Morphology of Sterile Anthers and Inheritance of Cytoplasmic-genetic Male Sterility in Zygotic Seedlings of Polyembryonic Acid Citrus

Abstract

In acid citrus, genetic control of male sterility, an important characteristic for breeding seedless fruit cultivars, is not precisely known because of the presence of barriers such as polyembryony and a long juvenile phase. In this study, 22 crosses with 16 male-fertile acid citrus cultivars were carried out and the zygotic seedlings were grafted onto adult satsuma mandarin trees to enhance flowering. Four crosses with two monoembryonic and male-sterile citrus plants (HY16 and 'Kiyomi') were also carried out and zygotic seedlings showing precocious flowering were used to examine the inheritance of male sterility. Of the 26 crosses, 21 with six cultivars as seed parents generated male-sterile and male-fertile zygotic seedlings with various segregation ratios, whereas five crosses with 'Sudachi' as a seed parent generated only male-fertile zygotic seedlings. The sterile anthers were categorized into undeveloped and underdeveloped by their size in most progenies. The result of these crosses showed that eight cultivars with male-sterile cytoplasmic factors of 'Yuzu', lemon, or satsuma mandarin generated male-sterile zygotic seedlings, while 'Sudachi' with male-fertile cytoplasmic factors of pummelo generated only male fertile zygotic seedlings. The result also suggested that a dominant nuclear fertility-restorer gene system comprising one epistatic gene R 1 and two complementary genes R 2 and R 3 controls the restoration of male fertility and male-sterile anther size in acid citrus plants with sterile cytoplasm (S). The complementary gene R 3 is located downstream from R 2 , and gene R 1 is epistatic to R 2 and R 3 genes. Genotypes (S)r 1 r 1 r 2 r 2 --are responsible for undeveloped anthers while genotypes (S)r 1 r 1 R 2 -r 3 r 3 are responsible for underdeveloped anthers. The identified genotypes for male sterility in major acid citrus cultivars will contribute to breeding seedless acid cultivars.

Allelic haplotype combinations at the MS-P1 region, including P-class pentatricopeptide repeat family genes, influence wide phenotypic variation in pollen grain number through a cytoplasmic male sterility model in citrus

“…Male sterility and fertility segregate in the F 1 populations of a cross between different varieties and selected strains harboring the Kishu-cytoplasm ( Yamamoto et al., 1992 ; Yamamoto et al., 1997 ; Nakano et al., 2001 ; Dewi et al., 2013 ; Goto et al., 2016 ). Specifically, the genomes in Japanese varieties and selected strains were constituted by genomic fragments (i.e., haplotype blocks) that are derived from limited founders ( Imai et al., 2017 ).…”

QTL mapping of male sterility and transmission pattern in progeny of Satsuma mandarin

“…Several reports suggested the involvement of nuclear genes in male sterility [ 5 , 35 – 38 ]. Guo et al [ 7 , 8 ] and Zheng et al [ 11 ] have tried to induce male sterility by replacing the cytoplasm by that of Satsuma type with cell fusion in Hirado buntan and Zheng et al observed aborted pollen grains in the regenerated plants [ 13 ].…”

Identification of Putative Parental Species of Yuzu (Citrus junos Sieb. Ex Tanaka) by Comparative Analyses of Variations in Chloroplast Genomes and Nuclear Single-copy Genes of Citrus

“…Two factors may contribute to the high level of heterozygosity of the yuzu genome. First, yuzu is predominantly reproduced through asexual nucellar embryony, a sporophytic apomixis (Dewi et al, 2013). Nucellar embryony is widespread among most commercial cultivars of sweet orange, mandarin, grapefruit, and lemon (Xu et al, 2021).…”