Fertility restoration locus and cytoplasm types in onion

Abstract

The objective of this study was the identification of the cytoplasmic types and the genotyping for the fertility restoration nuclear locus (Ms) in 59 onion accessions, aiming at the selection of 'A' and 'B' lines essential for the obtainment of hybrids. Three markers were used to identify the cytoplasm 5' cob, orfA501, and orf725, and two were used for the Ms locus (AcSKP1 and AcPMS1). The two types of male-sterile cytoplasm ('S' and 'T'), as well as fertile cytoplasm ('N'), and the Ms and ms alleles in both homozygosity and heterozygosity were detected in the 59 genotypes evaluated in the experiment. The frequencies of the 5' cob/orfA501 and orf725 markers, as well as of the markers AcSKP1 and AcPMS1, were close in the onion accessions evaluated in this study. In the Brazilian germplasm, the frequencies of the 'N', 'S', and 'T' cytoplasm were approximately 0.47, 0.28, and 0.25, respectively, whereas the allele frequencies of Ms and ms were 0.52 and 0.48, respectively. The accessions Régia, EHCEB 20146, EHCEB 201427, Alvorada, Serrana, Crioula Mercosul, EHCEB 20142, BRS 367, Rainha, Juporanga, and Alfa SF C-XI have potential for the identification of 'A' and 'B' lines, since they presented mixtures of cytoplasm and different allele frequencies for Ms. All the plants of the accessions EHCEB 20142040/EHCEB 20141040, EHCEB 20142028/EHCEB 20141028, and EHCEB 20112006/EHCEB 20111006 were in the Nmsms and Smsms conditions, and have the potential for 'B' and 'A' lines, respectively, for the CMS-S system. All the plants of the accessions EHCEB 20142027/EHCEB 20141027, EHCEB 20102019/EHCEB 20101019, and Alfa SF 'B'/Alfa SF 'A' were in Nmsms and Tmsms conditions, and have the potential for 'B' and 'A' lines, respectively, for the CMS-T system.

Partial success of marker-assisted selection of ‘A’ and ‘B’ onion lines in Brazilian germplasm

“…The plants of the accessions analyzed in this study presented a classification of 100% Smsms or Tmsms and 100% Nmsms, confirming previous evaluation performed with markers for cytoplasm type and Ms locus (Ferreira et al, 2017), and indicating their potential for the development of hybrids. The absence of segregation within 'A' and 'B' lines is essential for onion hybrid production, considering that the existence of segregants may decrease heterosis vigor and bulb uniformity, as well as the expected maturation in commercial hybrids.…”

“…Marker-assisted selection in onions has been used to differentiate 'N', 'S', and 'T' cytoplasm (Khar and Saini, 2016;Patil et al, 2016;Ragassi et al, 2012Ragassi et al, , 2010Santos et al, 2010), contributing to reduce the number of test crosses required to identify 'A' and 'B' lines. Markers for the Ms locus, developed by Huo et al (2015) and Kim et al (2015), enabled the full assisted identification of 'A' and 'B' lines, and have been applied in Indian germplasm (Khar and Saini, 2016) and in Brazilian germplasm (Ferreira et al, 2017) for the simultaneous identification of the cytoplasm type and recessive condition of the Ms allele.…”

“…Eleven accessions (Table 1) from the onion germplasm bank of EMBRAPA (Brazilian Agricultural Research Corporation) were evaluated in this study. The accessions had been previously identified (Ferreira et al, 2017) with potential for selection of 'A' and 'B' lines, as they presented either mixed cytoplasm and recessive ms alleles or 100% of plants at Nmsms and Smsms or Tmsms condition. Onion seedlings were transplanted in May/2016, in the experimental field of Embrapa Semiárido, Petrolina, PE, and harvested in September/2016.…”

“…Genomic DNA was extracted using the 2x CTAB protocol (Doyle and Doyle, 1990), as described by Ferreira et al (2017).…”

Perspective and application of molecular markers linked to the cytoplasm types and male‐fertility restorer locus in onion (Allium cepa)

“…Whereas the male sterility maintainer plants (N msms ) were noted at frequencies of 0.133 in Punjab Naroya, 0.231 in Punjab Selection and 0.182 in Punjab, frequencies were estimated by the aid of cob marker (Malik et al, 2017). The CMS-S, CMS-T and N cytoplasms frequencies were 0.47, 0.28 and 0.25, the Ms and ms allele frequencies were 0.52 and 0.48, respectively, noted by cob, orfA501 and orf725 genes-specific markers, and Ms/ms allelic markers of AcSKP1 and AcPMS1 genes were exploited in the MAS of maintainer lines among Brazilian onion germplasm (Ferreira et al, 2017). The frequency of male-sterile plants ranged from 0.77 to 0.80 across the openpollinated populations, the significant number of male-sterile lines was noted in the genotypes COHBONC03 (6.5%), COHBONC05…”