The seed production area (SPA) is defined as a phenotypically superior stand made up of vigorously growing healthy trees, upgraded by thinning to remove poorer phenotypes and treated and managed to cause abundant seed production. Tree improvement is a stepwise process involving exploration, collection, evaluation, breeding, multiplication, distribution and conservation of genetic resources. Developing seed production areas (SPAs) is one of the first steps in tree improvement programme that can be used to obtain genetically improved seed for immediate planting.
A 10 hectare seed stand of E. Camaldulensis, planted in 1978 at 0-7RD, Sangeeta Distributory, Suratgarh, Rajasthan was converted into seed production area after inter-comparing various other seed stands planted between 1975 to 1981 in Rajasthan state. Out of 5300 trees, 4500 plants have been culled and only 800 trees were retained after scoring each tree in the stand and ranking them in descending order. After culling the average height, clear bole, girth, diameter and volume have been shifted towards the higher side by 0.74 m, 1.86 m, 6.16 cm, 2.01 cm and 0.09 m3 respectively. Seeds collected after establishment of SPA showed improvement in seed weight and germination percentile.