Genetic variation within and among species of genus Arachis, section Rhizomatosae

The genus Arachis is endemic to South America and comprises 80 species, 69 of which have already been described and eleven not yet published. The genus includes the cultivated peanut (A. hypogaea) and several forage species, the most important ones being A. glabrata and A. pintoi. Accessions of section Rhizomatosae, including three tetraploid species 2n = 4x = 40 (A. glabrata, A. pseudovillosa and A. nitida nom. nud.) and one diploid species 2n = 2x = 20 (A. burkartii), were evaluated using RAPD markers to assay genetic variability within and among species. The ten random primers used yielded a total of 113 polymorphic bands. The data were scored as the presence or absence of each band in each sample. A distance matrix and dendrogram were obtained using Link's coefficient and the neighbor-joining method. Most accessions analyzed grouped into two major clusters: the first comprised most accessions of A. glabrata and accessions of A. nitida, and the second cluster comprised accessions of A. burkartii. Arachis pseudovillosa and a few accessions of A. glabrata and A. nitida were placed between these major clusters. The diploid and tetraploid species were grouped quite separately, suggesting that the tetraploids did not originate from the diploid species analyzed.     

Peanut variety response to postemergence applications of carfentrazone-ethyl and pyraflufen-ethyl

Field experiments were conducted in the south Texas and Texas High Plains area in 2005 and 2006 to evaluate peanut variety tolerance to carfentrazone-ethyl and pyraflufen-ethyl. Lactofen was used as the standard. Carfentrazone-ethyl at 0.03 and 0.04 kg ai/ha, pyraflufen-ethyl at 0.003 and 0.004 kg ai/ha, and lactofen at 0.22 kg ai/ha were applied 35 days after planting (DAP) in south Texas and 51–56 DAP in the High Plains area in weed-free plots. Peanut cultivars selected for evaluation were those normally used in each area. In south Texas, Tamrun 96, Tamrun OL 01, and Tamrun OL 02 were evaluated while in the High Plains area, Flavor Runner 458, GP-1, and Tamrun OL 02 were evaluated. No peanut cultivar by herbicide interaction was observed in south Texas but an interaction did occur in the High Plains. In south Texas, peanut stunting was 10% or less with both herbicides and rates. In 2005, carfentrazone-ethyl at 0.04 kg/ha resulted in a yield reduction when compared with the untreated check while in 2006 both rates of carfentrazone-ethyl and the high rate of pyraflufen-ethyl reduced yield compared to the untreated check. No grade differences were noted among herbicide treatments. In the High Plains area, the high dose of both carfentrazone-ethyl and pyraflufen-ethyl caused the greatest peanut injury (at least 25%) compared with lactofen (6% or less). In 2005, the high dose of pyraflufen-ethyl and lactofen reduced yield compared with the untreated check while in 2006 both carfentrazone-ethyl and pyraflufen-ethyl reduced yield compared with the untreated check.     

Differential Growth, Nodulation and Nitrogen Fixation Efficiency of Groundnut Cultivars Inoculated with Different Rhizobium Strains

Growth, nodulation and nitrogen (N) fixation efficiency of Banki (Local) and ICGS-44 (exotic) varieties of groundnut was significantly ( P < 0.05) improved by their inoculation either with NC-92 or Rudy Patric (R.P.) strains of rhizobium. Nodules did not form without inoculation in plants growing in sterilized sand. Inoculation with R.P. strain of rhizobium resulted in greater shoot growth, N content in shoot and number and weight of nodules in groundnut varieties. The R.P. inoculant increased agronomic efficiency by 112.5 % in Banki and 100 % in ICGS-44 variety of groundnut. Improvement in N fixation efficiency by inoculation with R.P. inoculant was 334 and 286% in Banki and ICGS-44 variety, respectively. However, Physiological efficiency was maximum in Banki variety when inoculated with NC-92 strain of rhizobium.     

Macromanagement of deficit-irrigated peanut with sprinkler irrigation

Precision irrigation management and scheduling, as well as developing site- and cultivar-specific crop coefficient (K_c), and yield response factor to water deficit (ky) are very important parameters for efficient use of limited water resources. This study investigated the effect of deficit irrigation, applied at different growth stages of peanut with sprinkler irrigation in sandy soil, on field peanut evapotranspiration (ETc), yield and yield components, and water use efficiencies (IWUE and WUE). Also, yield response factor to water deficit (ky), and site- and cultivar-specific K_c were developed. Four treatments were imposed to deficit irrigation during late vegetative and early flowering, late flowering and early pegging, pegging, and pod formation growth stages of peanut, and compared with full irrigation in the course of the season (control). A soil water balance equation was used to estimate crop evapotranspiration (ETc). The results revealed that maximum seasonal ETc was 488 mm recorded with full irrigation treatment. The maximum value of K_c (0.96) occurred at the fifth week after sowing, this value was less than the generic values listed in FAO-33 and -56 (1.03 and 1.15), respectively. Dry kernels yield among treatments differed by 41.4%. Deficit irrigation significantly affected yields, where kernels yield decreased by 28, 39, 36, and 41% in deficit-irrigated late vegetative and early flowering, late flowering and early pegging, pegging, and pod formation growth stages, respectively, compared with full irrigation treatment. Peanut yields increased linearly with seasonal ETc (R² = 0.94) and ETc/ETp (R² = 0.92) (ETp = ETc with no water stress). The yield response factor (ky), which indicates the relative reduction in yield to relative reduction in ETc, averaged 2.9, was higher than the 0.7 value reported by Doorenbos and Kassam [Doorenbos, J., Kassam, A.H., 1979. Yield response to water. FAO Irrigation and Drainage Paper 33, Rome, Italy, 193 pp.], the high ky value reflects the great sensitivity of peanut (cv. Giza 5) to water deficit. WUE values varied considerably with deficit irrigation treatments, averaging 6.1 and 4.5 kg ha⁻¹ mm⁻¹ (dry-mass basis) for pods and kernels, respectively. Differences in WUE between the driest and wettest treatment were 31.3 and 31.3% for pods and kernels, respectively. Deficit irrigation treatments, however, impacted IWUE much more than WUE. Differences in IWUE between the driest and wettest treatment were 33.9 and 33.9% for pods and kernels, respectively. The results revealed that better management of available soil water in the root zone in the course of the season, as well as daily and seasonal accurate estimation of ETc can be an effective way for best irrigation scheduling and water allocation, maximizing yield, and optimizing economic return.     

Identification of quantitative trait loci for protein content, oil content and oil quality for groundnut (Arachis hypogaea L.)

Very few efforts have been made to improve the nutritional quality of groundnut, as biochemical estimation of quality traits is laborious and uneconomic; hence, it is difficult to improve them through traditional breeding alone. Identification of molecular markers for quality traits will have a great impact in molecular breeding. An attempt was made to identify microsatellite or simple sequence repeat (SSR) markers for important nutritional traits (protein content, oil content and oil quality in terms of oleic acid, linoleic acid and oleic/linoleic acid ratio) in a mapping population consisting of 146 recombinant inbreed lines (RILs) of a cross TG26 × GPBD4. Phenotyping data analysis for quality traits showed significant variation in the population and environment, genotype × environment interaction and high heritability was observed for all the traits. Negative correlation between protein content and oil content, oleic acid and linoleic acid indicated their antagonistic nature. After screening >1000 SSR markers, a partial genetic linkage map comprising of 45 SSR loci on 8 linkage groups with an average inter-marker distance of 14.62 cM was developed. QTL analysis based on single marker analysis (SMA) and composite interval mapping identified some candidate SSR markers associated with major QTLs as well as several minor QTLs for the nutritional traits. Validation of these major QTLs using a wider genetic background may provide the markers for molecular breeding for improving groundnut for nutritional traits.     

中国花生青枯病抗性遗传改良研究进展

由Rastonia solanacearum E. F. Smith 引起的青枯病是中国及一些东南亚国家花生生产的重要限制因子。综述了近年来中国在花生青枯病的病原鉴定、抗病机理、抗性遗传规律、抗病种质鉴定发掘、抗病品种选育方面取得的研究进展及成就,并就存在的抗性品种产量较低、品质性状差、抗性鉴定费时费力、所利用抗源单一等问题进行了讨论,提出今后研究的重点在于采用多重杂交方式或借助现代生物技术引进疏枝亚种为抗源,同时要大力发掘利用野生花生抗性材料,完善分子标记辅助选择体系     

国槐DNA导入花生栽培品种引起性状变异的研究

以国槐为供体,花生栽培品种79266和辐8707为受体,采用花萼管注射法和柱头浸滴法将供体DNA导入受体。D1代变异率33．3％～63．4％,变异的性状包括单株果数、果形、果大小、内种皮颜色、株型、叶形、熟性、育性及产量性状。D2的大部分变异株能稳定遗传,不再分离,稳定株行占D2株行的75％～96％。试验表明,国槐DNA导入花生栽培品种,可以引起后代的变异,变异范围广,稳定快,是花生品种改良和创造新种质的有效方法途径。     

SSR analysis of cultivated groundnut (Arachis hypogaea L.) germplasm resistant to rust and late leaf spot diseases

Cultivated groundnut (Arachis hypogaea L.) is an agronomically and economically important oilseed crop grown extensively throughout the semi-arid tropics of Asia, Africa and Latin America. Rust (Puccinia arachidis) and late leaf spot (LLS, Phaseoisariopsis personata) are among the major diseases causing significant yield loss in groundnut. The development of varieties with high levels of resistance has been constrained by adaptation of disease isolates to resistance sources and incomplete resistance in resistant sources. Despite the wide range of morphological diversity observed in the cultivated groundnut gene pool, molecular marker analyses have thus far been unable to detect a parallel level of genetic diversity. However, the recent development of simple sequence repeat (SSR) markers presents new opportunities for molecular diversity analysis of cultivate groundnut. The current study was conducted to identify diverse disease resistant germplasm for the development of mapping populations and for their introduction into breeding programs. Twenty-three SSRs were screened across 22 groundnut genotypes with differing levels of resistance to rust and LLS. Overall, 135 alleles across 23 loci were observed in the 22 genotypes screened. Twelve of the 23 SSRs (52%) showed a high level of polymorphism, with PIC values ≥0.5. This is the first report detecting such high levels of genetic polymorphism in cultivated groundnut. Multi-dimensional scaling and cluster analyses revealed three well-separated groups of genotypes. Locus by locus AMOVA and Kruskal–Wallis one-way ANOVA identified candidate SSR loci that may be valuable for mapping rust and LLS resistance. The molecular diversity analysis presented here provides valuable information for groundnut breeders designing strategies for incorporating and pyramiding rust and late leaf spot resistances and for molecular biologists wishing to create recombinant inbred line populations to map these traits.E.S. Mace and D.T. Phong contributed equally to this work.     

Eupatorium Weed Species in Australia

Abstract

High temperature together with high rainfall favour infection and development of Erwinia stalk rot of maize (Erwinia chrysanthemi pv. zeae Victoria, Arboleda and Munoz). An attempt was made to correlate temperature, relative humidity, total rainfall and duration of bright sunshine with disease incidence in six maize cultivars during six crop seasons. Temperature and relative humidity did not fluctuate much during the flowering period at the time of disease appearance. Significant differences in total rainfall and duration of bright sunshine were observed. Longer duration of bright sunshine (8.2 h/day) along with moderate rainfall (81.7 mm) were recorded in high disease incidence years. Using these weather conditions a linear equation was derived to predict disease incidence.     

Weed control in groundnut (Arachis hypogaea L.) with polyethylene film mulching

Studies conducted during the winters of 1997 - 98 and 1998 - 99 (December - March) at the Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, India, revealed the usefulness of polyethylene film mulching in arresting weed growth and maximizing pod yield in groundnut. Among the various treatments, two (1) crop grown under polyethylene film mulching and (2) pre-planting incorporation of fluchloralin in the flat-bed system of sowing registered the lowest weed numbers at harvest (106.7 and 113.7/plot of 27 m 2 in 1997 - 98 and 1998 - 99 respectively), the lowest weed dry-matter production (51.2 and 54.5 g/plot of 27 m 2 ), maximum weed control efficiency (62.1 and 57.4%) and weed control index (83.0 and 81.1%), the highest number of matured pods/plant (17.6 and 18.0), 100 kernel weight (48.6 and 48.7 g), percentage shelling (72.6 and 72.8) and a dry pod yield of 2451 and 2468 kg ha -1 when compared with non-mulched plots. The net return and benefit:cost ratio was also highest with the same treatment in both the study periods.