Genetic Male Sterility (GMS) /Pollination Control

Genetic or nuclear male sterility is ordinarily governed by a single recessive gene, ms, but dominant genes governing male sterility are also known, eg. in safflower. GMS occurs widely in plants, and in given plant species, several different ms genes act monogenically to produce male sterility. For example, over 70 different ms genes are reported in maize, 64 in tomato, 57 in barely, 54 in peas and 25 in rice Male sterility alleles arise spontaneously or may be artificially induced. When a male sterile plant (ms ms is crossed with a male fertile (Ms Ms) one, the Films ) is male fertile. In F1 a 3 male fertile 1 male sterile ratio is obtained . A male sterile line may be maintained by crossing it with heterozygous male fertile (Ms ms) plants. Such a mating produces 1:1 male sterile and male fertile plants
A majority of the ms alleles have arisen due to spontaneous mutations, which occur frequently in flowering plant. In addition, both chemical and physical mutagens have been used, either singly or in combination, to induce mutations for male sterility in a variety plants, e.g., B. campestris, B. napus, cabbage, pigeonpea, barley, wheat, maize, rice, peas, tomato, tobacco, chillies, etc. The most commonly used mutagens were gamma-rays and EMS (ethylmethane sulphonate), but even colchicine (in jowar or sorghum), ethidium bromide (in groundnut, wheat and maize) and acetone (in barley) are reported to have induced mutations for male sterility.
Temperature Sensitive Genetic Male Sterility (TGMS)
.In this type of GMS, complete male sterility is produced by the ms gene at higher temperatures (e.g. 23.3°C or higher for rice TGMS fine Pei-Ai645), but at temperatures below this critical point there is normal fertility. The stage of development sensitive to temperature lasts from the formation of PMCs to meiosis in rice. Photoperiod has effect in determining the lowest temperature which complete sterility is produced. This type of genetic male sterility is being used to develop hybrid rice in China. Two rice TGMS lines (UPRI 95-140 TGMS and UPRI 95-167 TGMS) have been isolated as spontaneous mutants and registered as germplasm.
Photoperiod-Sensitive Genetic Male Sterility (PGMS)
In case of PGMS, expression of ms gene is drastically affected by the prevailing photoperiod, provided the temperature is within a critical range (e.g., 23-29°C for rice PGMS). Within this temperature range, complete sterility is obtained in rice plants grown under long-day conditions (day-length more than 13 hr 45 min), but under short-day conditions almost normal fertility is obtained. It is important that a temperature above the critical range leads to male sterility under any photoperiod, while those below the critical range produce male fertility irrespective of the photoperiod. This type of male sterility is being used to develop hybrid rice in ChinaTGMS & PGMS appears to be governed by two major recessive genes; their dominant alleles show complementary interaction.
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