Ex vitro recovery of rough lemon (Citrus jambhiri) hybrids and identification with SSR markers

Abstract

Rough lemon (Citrus jambhiri Lush) is one of the leading citrus rootstock around the world besides sour orange. In the present studies, rough lemon was crossed with X 639 and Swingle citrumelo at Department of Fruit Science, PAU Ludhiana during 2015-16. Cent per cent seed germination was recorded for both the crosses under in vitro conditions but, the germination rates with growing media in plug trays were significantly lower (91.3 and 89.2% for RL× X and RL × SC, respectively). Higher proportion of multi-foliate seedlings (26.89%) was recovered by in vitro seed culture over the ex vitro seed germination (5.20%). All the multi-foliate seedlings were confirmed by SSR analysis using two primers (F 29 and F 87). The SSR analysis showed that only 85% multifoliate seedlings were zygotic while, the rest were not confirmed to be zygotic. The SSR analysis of the 50 unifoliate F₁ seedlings each from both the crosses with 5 SSR primers differentiated seedlings into two groups, viz. zygotic and nucellar seedlings. In RL × X cross, the most efficient SSR marker was F29, which identified 30% F₁ unifoliate seedlings to be zygotic followed by CCSME31, which identified 26% unifoliate seedlings as zygotic seedlings while the remaining seedlings were nucellar. In the cross RL × SC, the primer F29 was most efficient as it identified 28% zygotic seedlings and 72% nucellar seedlings whereas, the primer F87 identified 24 and 76% zygotic and nucellar seedlings, respectively.