Amaranths (Amaranthus sp.) are a popular leafy vegetable grown and consumed by resource-poor people in many African countries. Greater awareness of the importance of nutritious foods has increased demand by African consumers for amaranth. Presently, most African farmers grow low-yielding local varieties of variable seed quality. High-yielding amaranth varieties that are adapted to the major agro-ecologies of eastern and southern Africa possess key traits needed by male and female farmers and meet diverse market preferences are required. The objective of this study was to identify amaranth lines adapted to major amaranth production environments in Kenya and Tanzania using a gender-disaggregated farmers participatory approach to explore possible gender differences in trait and variety preferences. Twenty amaranth entries were evaluated for vegetable yield, agronomic traits, and organoleptic taste tests in replicated, farmer-participatory variety selection trials at one location in Kenya and at four locations in Tanzania. Differences among entries (G), locations (E), and G × E interaction were significant or highly significant for marketable vegetable yield. Location followed by entry was the most important factor that explained differences in yield. G and G × E interaction biplot analysis classified the five locations into two different mega-environments, mainly based on altitude, temperatures, and soil characteristics. Marketable vegetable yield was positively correlated with leaf length, plant height, and the selection scores of female and male farmers at almost all locations. Selection scores of female and male farmers were positively correlated, indicating that male and female farmers shared similar amaranth variety preferences. Farmers identified and ranked important traits that can be used by breeders to design amaranth product profiles and develop amaranth breeding objectives. Lines combining high yield with high farmer and consumer preference scores have been retained for distinctiveness, uniformity, and stability tests for possible release as commercial varieties.
Fekadu Fufa Dinssa, Ruth Minja, Thomas Kariuki, Omary Mbwambo, Roland Schafleitner, and Peter Hanson
Adigun McLeod, Kelly Vining, Tyler Hoskins, and Ryan Contreras
As the industrial hemp (Cannabis sativa L.) market grows, there is a need for methods to clonally propagate parental breeding stock and new cultivars. Information is lacking on vegetative cutting propagation of hemp. We evaluated how propagation environment (intermittent mist vs. subirrigation under a humidity dome), indole-3-butyric acid (IBA) formulation (talc rooting powder vs. IBA in solution), and IBA concentration (0, 3000, or 8000 ppm) affected stem cuttings from ‘I3’, a cannabinoid-free cultivar of industrial hemp. Under mist or domes, rooting quality and percent declined at 8000 ppm IBA. Root and shoot quality and rooting percentage also were reduced in 3000 ppm IBA in solution treatment compared with talc. Our data show that for the cultivar tested, cuttings rooted at the highest percentage and produced the highest-quality roots and shoots with either no hormone or 3000 ppm talc powder. These treatments did equally well under humidity domes or intermittent mist.
Justine Beaulieu, Bruk Belayneh, John D. Lea-Cox, and Cassandra L. Swett
Containerized crop production faces increasing sustainability challenges with both soilless substrate and water use. To facilitate use of sustainable practices, we evaluated plant health impacts of two substrates, bark and wood fiber, which we contrasted with peat, a substrate that is slower to renew; this was overlaid with an analysis of the effects of water-saving–targeted irrigation reductions, compared with typical well-watered conditions. Health impacts were evaluated in two crops, considering both physiological and disease impacts for tomato with and without Phytophthora capsici, and chrysanthemum with and without Phytopythium helicoides. Substrate type was a strong determinant of plant health, wherein crops grown in a HydraFiber-peat mix (“fiber”) performed worse than those in bark and peat, with up to a 50% and 45% reduction in shoot biomass in tomato and chrysanthemum, respectively (P < 0.001). Tomato decline incidence from P. capsici was 3–6 times higher in fiber than other substrates, and fiber was the only substrate where the effect of P. capsici enhanced decline and rot development compared with noninoculated plants (P < 0.05). In bark, reduced irrigation consistently inhibited tomato and chrysanthemum growth and shoot water content (typically P < 0.001). In peat, whereas tomato growth was inhibited under reduced irrigation (P = 0.012–0.013), chrysanthemum growth was often unaffected. Growth in fiber was uniformly poor regardless of irrigation regime for both crops, and an irrigation treatment effect was not typically apparent. Reduced irrigation enhanced pathogen effects in fiber and peat for tomato and fiber and bark for chrysanthemum (P < 0.05). This is perhaps the first study to evaluate HydraFiber interactions with disease and reduced irrigation and suggests that this product consistently incurs costs to crop productivity. However, the peat-replacing bark substrate has strong potential to optimize plant growth physiologically and via disease suppression and can be used under reduced irrigation without compromising economic productivity of the system.
Eliezer Louzada, Omar Vazquez, Sandy Chavez, Mamoudou Sétamou, and Madhurababu Kunta
Citrus Huanglongbing (HLB, also known as “citrus greening”), an important disease worldwide, is associated with three species of phloem-limited Candidatus liberibacter, of which Candidatus L. asiaticus (CLas) is the predominant one that has severely affected citrus production. TaqMan real-time polymerase chain reaction (PCR) (TM) has been the standard and very efficient method to diagnose several strains of Candidatus Liberibacter in citrus; however, it detects total bacteria and is unable to differentiate dead from live Liberibacter. The detection of only live bacteria is essential for testing methods of control for this important citrus disease. It is well known that ethidium monoazide and propidium monoazide (PMA) are compounds that supposedly enter only dead or membrane-damaged bacteria, intercalate the DNA strand, and make the DNA unavailable for amplification by PCR. These compounds are widely used when extracting the plant DNA to detect only live bacteria. In this research, we tested primers amplifying products from 79 to 1160 bp in TM and SYBR Green real-time PCR (SG) and PMA as DNA intercalating compound. Specifically, primers amplifying a 500-bp amplicon in SG provided the most reliable live-only detection, whereas those producing a smaller amplicon were unable to distinguish between live and dead. This is the first report of testing primers amplifying various amplicon sizes for the detection of only live CLas cells in citrus.
Nathan J. Jahnke, Jennifer Kalinowski, and John M. Dole
Huihui Xu, Xi Wang, Xiaojuan Liu, Yingchao Li, Libing Wang, Haiyan Yu, and Quanxin Bi
Young-Sik Park, Je-Chang Lee, Haet-Nim Jeong, Nam-Yong Um, and Jae-Yun Heo
Because of the success of the grape cultivar Shine Muscat in Korea, consumer interest in high-quality seedless grapes has significantly increased (
Paul C. Bartley III, William C. Fonteno, and Brian E. Jackson
The physical, hydrological, and physico-chemical properties of horticultural substrates are influenced by particle shape and size. Sieve analysis has been the predominate method used to characterize the particle size distribution of horticultural substrates. However, the literature shows a diversity of techniques and procedures. The effects of agitation time and sample size on particle size distributions of soilless substrates were evaluated for several measures of sieve analysis, including sieve rate (a calculation of the percentage of material passed for each unit time of agitation), distribution median, sd, mass relative span, skewness, and kurtosis. To obtain the standard sieve rate (0.1%/min), pine bark, peat, perlite, and coir required agitation times of 4 minutes and 47 seconds, 7 minutes and 18 seconds, 10 minutes, and 11 minutes, respectively. However, there was concern that unwanted particle breakdown may occur during the particle size analysis of some materials. Therefore, a sieve rate (0.15%/min) for more friable materials was also determined. As a result, the endpoint of sieving was reached sooner for pine bark, peat, perlite, and coir, at 3 minutes and 10 seconds, 4 minutes and 42 seconds, 5 minutes and 14 seconds, and 6 minutes and 24 seconds, respectively. Increasing agitation time resulted in decreased distribution median, sd, and skewness for all materials. Sample sizes half and twice the volume of the recommended initial volume sieved did not change particle size distributions. For more precise characterization of particle size distributions when characterizing substrate components, agitation times and sample sizes should be specified for each material or collectively for all materials to ensure consistency and allow comparisons between results.