Cup quality profiles of Robusta coffee wilt disease resistant varieties grown in three agro-ecologies in Uganda.

BACKGROUND: The recently developed Robusta coffee wilt disease resistant (CWD-r) varieties in Uganda outperform the local landraces, both in yield and resilience. However, their uptake has been slow due to limited information on their cup worth. This study profiled the cup worth of the five most commonly grown CWD-r across the Lake Victoria Crescent, Western Mid-altitude farmland and Central Wooded Savannah agro-ecologies. RESULTS: Significant correlations (P ≤ 0.05) were observed between soil nutrients and coffee bean size but this was not the case for biochemical and cup quality. The proportion of coffee beans retained on screen 15; minimum acceptable size through coffee commercial markets, ranged from 58.09% in Mukono to 92.49% in Mityana. Interestingly, the bean size of variety KR4 was hardly influenced by environmental variations, with portions of beans retained on screen 15 being relatively the same (80.30% Ibanda, 89.50% Mukono, 98.20% Mityana). Coffee cup quality for most of the varieties was scored as premium (70-79%) across three agro-ecologies, with the exception of KR4, which was scored specialty grade (≥80%). Coffee blends generated were used to make coffee products with specialty score (82.25%) and a distinctive aroma complex. CONCLUSION: In this study, blends of CWD-r resulted in superior cup scores (76-82%). These findings show that CWD-r varieties have a high cup worth with potential for wide adaptation in Uganda's Robusta coffee growing agro-ecologies. Most importantly, variety KR4 has resilience across three agro-ecologies with a consistent high bean size and superior cup quality, making it a candidate variety for the market and breeding. © 2021 Society of Chemical Industry.

Intraspecific crossability and compatibility within Solanum aethiopicum.

Understanding hybridization barriers is relevant for germplasm conservation and utilization. The prezygotic barriers to hybridization include floral morphological differences like pistil and stamen length, pollen characteristics and pollen-pistil interactions. This study sought to elucidate the reproductive biology of Solanum aethiopicum; its mating systems and compatibility barriers. Eight genotypes of Solanum aethiopicum were examined for differences in floral morphology, phenology and cross compatibility in a full diallel mating design, with assessment of fruit set, seed set and seed viability. In-vivo pollen tube growth was observed for failed crosses at 24, 48 and 72 h after pollination. All genotypes had heterostyly flowers, with predominantly small white petals. Incompatibility was observed in five out of 39 combinations. All selfed genotypes displayed compatibility implying the genotypes are self-compatible. Pollen-pistil incompatibility, which was exhibited in four out of the five failed cross combinations, occurred on the stigma, upper style and lower style, a phenomenon typical in Solanaceae. Solanum aethiopicum is self-compatible and majorly self-pollinating but has features that support cross-pollination.

Farmer preferred traits and genotype choices in Solanum aethiopicum L., Shum group.

BACKGROUND: Solanum aethiopicum L. is a nutrient dense African indigenous vegetable. However, advancement of its improved varieties that can increase productivity, household income, and food security has not been prioritized. Further still, studies on some of the crops that have been worked have indicated that it is not a guarantee that the improved varieties will be accepted by the end users and therefore there is need to identify and profile what genotypes are of interest to farmers and their preferred traits through inclusive participatory evaluations. METHODOLOGY: Farmer participatory evaluations were conducted to profile farmers' traits of interest and preferred genotypes. A total of 24 genotypes were established in three replications in 6 farms in 3 districts; Wakiso, Mukono, and Luwero as these are the major producing districts of the vegetable in Uganda. A total of 177 sex-disaggregated farmers were engaged in scoring the genotypes for pest, disease and drought tolerance, general appeal, leaf yield, leaf texture, and seed yield for best 10 genotypes under each variable. RESULTS: Non-significant differences in trait (p > 0.05) and genotype preferences (p > 0.05) were obtained between men and women. The most desired farmer traits were seed and leaf yield, followed by pest and disease resistance. The overall preferred genotype in terms of disease and pest resistance, leaf yield, leaf texture, and seed yield were E12 followed by E11. CONCLUSION: Gender does not seem to influence farmer choices for the S. aethiopicum, Shum group, indicating an opportunity for single variety prototype advancement by breeders and dissemination by seed companies.

Identification of growth stage-specific watering thresholds for drought screening in Solanum aethiopicum Shum.

Effective phenotyping for drought resistance is a pre-requisite for identification of modest crop varieties for farmers. For neglected and underutilized crops such as Solanum aethiopicum Shum group, no drought screening protocol based on rigorous iterations has been documented. A split-plot nested treatment structure was arranged in an experiment to identify growth stage-specific watering thresholds for this crop. Three plant growth stages (main plot; seedling, vegetative and flowering), watering regime at plant growth stage (2 regimes; well-watered and drought stressed) and day since last watering at plant growth stage were evaluated for soil moisture content (SMC), leaf wilting score (LWS), number of green leaves per plant (LPP) and leaf blade width (LBW). Highly significant differences (p < 0.001) were found at the different plant growth stages, watering regime (WR) within plant growth stage, and day within WR and plant growth stage. Under drought stress treatment, SMC declined exponentially at each stage. The earliest leaf wilting, reduction in LPP and LBW were generally observed at flowering followed by vegetative and slowest at the seedling stage. For future effective drought phenotyping studies in S. aethiopicum Shum and related crops, we recommend setting minimum drought stress treatments below 18% SMC at which the LWS is ≥2 at the vegetative.

Accuracy of using leaf blade length and leaf blade width measurements to calculate the leaf area of Solanum aethiopicum Shum group.

Leaf area is an important parameter when determining growth response under normal as well as stressed environments. No attempt had been made to come up with an affordable but accurate alternative of measuring leaf size in research neglected leafy vegetable crops. Other techniques such as use of leaf area meters are either destructive, expensive or both. A study was conducted to determine leaf area in like-shaped leaves of research neglected crop plants, taking case of S. aethiopicum Shum group (SAS) germplasm. Data was collected on 552 individual plants (including pure lines and hybrids) at eight weeks after planting where a third fully open leaf from top of each plant was considered. Leaf blade length (LBL) and leaf blade width (LBW) were linearly measured while leaf area (LA) was measured using a leaf area meter. This was followed by correlation and regression analysis of LA with LBL, LBW, and LBL + LBW. Correlation coefficients at p < 0.001 ranged between 0.84 and 0.92, 0.79 and 0.88, 0.86 and 0.95 for total germplasm, pure lines and hybrids, respectively. The coefficient of determination (R2) ranged between 0.72 and 0.92. The best prediction for LA was obtained with hybrid plants (LA = -165.82 + 5.38LBL + 16.17LBW) at R2 of 92%. The implication is that we can accurately and affordably predict LA from duo measurements of LBL and LBW in SAS as well as in other crops having similar leaf shapes.