Identification of citrus polyploids using chromosome counts, morphological and SSR markers

Abstract

Polyploids play a key role in the improvement of citrus cultivars. Citrus breeding programs necessitate morphological, cytological and genetic characterization of cultivars. Here we analyze the polyploids using these three approaches. Cytological studies signify occurrence of spontaneous triploids (9.95%) and tetraploids (6.05%) in Kinnow mandarin and Succari sweet orange, respectively. Leaf characteristics were found directly proportional to the ploidy level; they change with an increase in the ploidy level. Genetic variability amongst morphologically distinct polyploids was confirmed using Simple Sequence Repeat (SSR) molecular markers. Accessions K 1, K 4, K 5 and K 7 of Kinnow, F 7 , F8 and F 10 of Feutrell’s Early, M 2 and M 4 of Mosambi, and S 1 and S 11 of Succari were found polymorphic, and are considered useful in current breeding programs in Pakistan. SSR loci genotyping, morphological selection and cytological screening of polyploids appeared to be an improved strategy for efficient screening and characterization of polyploids at seedling stage.