REACTION OF POTATO CULTIVARS AND CLONES TO Phytophthora infestans

Abstract

The in vitro and field reactions of 23 potato cultivars and clones to two isolates of Phytophthora infestans were tested. The in vitro test used the detached potato leaflets method, and disease severity was evaluated 6 days after inoculation. Field experiments were conducted in autumn of 2013, in two locations in Pelotas City, Rio Grande do Sul State, Brazil. Seven evaluations of the disease severity were performed. From the severity values, the area under the disease progress curve (AUDPC) was calculated. Tubers were harvested to determine the yield (g plot -1 ). The A2 mating type isolate was the most aggressive for the majority of the potato genotypes. It was possible to group the different reactions of the potato genotypes based on the AUDPC values. Clones C2553-1-06, C2573-4-06, C2550-4-06, C2551-2-06, and CIP392,617.54 showed moderate-tohigh resistance to the two isolates of P. infestans. The values of severity and AUDPC obtained in vitro and field tests were positively correlated for both P. infestans isolates, but in some interactions, inconsistencies were observed. Tuber yield was negatively correlated with AUDPC. REAÇÃO DE CULTIVARES E CLONES DE BATATA A Phytophthora infestansRESUMO -A reação in vitro e a campo de 23 cultivares e clones de batata a dois isolados de Phytophthora infestans foram avaliadas utilizando-se dois métodos. No teste in vitro, utilizou-se o método de folíolos destacadas cuja severidade da doença foi avaliada 6 dias após a inoculação. Os experimentos de campo foram conduzidos no outono de 2013, em dois locais distintos do Município de Pelotas, Estado do Rio Grande do Sul, Brasil. Foram realizadas sete avaliações da severidade da doença; e, a partir desses valores, foi calculada a área abaixo da curva de progresso da doença (AACPD). Os tubérculos foram colhidos para determinar o rendimento (g parcela -1 ). O isolado do grupo de compatibilidade A2 foi o mais agressivo para a maioria dos genótipos de batata. Com base nos valores de AACPD foi possível agrupar as diferentes reações dos genótipos de batata. Os clones C2553-1-06, C2573-4-06, C2550-4-06, C2551-2-06 e CIP392,617.54 apresentaram resistência moderada a alta aos dos isolados de P. infestans. Os valores de severidade e AACPD obtidos in vitro e nos testes a campo foram correlacionados positivamente para ambos os isolados de P. infestans, porém, em algumas interações, foram observadas inconsistências. A produção de tubérculos foi negativamente correlacionada com a AACPD.Palavras-chave: Solanum tuberosum. Requeima. Patótipos. Resistencia a doenças.

Resistance of potato genotypes to late blight

“…Although 'BRS Clara' has 'Catucha' as one of the parents in its genealogy, its resistance pattern has oscillated between moderately resistant and susceptible. This same oscillation performance has also been noticed for 'BRS Pérola' and Odone 80-02 (WOLTER et al, 2016), and for 'Camila', whose field reaction ranged from highly susceptible to resistant (CASA-COILA et al, 2019), being correlated with the race of P. infestans. According to studies conducted by Rocha (2015) specifically with 'BRS Clara', a high level of quantitative resistance to P. infestans associated with qualitative resistance was observed, showing that the R genes present in this cultivar did not provide full protection to the isolate under study.…”

“…The genetic resistance of 'Cristal', 'Catucha', 'F50-08-01', and the resistant control CIP392.617-54 have been verified in other field experiment studies in southern Rio Grande do Sul (GOMES et al, 2009;CASA-COILA et al, 2019;PEREIRA et al, 2022). The stability of resistance to late blight is a highly desirable genetic trait in a potato breeding program, given the great variability of P. infestans isolates that normally occurs in the production environment in different regions of the planet (SAVILLE; MARTIN; RISTAINO, 2016) and our conditions (SANTANA et al, 2013;CASA-COILA et al, 2019). Due to this important characteristic, 'Cristal' and 'Catucha' have been widely used in ecological cropping systems in southern Brazil (TÖFOLI et al, 2013;PASSOS et al, 2017;EICHOLZ et al, 2021).…”