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ARS Home » Southeast Area » Mayaguez, Puerto Rico » Tropical Crops and Germplasm Research » Research » Publications at this Location » Publication #319814
Title: Root rots of common and tepary beans in Puerto Rico

Author
item ESTEVEZ DE JENSEN, C. - University Of Puerto Rico
item Porch, Timothy - Tim
item BEAVER, J. - University Of Puerto Rico
item GONZALEZ, O. - University Of Puerto Rico

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/6/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Root rots are a disease complex affecting common bean and can be severe in bean growing areas in the tropics and subtropics. The presence of several pathogens makes it difficult to breed for resistance because of the synergistic effect of the pathogens in the host and the interaction of soil factors and environmental conditions. During 2015, isolates were collected from a root rot nursery in Isabela from common bean genotypes with symptoms of root rot. The most prevalent pathogens found were Rhizoctonia solani (Rs), Fusarium solani (Fs) and Pythium ultimum (Pu). Inoculation tests were carried out under screenhouse conditions using the local check ‘Verano’ and TARS-LFR1. Furthermore, to determine the resistance of elite tepary and common bean lines, a trial was carried out with each pathogen inoculated separately. In a complete randomized design replicated three times, tepary and common bean lines were sown in a PROMIX substrate. The inoculum consisted of an agar disk of Rs grown in an acidified potato-dextrose-agar (aPDA) placed under the seed at planting. For Fs, a suspension of 1 ml of 105 macroconidia ml-1 was inoculated at the seedling stage. An un-inoculated control was included and the evaluation was carried out 15 days after inoculation. Rs was evaluated using a disease severity (DS) scale of 1-5, where 1 = healthy root and hypocotyl, 2 = 1-25% of hypocotyl infected, 3 = 25-50% of hypocotyl affected, 4 = 25-50% hypocotyl affected and 5 = 75–100% hypocotyl affected, dead plant. For Fs, the DS scale used was 1-9. In tepary beans, reddish to brown lesions in the hypocotyl and depressions at the base of the stem were consistent with the inoculation of Rs. Results showed that tepary line Tep 32 (4.5) the interspecific hybrids INB-848 (DS 4), INB-846 (DS 4.6), INB-826 (DS 4.5) and INB-829 (DS 4.6) were susceptible to Rs. Tep 1 (DS 3), Tep 23 (DS 3.3) and INB-809 (DS 3) were intermediate in reaction to Rs. Interspecific hybrids INB-835 and TARS-LFR1 were resistant. The common beans ‘Verano’ (DS 5), ADP-269 (DS 4), AND-469 (DS 4.5), ADP-54 (DS 4), ADP-633 (DS 4.5), ADP-115 (DS 5) were susceptible to Rs when compared with TARS-LFR1 (DS 2), ADP-518 (DS 2.7), ADP-508 (DS 2) and ADP-475 (DS 1.7). Tepary beans inoculated with Fs did not develop symptoms, in contrast, common beans showed reddish lesions in the hypocotyl and browning of the tap rot. The results indicated that Rs and Fs independently produced hypocotyl and root rot and that the combination of the pathogens should be included in future studies.