Abstract
This paper studied the effects of 60Co-gamma ray on the pollen grains of upland cotton. The irradiation effects on pollen grains were tested in terms of the ultrastructural changes in the exine and interior of pollen grains, their germination rate, the single primer amplification reaction polymorphism of ovule developed after the pistils were pollinated by the pollen grains which had been irradiated with 60Co-gamma ray, and the law of genetic variation of their M1, M2 progeny. The results showed that 60Co-gamma ray had no effects on the exine wall of the pollen grains. The interior structure of pollen grain were destroyed significiantly. The interior wall became thin and irregular, and part of it concavitied to the inner. The endoplasmic reticulum depolymerized. The amount and the density of pollen grain inclusions increased. The number of pollen tubes in style decreased by 38%, compared with the control group (natural pollen grain). The single primer amplification reaction polymorphism of ovule increased. The germination percentage of M1 progeny was decreased by 41.03%. And with the cotton plants of M1 progeny, the length of taproot, longest lateral root, average lateral root, the number of lateral root, and the height of seedling decreased by 22.24%, 18.93%, 11.80%, 28.02%, 23.05%, respectively, compared with the control group. The percentage of sterility plants was 56.7%. The coefficients of variations of boll number, lint percentage, perimeter of stem, seed index, fruit branch number, longissimus fruit branch and plant height increased by 103.206%, 74.588%, 75.96%, 69.83%, 33.25% and 29.624%, 11.843%, respectively., compared with the control group. With the cotton plants of M2 progeny, the percentage of sterility plants was 56.7%. And the coefficients of variations of boll number, seed cotton yield, fruit branch number, plant height, boll height, and lint percentage increased by 21.944%, 16.261%, 3.827%, 3.986%, 7.25% and 0.497%, respectively., compared with the control group. The coefficients of variations and change range of agronomic traits in M2 progeny were less than them in M1 progeny.
Highlights
Because of the low genetic diversity among each variety, Gossypium hirsutum L. (Malvaceae) exhibits a deficiency in heredity (Misra, et al, 2003; Datta, et al, 2001; Selvi et al, 2007; Xu, et al, 2011; Liu, et al, 2003; Iqbal, et al, 1997; Song, et al, 2004)
The irradiation effects on pollen grains were tested in terms of the ultrastructural changes in the exine and interior of pollen grains, their germination rate, the single primer amplification reaction polymorphism of ovule developed after the pistils were pollinated by the pollen grains which had been irradiated with 60Co-γ ray, and the law of genetic variation of their M1, M2 progeny
After upland cotton pollen grains were treated with 20 Gy 60Co γ-rays, the outer surface morphologies of the pollen grains in the control group and the radiation-treated pollen grains were observed with field-emission scanning electron microscopes
Summary
Because of the low genetic diversity among each variety, Gossypium hirsutum L. (Malvaceae) exhibits a deficiency in heredity (Misra, et al, 2003; Datta, et al, 2001; Selvi et al, 2007; Xu, et al, 2011; Liu, et al, 2003; Iqbal, et al, 1997; Song, et al, 2004). By utilizing various mutation factors that effectively induce genetic mutations, chromosomal mutations and extra-nuclear mutations, we acquired numerous mutant types, which are not easy to obtain using general mutation methods (Sun, et al, 2006). Exposure to 60Co γ-rays is the most common mutation method applied in cotton breeding (Srivastava, et al, 2002). Fan (1980) used γ-rays and fast neutrons to treat cotton and showed improvements in cotton resistance, fiber length, fiber fineness and plant types. Gao (2004, 2006) established hybridization mapping of radiation mutants with respect to upland cotton by treating cotton with γ-rays at various intensities, followed by pollination. Some progress has been made in radiation breeding, radiation-induced mutations generally develop slowly due to the emphasis on mutations and the selection of character variations obtained in the early generations after mutagenesis.
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