Simple and multiple resistances to viruses in cowpea genotypes

Abstract

-The objective of this work was to identify new sources of simple and multiple resistances to Cowpea severe mosaic virus (CPSMV), Cowpea aphid-borne mosaic virus (CABMV) and Cucumber mosaic virus (CMV) isolates in cowpea (Vigna unguiculata). Thirty-three genotypes from the germplasm bank of Universidade Federal do Ceará were tested as to their resistance to four CPSMV isolates, two CABMV isolates and one CMV isolate. Twenty-five days after the first virus inoculations, all inoculated plants, including the asymptomatic ones, were tested by serology. Genotypes were classified as: immune, plants without symptoms and negative serology; resistant, plants with mild mosaic and positive serology; susceptible, plants with mosaic and positive serology; and highly susceptible, plants with severe mosaic, other systemic symptoms, including systemic necrosis, and positive serology. Simple and multiple resistances to viruses were identified among the evaluated genotypes, but none of them showed multiple immunities to all isolates. Four genotypes showed immunity to all CPSMV isolates, two were immune to CABMV and two showed immunity to CMV. Eleven genotypes showed multiple resistances to two viruses, allowing for the development of new cultivars with more stable and broader resistance. Genotypes Purple Knuckle Hull-55, MNC-03-731C-21 and CNCx284-66E show resistance to CABMV, even when inoculated with CMV.Index terms: Cowpea aphid-borne mosaic virus, Cowpea severe mosaic virus, Cucumber mosaic virus, Vigna unguiculata, serology, virus control. Resistência simples e múltipla a vírus em genótipos de caupi Resumo -O objetivo deste trabalho foi identificar novas fontes de resistência simples e múltiplas em genótipos de feijoeiro caupi (Vigna unguiculata) a isolados de Cowpea severe mosaic virus (CPSMV), Cowpea aphid-borne mosaic virus (CABMV) and Cucumber mosaic virus (CMV). Trinta e três genótipos do Banco de Germoplasma daUniversidade Federal do Ceará foram classificados quanto a sua resistência a quatro isolados de CPSMV, dois de CABMV e um de CMV. Após 25 dias da primeira inoculação dos isolados, todas as plantas que sofreram inoculação, incluindo as assintomáticas, foram testadas por meio de sorologia. Os genótipos foram classificados como: imune, plantas assintomáticas e sorologia negativa; resistentes, plantas com mosaico leve e sorologia positiva; suscetível, plantas com mosaico e sorologia positiva; altamente suscetível, plantas com mosaico severo, outros sintomas sistêmicos, como necrose sistêmica, e sorologia positiva. Foram identificadas fontes de resistência simples e múltipla às viroses, nos genótipos avaliados; no entanto, nenhum deles apresentou imunidade múltipla aos três vírus. Quatro genótipos apresentaram imunidade aos isolados de CPSMV, dois aos isolados de CABMV e dois ao CMV. Onze genótipos apresentaram resistência múltipla a dois vírus, o que possibilita o desenvolvimento de novas cultivares com resistência mais abrangente e estável. Os genótipos Purple Knuckle Hull-55, MNC-03-731C-21 e CNCx284-66E m...

Response to Cassava Brown Streak Disease Infections in Local and Improved Cassava Genotypes under Field and Greenhouse Assays in Lower Eastern Kenya

“…Similar taken for symptoms to develop upon grafting have also been reported includes 1 -2 WAG [17], 4 WAG [45, 10 WAG [12]. The delayed CBSD symptom development by the four improved genotypes compared to sensitive varieties that rapidly expressed CBSD, can be described as a resistance mechanism where the genotypes tolerates or systemically harbor the virus without symptoms which merely delay symptom expression after inoculation followed by mild symptoms [47]. This perhaps was also corroborated by 'severe' symptoms ( been reported.…”

Serological Screening of Cowpea Genotypes for Resistance against Cowpea Aphid Borne Mosaic Virus Using DAS-ELISA

“…Alternatively, it has been reported that under mixed infections, when symptoms are severe, one of the infecting virus generally is a Potyvirus (Kareem and Taiwo, 2007). Therefore, breeders should use cowpea genotypes with high resistance to viruses from the genus Potyvirus in the production of cowpea cultivars resistant to mixed infection (Lima et al, 2011). The CABMV resistant genotypes proclaimed in the present study could therefore be utilized to develop resistance against multiple viral infections.…”

Preferência do pulgão-preto, Aphis craccivora Koch (Hemiptera: Aphididae), a genótipos de feijão-caupi

“…No entanto, é atacado por diversos insetos-pragas durante o seu ciclo, limitando, dessa forma, o estabelecimento da cultura, além de comprometer a produção e a qualidade dos grãos. Entre os insetos-praga em condições de campo, destaca-se o pulgão-preto, Aphis craccivora Koch, 1854 (Hemiptera: Aphididae) (AGELE et al, 2006, LAAMARI et al, 2008BERBERET et al, 2009;MORAES & BLEICHER, 2007), que ocasiona danos diretos através da sucção da seiva das plantas, bem como, ainda, é responsável pela transmissão de vírus (KITAJIMA et al, 2008;BLEICHER, 2010;LIMA et al, 2011;FREITAS et al, 2012).…”

“…A fase inicial de desenvolvimento das plantas é a mais suscetível ao ataque desses insetos (SILVA et al, 2005). Dentre as formas de controle de A. craccivora, destacam-se os controles químico, cultural e biológico (OMKAR et al, 2005;RAKHSHANI et al, 2005;SILVA et al, 2011), além do uso de plantas resistentes (HALL et al, 2003).…”