INHERITANCE OF PHOSPHORUS USE EFFICIENCY & RESISTANCE TO ANTHRACNOSE IN SELECTED SORGHUM GENOTYPES GROWN IN THE ACID SOILS
Nyambok, A., Opio Oluge, R., Gudu, S., Ochuodho Julius and Okori. P
Statement of the problem1. NPK deficiency2. Diseases (Anthracnose and TLB)3. Al toxicity common in acid soils4. Soil acidity increases Pi fixation and therefore non-bioavailability to plants accounting in part to low grain yield (1.0t/ha) Al Toxicity and acidity associated with acidic soils red zones in map
Justification1. Losses of up to 70% may occur due to multiple stresses2. Most materials are susceptible to diseases and intolerant to Al toxicity Al toxicity and disease symptoms
Justification 3.Deployment of genotypes efficient in phosphorus use is cost effective.4.Breeding to address these challenges is the most cost effective way especially for resource poor farmers
ObjectivesPUE studies1. Mode of inheritance of PUE in crosses of selected sorghum genotypes2. Mode of inheritance of resistance to anthracnose in crosses of selected sorghum genotypesAl studies1. Establish aluminum tolerance levels of some selected sorghum accessions2. Establish the inheritance and mode of gene action controlling tolerance to aluminum toxicity in the selected sorghum genotypes
Materials & Methods 1(PUE & Anthracnose studies)Cultivars Source Anthracnose Phosphorus reaction reactionG2 MOI Resistant InefficientK5e MOI Susceptible InefficientL6 MOI Resistant to foliar, Efficient susceptible to stemP5 MOI Highly Efficient SusceptibleC1 ICRISAT Resistant EfficientO2 MOI Resistant Efficient
Cultivars Source Al status Phosphorus reactionC1 MOI Tolerant EfficientK5e MOI Unknown InefficientL5 MOI Susceptible -----------P3 MOI Unknown InefficientP5 MOI Unknown EfficientC1 ICRISAT Resistant Efficient160 lines MUK Unknown -----------O2 MOI Tolerant Efficient
Study1: Field evaluations for anthracnose resistance• Field screening of F2 population at an anthracnose hotspot• Plots laid down in a split plot design , 3 replications; Infector rows (P5 line) used to increase disease pressure• Inoculations will be done at 30 DAP using anthracnose infested kernels placed into developing leaf whorls
Study 1: Field evaluations for anthracnose resistance…• Foliar anthracnose severity visually rated weekly on 20 individual tagged plants, 45 DAP until Physiological Maturity, using a 1-9 severity rating scale (Thakur et al.,1998)• Severity data will be used to compute AUDPCs (Madden et al.,2008).
Study 2: Screening for Al3+ toxicity• Preliminary screening done according to Magnavaca et al., 1987) in hydroponic growth chamber Initial root length• Experimental design-split-plot design measurement with 83 genotypes as sub-plots (including 2 tolerant and 1 susceptible check) and Al treatments 0 and148μM Al as main plots
Study 2: Screening for Al3+ toxicity…• Initial root length taken at 4 days of initial germination and 5 days after growth in Al treated growth solution. Data subjected to ANOVA
Preliminary Results: PUE and anthracnose experiments• A six-parent half diallel cross used to generate F1 seed in Kibos, W. Kenya.12 successful crosses out of 15 obtained• F1 material advanced to F2, seed harvested in May,2012• F2 seed planted in the two hotspots in Sept, 2012.
Field observations from the crossing block• C1, G2 and O2 observed to be completely resistant to anthracnose,• L6 susceptible to stem anthracnose but completely resistant to foliar anthracnose,K5e susceptible, mostly to stem anthracnose• P5 highly susceptible to both stem and foliar anthracnose.
Preliminary Results : Al Study• Significant Difference among Genotypes• Non-significant Interaction (Genotypes X Al levels)
ANOVA of Screening Results (Net Root Length)Source df MS F Cal (V.R)Rep 1 25.95 98.79nsAl_Level 1 66.31 262.40*MP error 1 0.25 0.42nsGenotype 95 0.98 1.64**AL * Gen 95 0.40 0.68nsSP error 190 0.59
High and Low Mean Net Root LengthGenotype Mean02 2.40 (Tolerant)C1 1.77 (Tolerant)UNGB 2672 2.51UNGB 2671 2.79UNGB 2678 2.86L5 0.84 (Susceptible)UNGB 2730 0.48UNGB 2759 0.71UNGB 2856 0.92UNGB 2762 1.04CV% = 29.2 LSD = 1.52
Conclusions based on observation• Plant tissues specific reaction were observed (Thakur and Mathur ,2000)• Putative resistant genotypes identified. Most genotypes were susceptible• Inheritance studies will reveal more about the underlying observations