Fourth International Bemisia Workshop International Whitefly Genomics Workshop
Resistance of Common Bean Genotypes to Bemisia tabaci (Genn. 1889) Biotype B (Hemiptera: Aleyrodidae) in Two Growing Seasons
1 Departamento de Fitossanidade – Faculdade de Ciências Agrárias e Veterinárias – Campus de Jaboticabal/SP, Brasil. Correspondence: aboicajr@fcav.unesp.br
2 Setor de Entomologia, Instituto Agronômico-IAC, Campinas, SP, BR
Brazil is a major producer and consumer of common bean (Phaseolus vulgaris L.), which is the most important source of vegetable protein in the country. Among all pests attacking common bean, the whitefly Bemisia tabaci biotype B has become a key pest, causing substantial losses in many producing regions of the country. The whitefly transmits the bean golden mosaic virus (BGMV), which limits productivity and sometimes causes yield losses of 100%. Whitefly has been controlled with insecticides and cultural practices. Because of the environmental impacts of insecticides, alternative control methods have been sought. Another important approach is the use of resistant genotypes in an integrated pest management (IPM) program, which has shown great potential in controlling B. tabaci biotype B. In this work, we study the resistance of level of common bean genotypes to whiteflies in the rainy and dry seasons. The experiment was conducted from December 2005 to February 2006 (rainy season), and from May to June 2006 (dry season) at the experimental fields of the Department of Plant Protection (Departamento de Fitossanidade), FCAV/UNESP – Jaboticabal, SP – Brazil. Seed was sown in rows spaced 0.5 m at a density of 12 plants per meter. Fertilizer was applied at planting at a rate of 430 kg ha−1 of the formula 04-14-08 NPK, and 20 days after emergence (DAE) with 180 kg ha−1 of ammonium sulfate. The experiment was arranged in randomized blocks with three replications and nineteen treatments corresponding to the genotypes: IAC-Carioca Tybatã, IAC-Una, FT-Nobre, Pérola, Gen 96A98-15-3-32-1, Gen 96A45-3-51-52-1, Gen 96A98-13-1-52-1, Gen 96A98-5-1-1-55, Gen 96A3-P1-1-1, LP 98-122, LP 02-130, LP 01-38, LP 9979, BRS-Pontal, BRS-Requinte, BRS-Triunfo, BRS-Grafite, CV-48 and Z-28. Plots consisted of four rows of 4 m, covering 4.0 m2 of total area and 2.0 m2 of useful area. The total experiment area was 840 m2. Whitefly infestation was monitored on a weekly basis by counting B. tabaci biotype B eggs and nymphs on 10 leaflets per plot, until 60 day after emergence. The occurrence of BGMV was monitored 30 and 50 DAE, but no symptoms were observed. Data were analyzed by Fisher’s test and submitted to Duncan multiple range test at 5 % of probability. In the rainy season, a significantly higher egg count was observed only in FT-Nobre, at 53 DAE. The highest nymph counts were found on different dates in each genotype. From 25 to 39 DAE the nymph count varied, although highest counts were observed mostly at 32nd DAE. The highest egg count in the dry season experiment was seen on genotypes Gen 96A98-13-1-52-1 (39 DAE) and Gen 96A98-5-1-1-55 (53 DAE). The nymph population per leaflet was higher on most genotypes from 25 to 39 DAE, and then it tended to decrease. However, on genotype BRS-Pontal the highest population was observed 53 DAE, while in IAC Tybatã population peaks were seen 25 and 60 DAE. In Gen 96A98-5-1-1-55 only one peak was observed 60 DAE. Our results showed that in the rainy season the most critical attacks took place until 39 DAE, with a population peak at 32nd DAE. In the dry season, most genotypes showed infestation increases until 39 DAE, when the highest population was observed. The genotypes studied showed varying results in terms of B. tabaci biotype B oviposition, depending on the plant age and growing season (rainy or dry).