Identification of the tetrad-sterility-causing Solanum stoloniferum Schltdl. & Bouché cytoplasm in interspecific hybrids with S. tuberosum L.

Abstract

Tetrad sterility, in which only clumps of four premature pollen grains are released from anthers, has been observed in some modern potato cultivars. It is a form of cytoplasmic male sterility caused by the cytoplasm derived from the Mexican tetraploid species Solanum stoloniferum Schlechtd. et Bché., an important source of resistance to Potato virus Y in potato breeding. However, since S. stoloniferum is highly polymorphic, the source of tetrad-sterility-causing cytoplasm is unknown among diverse S. stoloniferum accessions. In this study, we directly crossed 24 S. stoloniferum accessions with pollen from 4x S. tuberosum and obtained 39 hybrids from 12 accessions. Nineteen hybrids from six accessions showed tetrad sterility, with either D/γ-or W/γ-type cytoplasm, and were triploid, tetraploid, or hexaploid.The W/γ-type cytoplasm was not necessarily associated with tetrad sterility. Sequence comparisons of 17 mitochondrial genes and their intergenic regions revealed a length polymorphism in the intergenic region between rpl5 and rps10, in which an ampli ed band of 859 bp was associated with tetrad sterility. This speci c cytoplasm causing tetrad sterility is named TSC sto . The 859-bp band would be a useful diagnostic marker for identifying TSC sto in potato breeding.

Discovery of a novel mitochondrial DNA molecule associated with tetrad pollen sterility in potato

“…All these clones have S. stoloniferum -derived cytoplasms: 17H131 has D/α-type cytoplasm, 15H156 and 18H225 have D/γ-type cytoplasm, and 17H117-9 and cv. Alwara have W/γ-type cytoplasm [ 33 ]. After base calling and elimination of low-quality reads, the mean quality score (QS) was approximately 11.3 for all the samples, and the read N50 ranged from 14.8 kb to 43.6 kb (Table S 1 ).…”

“…Since we previously found a diagnostic PCR marker for TSC sto in a location near rpl5 [ 33 ], the RC-I-specific intergenic region between rpl5-ψrps14 and nad6 in cv. Alwara was specifically investigated.…”

“…S. stoloniferum is a highly polymorphic wild species distributed from the southern United States of America to Mexico [ 32 ]. Among S. stoloniferum accessions, only those having a specific cytoplasm TSC sto exhibit T-CMS in interspecific hybrids [ 33 ]. TSC sto is associated with an 859-bp mitochondrial DNA fragment amplified from the intergenic region between rpl5 and rps10 [ 33 ].…”

“…Among S. stoloniferum accessions, only those having a specific cytoplasm TSC sto exhibit T-CMS in interspecific hybrids [ 33 ]. TSC sto is associated with an 859-bp mitochondrial DNA fragment amplified from the intergenic region between rpl5 and rps10 [ 33 ]. Within this intergenic region or in the nearby region, the presence of a part of the cob gene ( ψcob ), a pseudogene of the rps14 gene ( ψrps14 ), and a mutation hotspot are known [ 34 , 35 ].…”

“…Previously, we obtained interspecific hybrids from S. tuberosum crossed with different S. stoloniferum accessions as females, resulting in either fertile hybrids or tetrad sterile-type cytoplasmic male-sterile hybrids (hereafter referred to as T-CMS hybrids or clones) [ 33 ]. In this study, the mitogenomes of two fertile hybrids and three T-CMS hybrids were sequenced using Nanopore sequencing technology.…”