RESUMO

White mold caused by the fungus Sclerotinia sclerotiorum is the most yield-limiting disease of common bean in Brazil. To date, there has been no commercial cultivar resistant to this disease. In a greenhouse we evaluated white mold resistance sources (Cornell 605, A195 and G122) against eight isolates of S. sclerotiorum from five Brazilian states. A Brazilian cultivar (BRSMG Madrepérola) and a susceptible check (Beryl) were used as control. Treatments were arranged in factorial combinations (5 × 8) in a completely random design with four replicates. Disease severity was assessed on a rating scale of 1-to-9 together with lesion length, which was used to determine an area under the disease progress curve (AUDPC). Polymorphisms detected in ten microsatellite loci were used to assess variability between the isolates. Each isolate was a distinct haplotype; they formed a genetic tree with two clusters. One cluster was formed by three isolates collected from the states of Minas Gerais and São Paulo (southeastern); the others, by isolates from Paraná, Santa Catarina (southern), Goiás (Mid-western), and again, Minas Gerais. Genotype × isolate interaction was significant. In general, Beryl was more susceptible than BRSMG Madrepérola. Considering the AUDPC and/or the white mold reaction score, Cornell 605 exhibited more physiological resistance than BRSMG Madrepérola to seven isolates, A195 to five isolates, and G122 to two isolates. Our results suggest that Cornell 605 is the best source of resistance to white mold for the southern region, whereas Cornell 605 and A195 are somewhat superior to G122 for the southeastern and mid-western regions.

Assuntos

RESUMO

White mold caused by the fungus Sclerotinia sclerotiorum is the most yield-limiting disease of common bean in Brazil. To date, there has been no commercial cultivar resistant to this disease. In a greenhouse we evaluated white mold resistance sources (Cornell 605, A195 and G122) against eight isolates of S. sclerotiorum from five Brazilian states. A Brazilian cultivar (BRSMG Madrepérola) and a susceptible check (Beryl) were used as control. Treatments were arranged in factorial combinations (5 × 8) in a completely random design with four replicates. Disease severity was assessed on a rating scale of 1-to-9 together with lesion length, which was used to determine an area under the disease progress curve (AUDPC). Polymorphisms detected in ten microsatellite loci were used to assess variability between the isolates. Each isolate was a distinct haplotype; they formed a genetic tree with two clusters. One cluster was formed by three isolates collected from the states of Minas Gerais and São Paulo (southeastern); the others, by isolates from Paraná, Santa Catarina (southern), Goiás (Mid-western), and again, Minas Gerais. Genotype × isolate interaction was significant. In general, Beryl was more susceptible than BRSMG Madrepérola. Considering the AUDPC and/or the white mold reaction score, Cornell 605 exhibited more physiological resistance than BRSMG Madrepérola to seven isolates, A195 to five isolates, and G122 to two isolates. Our results suggest that Cornell 605 is the best source of resistance to white mold for the southern region, whereas Cornell 605 and A195 are somewhat superior to G122 for the southeastern and mid-western regions.(AU)

Assuntos

RESUMO

With the purpose to evaluate the intensity of angular leaf spot (ALS) and anthracnose (ANT) on pods, nine genotypes of common bean were planted in three cropping systems: monocrop (MC), monocrop grown on trellises (MCT), and intercrop with maize (ICM). In MC, beans were planted 0.5 m apart. Trelisses were set up with 1.8 m high bamboos and beans were sown 0.65 m apart. In ICM, beans were planted simultaneously with maize and in its rows. This cereal was sown 1.0 m apart with four plants per meter. Each cropping system was an independent trial installed close to each other. Climbing genotypes of beans most susceptible to ALS had less diseased pods in ICM than in both MC and MCT, but the less susceptible genotypes, regardless of their growth type, as well as the susceptible bush and semiclimbing genotypes, were similarly attacked by ALS in the three systems. ANT on pods of the susceptible bean cv. Pérola was less intense in MCT than in MC, and less intense in ICM than in MCT. ANT seed transmission was 11 percent, 9.1 percent, and 4.4 percent when seeds come from MC, MCT, and ICM, respectively.

Com o objetivo de avaliar a intensidade da mancha-angular (MA) e da antracnose (ANT) em vagens, nove genótipos de feijão foram plantados em três sistemas de plantio: monocultivo (MC), monocultivo com tutoragem artificial (MCT) e consórcio com milho (CCM). No MC, o feijão foi semeado no espaçamento entre fileiras de 0,50 m. Para o MCT, utilizaram-se varas de bambu formando "Vs" invertidos com 1,8 m de altura, nos quais foi mantido o espaçamento entre fileiras de 0,65 m na base. No CCM, o feijão foi plantado simultaneamente ao milho e em suas fileiras. Esse cereal foi semeado no espaçamento de 1,0 m, com quatro plantas por metro. Cada sistema de cultivo foi um ensaio independente, todos instalados na mesma área. Os genótipos trepadores mais suscetíveis à MA apresentaram menos vagens doentes no CCM que no MC e MCT, mas os genótipos menos atacados pela MA, independentemente do tipo de crescimento, como também os outros genótipos suscetíveis de porte anão e semitrepador, foram infectados de forma semelhante nos três sistemas de plantio. A ANT nas vagens do cv. Pérola foi menos intensa no MCT que no MC, e menos intensa no CCM que no MCT. A transmissão da ANT pela semente foi de 11 por cento, 9,1 por cento e 4,4 por cento quando as sementes foram colhidas no MC, MCT e CCM, respectivamente.

RESUMO

Foram conduzidos três ensaios em município de Minas Gerais, com inverno ameno, para estudar a viabilidade do cultivo do feijão-arroz no outono-inverno. Os ensaios foram instalados em Leopoldina, nestas datas: 3 de maio de 1996, 18 de abril de 1997 e 11 de maio de 1998. Foram usados 12 genótipos de feijão-arroz; uma cultivar de feijão-comum foi usada para comparação. Foi empregado o delineamento em blocos ao acaso, com 4 repetições. As plantas foram irrigadas por aspersão, e o controle de pragas com inseticida foi feito quando necessário. Os ciclos de vida do feijão-arroz variaram de 99 a 111 dias (da emergência à colheita), enquanto os do feijão-comum variaram em torno de 90 dias. Não foi observada doença na folhagem do feijão-arroz. As produtividades médias variaram de 1164 (11 de maio) a 2261 kg ha-1 (18 de abril). O feijão-arroz foi tão produtivo quanto o feijão-comum. Conclui-se que é viável o cultivo do feijão-arroz [Vigna umbellata (Thunb.) Ohwi & Ohashi] no outono-inverno em regiões de inverno ameno.

Three trials were carried out in a municipality of the state of Minas Gerais of mild winter to study the viability of rice bean cultivation in fall-winter season. Trials were installed in Leopoldina on the following dates: May 3, 1996; April 18, 1997; and May 11, 1998. Twelve genotypes of rice bean were used; one cultivar of common bean was also included for comparison. A randomized complete-block design with 4 replications was used. Plants were sprinkler irrigated and insecticide was applied when necessary. Rice bean life cycles varied from 99 to 111 days (from emergence to harvest), while common bean life cycles varied around 90 days. No foliar disease was observed on rice bean plants. Yields ranged from 1164 (May 11) to 2261 kg ha-1 (April 18). Rice bean yielded as much as common bean. One concluded that the cultivation of rice bean [Vigna umbellata (Thunb.) Ohwi & Ohashi] in fall-winter in regions of mild winter is viable.