Biochemical quality indices of sorghum genotypes from east Africa for malting and brewing

There is a gradual shift to substitute barley with sorghum in brewing industry to reduce the cost of doing business and make beer products more competitive. This study evaluates the sorghum genotypes for desirable malting and brewing characteristics. Biochemical characteristics assayed for 131 sorghum [Sorghum bicolor (L) Moench] accessions included total starch, amylopectin, amylose, proteins, tannins contents, germination energy and germination capacity. Results indicate that starch contents ranged from 22.8 - 81.2%, amylose from 11.5 - 30.2% while the amylopectin content ranged from 6.6 - 59.8%. Generally, amylose contents of sorghum genotypes were lower than their amylopectin contents, with a ratio of 1:2. The mean protein content for the sorghum accessions was 9.4% with a range of 3 - 18%, while that of barley was from 7.7 - 9.8%. Germination energy and germination capacity for sorghum ranged from 82.9 - 99.8% and 74.0 to 99.5%, respectively. Barley varieties showed germination energy and capacity greater than 98%. Sorghum tannin contents ranged from 2.55 mg/100 ml to as high as 100 mg/100 ml while barley varieties had tannin contents of 8.9 to 10.3 mg/100 ml. Two genotypes, SDSA 1x ICSR 43 and SP 993520-1 were the most favorable for brewing.Keywords: Sorghum, starch, protein, tannin, germination energy, malting and brewingAfrican Journal of Biotechnology, Vol. 13(2), pp. 313-321, 8 January, 201

Cane Yield and Juice Volume Determine Ethanol Yield in Sweet Sorghum (Sorghum bicolor L. Moench)

Sweet sorghum (Sorghum bicolor L. Moench) contains fermentable sugars in the stem that can be converted to ethanol. The current study aimed at evaluating the performance of three sweet sorghum genotypes with five checks and contributes towards availing suitable sweet sorghum for industrial ethanol production. Field studies were carried out in Kenya at varied locations in a randomized complete block design with three replications. Sorghum was harvested at hard dough stage of grain development and evaluated for several stem juice production traits including plant height, cane yield, juice volume, degrees Brix, total, reducing, and non-reducing sugars, and ethanol yield via juice fermentation. Analyses of variance using SAS version 9.1 showed a significant effect of genotype for morphological characters and ethanol yield. Genotype EUSS10 produced the greatest cane (27.4 T/ha) and juice yield (7806.7 L/ha) whereas ACFC003/12 recorded the greatest ethanol yield (423.1 L/ha). At all sites, EUSS10 had the greatest plant height and days to 50% heading whereas SS04 had the greatest Brix and total sugar concentration. The greatest grain yield and non-reducing sugar concentration was produced by SS17 and SS21, respectively. Results of this study show that though Brix and total sugars are desirable for ethanol yield, cane yield, and juice volume of sweet sorghum determines the ultimate volume of ethanol produced

Flowering margins support natural enemies between cropping seasons

Here we investigated how agricultural landscapes support natural pest regulating insects between cropping seasons; an important challenge in Pest Management by Small-Holder Farmers so aligns with this special issue. Smallholders in East Africa clear margins to provide fodder for cattle or livestock or simply to reduce the ingression of weeds into crop fields. We show that there was a significant seasonal variation in plant species richness and diversity around crops and the abundance of margin plants was strongly linked to abundance of natural enemies in the off season. The time since harvesting was also a significant factor influencing the overall abundance of natural enemies. Our paper reinforces our understanding of the importance flowering plants in agricultural systems as a refuge for natural enemies and other beneficial insects but uniquely emphasising the time between cropping seasons. Improving agricultural landscapes between crops to better support invertebrates will lead to more effective natural pest regulation early in the following crop with positive outcomes for the farmers and their families

Flowering margins support natural enemies between cropping seasons

IntroductionPopulations of natural enemies of insect pests are declining owing to agricultural intensification and indiscriminate use of pesticides, and this may be exacerbated in agricultural systems that clear all margin plants after the cropping season for other uses such as fodder. Retaining a diversity of non-crop flowering vegetation outside the cropping season may support more resilient and effective natural pest regulation.MethodsWe tested the potential for non-crop vegetation to support natural enemies in fields across two locations after harvesting the primary crops of lablab and maize.ResultsA total of 54 plant species were recorded across the sites in Kenya with 59% of them being annuals and 41% perennials. There was a significant seasonal variation in plant species richness (ANOVA: F1, 16 = 33. 45; P< 0.0001) and diversity (ANOVA: F1, 16 = 7.20; P = 0.0511). While time since harvesting was a significant factor influencing the overall abundance of natural enemies (ANOVA: F2, 1,133 = 8.11; P< 0.0001), they were generally higher in abundance in locations with margin plants or where a diversity of margin plants was observed.DiscussionThese findings demonstrate that flowering plants in agricultural systems offer refuge and alternative food for natural enemies and potentially other beneficial insects between cropping seasons. The conservation of natural enemies between crops may lead to more effective natural pest regulation early in the following crop, thus reducing reliance on insecticides application

Intercropping and diverse field margin vegetation suppress bean aphid (Homoptera: Aphididae) infestation in dolichos ( Lablab purpureus L.).

Dolichos (Lablab purpureus L.) is a drought tolerant legume used as food/feed and im- provement of soil fertility. The production of dolichos in Kenya, Nakuru County is however limited by insect pests like bean aphids, pod borers and whiteflies. Field stud- ies were conducted to determine the effect of cropping systems (dolichos monocrop and maize-dolichos intercrop) and field margin vegetation on bean aphids and their natural enemies. The experiment was conducted in Njoro (high field margin vegetation) and Ron- gai (low field margin vegetation) during May–December 2019 and March−November 2020 cropping seasons. Bean aphid percent incidence, severity of damage and abundance was assessed at seedling, early vegetative, late vegetative and flowering dolichos growth stages. The populations of natural enemies in the plots and field margin vegetation were monitored using pan traps and sweep nets. Species diversity and composition of the field margin ve-getation was determined using a quadrat. Results showed that location and cropping system had significant effects on bean aphid infestations. A high bean aphid incidence (38.13%) was observed in Njoro compared to Rongai (31.10%). Dolichos monocrop had significantly higher bean aphid infestation (51.63%) than the maize-dolichos intercrop system (24.62%). A highly diverse Shannon-weaver index was observed in Rongai (1.90) compared to Njoro (1.67). Dolichos monocrop had a more diverse Shannon-weaver index (1.8) than the maize- dolichos intercrop system (1.7). Rongai had the most abundant annual and perennial field margin vegetation species. The field margin species richness and diversity were higher in Rongai (81%) than in Njoro (54%). The findings of this study have demonstrated that a maize-dolichos intercrop in Rongai can reduce bean aphid damage in dolichos

Lablab (Lablab purpureus L.) genotypes and field margin vegetation influence bean aphids and their natural enemies

Dolichos bean (Lablab purpureus L.) is an important food and livestock feed legume that can also enhance soil fertility. However, its production is limited by insect pests, notably the black bean aphid (Aphis fabae). The present field study was conducted to determine the difference in contribution of dolichos genotypes and natural field margin vegetation (FMV) on the abundance and diversity of natural enemies and the damage, incidence and abundance of bean aphids. Eighteen lablab genotypes were planted in the presence or absence of FMV in a randomized complete block design 24 experiment replicated four times. Data on aphid abundance, incidence and severity of damage were collected at four growth stages of the crop. Dolichos genotypes significantly influenced aphid incidence thereby suggesting some level of tolerance to aphid colonization. Findings showed that dolichos genotypes were significant for natural enemies species richness with no statistical difference for abundance and natural enemies species diversity. However, the genotypes did not vary significantly in their influence on numbers of aphid natural enemies. FMV was associated with low bean aphid damage. Overall, the presence or absence of FMV did not influence the number of natural enemies caught on the crop. This concurs with recent work that shows similar numbers of natural enemies with field margin plants but may reflect the reduced number of pest insects. Cropping seasons influenced aphid abundance and damage severity, with the populations developing at early stages of lablab development and decreasing as the crop advanced. This pattern was similar both in presence or absence of FMV. The findings of this study highlight the important contribution of crop genotype together with the presence of field margin species in the regulation of aphids and their natural enemies in lablab