Variations in infectivity of indigenous rhizobial isolates of some soils in the rainforest zone of Nigeria

Nodule formation in legumes is a process that starts with root infection by rhizobia. The present study assessed the population and infectivity of the indigenous rhizobial strains in rainforest soils of Nigeria. Soils were collected from three sites – Idi-Ayunre, Orile-Ilugun (OI) and the University of Ibadan Teaching and Research Farm (UITRF) – and analysed for physico-chemical properties and rhizobial population. Soybean varieties TGx1448-2E and TGx1456-2E and a cowpea variety IT89KD-288 were planted as trap crops on each of the soils, and rhizobia were isolated from their nodules. Infectivity assay was conducted using eight varieties of soybean and a cowpea variety. Most probable number estimate of the rhizobial population showed that the UITRF had significantly higher rhizobial population than the other two locations. OI and the UITRF soils planted with TGx1448-2E had significantly higher nodules and number of strains than other treatments. Among the 70 slow-grower strains isolated, only nine were infective. Three of the nine strains – IDC8, TRC2 and OISa-6e – nodulated at least seven of the eight soybean varieties used for infectivity test. Indigenous rhizobial infectivity of the studied locations was low, and cultivation of grain legume may require rhizobial inoculation for high productivity.     

Water use efficiency and uptake patterns in a runoff agroforestry system in an arid environment

Water is the most limiting factor for plant production in arid to semiarid regions. In order to overcome this limitation surface runoff water can be used to supplement seasonal rainfall. During 1996 we conducted a runoff irrigated agroforestry field trial in the Turkana district of Northern Kenya. The effects of two different Acacia saligna (Labill.) H. Wendl. tree planting densities (2500 and 833 trees per ha), tree pruning (no pruning vs. pruning) and annual intercrops (no intercrop vs. intercrop: Sorghum bicolor (L.) Moench during the first season and Vigna unguiculata (L.) Walp. during the second season) on water use were investigated. The annual crops were also grown as monocrops. Water consumption ranged from 585 to 840 mm during the first season (only treatments including trees). During the second season, which was shorter and the plants relied solely on stored water in the soil profile, water consumption was less than half of that during the first season. Highest water consumptions were found for non-pruned trees at high density and the lowest were found for the annual crops grown as monocrops. Tree pruning decreased water uptake compared to non-pruned trees but soil moisture depletion pattern showed complementarity in water uptake between pruned trees and annual intercrops. The highest values of water use efficiency for an individual treatment were achieved when the pruned trees at high density were intercropped with sorghum (1.59 kg m^–3) and cowpea (1.21 kg m^–3). Intercropping and high tree density increased water use efficiency in our runoff agroforestry trial. We ascribe the observed improvement in water use efficiency to the reduction of unproductive water loss from the bare soil.This revised version was published online in November 2005 with corrections to the Cover Date.     

Genetic analysis of Fusarium wilt resistance in cowpea (Vigna unguiculata Walp.)

This study investigated the inheritance of resistance to Fusarium oxysporum f.sp. tracheiphilum (Fot) in cowpea lines. Resistant and susceptible cowpea lines were crossed to develop F₁, F₂ and backcross populations. Reaction to Fot was evaluated in 2015 and 2016 using seed soak and modified root‐dip inoculation methods. The expression of resistance reaction in the F₁ and segregation in F₂ generations indicated the role of dominant gene controlling Fot in cowpea. These results were further supported by the result of backcross (BC₁P₁F₁ and BC₁P₂F₁) progeny tests. The backcross of F₁ with the resistant parent produced progeny that were uniformly resistant, whereas backcross of F₁ with the susceptible parent produced progeny that segregated into 1:1 ratio. The F₂ segregation ratio in the reciprocal cross showed no evidence of maternal effect in the inheritance of the resistance. Allelism test suggests that the gene for resistance in TVu 134 was the same in TVu 410 and TVu 109‐1. We also identified an SSR marker, C13‐16, that cosegregated with the gene conferring resistance to Fot in cowpea.     

水肥耦合效应对设施豇豆生理特性的影响

为了探究设施豇豆对不同水肥耦合效应的响应,在滴灌施肥条件下试验研究了水肥耦合对温室豇豆生长、生理、产量和品质的影响,从而制定出高产、优质、高效的滴灌施肥制度.试验采用二因素三水平完全组合设计3个灌水水平、3个施肥水平,共9个处理,分析了水肥耦合对豇豆光合特性、品质及水分利用效率的影响.结果表明:滴灌施肥对豇豆株高和茎粗的影响具有统计学意义,适宜水肥配比有利于植株生长,高水高肥则引起“徒长”,进而影响后期产量与品质的形成;随着生育期的推进,净光合速率、气孔导度及蒸腾速率都呈双峰曲线型变化趋势:苗期温度低,光合作用较弱,增加水肥有利于光合指标的提高,伸蔓期光合强度增强,中水高肥处理效果最佳但与中水中肥之间的差异不具有统计学意义;结荚期豇豆光合能力达到最大,并随着水肥梯度增大而先增后减,趋势变化平缓,水肥需求量最大;豇豆产量与水分利用率均随着灌水施肥定额增加而先增后减,中水中肥处理的产量最高,临界值为28 598 kg/hm²,水分利用率高达95.33 kg/m³,并且水分利用率对水分的敏感度高于肥料,水肥交互作用对其影响不具有统计学意义;综合品质指标分析,中水中肥处理各指标效果表现最好,并且能够控制硝酸盐含量增加,维生素C、可溶性糖及可溶性蛋白的质量比分别达到285.3 mg/kg,90.48 g/kg,52.82 mg/g.     

秸秆腐解物对豇豆连作土壤性质及幼苗生理指标的影响

为探究不同秸秆腐解物对豇豆连作土壤微生态环境和豇豆幼苗相关生理指标的影响,选用豇豆为试验材料,共设置芥菜秸秆腐解(T1)、大蒜秸秆腐解(T2)、对照处理(不加任何植株粉碎物的豇豆连作土,CK)3个处理,测定在不同处理下,豇豆连作地土壤微生物数量、土壤酶活性、土壤pH值和电导率,以及豇豆生长指标、叶绿素含量和抗氧化酶活性。结果表明,与CK相比,T2和T1处理均能显著提高土壤细菌数量,分别增加了50.02%和111.71%,放线菌分别显著增加了46.22%和17.53%,真菌分别显著降低了45.08%和33.80%。T2和T1处理均能提高土壤酶活性,其中T1处理的土壤脲酶、多酚氧化酶和蔗糖酶活性均为最高,与CK相比分别显著增加了10.74%、93.02%和283.83%;而T2处理的酸性磷酸酶活性最高,增幅为175.80%。此外,T2和T1处理均能显著提高豇豆连作土壤pH值,降低土壤电导率。种植豇豆后,T1处理能显著提高豇豆幼苗株高、茎粗、鲜重、干重和壮苗指数等指标,分别较CK增加了34.73%、9.33%、87.11%、100%和108.77%;但T2处理下豇豆的各生长指标与CK相比无显著性差异。T2和T1处理均能显著提高豇豆叶片叶绿素含量,显著降低丙二醛(MDA)含量,其中T1处理能提高豇豆幼苗过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性,与CK相比分别显著增加了16.32%、19.21%和10.92%。综上,秸秆腐解物可为土壤生物提供不同的碳源和能源,维持土壤微生物群落多样性,改善土壤理化性质,从而促进豇豆根系吸收更多的养分,进而提高豇豆幼苗叶片叶绿素含量和抗氧化能力,有利于豇豆幼苗生长发育,达到缓解豇豆连作障碍的目的。本研究结果为实现豇豆生产的可持续性发展提供了理论依据。     

一种新的豇豆根腐病病原菌鉴定及室内药剂筛选

本文对四川成都发生的豇豆根腐病病原菌进行鉴定,为豇豆根腐病的药剂防治提供依据。采集了成都市豇豆种植区豇豆根腐病病株,经常规组织分离并纯化获得116株分离菌株,对分离菌株进行致病性测定、形态学鉴定及rDNA-ITS序列分析。结果表明,分离到的镰孢菌中有10株为Fusarium commune,分离频率为8.62%。对该10株菌进行致病性测定,均为致病菌株;其中MW4-11菌株致病性最强。该致病菌株的最适生长温度为25~30℃,菌丝致死温度为70℃。选用7种杀菌剂通过平皿培养法对MW4-11菌株进行室内毒力测定。结果表明,75%肟菌·戊唑醇水分散粒剂对该致病菌株的毒性最强,EC50为0.030μg/mL。     

超高效液相色谱-串联质谱法测定豇豆中8种农药残留

本文建立了超高效液相色谱-串联质谱法(UPLC-MS/MS)同时测定豇豆中啶虫脒、阿维菌素、甲氨基阿维菌素苯甲酸盐、氟啶虫胺腈、灭蝇胺、苯醚甲环唑、吡唑醚菌酯和烯酰吗啉残留量的方法。样品经乙腈提取,采用ACQUITY_UPLCTMBEH C18色谱柱分离,应用UPLC-MS/MS正离子扫描进行定性定量分析。结果表明,在0.01~1μg/mL范围内,8种农药色谱峰面积与浓度均呈线性相关;3个添加水平下,回收率均在90%以上;8种农药在豇豆中的检出限为0.08~1.81μg/kg,定量限为0.024~0.603μg/kg。在实际豇豆样品检测中检测到5种农药残留,本方法灵敏度高、速度快,可为检测豇豆中8种农药残留量提供参考。     

豇豆抗锈病性苗期鉴定技术研究

根据不同的接种方法、接种物浓度、保湿时间和温度对豇豆锈病苗期抗病性表现的影响,筛选出一套方便、可行的苗期抗病性鉴定技术：即在２０￣３０℃温度下,用每视野含３０个孢子（１０×６倍）的夏孢子悬浮液于１￣２处复叶的喷雾接种,保湿１８￣２４ｈ,接种后１０￣１４ｄ调查２１个供试品种的病指指数,结果表明品种间抗病性差异显著,其中,益农红仁特长豆角表现免疫,金山长豆和成都紫荚白露表现为高抗。     

不同豇豆品种资源的营养品质分析

以26个豇豆品种为材料,对其可溶性固形物、还原糖、蛋白质、粗纤维和维生素C含量进行测定和评价。结果表明:5个营养性状在26个品种间均存在显著差异,其中,还原糖与可溶性固形物含量在0.01水平上极显著相关,蛋白质与还原糖、粗纤维和维生素C含量在0.05水平上显著相关,而粗纤维和可溶性固形物、维生素C含量呈负相关关系,其他两两营养指标含量均为正相关关系,相关性不显著。通过隶属函数分析可知,26个豇豆品种中,综合营养品质比较好(X0.5)的品种有11个。其中,营养品质最佳(X0.6)的品种有6个,分别是黑白珠豆、APDRE豇豆、白籽油白、穗青豇豆、褐籽油青和黑籽珠豆。在实际生产应用中,可以上述品种资源为亲本进行优质杂交选育新品种。     

Selection of cowpea genotypes based on grain mineral and total protein content

Grain legumes, including cowpea, are the cheapest sources of minerals and protein to enhance human nutrition. Cultivar development and deployment of cowpea with increased grain mineral content and protein composition rely on selection of genetically unique and complementary breeding lines. The objective of this study was to assess the grain minerals and protein composition of diverse cowpea collections of eastern, southern and western Africa to select promising parents to develop a breeding population. Twenty-two genetically diverse cowpea genotypes were field evaluated using a randomised complete block design with three replications in two locations in South Africa. The dried grain mineral contents were determined using an Atomic Absorption Spectrophotometre, while the protein content was determined by the combustion method. Analyses of variance showed significant (P?<?0.05) effects of genotypes, locations and their interactions. The test genotypes showed considerable variation for the following nine mineral contents: calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), and zinc (Zn) varying from 0.07 to 0.12?mg?kg^?1; 4.46 to 7.81?mg?kg^?1; 0.06 to 0.11?g; 11.82 to 14.45?g; 1.86 to 2.27?g; 9.24 to 13.30?mg?kg^?1; 0.26 to 0.80?g; 4.63 to 5.92?g and 0.03.00 to 0.05?g, respectively. Further, the total protein content varied from 23.16 to 28.13%. Significant correlations were detected among some mineral elements and total protein content, suggesting the possibility of simultaneous selection for these traits. The principal component analysis (PCA) identified four principal components (PCs) contributing to 70.93% of the total explained variation amongst genotypes. Overall the following genotypes with desirable grain mineral and protein attributes were selected: IT90K-59 (Ca), 98K-5301 (Ca and protein), ITOOK-1060 (Cu), ITOOK-1217 and IT845-2246 (Fe), Bensogla (K, Na, and P), TVU11424 and ITOOK-1217 (Mg), CH14 (Mn and Na), TVU12637 (Mn) and Glenda and Vuli (Zn). The selected cowpea genotypes are useful genetic resources for population and cultivar development for grain nutrients composition.