Levels of angular leaf spot (ALS) resistance in common bean (phaseolus vulgaris. l) populations developed for als resistance
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Date
2008
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Sokoine University of Agriculture
Abstract
Angular leaf spot (ALS) incited by Phaeoisariopsis griseola is wide spread in all
bean growing areas in Tanzania. It is of great concern in wet bean growing areas of
the country, yet little information is available in Tanzania on cultivars resistant to the
disease. The objective of this work was to incorporate angular leaf spot (ALS)
resistance in adapted common bean lines through backcrossing procedure, determine
inheritance of ALS in the crosses and screen advanced backcross lines for ALS
resistance. Backcrossing was done in the screen house at SUA where G5686 x
C/wonder, Amendoim x Rojo and Mexico54 x Soya were crossed to their respective
parents. The backcrossed lines obtained together with the advanced bean lines from
Prosser USDA-ARS Washington were evaluated for resistance to ALS. Completely
randomized design (CRD) was used in screen house and Randomized Completely
Block Design (RCBD) was used for field trials. For F2, F3, BC m and BC1.2 there was
no randomization nor replication as this has no effect in early generations of bean
improvement. For the advanced lines there were three replications in each of the two
different locations i.e. SUA-Morogoro and Madira, Arusha. An appreciable amount
of genetic variation (P < 0.05) for ALS resistance, pods per plant and seed yield was
observed. The following advanced lines were found resistant to ALS in both
locations PSO4・336Ab・7, PSO4-126Aa-8, PSO4-335B-1, PSO4-139Ba-l, PSO4-
139Bb-5, PSO4-139Bb-l, PSO4-106Ba-2, PSO4-139Bb-4, PSO4-126Ab-8, PSO4-
139Ba-7, PSO4-139Ab-10 and PSO4-126Aa-6. Both lines showed intermediate or
resistant reaction to ALS disease, moreover, some of these did not develop any
disease symptoms and thus could be immune to the disease or have escaped the
disease. Significant and positive correlation between number of pods per plant and yield was observed in advanced lines where r = 0.751, (P < 0.001) fbr Morogoro trial
where r = 0.509 and (P < 0.001) for Arusha trial. Heritability estimates were low
0.190 to medium 0.228 for disease resistance and moderate 0.30 to high 0.73 fbr
number of pods per plant. It is recommended that further studies be conducted
among the lines evaluated and the best performing lines to be selected then advanced
and later be evaluated for other characteristics such as size, cooking time and protein
concentration.
Description
Dissertation
Keywords
Bean growing, Phaeoisariopsis griseola, Angular leaf spot (als), Tanzania