8. Thesis outline
3.3 Results
3.3.1 Screen house evaluations
80 analysed for protein and oil content using a Near-Infrared Spectroscopy system in ABSTCM limited laboratory4.
3.2.6 Data analysis
Data was subjected to analysis of variance using Genstat statistical package (12th edition) (Payne et al., 2009) for all the traits.
Area under disease progress curve (AUDPC) values were calculated using the formula below as presented by Kumudini et al. (2008);
AUDPC =
Where, Xi = the disease severity score at the ith observation;
ti = the time (day) at the ith observation;
ti+1 –ti = the interval (days) between two consecutive assessments n = the number of assessments.
To compare genotypes across the seasons, AUDPC were standardized by dividing AUDPC values with the total duration of the disease in each season (Mohapatra et al., 2008). The duration of the disease epidemic was 34, 28, 42 and 30 days for the KARI-Embu long rain seasons of 2010 and 2011, and the cold season of 2011, and for the KARI-Mwea long rains of 2011, respectively.
Pearson’s phenotypic correlation estimates for ASR rust severity, sporulation scores and AUDPC with grain yield, days to 75% maturity, plant height, 100 seed weight, oil and protein content were computed using Genstat statistical package (12th edition).
81 and sporulation scores were variable in the two seasons with the highest scores recorded in the first season. In this evaluation there were no categories of immune or resistant genotypes.
However, about 9% of the genotypes were moderately resistant with severity scores of less than 6.0. About 6.4% had moderate susceptible infections with mean rust score of 6.0 to 7.0 while more than 90% were highly susceptible with rust severity scores ranging between 8.0 and 9.0.
Table 3.4: Soybean rust severity scores, sporulation, lesion type and rust reaction of genotypes evaluated in the screen house for 2 seasons at KARI-Embu.
Rust severity (1-9 score) Rust sporulation (1-5 score)
Genotype code
Season 1
Season 2
Mean scores
Season 1
Season 2
Mean scores
Lesion
type Rust reaction classification
G10428 4.67 4.00 4.33 1.00 1.00 1.00 RB MR
MAK BLD11.3 4.33 4.33 4.33 1.00 1.00 1.00 RB MR
G8586 4.00 5.00 4.50 1.00 1.33 1.17 RB MR
GC0013829 5.67 4.33 5.00 2.00 1.33 1.67 RB MR
G58 5.67 5.33 5.50 2.00 1.00 1.50 RB MR
G7955 5.67 5.33 5.50 1.00 1.33 1.17 RB MR
Namsoy4M 6.00 5.00 5.50 2.33 1.00 1.67 RB MR
Tainung 6.00 5.00 5.50 2.33 1.33 1.83 RB MR
PI200477A 5.67 6.00 5.83 2.33 2.00 2.17 RB MR
UFV3 6.33 5.33 5.83 2.00 1.67 1.83 RB MR
UG-5 6.00 7.33 6.67 2.33 1.67 2.00 TAN MS
SB-19 8.00 5.67 6.83 3.33 1.00 2.17 TAN MS
Dowling 7.00 7.33 7.17 3.67 3.00 3.33 TAN MS
Maksoy1N 7.67 6.67 7.17 3.00 2.33 2.67 TAN MS
EXKirinyaga 7.00 8.00 7.50 3.67 3.67 3.67 TAN MS
GBK 029511 7.33 8.33 7.83 2.33 3.67 3.00 TAN MS
SB-8 8.33 7.33 7.83 3.67 3.00 3.33 TAN MS
GBK 029574 7.33 8.67 8.00 3.67 4.00 3.83 TAN HS
GBK 033215 7.33 8.67 8.00 3.67 4.67 4.17 TAN HS
SB-17 8.67 7.33 8.00 4.00 3.33 3.67 TAN HS
GBK 029600 8.67 7.67 8.17 3.00 3.33 3.17 TAN HS
911/6/3 7.33 9.00 8.17 3.67 4.33 4.00 TAN HS
Maksoy-2N 8.33 8.00 8.17 4.00 3.33 3.67 TAN HS
GBK 029570 8.33 8.33 8.33 4.67 4.00 4.33 TAN HS
932/5/36 8.33 8.33 8.33 3.33 3.67 3.50 TAN HS
SB-37 8.33 8.33 8.33 4.33 4.67 4.50 TAN HS
GBK 029575 8.67 8.33 8.50 4.33 3.67 4.00 TAN HS
GBK 029611 8.67 8.33 8.50 3.00 4.00 3.50 TAN HS
GBK 029612 8.67 8.33 8.50 4.33 3.67 4.00 TAN HS
82
GBK 029621 8.67 8.33 8.50 3.33 3.33 3.33 TAN HS
GBK 033209 8.67 8.33 8.50 4.33 4.00 4.17 TAN HS
GBK 033226 8.67 8.33 8.50 3.67 3.00 3.33 TAN HS
GBK 033242 8.67 8.33 8.50 4.00 3.67 3.83 TAN HS
GBK 033246 8.67 8.33 8.50 4.33 3.67 4.00 TAN HS
GBK 033249 8.67 8.33 8.50 4.00 3.33 3.67 TAN HS
GBK 033250 8.67 8.33 8.50 4.33 4.00 4.17 TAN HS
GBK 033252 8.33 8.67 8.50 4.33 4.00 4.17 TAN HS
GBK 033253 8.67 8.33 8.50 4.67 4.00 4.33 TAN HS
GBK 033254 8.67 8.33 8.50 4.33 3.67 4.00 TAN HS
GBK 033255 8.33 8.67 8.50 4.00 3.67 3.83 TAN HS
GBK 045342 8.67 8.33 8.50 4.67 3.67 4.17 TAN HS
BlackHawk 8.33 8.67 8.50 4.00 4.67 4.33 TAN HS
BRSSambaiba 8.67 8.33 8.50 4.33 3.67 4.00 TAN HS
Kissi 8.67 8.33 8.50 4.33 4.00 4.17 TAN HS
SB-20 8.67 8.33 8.50 4.33 3.67 4.00 TAN HS
GBK 028397A 8.67 8.67 8.67 4.33 3.67 4.00 TAN HS
GBK 029573 8.67 8.67 8.67 3.00 4.67 3.83 TAN HS
GBK 029577 8.67 8.67 8.67 3.67 3.67 3.67 TAN HS
GBK 029610 8.67 8.67 8.67 4.00 3.67 3.83 TAN HS
GBK 029614 8.67 8.67 8.67 4.33 3.67 4.00 TAN HS
GBK 033204 9.00 8.33 8.67 4.33 3.67 4.00 TAN HS
GBK 033208 8.67 8.67 8.67 3.00 3.00 3.00 TAN HS
GBK 033210 8.67 8.67 8.67 4.33 3.67 4.00 TAN HS
GBK 033213 8.67 8.67 8.67 4.00 4.33 4.17 TAN HS
GBK 033217 8.67 8.67 8.67 2.67 4.33 3.50 TAN HS
GBK 033221 8.67 8.67 8.67 4.00 3.67 3.83 TAN HS
GBK 033222 9.00 8.33 8.67 4.67 3.67 4.17 TAN HS
GBK 033223 8.67 8.67 8.67 4.33 4.00 4.17 TAN HS
GBK 033224 8.67 8.67 8.67 4.33 4.67 4.50 TAN HS
GBK 033229 8.67 8.67 8.67 4.67 3.67 4.17 TAN HS
GBK 033230 8.67 8.67 8.67 4.67 3.33 4.00 TAN HS
GBK 033231 8.33 9.00 8.67 4.67 4.33 4.50 TAN HS
GBK 033234 8.67 8.67 8.67 4.33 3.67 4.00 TAN HS
GBK 033236 8.67 8.67 8.67 4.33 3.67 4.00 TAN HS
GBK 033243 8.67 8.67 8.67 4.33 3.67 4.00 TAN HS
GBK 033245 8.67 8.67 8.67 3.33 3.67 3.50 TAN HS
GBK 033251 8.67 8.67 8.67 4.67 4.67 4.67 TAN HS
GBK 033257 8.67 8.67 8.67 4.33 3.67 4.00 TAN HS
835/5/30 8.67 8.67 8.67 4.67 5.00 4.83 TAN HS
916/5/19 8.67 8.67 8.67 5.67 4.67 5.17 TAN HS
BRS217Flora 8.67 8.67 8.67 4.67 4.33 4.50 TAN HS
Duicker 8.67 8.67 8.67 4.33 4.00 4.17 TAN HS
83
EAI 3600 8.67 8.67 8.67 3.00 4.67 3.83 TAN HS
Sable 8.67 8.67 8.67 4.33 4.33 4.33 TAN HS
SB-4 8.33 9.00 8.67 4.00 3.67 3.83 TAN HS
GBK 010246 9.00 8.67 8.83 3.67 3.67 3.67 TAN HS
GBK 029571 9.00 8.67 8.83 3.33 4.00 3.67 TAN HS
GBK 029616 9.00 8.67 8.83 4.33 4.33 4.33 TAN HS
GBK 029617 9.00 8.67 8.83 4.33 4.00 4.17 TAN HS
GBK 029620 8.67 9.00 8.83 4.67 4.33 4.50 TAN HS
GBK 029622 8.67 9.00 8.83 4.00 4.00 4.00 TAN HS
GBK 033203 8.67 9.00 8.83 4.33 4.00 4.17 TAN HS
GBK 033205 8.67 9.00 8.83 4.00 4.00 4.00 TAN HS
GBK 033206 8.67 9.00 8.83 4.33 4.00 4.17 TAN HS
GBK 033207 8.67 9.00 8.83 4.33 4.67 4.50 TAN HS
GBK 033211 8.67 9.00 8.83 4.00 4.00 4.00 TAN HS
GBK 033214 8.67 9.00 8.83 4.33 4.00 4.17 TAN HS
GBK 033218 8.67 9.00 8.83 4.33 3.67 4.00 TAN HS
GBK 033220 9.00 8.67 8.83 3.33 4.00 3.67 TAN HS
GBK 033225 8.67 9.00 8.83 4.00 4.00 4.00 TAN HS
GBK 033233 8.67 9.00 8.83 4.33 4.33 4.33 TAN HS
GBK 033237 8.67 9.00 8.83 4.67 4.33 4.50 TAN HS
GBK 033247 9.00 8.67 8.83 4.33 3.67 4.00 TAN HS
GBK 033248 9.00 8.67 8.83 4.67 4.00 4.33 TAN HS
915/5/12 8.67 9.00 8.83 4.00 5.00 4.50 TAN HS
917/5/16 8.67 9.00 8.83 4.33 3.67 4.00 TAN HS
931/5/34 8.67 9.00 8.83 4.00 3.67 3.83 TAN HS
Bossier 8.67 9.00 8.83 4.33 4.67 4.50 TAN HS
BRS MG46 8.67 9.00 8.83 4.00 4.67 4.33 TAN HS
Ex-Japan 8.67 9.00 8.83 4.33 4.67 4.50 TAN HS
FH-1 8.67 9.00 8.83 4.33 4.67 4.50 TAN HS
Gazelle 9.00 8.67 8.83 4.33 4.33 4.33 TAN HS
Hill 8.67 9.00 8.83 3.33 4.00 3.67 TAN HS
GBK 033277 8.67 9.00 8.83 3.00 4.33 3.67 TAN HS
GBK 028397B 9.00 9.00 9.00 4.00 4.67 4.33 TAN HS
GBK 033232 9.00 9.00 9.00 4.33 3.67 4.00 TAN HS
GBK 033241 9.00 9.00 9.00 5.00 4.00 4.50 TAN HS
LS6161RR 9.00 9.00 9.00 4.00 4.00 4.00 TAN HS
Nyala 9.00 9.00 9.00 4.33 3.67 4.00 TAN HS
SCS-1 9.00 9.00 9.00 4.33 4.67 4.50 TAN HS
mean 8.27 8.24 8.26 3.84 3.66 3.75
Sed 0.80 0.49 0.07 0.92 0.66 0.08
CV (%) 11.80 7.30 10.40 29.20 22.20 26.30
84 MR is moderately resistant; MS is moderately susceptible; HS is highly susceptible; RB is red brown lesions; and TAN is tan reactions.
Soybean genotypes differed in their reactions to ASR. Plant introductions G10428 (Rpp4) and G8586 (Rpp2) exhibited moderate levels of resistance with rust severity scores of 4.3 and 4.5, respectively. MAK BLD 11.3 also had a rust score of 4.3. Plant introductions G7955 (Rpp3), G58 (Rpp1) and Tainung 4 (Rpp1) all had a moderate rust severity score of 5.5. Among the moderate resistant lines previously evaluated in Uganda and South Africa, GC 00138-29, PI 200477A, UFV3 and Namsoy 4M had rust severities ranging between 5.0 and 5.8. On the other hand, genotypes UG-5, Maksoy 1N, Maksoy 2N had high rust severity scores ranging between 6.7 and 8.2. The highest disease severity scores of 7.0 and above were observed mainly on genebank genotypes, advanced lines and commercial varieties, as well as landrace collections from farmers’ fields. Commercial variety SCS-1 and LS6161RR from South Africa had the highest rust severity score (9.0), similar to the susceptible check variety Nyala.
It was also observed that genotypes with low rust severity scores had red brown reactions with low sporulation levels, while those with high rust severities had tan reactions with higher levels of spore production. For example, genotypes G10428 and G8586 with Rpp4 and Rpp2, respectively had low rust severity scores that were associated with dark red brown lesions.
These genotypes had low sporulation rates ranging from 1.0 to 1.2. Other genotypes with moderate rust severity scores ranging between 4.0 to 5.8 including G58 (Rpp1), G7955 (Rpp3), MAK BLD 11.3, GC 00138-29, UFV3, PI 200477A and Namsoy 4M expressed red brown lesions that differed in colouration, with sparsely sporulating uredinia with scores of less than 3.
However, most of the commercial varieties, genebank genotypes and advanced lines developed higher levels of rust severity, which were related to high occurrence of tan reactions. In addition, these genotypes recorded the highest levels of sporulation with scores ranging from 3.0 to 4.5.