Influence of Soil Moisture and Fertilizer Potassium on the Vegetative Growth of Mungbean (Vigna radiata L. Wilczek) and Cowpea (Vigna unguiculata L. Walp)

Tropical food legumes are grown in a wide range of environments, and water stress is considered the principal environmental factor limiting growth and yield. Potassium fertilizer mitigates the impact of water stress in plants. However, the benefits of potassium in overcoming stress in tropical food legumes have not been investigated in comparative studies. The purpose of this study was to determine the benefits of potassium in overcoming water stress in mungbean and cowpea, two important tropical food legumes with different adaptabilities to soil moisture regimes. The experiment carried out under controlled conditions placed emphasis on vegetative growth and selected physiological parameters. The impact of potassium was different in the two legumes grown at optimal and suboptimal soil moisture. Potassium increased shoot growth of mungbean to a greater extent than in cowpea under suboptimal moisture conditions. The roots of cowpea showed a greater response to potassium fertilizer than in mungbean under suboptimal soil moisture. The plant water relations and photosynthetic rates of mungbean were improved to a greater extent by potassium under suboptimal soil moisture than those of cowpea. Although differences were observed in the responses of the vegetative growth of these species to moisture and potassium, in overall terms potassium promoted growth of both species when subject to suboptimal soil moisture. While field studies are required to validate the results, the application of potassium fertilizer can be considered a significant factor in overcoming soil moisture stress in these legumes commonly grown in tropical cropping systems.     

Impact of Different Weed Types on Growth and Yield of Mungbean (Vigna radiata L. Wilczek)

The influence of different weed types (grass, broadleaved and sedge species) on growth and yield parameters of mungbean ( Vigna radiata L. Wilczek) was evaluated under field conditions. The presence of all types of weeks had the most significant effect on growth and yields of mungbean. Broadleaved species alone had a greater adverse effect than grasses, and the influence of sedges was the lowest. The adverse effect of weeds was most prominent on vegetative growth. The influence on yield components reduced with time. However, the adverse impact of weeds on yields was similar to that on vegetative growth. A significant correlation between weed biomass and yield loss was observed. The study indicated the critical competitive period to be in the vegetative phase. Some possible implications for selective weeding are presented.     

Regulation of Leaf Senescence and Yield in Mungbean (Vigna radiata L. Wilczek)

Foliar application of benzyladenine at preanthesis stage retarded leaf senescence in mungbean. Chemical spray increased leaf chlorophyll, soluble protein, specific leaf weight, net photosynthetic rate and nitrate reductase activity. Number of pods, grain yield, harvest index and 100-seed weight were significantly improved by benzyladenine treatment. The possibility of higher pod-filling and thus, yield by chemical regulation of leaf senescence is evident in mungbean.     

Physiological Analysis of Yield Variation in Mungbean (Vigna radiata [Roxb.] Wilczek)

Two mungbean varieties, Guj-1 and PIMS-1 differing in their productivity potential, were examined to investigate their photosynthetic system at various stages of growth in relation to yield with two different dates of sowing. Vertical leaves were found to be beneficial. On the other hand, excessive leaf area during the later stages of growth may be detrimental to yield. Lower LAD at seedling stage and overall high NAR values may be reflected in higher grain yield. NAR declined as season progressed and this, in turn, may be related with increase in LAI. The grain yield was considerably more at the first date of sowing as compared to second date of sowing, the effect was being more pronounced in var. PIMS-1 . Various environmental factors recorded at two different dates of sowing and at various stages of growth indicated that these factors may have influenced the yield potential at two different dates of sowing.     

Effect of Shading on the Growth and Yield of Mungbean (Vigna radiata [L.] Wilczek)

Mungbean grown as intercrop suffers shading stress form companion crop at different growth stages. Grain filling stage, which appears to be very much sensitive to light conditions, needs special attention to deal with, in order to maximize the benefit from intercropping systems. Growth and yield response of mungbean to different shading conditions imposed at the onset of pod formation stage was evaluated. Shading nets were used to cut down the incident photosynthetic active rediation by 15 %, 45 % and 75 %. There was almost no difference between the control and 15 % shaded plants for all the parameters studied. Total dry weight was found to decrease with increase in shading intensity and this phenomenon continued till the maturity of the crop. The crop growth rate, relative growth rate and net assimilation rate decreased due to shading. Lower specific leaf weight and higher chlorophyll content were due to increased shading. Decreased photosynthetic active radiation caused significant reduction in pods per plant and thus there was a significant decrease in seed yield per plant. In order to avoid yield loss due to shading at grain filling stage, agronomic manipulation and selection of suitable genotypes are necessary.     

Effects of Cadmium on Carbon and Nitrogen Assimilation in Shoots of Mungbean [Vigna radiata (L.) Wilczek] Seedlings

Increased cadmium (Cd) uptake from contaminated soils damages plant metabolism. The purpose of this study was to determine Cd‐induced time‐related changes in some shoot growth and physiological attributes, and their interrelationships in Cd‐tolerant (NM‐98) and sensitive (NM‐28) mungbean varieties. Shoot Cd and leaf chlorosis increased with a concomitant reduction in shoot dry weight, leaf area, relative growth rate (RGR), net assimilation rate (NAR) and relative leaf expansion rate. Reduction in transpiration rate (E) and stomatal conductance (g_s) and increase in substomatal CO₂ level (C_i), indicated that Cd reduced net photosynthesis (P_n) by reducing CO₂ fixation by Rubisco, albeit these changes were less pronounced in NM‐98. A positive correlation of chlorosis with shoot Cd, and negative relationships of chlorosis and shoot Cd with P_n revealed that Cd damages the photosynthetic apparatus in mungbean. Time course decrease in in vivo nitrate reductase activity (NRA) and an increase in soluble nitrate in NM‐28 revealed that Cd markedly hampers nitrogen assimilation. Positive correlations of RGR and NAR with P_n and NRA and negative ones with chlorosis, shoot dry weight, shoot Cd and C_i in NM‐98 suggested that mungbean sensitivity to Cd is due to perturbed C and N assimilation.     

Alternate Selection Indices for Leaf Photosynthetic Rate in Greengram (Vigna radiata [L.] Wilczek) Cultivars

Significant differences were observed for leaf net photosynthetic rate, chlorophyll content, soluble protein content, nitrate reductase activity, stomatal frequency and specific leaf mass among ten greengram cultivars. Leaf net photosynthetic rate had significant positive correlation with soluble protein, nitrate reductase activity, stomatal frequency and specific leaf mass. Leaf net photosynthetic rate had no relationship with leaf chlorophyll content in greengram.     

Nitrogen and Carbofuran Effects on the Growth and Yield Performance of Mungbean (Vigna radiata [L.] Wilczek)

Studies were carried out both in the semi-controlled environment and in the field to evaluate the influence of nitrogen and carbofuran in the growth, dry matter partitioning and yield of mungbean. Both nitrogen and carbofuran increased leaf area, leaf N content, NAR, dry matter, most of the yield attributes, and grain yield. Dry matter accumulation during the reproductive phase was significantly influenced by nitrogen and carbofuran, and method of N application. Plants treated with nitrogen fertilizer and carbofuran produced higher amount of dry matter after flowering; but gave low harvest index values compared to control. The results suggest that mungbean yield can be substantially increased through efficient dry matter partitioning employing agronomic manipulations.     

Effect of Seed Size on Germination and Seedling Growth in Greengram (Vigna radiata L. Wilczek) and Blackgram (Vigna mungo L. Hepper) Cultivars

The effect of seed size on germination and seedling growth was assessed using cultivars of greengram and blackgram. Significant positive correlation was noticed between seed size and germination, seedling height, root length, primary leaf size and seedling weight. The possible advantages of choosing cultivars with heavier seeds for attaining better crop stand especially under rainfed situation are discussed.     

Effect of Water Stress on the Photosynthesis, Productivity and Water Status of Mung Bean (Vigna radiata L. Wilczek)

The effect of water stress and its subsequent recovery on the photosynthesis, productivity and water status, was examined in three mungbean varieties ( Vigna radiata L. Wilczek) i.e. PS 16, P 105 and Pusa Baisakhi. The variety P 105 was found relatively less susceptible to water stress compared to high susceptibility in Pusa Baisakhi and PS 16. The adverse effect of stress was comparatively higher at the post-flowering and pod development stages. It was observed that variety P 105 had inherently maintained higher water status by retaining higher water potential and water content under water stress condition, thereby effectively reducing the water loss. The higher transpiration rate in this variety regulates the flow of water within the plant. This type of regulation of water flow and maintenance of high water status in P 105 helped to resist the adverse effect of water stress on photosynthesis and productivity. Such adaptation mechanism was not observed in varieties PS 16 and Pusa Baisakhi. The recover) mechanism was, however, operated efficiently in susceptible varieties PS 16 and Pusa Baisakhi particularly for recouping the vegetative growth, but its effect could not be retained for reproductive characters, wherein also variety P 105 due to its efficient partitioning system yielded better than other cultivars.     

Inheritance of seed resistance to bruchids in cultivated mungbean (Vigna radiata, L. Wilczek)

Bruchid beetles or seed weevils are the most devastating stored pests of grain legumes causing considerable loss to mungbean (Vigna radiata (L.) Wilczek). Breeding for bruchid resistance is a major goal in mungbean improvement. Few sources of resistance in cultivated genepool were identified and characterized, however, there has been no study on the genetic control of the resistance. In this study, we investigated the inheritance of seed resistance to Callosobruchus chinensis (L.) and C. maculatus (F.) in two landrace mungbean accessions, V2709BG and V2802BG. The F₁, F₂ and BC generations were developed from crosses between the resistant and susceptible accessions and evaluated for resistance to the insects. It was found that resistance to bruchids in seeds is controlled by maternal plant genotype. All F₁ plants derived from both direct and reciprocal crosses exhibited resistance to the bruchids. Segregation pattern of reaction to the beetles in the F₂ and backcross populations showed that the resistance is controlled by a major gene, with resistance is dominant at varying degrees of expressivity. Although the presence of modifiers was also observed. The gene is likely the same locus in both V2709BG and V2802BG. The resistant gene is considered very useful in breeding for seed resistance to bruchids in mungbean.     

Inheritance of seed phytate in mungbean (Vigna radiata (L.) Wilczek)

Phytic acid (PA) is the main storage organic form of phosphorus (P) in seeds of cereals and legumes. It is a strong inhibitor against the absorption of nutrients in monogastric animals. The objective of this study was to determine the variation of total P (TP) in seeds of mungbean germplasm and investigate the inheritance of seed P compound and phytate contents. TP content in seeds of 250 accessions were found to range from 2.34 to 5.75 mg/g. The inheritance was studied in the F₂ population derived from a cross between 2 accessions with the lowest and highest PA contents, viz. V1658BBR and V1141BG. Broad-sense heritability estimates of TP, inorganic P (IP), and phytate P (PhyP) contents were 80.8, 78.6 and 80.7%, respectively. The 9:7 segregation ratio of F₂ population in this study indicated that high TP and PhyP were controlled by dominant alleles at 2 independent loci of major genes showing duplicated recessive epistasis.     

Genetic variability in flooding tolerance of mungbean (Vigna radiata L. Wilczek) genotypes

The study was an exploratory in nature conducted using a large number of mungbean (Vigna radiata L. Wilczek) genotypes of diverse growth habit and adaptive characters. Soil flooding induced changes in eleven morpho-physiological characters of one-week old seedlings of 530 mungbean genotypes was compared in the study. The first and second principal components (PC) of principal component analysis (PCA) results accounted for 58 and 14%, respectively of the total variations of mungbean genotypes. The variation for first PC was composed mainly of relative dry weight (DW) of shoot and leaf as well as total DW. The second PC distinguished the genotypes that produced larger root system. There were seven clusters distinguished in the cluster analysis. The genotypes in cluster 4 and 6 performed better in respect of relative total DW and relative root DW, respectively and hence having flooding tolerance. The genotypes in clusters 7 and 1 performed very poorly and those of under clusters 3, 2 and 5 were moderate to poor. D² analysis indicated that the clusters differed significantly from each other. Discriminant function analysis (DFA) reaffirmed that more than 90% of the genotypes were correctly assigned to clusters. Both PCA and DFA confirmed that the relative total DW followed by shoot and leaf DW as well as leaf area were the major discriminatory variables and the root : shoot ratio and root DW were the secondary important variables to distinguish genotypes into groups. In this study, multivariate analyses were used in identifying the mungbean genotypes of desirable traits for flooding tolerance.     

绿豆几个表型性状的遗传特性分析

种皮色泽和花青甙显色是绿豆(Vigna radiata)的重要性状,可在纯度鉴定、辅助选择育种等研究中发挥作用。本研究以绿豆核心种质种皮色泽、花青甙显色性状分析为基础,配制杂交组合,根据不同世代的表型调查,探讨绿豆种皮颜色、光泽和花青甙显色等性状的遗传特征。结果表明,绿种皮对黄种皮为单基因控制,绿色为显性;黑种皮对绿种皮为单基因控制,黑色为显性。绿豆种皮光泽不符合简单性状的遗传规律,且不同组合间后代的表型分布存在差异。绿豆种皮色与光泽间并无连锁关系。植株各部位的花青甙显色对不显色为显性,均符合简单单基因的分离规律。进一步分析表明,不同部位花青甙显色的相关性不一致,其中控制幼茎色基因与控制复叶基部花青甙显色基因紧密连锁在一起,或为一个基因,而控制龙骨瓣花青甙显色的基因与其他相关基因的遗传连锁程度最低。本文对绿豆种皮相关性状及植株花青甙显色性状的遗传分析将为这些性状的育种利用及深入研究奠定基础。     

Inheritance of photoperiod response in mungbean (Vigna radiata [L.] Wilczek)

Summary A dominant or partially dominant gene for sensitivity to photoperiod in mungbean strain PI 180311 was identified and labeled Ps. The gene was expressed when strain P1180311, or crosses involving PI 180311 were grown in 16- or 14-hour photoperiods but was not expressed when the populations were grown in a 12-hour photoperiod or in the field at Columbia, Missouri. Dominance × dominance epistatic effects were indicated as governing days to flower in absence of the obvious effect of the Ps gene. A gene A for purple hypocotyl was independent of the gene Ps.Contribution No. 7894 from the Missouri Agriculture Experiment Station.     

绿豆遗传连锁图谱的整合

利用绿豆及其近缘种的701对SSR引物,对现有绿豆遗传连锁图谱进行补充,结果在高感豆象绿豆栽培种Berken和高抗豆象绿豆野生种ACC41两亲本间筛选到多态性SSR引物104对。群体分析后,结合其他分子数据,使用作图软件Mapmaker/Exp 3.0b,获得一张含有179个遗传标记和12个连锁群,总长1831.8cM、平均图距10.2cM的新遗传连锁图谱,包括97个SSR标记,91个来自绿豆近缘种;RFLP标记76个;RAPD标记4个;STS标记2个。对32个绿豆、小豆共用SSR标记在遗传连锁图谱的分布分析发现,二个基因组间有一定程度的同源性,共用标记在连锁群上的排列顺序基本上一致,只有部分标记显示绿豆和小豆基因组在进化过程中发生了染色体重排;利用新图谱对ACC41的抗绿豆象主效基因重新定位,仍定位于I(9)连锁群,与其相邻分子标记的距离均小于8cM,其中与右翼SSR标记C220的距离约2.7cM。与原图谱比较,新定位的抗性基因与其相邻标记的连锁更加紧密。     

Genetics of the resistance to powdery mildew disease in mungbean (Vigna radiata (L.) Wilczek)

Powdery mildew disease caused by the fungus Erysiphe polygoni D.C. is an important disease of mungbean. Loss can be more serious if the disease attacks at seedling stage. In this paper, we report genetics of the resistance to powdery mildew disease in mungbean using a recombinant inbred line (RIL) population derived from a cross between the susceptible parent “KPS1” and the resistant parent “VC6468-11-1A”. Five hundred and ninety-two RILs were developed by random descending from 200 F₂ plants. The population was evaluated against the fungus in field and greenhouse conditions. The data were analyzed following a nested design for selfpollinating plants to determine genetic heritability of powdery mildew resistance. The severity of the infestation was measured by using disease index (DI) and area under disease progress curve (AUDPC). Both values showed continuous distribution in the RILs. Under field conditions, the narrow-sense heritability of DI and AUDPC were 0.67 and 0.48, respectively. While under greenhouse conditions, the values were 0.68 and 0.62, respectively. The results suggested that the resistance is quantitatively inherited with high heritability and predominantly additive gene action. To develop powdery mildew-resistant mungbean varieties, the plant breeder can select for resistant lines by using standard selection procedures for self-pollinating crops, viz. pedigree selection, bulk selection, early generation testing, and single-seed descent.     

Effects of photoperiod and temperature on flowering in mungbean (Vigna radiata (L.) Wilczek)

Summary Forty strains of mungbeans, including all of the entries in the 1st and 2nd International Mungbean Nurseries (IMN), were grown in plant growth chambers in photoperiods of 12, 13, 14, 15, and 16 hours and mean temperatures of 18, 23, and 28°C. Results show that (1) mungbean strains differ in their flowering response to photoperiod and to mean temperature; (2) increasing the photoperiod of reducing the mean temperature delayed flowering, the amount of delay varied with the strain: (3) variations in mean temperature may alter the effect of the photoperiod on flowering in particular strains. Twenty-five strains which flowered in all photoperiod-temperature treatments could be divided into four groups, each group being successively later in flowering. The remaining 15 strains could be divided into four groups, according to their failure to flower within 105 days in specific photoperiod-temperature treatments. Flowering response in the growth chamber is useful in explaining flowering response in the 2nd IMN at three locations varying from 14°N to 49°N latitude.Contribution No 7516 from the Missouri Agricultural Experiment Station.     

Response of Mung Bean (Vigna radiata (L.) R. Wilczek) to an Increasing Natural Temperature Gradient under Different Crop Management Systems

Increasing temperatures pose a significant threat to crop production in the tropics. A field experiment was conducted with mung bean at three locations in Sri Lanka representing an increasing temperature gradient (24.4–30.1 °C) during two consecutive seasons to (i) determine the response of mung bean to increasing temperature and (ii) test a selected set of crop management practices aimed at decreasing essential inputs such as water, synthetic pesticides and inorganic nitrogen fertilizer. The control treatment (T₁) consisted of standard crop management including irrigation, chemical crop protection and inorganic fertilizer application. Adaptation system 1 (T₂) included mulching with rice straw at 8 t ha^?1 with 30 % less irrigation and crop protection and nutrient management as in T₁. Adaptation system 2 (T₃) included crop protection using a pretested integrated pest management package with water and nutrient management as in T₂. In adaptation system 3 (T₄), 25 % of the crop's nitrogen requirement was given as organic manure (compost) at 0.8 t ha^?1 while 75 % was given as inorganic fertilizer with water management and crop protection as in T₃. Durations of both pre‐ and post‐flowering phases were reduced with increasing temperature. In the warmer (25.4–30.1 °C) yala season, seed yield (Y) of T₁ decreased with increasing temperature at 366 kg ha^?1 °C^?1. However, in maha season, Y did not show a significant relationship across the narrower temperature gradient from 24.4 to 25.8 °C. Pooling the data from both seasons showed a second‐order polynomial response with an optimum temperature of 26.5 °C. In addition to shortened durations, reduced crop growth rates and reduced pod numbers per plant were responsible for yield reductions at higher temperatures. In yala, yields of all adaptation systems at all locations were on par with yields of the respective controls. Furthermore, yala yields of T₂ and T₃ were less sensitive than T₁ to increasing temperatures (265 and 288 kg ha^?1 °C^?1). In maha, T₃ and T₄ had greater yields than the control at the relatively cooler site while having lower yields than the control at the warmer site. Maha yields of T₂ were on par with the control at both temperature regimes. While demonstrating the significant temperature sensitivity of mung bean yields, results of the present work showed that components of the tested adaptation systems could be promoted among smallholder farmers in Asia, especially in view of their long‐term environmental benefits and contributions to sustainable agriculture in a warmer and drier future climate.