Water regimes in selected fodder radish (Raphanus sativus) genotypes: Effects on nutritional value and in vitro ruminal dry matter degradability

Fodder radish is widely used as a livestock supplement, however, the nutritional value of fodder radish under different water conditions remains insufficiently understood. This study aimed to assess the chemical components and in vitro, ruminal dry matter degradability of two fodder radish genotypes (Endurance and Line 2) subjected to three irrigation regimes: well-watered (W1), moderate water stress (W2), and severe water stress (W3). The analysis revealed statistically significant effects of the main factors on the chemical composition and estimates of fodder radish leaves and tubers, particularly in terms of Crude Protein (CP) and Ether Extract (EE) across genotypes. Both Endurance and Line 2 leaves exhibited interaction effects on N, P, Ca, Mg, K, Na, Fe, Zn, Cu, Mn and Al. Meanwhile only Na, K, Zn, and Cu were affected in tubers. Endurance tubers, specifically, displayed significantly higher (p < 0.05) CP content, with Line 2 tubers showing the highest CP content under W1. Furthermore, Endurance leaves had higher levels of Neutral Detergent Fibre, EE, and Non-Structural Carbohydrate (NSC) compared to Line 2 leaves under W1. Notable differences in tuber fibres were found, specifically in Acid Detergent Fibre for Endurance, with W3 exhibiting a higher concentration level. Both genotypes displayed higher NSC under W3. Significant variations in macro and mmicro minerals were observed between water levels in both genotypes. In terms of in vitro degradability during the 24 h and 48 h incubation periods, all treatments met the acceptable level of 60-80 %. Regardless of water regimes, both Endurance and Line 2 showed nutrient concentrations meeting the minimum requirements for optimal animal production. Though, Line 2 exhibits significantly higher nutritional value and in vitro ruminal dry matter degradability than Endurance, evident in both leaves and tubers. Notably, moderate water stress conditions yielded better nutritional quality and in vitro ruminal dry matter degradability compared to both well-watered and severe water stress treatments. This suggests that applying 180-220 mm of water per season can also yield better nutritive value of these genotypes.

Differences in parasitism of root-knot nematodes (Meloidogyne spp.) on oilseed radish and oat

Oilseed radish and oat are cool season annual crops that are potentially used as “trap” or “biofumigant” crops for the suppression of plant-parasitic nematodes in soil. Cultivars of oilseed radish (Carwoodi, Cardinal, Final, Image, Concorde, Control, Eco-Till, Karakter and Cannavaro), white (Tachiibuki) and black (Pratex) oats were evaluated for their ability to reduce reproduction of three root-knot nematode species: Meloidogyne javanica, M. incognita race 3, and M. arenaria race 1. Nematode penetration and development were also evaluated using selected resistant and susceptible cultivars under greenhouse conditions. Root galling severity, number of eggs per gram of fresh root, and rate of reproduction varied among the cultivars in response to nematode infection. Oilseed radish cv. Carwoodi was resistant to M. javanica, whereas Karakter and Concorde were maintenance hosts allowing the nematode to maintain or increase its population on the plants. For M. incognita, Control and Carwoodi oilseed radish and Tachiibuki oat were resistant hosts. The cultivars that supported little reproduction of M. arenaria were Karakter and Carwoodi radish, and Tachiibuki oat. Comparable numbers of nematodes entered the roots of susceptible and resistant cultivars of oilseed radish and oat during early stages of infection. However, the development of the nematodes as evident from counting young and egg-laying females in roots were significantly decreased or inhibited in the resistant cultivars compared to the susceptible cultivars indicating that resistance occurs at post-infection stages. Histopathological examinations of galled-root tissues also revealed the susceptibility and resistance responses of selected cultivars of oilseed radish and oat to these nematode species.

The effect of storage time and temperature on the population dynamics and vitality of Meloidogyne chitwoodi in potato tubers

The population densities of Meloidogyne chitwoodi in potato tubers stored at 4, 8 and 12°C after 0, 60, 120, 180 and 240 days of storage were assessed. Compared to day 0, storage temperatures of 4 and 8°C reduced population densities to 9 and 35%, respectively, after 240 days of storage, while nematode numbers in tubers stored at 12°C increased 2.5 times. The maximum hatching rate of nematodes from tubers stored at 8 and 12°C increased linearly with storage time. At 4°C it remained constant. The time required for the hatching process to reach the maximum number of second-stage juveniles (J2) decreased with increasing storage temperature. Recovered juveniles of M. chitwoodi from tubers after 180 and 240 days of storage at all three temperatures were still infective and able to multiply on ‘Desiree’ with estimates of the maximum multiplication rate (a) and the maximum population density (M) of 63.6 and 70.8 J2 (g dry soil)−1, respectively.

Effects of Cover Crops on Pratylenchus penetrans and the Nematode Community in Carrot Production

Cover cropping is a common practice in U.S. Midwest carrot production for soil conservation, and may affect soil ecology and plant-parasitic nematodes-to which carrots are very susceptible. This study assessed the impact of cover crops-oats (Avena sativa), radish (Raphanus sativus) cv. Defender, rape (Brassica napus) cv. Dwarf Essex, and a mixture of oats and radish-on plant-parasitic nematodes and soil ecology based on the nematode community in Michigan carrot production systems. Research was conducted at two field sites where cover crops were grown in Fall 2014 preceding Summer 2015 carrot production. At Site 1, root-lesion (Pratylenchus penetrans) and stunt (Tylenchorhynchus sp.) nematodes were present at low population densities (less than 25 nematodes/100 cm3 soil), but were not significantly affected (P > 0.05) by cover crops. At Site 2, P. penetrans population densities were increased (P ≤ 0.05) by 'Defender' radish compared to other cover crops or fallow control during cover crop growth and midseason carrot production. At both sites, there were few short-term impacts of cover cropping on soil ecology based on the nematode community. At Site 1, only at carrot harvest, radish-oats mixture and 'Dwarf Essex' rape alone enriched the soil food web based on the enrichment index (P ≤ 0.05) while rape and radish increased structure index values. At Site 2, bacterivore abundance was increased by oats or radish cover crops compared to control, but only during carrot production. In general, cover crops did not affect the nematode community until nearly a year after cover crop growth suggesting that changes in the soil community following cover cropping may be gradual.

Tuber and root resistance of potato genotypes against Meloidogyne chitwoodi in the presence of Avena strigosa, related to tuber quality

Relative tuber infestation and quality of two Meloidogyne chitwoodi resistant potato genotypes, AR04-4096 and 2011M1, were compared in glasshouse experiments at initial population density () = 16 second-stage juveniles (g dry soil)−1 in the presence and absence of the bristle oat, Avena strigosa. When A. strigosa was added, ( final population) on both AR04-4096 and 2011M1 increased 130×, increased 1.9 and 3.7×, respectively, while × fresh root weight (FRW)−1 was the same. Nematode hatch from peel of AR04-4096, without A. strigosa, was delayed by 3 weeks but relative hatching rate was increased. Although the RStuber (RS = Relative Susceptibility) of both AR04-4096 and 2011M1 were lower than 1%, in the presence of A. strigosa tuber quality of 2011M1 dropped below the marketable level, while that of AR04-4096 was hardly affected. We conclude that: i) is influenced by root mass; ii) root quality influences nematode hatch; iii) tuber quality is not an estimator for tuber resistance, and the reverse; iv) root resistance is equal to tuber resistance.

A routine test for the relative susceptibility of potato genotypes with resistance to Meloidogyne chitwoodi

The population dynamics of Meloidogyne chitwoodi on eight potato genotypes was compared to the susceptible cv. Desiree in four glasshouse experiments. The initial nematode densities consisted of log series 2x, with . Seinhorst’s logistic model was fitted to the final population densities to estimate the parameters maximum multiplication rate (a), maximum population density (M) and the ratios RSa, RSM and . Average RSa and RSM of the seven resistant genotypes were smaller than 0.29%. The ratios on six resistant genotypes and cv. Desiree were the same, 1.3, indicating independence of RS. One genotype stood out with , whereby RSa < RSM. Both RS and were unaffected by pot size or experimental conditions. Screening protocols at second-stage juveniles (g dry soil)−1 in 2 or 3 kg pots were evaluated for distinctiveness between the two genotype groups. Based on the results, an optimal protocol for a routine resistance test is proposed.

Research on plant-parasitic and entomopathogenic nematodes in Ethiopia: a review of current state and future direction

Food self-sufficiency is Ethiopia’s national priority goal. Given that pest management seriously impacts agriculture, research on crop diseases is of paramount significance to the national goal. Here we provide a comprehensive account of research on plant-parasitic and entomopathogenic nematodes in Ethiopia. We show that the limited information available indicates that plant-parasitic nematodes impact crop production. There exists a serious gap in knowledge with regard to the effects of plant-parasitic nematodes on almost all major crops. This gap includes surveys with appropriate levels of identification, distribution, and yield loss and damage threshold studies on target crops. The current state of knowledge hinders the nation’s ability to design and implement appropriate control strategies for plant-parasitic nematodes. We propose a strategic assessment of plant-parasitic nematodes of all major crops, the need for systematic manpower training and continued search for entomopathogenic nematodes in the major agro-ecological zones of the nation and further research on those entomopathogenic nematodes already identified.

Damage thresholds and population dynamics of Meloidogyne chitwoodi on carrot (Daucus carota) at different seed densities

Yield loss of carrot (Daucus carota) cv. Nerac caused by Meloidogyne chitwoodi and population dynamics of this nematode were studied using a range of 13 nematode densities at three seed densities (2, 4, 18 seeds pot−1) in a climate-controlled glasshouse. Yield and quality data were fitted to Seinhorst’s yield models. Final population densities were fitted to the population dynamic models for sedentary and free-living nematodes. The tolerance limits for yield loss were 0.34, 0.62 and 0.50, while that of quality were 0.012, 0.142 and 0.813 second-stage juveniles (J2) (g dry soil)−1 at increasing seed densities, respectively. The minimum yield (m), increased with seed density: 0.25, 0.30 and 0.50; the minimum quality yield was 0.10, 0.08 and 0.15 J2 (g dry soil)−1 at increasing seed densities, respectively. Both maximum multiplication rates and maximum population densities increased with increasing seed density but were generally low. Carrot cv. Nerac can be considered a bad host for M. chitwoodi.