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Improvement of Eri Silkworm (Samia ricini D.) Tolerant to High Temperature and Low Humidity Conditions by Continuously Regime

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Duanpen Wongsorn, Sivilai Sirimungkararat and Weerasak Saksirirat

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Improvement of eri silkworm tolerant to high temperature condition was carried out by selection and continuous rearing (1-12 generation) under high temperature (42?1 ?C) and low relative humidity (50?5%R.H.). The eri silkworm rearing at a normal temperature (25?2 ?C; 80?5%R.H.) served as control treatment. The result revealed that eri silkworm was continuously tolerant to high temperature of 42?1?C with low relative humidity (50?5%R.H.) up to 12 generations. Among treated generations with high temperature, the silkworms survived from larva stage (1 st-5 th instar) to adult in all generations ranking 16.67-54.17%. Between F12 and F1, survival rate of larva-adult stage of F12 was 43.33% less than F1 (54.17%), but not signifiantly different (P<0.05). For cocoon yields, fresh cocoon weight, pupa weight and cocoon shell weight of F12 were lower than F1. Of F12, shell ratio (11.84%), total cocoon shell weight (5.72g) and fresh cocoon weight/10,000 larvae (9.39 kg) were not signifiantly different to F1 (11.61 %, 6.10 g and 10.55 kg, respectively). It was clearly, if the egg yields were considered, egg laying/moth, total egg laying and total hatchability of F12 were higher than F1. The result indicates that the thermotolerant property of eri silkworm SaKKU1 is heritable by high temperature at least 12 generations. This study is a fist report on continuously heat tolerant improvement of eri silkworm in Thailand and elsewhere.

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eri silkworm, tolerance, high temperature, low humidity, Samia ricini