Response of wheat to foliar phosphorus treatments under field and high temperature regimes

Potassium phosphate (KH₂PO₄) is applied commonly in dilute foliar sprays to wheat (Triticum aestivum L.) in China. Yield responses to foliar P sources have also been reported for several crop species in other countries. Experiments were conducted to determine efficacy of four P sources and four rates of KH₂PO₄ as foliar treatments on wheat under field conditions and KH₂PO₄ under two controlled temperature regimes. Grain yields were increased most by KH₂PO₄ followed by β‐glycerophosphate and tripolyphosphate; only phytic acid was ineffective. All rates of 1 to 4 kg ha^‐1 KH₂PO₄ increased grain yields. Foliar KH₂PO₄ applications increased grain weight early under low controlled temperatures, but did not affect final grain weight under either temperature regime. Beneficial effects of foliar P treatments were associated with increased plant P content, which may have increased cell sugar content and protected membranes. Although preliminary results are favorable, additional research is needed to determine optimum methods and conditions for treating wheat with foliar P sources.     

Population structure analysis and association mapping for iron deficiency chlorosis in worldwide cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis> (L.) Walp) germplasm

Cowpea (Vigna unguiculata L. Walp) is a legume consumed for its high protein content. It provides nutrient-dense food opportunities for human consumption. Iron deficiency chlorosis (IDC) manifests as yellowing of the leaves and reduced plant growth, resulting in reduced yield potential. Use of IDC tolerant cowpea cultivars is an efficient method to address this problem. The objectives of this study were to conduct a population structure analysis, to carry out an association mapping study, and to identify SNP markers associated with IDC tolerance in cowpea. A total of 353 cowpea accessions were evaluated for tolerance/susceptibly to low soluble iron conditions on higher pH soils. A total of 1006 SNP markers postulated from genotyping-by-sequencing were used after filtering for population structure and association analysis studies. Results revealed that: (1) a substantial variability in degree of tolerance to low soluble iron conditions was found among the cowpea accessions; (2) delta K peak was identified at K equal to 2, indicating two subpopulations within the cowpea accessions tested for adaptation to IDC, a second delta peak corresponding to K equal to 3 was also found; and (3) nine SNP markers, C35081162_3130, Scaffold16136_2033, Scaffold1764_4741, Scaffold18262_4480, Scaffold30165_15499, Scaffold47194_5530, Scaffold73235_6677, Scaffold77932_9959, and Scaffold86559_7193, were significantly associated with IDC tolerance in cowpea. These results can be used as tools to select cowpea genotypes tolerant to IDC under low soluble iron conditions.     

NaCl及生物降解活性剂对曝气灌溉水氧传输特性的影响

曝气灌溉可有效调节植物根区环境、改善土壤通气性。微咸水中NaCl的存在及活性剂添加对提高曝气灌溉的氧传质效率,实现节能高效的灌溉有重要作用。为研究NaCl介质及生物降解活性剂对纯氧曝气灌溉水氧传输特性的影响,该文采用变压分离制氧技术-氧气扩散系统-空气注射技术耦合系统,分析NaCl介质(未添加和添加)及生物降解活性剂BS1000(醇烷氧基化物质量浓度0、1、2、4 mg/L)2个因素对氧总传质系数、溶氧饱和度、流量均匀系数和溶氧均匀系数的影响。结果表明:BS1000的添加促进氧传质过程的发生,提高了曝气水中的溶氧饱和度;随着BS1000浓度增加,氧总传质系数逐渐增加,而溶氧饱和度呈现下降的趋势;BS1000质量浓度在2 mg/L及以上时,NaCl介质对氧总传质系数的增幅显著;NaCl介质对曝气水中的溶氧饱和度起到抑制作用。各组合条件下,曝气滴灌中流量均匀系数均在95%以上,溶氧均匀系数均在97%以上。添加活性剂BS1000可使氧总传质系数平均提高18.85%以上(P0.05)。无论添加NaCl与否,添加1 mg/L BS1000的溶氧饱和度均最大,故1 mg/L BS1000是适宜的活性剂添加浓度。     

Resistance to Xanthomonas perforans race T4 causing bacterial spot in tomato breeding lines

Tomato (Solanum lycopersicum) is the second most important vegetable crop in the world. Bacterial spot (BS) of tomato, caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri, results in severe loss in yield and quality due to defoliation and formation of lesions on fruits, respectively. Currently management practices do not offer effective control under conditions of high disease pressure. Thus, developing BS resistance is a critical priority for tomato growers in order to minimize crop losses. Sixty‐three advanced tomato breeding lines, heirlooms and wild tomato lines with diverse genetic backgrounds were screened under greenhouse and field conditions for BS resistance using X. perforans race T4, which was found to be a prevalent race in North Carolina. Race T4 isolate 9 was used to inoculate the plants by spraying, and disease severity was measured using the Horsfall–Barratt scale. Tomato lines 74L‐1W(2008), NC2CELBR, 081‐12‐1X‐gsms, NC22L‐1 (2008) and 52LB‐1 showed resistance to BS in the field and/or greenhouse trials. These lines were derived from S. pimpinellifolium L3707. Screening L3707 followed by development of a mapping population and mapping resistance genes might be useful for breeding resistance against BS in future breeding programmes.     

Do socio-psychological factors matter in agroforestry planning? Lessons from smallholder traditional agroforestry systems

Most of the well planned rural development forestry programs of the 1970s, and agroforestry in particular, were either not adopted by the intended beneficiaries or failed to meet the needs and aspirations of the rural people, particularly in the developing countries. The reasons for non-adoption in some cases appear to be technical, bio-physical, social and economic (termed as rational reasons by the planners), but in other situations the reasons are not so easily recognisable and comprehended (termed irrational reasons). These irrational reasons are the perceptions and attitude of the farmer towards farm practices, and their role in agroforestry planning has remained almost completely neglected. The present study is based on a household survey of the farmers in traditional agroforestry systems of Western Himalaya and investigates the importance of perceptional and attitudinal aspects of the farmers with regard to agroforestry adoption and extension. In the present study, farmers’ perceptions of restrictions on felling of trees from their own land and attitudes towards agroforestry were the most important sociopsychological factors which influenced tree growing. This study implies a need to take into account the socio-psychological factors of the farmers for planning socially acceptable agroforestry programs. The importance of study of various de jure rules and regulations controlling the use of on-farm tree resources and related exemptions and their association with farmers’ perceptions and tree growing is highlighted to develop policies to encourage tree growing in agroforestry.     

Effect of botanical extracts on the biological activity of granulosis virus against <Emphasis Type="Italic">Pieris brassicae</Emphasis>

A granulosis virus strain infecting Pieris brassicae (PbGV) was isolated from the dry temperate region of northwestern Himalayas as a potential microbial agent for its management. The effect of different botanicals (having insecticidal action against P. brassicae) on the bioefficacy of PbGV was evaluated under laboratory conditions using leaf disc bioassays on cabbage for improving the insecticidal performance of the PbGV. The synergistic action of different botanical extracts was evident in terms of reduction in LC₅₀ values against different botanical extracts. Among different extracts, petroleum-ether extract of neem seed kernel (NSK) when combined with PbGV resulted in maximum reduction of LC₅₀ value (4.39 × 10² occlusion bodies [OBs] ml⁻¹) followed by methanolic extract (7.38 × 10² OBs ml⁻¹) and aqueous extract (9.36 × 10³ OBs ml⁻¹) as compared with PbGV alone (1.85 × 10⁴ OBs ml⁻¹) for 2nd instar larvae of the test insect. These trends were found analogous in cases of 3rd and 4th instars of P. brassicae with different solvent extracts of NSK. The other botanicals evaluated, viz., Eupatorium and Artemesia, also resulted in reduction of LC₅₀ values for 2nd, 3rd and 4th instars as compared with PbGV alone when different extracts were combined with virus for bioassays. The studies suggest that the PbGV in combination with botanical pesticides could be more useful as a bio-pesticide against cabbage butterfly (P. brassicae) in IPM programs.     

Intergeneric hybrid of two rare and endangered orchids, <Emphasis Type="Italic">Renanthera imschootiana</Emphasis> Rolfe and <Emphasis Type="Italic">Vanda coerulea</Emphasis> Griff. ex L. (Orchidaceae): Synthesis and characterization

Renanthera imschootiana and Vanda coerulea are two rare and endangered orchid species featuring in IUCN Red List of Threatened Plants as well as in Red Data Book of Indian Plants, and are renowned for their unique ornamental traits. Renanthera imschootiana and V. coerulea have different flowering periods and by taking opportunity of off-season flowering of V. coerulea which happened during the flowering season of R. imschootiana, the hybridization was effected by hand-pollination. Viable pollinia were present in the off-season flowers of V. coerulea and one out of four cross was successful when R. imschootiana was taken as female parent. Reciprocal cross was unsuccessful. The resulting immature hybrid embryos were germinated in vitro on Vacin and Went medium supplemented with 15% v/v coconut water. Best seedling growth was observed on half-strength Murashige and Skoog medium devoid of any plant growth regulators while the transplanted seedlings grew best on brick chips:charcoal pieces (2:1) potting mix in community earthen trays. First flowering of the hybrid seedlings happened four years ten months after transfer to ex vitro environment. RAPD markers generated by the decamer primer OPA1 convincingly confirmed the hybridity. Registration of the hybrid was made with the Royal Horticultural Society with the grex Renantanda Kebisana Shija.