and big way to completion of this study THANK YOU