PERFORMANCE OF SOME EGYPTIAN CLOVER CULTIVARS AND THEIR TOLERANCE TO DODDER INFESTATION

Dodder parasite (Cuscuta planiflora. L) is the main obstacle which causes drastic yield losses in Egyptian forage clover crop in Egypt, accompanied with seed contamination by dodder seeds due to their similarity in size and shape to clover seeds. The present study aimed to determine the magnitude of yield losses due to dodder infestation and to estimate the degree of tolerance of some important Egyptian clover cultivars to dodder infection. Five forage clover cultivars, namely Gemmeza 1, Giza 6, Sakha 4, Helaly and Serw were tested to determine the magnitude of yield losses in these cultivars to dodder infestation and their degree of dodder tolerance under five dodder artificial infestation rates, 0, 0.01, 0.02, 0.03 and 0.04 g/pot of dodder seeds carried out in two pot experiments during 2015/2016 and 2016/ 2017 winter seasons in complete randomized block design. Under dodder infestation rates at 0.01, 0.02, 0.03 and 0.04 g/pot the dry forage yield of clover losses were estimated by 32.6,37.9,47.8 and 54.4%, respectively, in 2016 season, and 31.8,46.6,54.6 and 63.7%,, respectively, in 2017 season as compared with the yield of clover free from dodder infestation. The effect of interaction between clover cultivars X dodder seeding infestation rate (g/pot) show that studied cultivars namely Gemmeza 1, Giza 6, Helaly, and Sakha 4 had the lowest infestation rates under 0.01-0.02g/pot of dodder seeds accompanied with increases in fresh and dry weight forage /pot, stem weight and stem length and high tolerance index (70-73%) with Sakha 4compared to El Serw 1 cultivar with the lowest tolerance index (26.1-32.9%), and can be classified as susceptible cultivar to dodder infestation. Such results suggest that breeders can select highest tolerant cultivars of clover under artificial infestation rates accompanied with decrease in dodder infestation %.