Commercial Hybrid Seed Production
Corn breeders first recognized its potential for increasing yields and developed procedures for commercial production of hybrid seed. If the biological requirements have been met in a species, a practical program of seed production on a large scale must be developed before hybrids can be used by farmers. This chapter describes practical aspects of commercial production of hybrid seed. The common type of commercial hybrid is a single cross between two unrelated inbred lines. Desirable fields are important contributors to purity, yield, and quality of hybrid seed. The chapter illustrates the principles of commercial production of hybrid seed with four crop species whose biological characteristics necessitate the use of different techniques for some aspects of seed production. The crop species are corn, sunflower, sorghum, and wheat. Seed of all crops must be handled gently to avoid seed damage during harvest, drying, storage, and conditioning. Artificial emasculation can be used for hybrid seed production of corn. 
Photosynthate and Nitrogen Requirements for Seed Production by Various Crops
Seed biochemical composition was the basis for segregating 24 crops into four distinct groups. Nitrogen requirements of pulses and soybeans were so great that sustained seed growth demanded continued nitrogen translocation from vegetative tissues. This translocation must eventually induce senescence in these tissues, restrict the duration of the seed-fill period, and limit seed yield. 
Estimating the Mean Annual Seed Production of Trees
Intraspecifically, plant seed production is a function of both seed size (mean mass per seed) and plant size. In this paper we examined the interspecific relationship between the size of seeds and plants and the mean long—term annual seed production per tree. For canopy trees, we show that seed production is highly (inversely) correlated with the mean seed mass as a power law argument. Tree size (basal area or leaf mass) is directly proportional to seed production over a limited range. Analysis of seed production for herbaceous plants indicates a relationship similar to that for trees. As the exponent relating seed size to seed production is >°1.0, it follows that large—seeded plants produce more total annual crop mass than do small—seeded species. However, this is balanced by the greater investment in ancillary reproductive tissue by smaller seeded species. The results obtained here ought to be of theoretical and applied interest in, for example, stand—level simulations of population dynamics or for planning the optimal size and shape of clearcuts intended to be regenerated naturally. 
A Study on Comparative Economics of Grain and Seed Production of Groundnut in Karnataka, India
The present study was based on primary data collected for 100 farmers from Chitradurga district of Karnataka during the agricultural year 2013-14. Tabular analysis and discriminant function analysis was used in the present study. The analysis of data reveals that human labour occupied the major share (27.07%) of total cost in seed production and bullock and machine labour occupied the major share (29.38%) of total cost in grain production of groundnut. The higher human labour requirement in seed production was mainly due to activities like rouging, gap filling etc. The variable cost was comparatively higher in seed production (Rs. 25745.0 per ha) over grain production (Rs. 20752.0 per ha). The total cost of cultivation in groundnut seed production was around 18% higher than grain production. The gross return was about 27% higher in seed production than grain production and net return from seed production of groundnut was 44% higher than grain production. The BC ratio was 1.73 in case of groundnut seed production as compared to 1.60 in grain production. The discriminant analysis indicated that human labour with 45.56% followed by gross return (35.83%), seed (17.50%), manures and fertilizers (0.69%), bullock and machine labour (0.42%) contributed to discriminate between the seed and grain production of groundnut. The net return from groundnut seed production was encouraging, therefore the area under seed production may be increased for higher profitability and timely supply of quality seed to the farmers. 
Assessment of Spider Plant (Cleome gynandra L.) Germplasm for Agronomic Traits in Vegetable and Seed Production: A Green House Study
Aims: Spider plant (Cleome gynandra L.) is one of the most important traditional vegetables in Kenya, albeit underutilized. Concurrently, scanty information is available on its potential for vegetable and seed production. The objective of this study was therefore to evaluate spider plant germplasm for agronomic traits pertinent to seed and vegetable production.
Study Design: A complete randomized design (CRD) with three replicates was used.
Place and Duration of Study: Two greenhouse experiments were conducted at Upper Kabete Field Station of the University of Nairobi, Kenya, for a period of 180 days (March-August, 2014).
Methodology: Twenty-five genotypes obtained from the Gene bank of Kenya and farmers’ fields were grown in 10 kg pots filled with a mixture of soil and cow manure at ratio of 1:2. Three seeds of each genotype were planted per pot and evaluated for days to seedling emergence, germination percent, leaf formation, days to flowering, days to pod formation, number of pods per plant, number of seeds per pod and weight of 100-seeds.
Results: Seedling emergence, leaf formation, days to flowering, days to pod formation, number of pods per plant, number of seeds per pod and 100-seed weight varied significantly (P=.05) between genotypes. Nineteen out of 25 genotypes emerged within 5 to 7 days, time to flowering ranged between 30 days in GBK-045494, and 42 days in GBK-040449, GBK-032229 and GBK-032134. Eight genotypes produced between 11 and 13 leaves per plant within six weeks. All the genotypes had a low (<50%) germination percentage.
Conclusion: GBK-040449, GBK-027212, GBK-032210 and GBK-032340 with; 4-7 days to emergence, >11 leaves per plant and ≥35 days to flowering are desirable for vegetable production, whereas, GBK-040449, GBK-045494 and SN 1 with ≥40 Days to pod formation, 6-9 pods per plant; ≥100 seeds per pod and 0.14-0.16g per 100-seeds are recommended for seed production. GBK 040449 was found to have traits suitable for both vegetable and seed production. 
 Wright, H., 1980. Commercial hybrid seed production. Hybridization of crop plants, pp.161-176.
 Sinclair, T.R. and de Wit, C.T., 1975. Photosynthate and nitrogen requirements for seed production by various crops. Science, 189(4202), pp.565-567.
 Greene, D.F. and Johnson, E.A., 1994. Estimating the mean annual seed production of trees. Ecology, 75(3), pp.642-647.
 Pal, G., Radhika, C., Bhaskar, K., Ram, H. and Prasad, S. (2016) “A Study on Comparative Economics of Grain and Seed Production of Groundnut in Karnataka, India”, Journal of Experimental Agriculture International, 14(5), pp. 1-9. doi: 10.9734/JEAI/2016/29405.
 Onyango, C. M., Onwonga, R. and Kimenju, J. (2015) “Assessment of Spider Plant (Cleome gynandra L.) Germplasm for Agronomic Traits in Vegetable and Seed Production: A Green House Study”, Journal of Experimental Agriculture International, 10(1), pp. 1-10. doi: 10.9734/AJEA/2016/20209.