Duanpen Wongsorn, Sivilai Sirimungkararat, and Weerasak Saksirirat

pp. 401 - 408

Abstract

Improvement of eri silkworm tolerance to high temperature was carried out under high temperature (42±1°C) and low
relative humidity (50±5% R.H., relative humidity). Eri silkworm rearing at normal temperature (25±2°C; 80±5% R.H.) served as
control treatment and was compared to rearing at high temperatures. Directional selection was undertaken with the batches
reared at 42±1°C and 50±5% R.H. until the 5^th generation. From 6^th, 8^th, 10^th and 12^th generations, rearing was conducted as
normal rearing (25±2°C; 80±5% R.H.), while for 7^th, 9^th, and 11^th generations directional selection was done as 1^st – 5^th generations. Various parameters were used as indexes for high temperature tolerance. When the silkworms were reared until to F12
(12^th generation), the survival rate of larva (1st–5th instar) (95.33%) and larva (1^st–5^th instar) – adult (69.33%) including cocooning
rate (80.67%) of F12 were the highest compared to F1 and F11. For cocoon yields among F1, F11, and F12, the highest values
of fresh cocoon weight (2.7144 g), pupa weight (2.3490 g), shell weight (0.3671 g), shell ratio(13.53%), total cocoon shell
weight(17.01 g), and fresh cocoon/10,000 larvae (25. 16 kg) were achieved from F12, which were significantly different (P<
0.05) to F1 and F11. In the same manner for egg yields, F12 provided the maximum numbers in case of eggs/moth (311.33
eggs), total eggs (6,693.33 eggs) and total hatching eggs (4,842.67 eggs) except hatching eggs (73.15%). Of these evaluations
between F11 and F1, it was found that F11 was higher than F1 and statistically different (P<0.05) in all parameters excluding
the percentage of hatching eggs, which was not significant difference. These results indicate that the property of high
temperature tolerance was improved and heat tolerant property of eri silkworm (SaKKU1) is heritable. This is a first to report
on heat tolerance improvement of eri silkworm. Although it is a first trial that was carried out in a laboratory, it can be applied
on eri silkworm rearing in the future to cope with recent global warming trends.