Speed Breeding of Short-Day Crop Okra: Revolutionizing Variety Development

Speed Breeding of a Short-Day Crop – Okra

Introduction : Developing crop varieties typically involves a lengthy generation time to allow for the formation of homozygous lines after hybridization. With the conventional approach, only 1-2 crop generations can be produced annually, it takes 5 to 7 years for a homozygous line to develop. However, to address the increased demand for food and vegetables due to global population growth, faster crop breeding methods are needed. Speed breeding techniques manipulate environmental conditions to expedite flowering and fruiting, resulting in shorter reproduction cycles.

The light environment is a crucial factor in speed breeding, with three elements – light quality, light intensity & photoperiod, directly influencing plant photosynthesis & photomorphogenesis. Plants can perceive changes in light quality through specialized photoreceptors like phytochromes, which can exist in active or inactive forms. The ratio of red-to-far-red radiation in the surrounding environment dictates the equilibrium between these two forms.

Material & Methods : Speed Breeding trials were conducted in a Controlled Environment Growth Chamber fitted with 3-in-1 Grow Light (GHGL-3S, Nexsel) to provide the necessary lighting required by the plants. Two cultivars viz. Aishwarya (Hi-Tech Agri Genetics) & JKOH-7315 (J.K. Seeds) were selected for the study. Seeds were soaked in 0.1% (W/V) Humic Acid Solution for 24 hours before sowing. Seeds were then sowed in a 6” pot containing Soil & Cocopeat (70:30) & were kept in the dark. Three days later the germinated seeds were subjected to light with an average intensity range from 300 to 500 μmol/m²/s keeping the DLI same throughout the growth cycle.

Crop Phase	Intensity	Photoperiod
Vegetativee	300-500 μmol/m²/s	12 to 20 hours
Reproductive	300-500 μmol/m²/s	12 to 20 hours
Maturation	300-500 μmol/m²/ss	12 to 20 hours

Spectra Composition : Three Spectra were employed in different stages of plant growth, each tailored for specific plant development. viz. Vegetative with high percentages of Blue over Red. Followed by Bloom having higher percentages of Red over Blue & some Far-Red to induce & facilitate flowering. The third spectra had similar percentages of Blue & Red & R:Fr of 3.5 to 4.0

Environmental Parameters : Set Temperature was 22 to 28 °C during the vegetative & reproductive phases & 30 to 35 °C during the maturation stage. Set Relative Humidity (RH) was 50 to 60% throughout the growth cycle. Plants were fertigated as per the fertigation schedule designed by the agronomy team. Watering was stopped 5-8 days prior to harvesting to facilitate the natural drying of pods on the plants themselves.

Data Collection : Daily observations were conducted on the plants, noting the duration in days for various growth stages to occur: the emergence of the first flower bud, the initiation of anthesis & the subsequent stages of pod development & maturation.

Seed Quality Assessment : The dried pods were harvested 65 to 70 days after sowing. The seeds were collected from the pods. After 2 days of storing, the seeds were treated with 0.1% (W/V) Humic Acid Solution for 24 hours prior to sowing. Seeds were later planted in a pot containing Soil & Cocopeat (70:30). The germinated seeds were counted & germination rate was calculated

Results: Results showed that the seeds harvested from speed-bred Okra plants had a similar germination rate, if not higher than the seeds harvested from traditionally bred Okra plants. This finding suggests that the quality of seeds produced is not compromised by the implementation of speed breeding techniques.

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