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India is the second-largest producer of vegetables in the world (FAO, 2021). Its diverse soil and climate condition provides ample opportunity to grow a variety of crops (be it tropical, semi-temperate, or temperate type). Vegetables form a significant part of the total agricultural production of the country. India grows vegetables in an area of 10.86 mha with annual production of 200 million tonnes (NHB, 2021). Vegetables alone contribute 66.97 % of the total horticultural production (341.63 million tonnes). During 2021-22, India exported vegetables worth Rs. 5,745.54 crore. The growth in vegetable production is largely due to an increase in productivity of average productivity is 18.18 tonnes per hectare, The increase in productivity has led to improved per caput availability of over 250g.

Improved production technology is an integral part of hybrid seed production technology, which is a very high venture practice. This is because like several factors (climate, availability of parental lines and technical labour etc), success of hybrid seed production also depends on the success of crop management in the hybrid seed production field

A hybrid is the first generation progeny of a cross between two genetically different identical inbred lines. The individual lines are known as inbreds.  Ineffective cross-pollination is a major constraint in a commercial production of hybrid seeds in many crop species. In such crops manual pollination is the way to produce hybrid seeds. Eg. Cotton. In the case of rice it is highly self-pollinated crop and cross-pollination is a big problem. The increased vigour, uniformity and yield of F1 hybrid have been exploited in most crops where the pollination system allows for convenient and economic cross hybridization.  This system is called breeding tool in exploiting the hybrid vigour.

The term heterosis from Greek means hetero different, osis-condition was coined by skull (1914).

Heterosis or hybrid vigour, refers to the increase or decrease in vigour of off spring (hybrid) over parents. Usually, theses two terms are used synonymous.   But hybrid vigour refers to increased vigour; Heterosis both increased and decreased vigour.

Superiority of the hybrid as hybrid vigour and the mechanism by which this superiority is developed is heterosis (Rangaswamy, 1998).

Hybrid Seed Production Technology At a Glance

3.1. Natural cross-pollination

Breeding procedures in any plant species of economic importance are guided by its reproductive system particularly, pollination mechanism. In the cereal crops such as maize, pearl millet etc., where cross-pollination is facilitated by wind, the breeders have developed schemes for commercial exploitation of dominance and epistatic genetic variation through hybrid and population breeding. In contrast in self-pollinated crops, the efforts are always made to exploit additive genetic variation primarily through pedigree and mass selection.
 
In pulses, self-pollination is a rule and pigeonpea is no exception. However under field conditions, occurrence of hybrid plants in the populations is not uncommon; and it happens due to some degree of natural out-crossing that took place in the preceding generation. This type of partial natural out-crossing in pigeonpea is affected by a variety of insects (Fig 10) which forage on its large flowers to collect the nectar. These minor incidences of out-crossing are the primary source of varietal deterioration. Recently, the pigeonpea breeders converted this constraint into an opportunity for genetic enhancement of yield through exploitation of hybrid vigor and developing commercial hybrids.

1. TECHNIQUES OF HYBRID SEED PRODUCTION

1.1. Field crops

Table 1: Techniques of hybrid seed production in field crops

Heterosis

The superiority of F₁ hybrid over both its parents in terms of yield or some other characters or heterosis is increased vigours, growth, yield or function of a hybrid over the parents, resulting from crossing of genetically diverse organisms. The term heterosis was first coined by Shull in 1914. Generally heterosis manifested as an increase in vigour, size, growth, yield or some other characteristics. But in some cases, hybrid may be inferior to the weaker parent this is also regarded as heterosis.

Hybrids are released for commercial cultivation either by the Central or State Varieties Release Committee. The release of a hybrid for commercial cultivation is based on conclusive demonstration of its superiority over the best existing hybrids (included as check in evaluation trials) in yielding ability or in some other features of economic importance, e.g. abiotic and biotic stresses etc. Due to above reason, hybrids are extensively evaluated for their performance, resistance to diseases and insects, and quality in multilocational trials. The multilocational trials are conducted under All India Coordinated Vegetable Improvement Projects, which play a key role in testing, identification and release of new hybrids. Before release of hybrids, three activities and operations are involved. These are:

India has emerged as the second largest producer of vegetables 176.17 mt after China 573.93 mt in the world and is gradually striding towards achieving food and nutritional security at national level. The average productivity of vegetable crops is 17.6 t/ha (NHB, 2015) which is comparatively lower than the productivity of China (23.4t/ha), Spain (39.3t/ha) and USA (32.5t/ha). The lower productivity could be attributed to limited use of quality seeds, inefficient production management, impact of biotic stress and climatic factors during crop production. Among the limiting factors limited availability of quality seed is one of the important factors. Since, the performance of other inputs is also depend on the quality of seed. At present the seed replacement rate among vegetable crops is around 25%, whereas highest in cabbage (>90%) followed by tomato, capsicum, bitter gourd, muskmelon, bottle gourd etc.The use of hybrid seed is in increasing due to higher productivity, tolerance to biotic and a biotic stresses and better market value than the open pollinated varieties but the higher price of the hybrid and their availability is still a constraint in adopting the use of hybrid seeds among small and marginal farmers.

Ash gourd (syn:wax gourd, winter melon, white gourd, white pumpkin, ash pumpkin, Chinese preserving melon and hairy melon) is a vegetable belonging to family Cucurbitaceae and genus Benincasa with only one cultivated species, Benincasa hispida (Thunb.) Cogn. (2n=2x=24). Ash gourd is an important vegetable especially in the Indo-China region, which is also the major producer of ash gourd (Rubatzky and Yamaguchi, 1997), but it is also a potential crop of tropical Africa and America (Sirohiet al., 2005).

Hybridisation

Hybridisation occurs when two species cross to form a new species. If they are named before their hybrid nature has become apparent, the names would become invalid as soon as the hybridity of the specimen has been established.

Hybridism can be of three types:

1. Sympatric Hybridisation

When individuals in two regions overlap in an otherwise well-defined species, they are called sympatric hybridisation. This is common in bird of paradise and humming birds. This hybridisation is listed as cross of two parental species.

14.1 Introduction

The mating or crossing of genetically dissimilar individuals is called hybridization. Hybridization results in recombination that in turn widens the spectrum of variation among individuals. So, the reason for genetic diversity in progenies of crosses is the formation of new combinations of genes. This newly created variability is then channelized into development of better cultivars.

The importance of pure line selection as a method of breeding started decreasing when plant breeders felt that the genetic variability existing in the land races of self-pollinated crops had been almost completely exploited and there was little chance for further improvement in these crops by using pure line breeding. Therefore, no option was left for plant breeders except to cross diverse individuals and combine together desirable characters in a single genotype from two or more parents. The planned hybridization which could avoid self-pollination and chance cross-pollination, soon became the main feature of almost all plant breeding programmes.

The mating or crossing between two genetically dissimilar plants or lines is known as hybridization. In other words, hybridization is an artificial controlled pollination in which pollen grains of desired male parent is transferred on the stigma of the desired female parent.

Objectives of Hybridization

To create genetic variability, which is pre-requisite for crop improvement programme.

To transfer one or more characters into single plant.

To know the inheritance of the characters.

To estimate the general combining ability of the parents and specific combining ability of the crosses.

To exploit and utilize the hybrid vigour.

To produce hybrid/synthetic varieties.

This chapter introduces hybridoma technology and its application in producing monoclonal antibodies. It explains the fusion of antibody-producing B lymphocytes with immortal myeloma cells, selection in HAT medium and the roles of HGPRT and polyethylene glycol. The survival and cloning of hybrid cells and the advantages of monoclonal antibodies are considered. The chapter also discusses tissue and organ transplantation, including autografts, isografts, allografts and xenografts. The immunological mechanisms of acute graft rejection, donor histocompatibility antigens and the involvement of T lymphocytes are addressed. These questions connect laboratory antibody production with transplantation immunology and its diagnostic, therapeutic and research applications.

The genus Hydrangea is the best-known member of family Hydrangeaceae tribe Hydrangeae from the Asterid order Cornales. With more than two centuries of horticultural trade, Hydrangea cultivars are among the most popular ornamental shrubs worldwide (McClintock, 1957 and Kardos et al., 2009). Hydrangea (Hortensia) is a very popular ornamental plant for gardens. Hydrangeas occur most often on partly shaded but open slopes, rock edges, cliffs, roadside banks, edges of woods, or in moist open woods. Usually, restricted to the more moist, protected slopes. Recently it is commercialized for the production of cut flowers (Sacco et al., 2012). In India is widely grown in hilly areas.

ORIGIN AND DISTRIBUTION

The species of genus Hydrangea L. grow naturally in temperate areas of Eastern Asia, including some Pacific islands adjacent to Eastern Asia (Philippines, Taiwan, etc.), in temperate Northeastern America, in subtropical Middle and South America (McClintock, 1957). Throughout the eastern United States, ranging from the middle Atlantic States southward through the Southern Appalachians, and westward into the Ozarks and lower Midwest, numerous populations of shrubs with large, ovate, opposite leaves and compound cymes of small white flowers are en-countered. These are the wild hydrangeas.

SPECIES

Hydrangea is a genus of about 75 species of flowering plants native to southern and eastern Asia and North and South America. Most are shrubs 1-3 tall, but some are small trees and others lianas (Sacco et al., 2012). Species differ qualitatively in flavonoid constituents.

The genus Hydrangea is the best-known member of family Hydrangeaceae tribe Hydrangeae from the Asterid order Cornales. With more than two centuries of horticultural trade, Hydrangea cultivars are among the most popular ornamental shrubs worldwide (McClintock, 1957 and Kardos et al., 2009). Hydrangea (Hortensia) is a very popular ornamental plant for gardens. Hydrangeas occur most often on partly shaded but open slopes, rock edges, cliffs, roadside banks, edges of woods, or in moist open woods. Usually, restricted to the more moist, protected slopes. Recently it is commercialized for the production of cut flowers (Sacco et al., 2012). In India is widely grown in hilly areas.

Three types of water movement within the soil are recognized. They are

1. Saturated flow
2. Unsaturated flow
3. Water vapour movement

Saturated flow

This occurs when the soil pores are completely filled with water. This water moves at water potentials larger than 33 kPa. Saturated flow is water flow caused by gravity’s pull. It begins with infiltration, which is water movement into soil when rain or irrigation water is on the soil surface. When the soil profile is wetted, the movement of more water flowing through the wetted soil is termed percolation.

Hydraulic conductivity can be expressed mathematically as

Hydraulic pumps are the devices utilized to transfer pressure energy to liquids at the expense of electrical energy. The electrical energy is transferred to a motor which converts it into mechanical work and a pump is coupled to the shaft. The pump converts the mechanical energy to hydraulic or potential energy. 

INTRODUCTION
Hydraulics is the study of liquids and their behavior, specifically focusing on the use of pressurized fluid to generate power in engineering systems. Hydraulic systems operate by applying pressure to a small amount of fluid, which in turn generates significant power. The development of hydraulic technology has enabled major advancements, such as lifting heavy loads and rotating large shafts with minimal effort through mechanical linkages.
Compared to mechanical and electrical systems, hydraulic power systems offer greater flexibility and produce more power relative to their size. They also provide quick and precise responses to control inputs. As a result, hydraulic systems are widely used in modern applications such as aircraft, automobiles, heavy industrial machinery, and various machine tools. This article will focus on the hydraulic systems used in tractors.
HYDROSTATIC TRANSMISSION
Hydrostatic transmissions rely entirely on hydraulics, using the power of oil to transmit energy. The system consists of two main components: a variable displacement pump and a hydraulic motor. The pump’s displacement is controlled by a movable swash plate, which adjusts the piston stroke. Essentially, the system operates as a variable-displacement hydraulic pump driving a fixed-displacement hydraulic motor.
The key benefits of hydrostatic transmissions include the ability to infinitely vary ground speed and rapidly change directions. They are also known for their reliability, with self-protecting features that prevent operator abuse.
Additionally, foot pedal-controlled systems have a built-in safety feature that allows for a controlled stop simply by lifting the foot from the pedal. However, hydrostatic transmissions have some drawbacks, including high cost, sensitivity to contamination, and slight power loss at the PTO shaft. Additionally, when