Question

What is Jaya and Ratna?

Answer 1

Semi-dwarf varieties are shorter variants of wild types (natural). They don't fall over the wind, also they have stronger stalks. It takes less time for the plant to grow to the height needed to produce grain.

Complete solution:
Jaya and Ratna are high yielding semi-dwarf varieties of rice developed in India during the green revolution.
Rice and wheat form the staple diet for a majority of the population in India.
The increase in production of Semi-dwarf varieties (rice, wheat, sugarcane, etc) was due to the introduction of semi-dwarf varieties of wheat and rice. Semi-dwarf varieties of rice developed by Norman E. Borlaug, at the international center for Wheat and Maize improvement in Mexico.
Semi-dwarf varieties of rice were developed from IR-8(developed at an international rice research institute) and Taichung Native-1 Taiwan.
High yielding and disease-resistant wheat varieties were introduced in India in 1963 (Sonalika, Kalyana Sona).
Semi-dwarf varieties were introduced in India in 1966. India later developed better rice varieties like Jaya and Ratna.
Millets
Hybrid breeding has led to the development of several high-yielding varieties resistant to water stress. Several high-yielding varieties of hybrid maize, jowar, bajra have been successfully developed in India.
Sugarcane
Saccharum officinarum and Saccharum barberi were crossed to obtain sugarcane varieties having desirable qualities.
S. barberi was grown in North India, had poor sugar content and yield. S. officinarium did not grow in North India but had thicker stems and higher sugar content. The new sugarcane varieties formed by crossing the two had the following qualities
1 High yield
2 Thick stem
3 High sugar content
4 Ability to grow in North India.

Note:
Cowpea is a variety developed by the conventional breeding method. It is resistant to bacterial blight and mustard is a variety developed by hybridization and is resistant to aphids.