Abstract
ABSTRACT Bacterial wilt (BW), or brown rot, caused by the soil and seed borne bacterium Ralstonia solanacearum, is one of the most devastating diseases of potatoes cultivated in warmer regions of the world. There are no potato cultivars with a desirable level of BW resistance, although it has been recognized that resistance can be an outstanding component for disease management. However, the sources of resistance available lack agronomic traits required by potato growers, therefore being of little interest to breeders. The objective of this work was to evaluate the performance of 11 clones selected for BW resistance and improved for tuber traits upon selection in the last two decades. The clones under test were compared with susceptible and resistant clones and cultivars, in a completely randomized blocks design with three replications of single lines of 10 plants, in a field naturally infested with race 1, biovar 1, phylotype II of R. solanacearum. BW incidence was assessed 60-70 days after planting and total tuber yield in each plot was recorded 110 days after planting. All the evaluated clones presented higher levels of resistance to BW compared with the commercial varieties, not differing from the resistant, not commercial, controls. In a next step, these clones will be characterized for other desirable traits and those which combine high level of resistance and commercial characteristics will be recommended for breeders for enriching the genotypic background in the search for commercial varieties. We also confirmed that the cultivar BRSIPR Bel displays an intermediate level of resistance, what makes it an interesting genitor for its good agronomic characteristics. The findings of this work demonstrate that the improved potato clones selected under tropical conditions in the Embrapa’s pre-breeding project possess high and stable levels of resistance to bacterial wilt, being a valuable resource for breeders.
Highlights
Comportamento de clones de batata resistentes à murcha bacteriana, derivados de Solanum phureja, em campo naturalmente infestado com Ralstonia solanacearum no Brasil Central
This is especially relevant in tropical and subtropical regions like those that occur in Brazil. These conditions favor the establishment and the intensity of diseases like bacterial wilt (BW), or brown rot, caused by the soil and seed borne bacterium Ralstonia solanacearum, one of the most devastating diseases of potatoes cultivated in warmer regions of the world (Lopes et al, 2011; Yuliar & Toyota, 2015; Lopes & Rossato, 2018; Elphinstone, 2020)
BW induces foliage wilt followed by plant death and tuber rotting, resulting in yield losses that can reach up to 80% in a susceptible cultivar whenever environmental conditions are favorable for disease onset and spread (Champoiseau et al, 2009)
Summary
Comportamento de clones de batata resistentes à murcha bacteriana, derivados de Solanum phureja, em campo naturalmente infestado com Ralstonia solanacearum no Brasil Central. Growers worldwide live with an already existing risk of cultivating potatoes (Solanum tuberosum) in regions and seasons with environmental conditions which deviate from the ideal for the crop This is especially relevant in tropical and subtropical regions like those that occur in Brazil. Economic losses can be even greater, since the bacterium infests the soil, making it impossible to grow many susceptible Solanaceae species for years (Elphinstone, 2020) Cultural practices, such as crop rotation, planting season and use of disease-free seeds are control measures that significantly contribute to reduce bacterial wilt losses, host plant resistance can be an additional effective strategy for fighting the disease (Mihovilovich et al, 2017; Muthoni et al, 2020). The available partial resistance is not enough to protect the crop in excessively hot or wet conditions (Carvalho et al, 2017; Elphinstone, 2020; Muthoni et al, 2020)
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