Morpho-genetic diversity in zygotic populations derived from Rough lemon (Citrus jambhiri Lush.) and their tolerance against Phytophthora

Abstract

Introduction The Rough lemon is a rootstock of choice in the citrus industry of the Indian subcontinent due to vigour, high yield, resistance against tristeza virus, exocortis viroid, and suitability to high pH soils. The prevalence of Rough lemon rootstock is presently threatened by the spread of Phytophthora root rot. Development of Phytophthora resistant rootstock is a priority for a sustainable citrus industry. The production of hybrids with introgression of the desired dominant traits, irrespective of the heterozygosity level of the parents, is an effective way to develop new candidate rootstocks. Materials and methods In this study, Rough lemon was hybridized with GouTou Cheng (Sour orange), Poncirus trifoliata, Rangpur lime, Swingle citrumelo, and X-639 citrandarin. Highly polymorphic and co-dominant SSR markers and visual selection based on the leaf morphology between bifoliate and trifoliate leaves was used to identify zygotic seedlings derived from different cross combinations. Results and discussion Leaf area of the nucellar seedlings was higher than zygotic seedlings in all the crosses. SSR markers TAA1, F02, and CCSMEc7 were the most informative markers identified 12.7942.52% hybrid seedlings in different cross combinations. The F1 hybrids varied in their reaction to Phytophthora nicotianae in leaf bait technique. Conclusion The hybrids from the crosses of Rough lemon x P. trifoliata and Rough lemon x Swingle citrumelo showed highest tolerance levels to Phytophthora as compared to other cross combinations.