STORAGE PROBLEMS OF RECALCITRANT SEEDS & THEIR CONSERVATION

Abstract

A seed is a little embryonic plant that is wrapped in a seed coat, which normally contains some stored nourishment. It is the most important agricultural input with farmers, breeders and seed companies all relying on it. Based on desiccation tolerance and storability, seeds are categorized as orthodox and recalcitrant seeds. In ex situ conservation, orthodox seeds (desiccation-tolerant seeds) are those, which resist drying and freezing. The ability of orthodox seeds to endure drying and freezing varies; some seeds have been observed to be more sensitive than others. These are often long-lived seeds that may withstand dry-tomoisture ratios as low as 5% without suffering any harm. Furthermore, with low moisture content and cold conditions, orthodox seeds have a longer life. Ex-situ conservation of orthodox seeds is thus not much problematic. Seeds from most annual crops, biennial crops and agroforestry species are examples of orthodox seeds like Capsicum annum, Citrus aurantifolia, Hamelia patens, Pisidium guajava, Anacardium etc. Whereas seeds that are resistive to drying and freezing in ex situ conservation are known as recalcitrant seeds (desiccation sensitive seeds). They cannot be stored for extended periods like conventional seeds since their viability is lost (Chin, 1978). Recalcitrant seeds are often enormous in size and may be damaged if they are dried below 20-30 percent relative moisture content. Ex-situ conservation presents a challenge particularly in recalcitrant seeds because of high moisture content, which promotes microbial growth and causes seed decay quickly. Trees and shrubs are recalcitrant species, including Avocado, chocolate, coconut, mango, rubber, tea, etc. Furthermore, these seeds have a short lifespan, ranging from a few weeks to months.