Adaptability, Stability and Post-harvest Management of Selected Green Vegetable Pigeon Pea (Cajanus Cajan) Genotypes in Eastern Region of Kenya

Abstract

Pigeon pea (Cajanus Cajan) is an important food security crop grown in the marginal Arid and semi-arid regions of Kenya. Its production and productivity are limited due to moisture stress and poor genotype adaptability to different Agro-ecological zones. The objective of this study was to identify stable, adapted genotypes to different agro-ecological zones and post-harvest management options. Yield stability and adaptability of green vegetable pigeon pea genotypes, ICEAP 00557, ICEAP 00554, KAT 60/8, KIONZA (Local) and MZ 2/9 was evaluated in a Randomized Complete Block design (RCBD), replicated three times during all seasons. Planting was done at Katumani and Kambi ya Mawe during the main seasons (October 2016) while at Kabete and Kiboko, the genotypes were planted in two seasons, March 2016 and October 2016. Therefore, the genotypes were tested for adaptability and stability in six seasons in total . Combined analysis of variance (ANOVA) revealed highly significant (P<0.01) variations in GxE interactions for yield (Kg/ha), 100 Seed mass (g/100 seed), days to flower and maturity (𝑃<0.05). AMMI model for grain yield IPCAs, explained 96.5% of the total yield variation. The cultivar MZ 2/9 and KAT 60/8 recorded a lower IPCA1, indicating a wider adaptation and stability. Kambi ya Mawe, Katumani and Kiboko (October planting) had higher IPCA1, indicating greatest interactive environments for adapted genotypes. The response of green vegetable pigeon pea genotypes ICEAP 00554, ICEAP 00557, MZ 2/9 and KAT 60/8 were evaluated at Kiboko in 2017-18 under open field and at Kabete in 2018-2019 under high tunnel to determine their response to intermittent and terminal moisture stress at vegetative, flowering, and podding phases of growth. There was significant different (P≤0.001) among the moisture regimes for seed weight, number of days to flower, number of pods and seed per pod at both locations. Combined analysis of variance revealed a significant (P≤0.01) interaction between moisture regimes and genotypes for seed weight, days to flower under open field and 100 seed mass, days to flower, harvest index, number of pods and plant height under high tunnel (P≤0.001). Moisture stress at flowering reduced yields, pods per plant and secondary branches under high tunnel by 77%, 72% and 60 % respectively, while under open field, it reduced yield, pod length and harvest index by 43%, 14% and 10%.

The effect of different pre-treatments and storage duration on green vegetable pigeon peas was determined. The pre-treatments included five treatments: Threshed fresh sample stored in a deep freezer at -180C; Threshed fresh sample, dehydrated then stored under room conditions; Threshed fresh sample, blanched then stored in a deep freezer at -180C; Threshed fresh sample, blanched, dehydrated then stores under room condition; and peas stored in pods. Iron (Fe), Zinc (Zn), protein, total sugars, vitamin A and vitamin C concentration was determined before and after the pre-treatment, and subsequently at 0-, 14-, 22- and 60-days of storage. There was significant difference among the pre-treatments (P<0.001) and duration of storage (P<0.001) for all the nutrients. Significant interaction between pre-treatment and storage duration was also noted (P<0.001) among all nutrients profiled. Blanching led to reduction in nutrient concentration, with significant reduction of 43% observed in vitamin C. Blanching of fresh vegetable pigeon peas and keeping them in a deep freezer recorded a mean nutrient loss of 7.7%, after 60 days of storage. Blanching of fresh peas and subsequent dehydration pre-treatment recorded the lowest mean nutrient reduction of 7.4% after 60 days of storage. Local consumer acceptance for processed and stored green vegetable after 22 days was determined by a team of semi-trained panellists based on 7 – point hedonic scale. There was significant difference (P<0.05) among the panelists on appearance, color, odor/smell and seed tenderness, but no significant difference was noted on taste and overall preference (P>0.05). The average sensory score among the panelists on physical appearance of samples stored in pods was 6.3, indicating high acceptability, while blanched samples had an average of 6.0 rating on a 7-point hedonic scale. The podded, blanched + oven dried recorded an average of 5.6, 6.6, and 6.1 scores, respectively on seed tenderness. Future research opportunities need to promote the stable and moisture stress genotypes (MZ 2/9, ICEAP 00557 and KAT 60/8) through participatory on-farm demonstrations for adoption. Development of blanching and dehydration protocol and capacity development of the rural and urban consumers will improve the shelf life, consumer preference and keeping quality of green vegetable pigeon peas for improved livelihoods