Development of Rough lemon hybrids using embryo rescue and their identification with microsatellite markers
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
The present study was carried out in 2017-18 to develop Rough lemon × X-639 hybrids using embryo culture and their differentiation by SSR markers. The fruit setting and final retention of the crossed fruits was higher in the year 2018 than in 2017. Of the 3731 sown crossed seeds under net house condition, 2337 (62.63%) showed germination while cent per cent seed germination was recorded through embryo culture. Embryo culture was performed from fruits harvested at 75, 100 and 125 days after pollination (DAP) in 2017 and at 90 and 160 DAP in 2018. The frequency of monoembryonic seeds significantly varied from 23% at 75 DAP to 3.4% at 160 DAP. Out of the four stage (globular, heart, torpedo and cotyledonary) of embryos, the cotyledonary embryos were most abundant (>90%) at all DAP. With increase in DAP, the size of the cotyledonary embryos increased. The cotyledonary embryos recorded higher germination than that of pro-embryos. Thirty six SSRs were tested between Rough lemon and X-639, 13 were polymorphic and three were used for hybrid identification. From the 1233 analyzed seedlings derived from 853 seeds, 109 seedlings were identified as zygotic by three SSRs. The SSR markers Ci08C05, DY287851 and CCSM-4 identified a total of 100, 96 and 38 hybrids with hybrid detection efficiency of 91.74%, 88.07% and 34.86% respectively. The hybrids recovery through embryo culture was higher than that of seed sowing experiment. Under embryo rescue, 27.27% and 15.68% zygotic hybrids were recovered at 90 and 160 DAP, respectively. The hybrids displayed great variation in leaf lamina and leaf apex shapes. For leaf division and petiole wing shape, the progeny was present in two different classes. In conclusion, the study has developed a hybrid population, which can be screened against Phytophthora and soil salinity for determining their relative tolerance against these stresses.
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