QTL analysis reveals quantitative resistant loci for Phytophthora infestans and Tecia solanivora in tetraploid potato (Solanum tuberosum L.)

Abstract

Late blight and Guatemalan potato tuber moth caused by Phytophthora infestans and Tecia solanivora, respectively, are major phytosanitary problems on potato crops in Colombia and Ecuador. Hence, the development of resistant cultivars is an alternative for their control. However, breeding initiatives for durable resistance using molecular tools are limited due to the genome complexity and high heterozygosity in autotetraploid potatoes. To contribute to a better understanding of the genetic basis underlying the resistance to P. infestans and T. solanivora in potato, the aim of this study was to identify QTLs for resistance to P. infestans and T. solanivora using a F1 tetraploid potato segregant population for both traits. Ninety-four individuals comprised this population. Parent genotypes and their progeny were genotyped using SOLCAP 12K potato array. Forty-five percent of the markers were polymorphic. A genetic linkage map was built with a length of 968.4 cM and 1,287 SNPs showing good distribution across the genome. Severity and incidence were evaluated in two crop cycles for two years. QTL analysis revealed six QTLs linked to P. infestans, four of these related to previous QTLs reported, and two novel QTLs (qrAUDPC-3 and qrAUDPC-8). Fifteen QTLs were linked to T. solanivora, being qIPC-6 and qOPA-6.1, and qIPC-10 and qIPC-10.1 stable in two different trials. This study is one of the first to identify QTLs for T. solanivora. As the population employed is a breeding population, results will contribute significantly to breeding programs to select resistant plant material, especially in countries where P. infestans and T. solanivora limit potato production.

Fig 1. Histogram of severity of Phythopthora infestans.

The x-axis shows the relative area under the disease progress curve (rAUDPC) and the y-axis the number of genotypes can be observed. The dash lines indicate the average trend for each year. The black and grey triangles indicate the phenotypic parent values of Roja Nariño and BGVCOL 15062384 in 2016, respectively.

Fig 2. Population screening of Tecia solanivora.

Fluctuation of adult male populations of Tecia solanivora during the field trials for years 2015 and 2016. Evaluations were conducted weekly using a sexual pheromone trap during two crop cycles in consecutive years 2015 (continuous line) and 2016 (dotted line).

Fig 3. Incidence of Tecia solanivora.

Histogram of incidence of number of individuals of Tecia solanivora under field conditions in two consecutive years (2015 and 2016). The black triangle indicates the phenotypic value of Roja Nariño and the grey one indicates the value of BGVCOL 15062384.

Fig 4. Incidence (IPA) and severity (SPA) of Tecia solanivora under storage conditions.

Severity (SPA) and incidence (IPA) values are shown in dark gray and light-grey bars, respectively. The dash line indicates the SPA trend average and the dotted line indicates the IPA trend average. The black and gray symbols indicate the phenotypic value of Roja Nariño and BGVCOL 15062384. Triangles and stars indicate IPA and SPA respectively.

Fig 5. Tecia solanivora severity based on number of output holes (OPA).

The x-axis shows the output holes number in each tuber, while on the y-axis shows number of individuals. The dotted line indicates the average trend. The black triangle indicates the phenotypic value of Roja Nariño and the grey one de value of BGVCOL 15062384.

Fig 6. Linkage map and QTLs for Tecia solanivora and Phytophthora infestans.

The position of the marker in centimorgans is shown in the y-axis. Black bars show T. solanivora QTL locations, meanwhile white bars show P. infestans QTL locations.