Milk vetch dwarf virus infection in the Solanaceae and Caricaceae families in Southeast Asia

Milk vetch dwarf virus (MDV) is an important member of the genus Nanovirus and is transmitted by the aphid Aphis craccivora. MDV has multiple single-stranded DNA genome components, each approximately 1 kb, and two or three alpha-satellite molecules. It mainly infects plants of the legume family Fabaceae. Recently, papaya (Carica papaya) collected in Yesan, South Korea, displaying symptoms of leaf yellowing and dwarfism, was identified as a new host for MDV. To examine the geographical distribution of MDV, papaya samples with symptoms were harvested in South Korea, Vietnam, and Taiwan in August 2018, along with tomato and pepper samples grown in adjacent fields in Vietnam. The results revealed the presence of MDV not only in papaya but also in pepper and tomato. This MDV infection in members of the Solanaceae family was confirmed by Southern blot hybridization performed using a PCR product of segment S as a probe. Based on sequence analysis of three MDV components (M, S, and C3), we verified the presence of three different isolates of MDV in these three countries and homology between sequences of isolates from papaya and from members of the Solanaceae from Vietnam. Taken together, our results clearly demonstrate MDV infection in Vietnam and Taiwan for the first time and confirm that MDV can infect economically important pepper and tomato.     

Variations of SOC and MBC observed in an incubated brown loam soil managed under different tillage systems for 12 years

To assess changes in organic carbon pools, an incubation experiment was conducted under different temperatures and field moisture capacity (FMC) on a brown loam soil from three tillage practices used for 12 years: no‐till (NT), subsoiling (ST) and conventional tillage (CT). Total microbial respiration was measured for incubated soil with and without the input of straw. Results indicated that soil organic carbon (SOC) and microbial biomass carbon (MBC) under ST, NT and CT was higher in soil with straw input than that without, while the microbial quotient (MQ or MBC: SOC) and metabolic quotient (qCO₂) content under CT followed the opposite trend. Lower temperature, lower moisture and with straw input contributed to the increases in SOC concentration, especially under NT and ST systems. The SOC concentrations under ST, with temperatures of 30 and 35°C after incubation at 55% FMC, were greater than those under CT by 28.4% and 30.6%, respectively. The increase in MBC was highest at 35°C for 55%, 65% and 75% FMC; in soil under ST, MBC was greater than that under CT by 199.3%, 50.7% and 23.8%, respectively. At 30°C, the lower qCO₂ was obtained in soil incubated under NT and ST. The highest MQ among three tillage practices was measured under ST at 55% FMC, NT at 65% FMC and CT at 75% FMC with straw input. These data indicate the benefits of enhancing the MQ; the low FMC was beneficial to ST treatment. Under higher temperature and drought stress conditions, the adaptive capacity of ST and NT is better than that of CT.     

Effect of conservation agriculture on soil organic and inorganic carbon sequestration and lability: A study from a rice–wheat cropping system on a calcareous soil of the eastern Indo-Gangetic Plains

Increasing soil carbon (C) in arable soils is an important strategy to achieve sustainable yields and mitigate climate change. We investigated changes in soil organic and inorganic carbon (SOC and SIC) under conservation agriculture (CA) in a calcareous soil of the eastern Indo-Gangetic Plains of India. The treatments were as follows: conventional-till rice and wheat (CT-CT), CT rice and zero-till wheat (CT-ZT), ZT direct seeded rice (DSR) and CT wheat (ZT-CT), ZTDSR and ZT wheat without crop residue retention (ZT-ZT), ZT-ZT with residue (ZT-ZT+R), and DSR and wheat both on permanent beds with residue (PB-PB+R). The ZT-ZT+R had the highest total SOC in both 0–15 and 15–30 cm soil layers (20% and 40% higher (p < .05) than CT-CT, respectively), whereas total SIC decreased by 11% and 15% in the respective layers under ZT-ZT+R compared with CT-CT. Non-labile SOC was the largest pool, followed by very labile, labile and less labile SOC. The benefits of ZT and residue retention were greatest for very labile SOC, which showed a significant (p < .05) increase (~50%) under ZT-ZT+R compared with CT-CT. The ZT-ZT+R sequestered ~2 Mg ha⁻¹ total SOC in the 0–15 cm soil layer in 6 years, where CT registered significant losses. Thus, the adoption of CA should be recommended in calcareous soils, for C sequestration, and also as a reclamation technique.     

Frequency and fertility restoration efficiency of Rf3 and Rf4 genes in Indian rice

Identification of new parental lines is crucial for developing ecology‐specific hybrids with ideal agronomic performance. We screened a total of 570 different ecology‐specific Indian rice varieties for the presence of fertility restorer genes, Rf3 and Rf4 using tightly linked markers DRRM Rf3‐10 and RM6100, respectively. Among these varieties, 13% carried Rf3Rf3/Rf4Rf4, 31% carried rf3rf3/rf4rf4, 6% carried Rf3Rf3/rf4rf4 and remaining 50% carried Rf4Rf4/rf3rf3 allelic combinations. A mini set of 40 varieties with variable allelic combinations of fertility restorer genes were testcrossed with WA and Kalinga‐based CMS lines. All the 80 F₁s were evaluated for spikelet fertility and fertility restoration ability. Rf3Rf3/rf4rf4 genotypes mostly behaved as partial maintainers or partial restorers. In contrast, rf3rf3/Rf4Rf4 genotypes were partial or effective restorers. However, double dominant genotypes showed better fertility restoration than the genotypes containing Rf3 or Rf4 individually. Some of the genotypes showed unexpected restoration pattern implying occurrence of other fertility restorer(s) apart from Rf3 and Rf4. The perfect restorers and maintainers identified in this study can be directly used in hybrid rice breeding.     

Carbon Depletion by Plowing and its Restoration by No‐Till Cropping Systems in Oxisols of Subtropical and Tropical Agro‐Ecoregions in Brazil

The continuous use of plowing for grain production has been the principal cause of soil degradation. This project was formulated on the hypothesis that the intensification of cropping systems by increasing biomass‐C input and its biodiversity under no‐till (NT) drives soil restoration of degraded agro‐ecosystem. The present study conducted at subtropical [Ponta Grossa (PG) site] and tropical regions [Lucas do Rio Verde, MT (LRV) site] in Brazil aimed to (i) assess the impact of the continuous plow‐based conventional tillage (CT) on soil organic carbon (SOC) stock vis‐à‐vis native vegetation (NV) as baseline; (ii) compare SOC balance among CT, NT cropping systems, and NV; and (iii) evaluate the redistribution of SOC stock in soil profile in relation to soil resilience. The continuous CT decreased the SOC stock by 0·58 and 0·67 Mg C ha⁻¹ y⁻¹ in the 0‐ to 20‐cm depth at the PG and LRV sites, respectively, and the rate of SOC sequestration was 0·59 for the PG site and ranged from 0·48 to 1·30 Mg C ha⁻¹ y⁻¹ for the LRV site. The fraction of C input by crop residues converted into SOC stock was ~14·2% at the PG site and ~20·5% at the LRV site. The SOC resilience index ranged from 0·29 to 0·79, and it increased with the increase in the C input among the NT systems and the SOC sequestration rates at the LRV site. These data support the hypothesis that NT cropping systems with high C input have a large potential to reverse the process of soil degradation and SOC decline. Copyright © 2013 John Wiley & Sons, Ltd.     

Biology and life table of Diaeretiella rapae against Brevicoryne brassicae on different cultivars of cauliflower

Phytoparasitica - Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) is one of the most promising, effective and a common endoparasitoid of different aphid species including cabbage aphid,...     

Phytosanitary importance of Heterodera glycines for South-east Asian countries

Heterodera glycines is not known to occur in South-east Asian countries except in Indonesia. Specific surveys carried out recently in central India indicate absence of the nematode. The region has a large area under cultivation of soybean, and also other crop and wild hosts. H. glycines causes annual yield losses of about half a million metric tons in 10 major soybean-growing countries. Asia has to import half its demand of soybeans, mainly from North America and Brazil, where H. glycines occurs. Spread is mainly through soil mixed with seeds, or by spillage of grain. A preliminary pest risk analysis suggests that the South-east Asian region is suitable for the introduction and spread of H. glycines . Management practices are suggested to delay its introduction.     

Some studies on the chemical composition of cucurbit kernels and their seedcoats

Chemical composition of the kernels and seedcoats of 8 cucurbit species, viz watermelon, muskmelon, cucumber, pumpkin, spongegourd, bottlegourd, bittergourd and snakegourd have been studied. The proportion of kernels in these seeds ranged from 48.0 to 75.5%. Oil content in kernels varied from 41.0 to 56.5%, protein 28.07 to 34.34%, crude fibre 1.25 to 2.60% and mineral matter 3.01 to 5.01%. Kernels were quite rich in calcium, iron and phosphorus. The cucurbit species compared well with some of the conventional kernels such as cashewnut and almond in their chemical make-up. Although quite low in fat and protein, the seedcoats of these cucurbit species were quite rich in crude fibre and mineral matter and could be of use as animal feed.     

Soil erosion on Alfisols in Western Nigeria: V. The changes in physical properties and the response of crops

Erosion-induced changes in the physical characteristics of the surface soil under different soil and crop management treatments were monitored over a period of two years. These studies were conducted on field runoff plots established on natural slopes of 1, 5, 10 and 15%. The soil and crop management treatments consisted of bare-fallow, maize-maize (plowed and mulched), maize-maize (plowed), maize-cowpeas (no-till) and cowpeas-maize (plowed).Soil erosion increased the gravel content and decreased the silt and clay contents of the surface horizon. The moisture retention capacity of the surface soil decreased significantly. The infiltration rate decreased from 3.5 cm/min on all plots in February 1972 to 0.2 cm/min under bare-fallow, to 0.6 cm/min under maize-maize (mulch), to 1.5 cm/min under maize-cowpeas (no-till) and to 0.1 cm/min under maize-maize (plowed) in February 1974. Maize yields on the mulch and no-till treatments were maintained while those on plowed plots declined. Artificial soil removal resulted in significant reductions of maize and cowpea yields.     

Agroforestry systems and soil surface management of a tropical alfisol:

Field runoff plots, 70 x 10 m each, were established on a tropical Alifisol in southwestern Nigeria to monitor water runoff, soil erosion and nutrient loss in water runoff. The non-agroforestry control treatment (A) was established at two levels: plow-till and no-till systems of seedbed preparation. There were two agroforestry systems based on contour hedgerows of (B) Leucaena leucocephala and (C) Gliricidia sepium established at 4-m and 2-m spacings. Field plots were established in 1982 and hydrological measurements were made for uniform maize-cowpea rotation for 12 consecutive growing seasons from 1982 through 1987. Once established hedgerows of Leucaena at 2-m spacing were extremely effective in reducing water runoff and controlling erosion. Runoff, erosion and nutrient losses were generally more from maize grown in the first season than from cowpea grown in the second. Mean seasonal erosion from maize was 4.3, 0.10, 0.57, 0.10, 0.64 and 0.60 t/ha for plow-till, no-till, Leucaena-4m, Leucaena-2m, Gliricidia-2m treatments, respectively. Mean runoff in the first season from treatments listed in the order above was 17.0, 1.3, 4.9, 3.3, 4.3, and 2.4 percent of the rainfall received. There were high losses of Ca and K in water runoff from the plow-till treatment. In contrast to runoff and erosion, losses of bases in water runoff from agroforestry treatments were relatively high, high concentration of bases in runoff was probably due to nutrient recycling by the deep-rooted perennials.