A restorer gene for genetic-cytoplasmic male sterility in cultivated potatoes

Abstract

Fifty-nine clones (cultivars and advanced selections) ofSolanum tuberosum Group Tuberosum were pollinated with two Group Phureja-haploid Tuberosum hybrids, which produce FDR 2n pollen (ps/ps) and are heterozygous for a dominant gene (Ms/ms) which interacts with Tuberosum cytoplasm to result in male sterility. Twenty-eight and thirty-four plants from each family were transplanted to the field in two different locations, respectively. Pollen samples were collected from each plant and stained with acetocarmine glycerol jelly. Plants with over 95% unstainable pollen were considered male sterile. The families could be put into distinct classes according to the ratio of male sterile to male fertile plants; 3 sterile: 1 fertile (23 clones), 2 sterile: 3 fertile (24 clones), 1 sterile: 5 fertile (3 clones), and 0 sterile: 1 fertile (3 clones). Four families deviated significantly from any expected ratio. The variation for male fertility among families resides in the tetraploid parent, since the male parents have the same genotype (Ms/ms) for theMs locus. The locus of this gene is very distal to the centromere such the 2n gametic output is 1 Ms/Ms : 2 Ms/ms : 1 ms/ms. The variation in male sterility is explained by the presence or absence of a dominant allele of a restorer gene (Rt) in tetraploid Tuberosum. This locus is also very distal to the centromere. The frequency of theRt gene was estimated to be 0.20 in Tuberosum. The finding ofRt gene explains some of the conflicting results in male fertility of haploid Tuberosum x 2x cultivated and wild species hybrids. It also provides an opportunity to partially circumvent this male sterility. Haploids (2n = 2x = 24) extracted from 4x clones withRt genes would have male fertile progeny in crosses with species carrying theMs gene.

Compendio

Cincuenta y nueve clones (cultivares y selecciones avanzadas) deSolanum tuberosum Grupo Tuberosum fueron polinizadas con dos hibridos entre Grupo Phureja - haploides de Tuberosum, que producen polen 2n por restitucion nuclear de la primera division (ps/ps), y son heterozigotes para el gen dominante (Ms/ms), que interactua con el citoplasma de Tuberosum produciendo esterilidad masculina. Veinte y ocho y treinta y cuatro plantas de cada familia fueron transplantadas al campo en dos diferentes localidades, respectivamente. Muestras de polen fueron colectadas en cada planta individualmente y tenidas con acetocarmin glicerol jelly. Plantas con menos de 5% de polen tenido fueron consideradas macho-esteriles. Las familias pudieron ser agrupadas de acuerdo a la proporcion de plantas machoesteriles a macho-fertiles; 3 esteriles : 1 fertil (23 clones), 2 esteriles : 3 fertiles (24 clones), 1 esteril : 5 fertiles (3 clones), y 0 esteril : 1 fertil (3 clones). Cuatro familias se desviaron significativamente de la proporcion esperada. La variacion de fertilidad masculina entre las familias se debe al progenitor tetraploide, ya que los progenitores masculinos tienen el mismo genotipo (Ms/ms) para el locusMs. El locus de este gen esta ubicado muy lejos del centromero, de tal modo que la produccion de gametos 2n es 1 Ms/Ms : 2 Ms/ms : 1 ms/ms. La variacion en esterilidad masculina es explicada por la presencia de un gen dominante restaurador de fertilidad (Rt) presente en el progenitor tetraploide Tuberosum. La frecuencia del genRt fue estimada en 0.20 en Tuberosum. El hallazgo del genRt explica algunos de los resultados conflictivos en esterilidad masculina de hibridos entre haploides de Tuberosum y especies cultivadas y silvestres. Asimismo, provee una oportunidad para parcialmente evitar esta esterilidad masculina. Haploides (2n = 2x = 24) extraidos de clones 4x con genesRt tendrian progenies macho-fertiles en cruzamientos con especies que poseen el genMs.