A stability analysis of time to flowering as a screen for responsiveness to temperature and photoperiod in cowpea (Vigna unguiculata)

Summary Twenty-one genotypes of cowpea (Vigna unguiculata), comprising landraces and varieties, were grown in 22 photothermal environments in Nigeria and Niger, West Africa, and a stability analysis of days from sowing to flowering (f) was carried out. Cowpeas are rarely insensitive to photoperiod; they are typically quantitative shortday plants wherein f is delayed when photoperiod (P) is longer than the critical photoperiod (P _c ). Therefore, in order to quantify genotypic variation in temperature sensitivity, genotype f was regressed against the mean trial f in circumstances where P c (i.e. approximately 13 hd^-1) and mean temperature (T) was between 19° and 28° C. Correspondingly, in order to assess genotypic variation in photoperiod sensitivity, trials where T was near optimal (25°–28° C) but where P ranged from 10–14.5 hd^-1 were used. These stability analyses detected no significant differences (P>0.05) between genotypes 9n temperature sensitivity but revealed significant differences (P<0.001) in photoperiod sensitivity. Regression coefficients from the stability analysis were strongly correlated (r=0.94, 19df) with a photoperiod sensitivity constant, c, determined from a photothermal flowering model. A stability analysis of f from field trials can therefore identify and quantify genotypic variation in response to temperature and photoperiod in cowpea.Abbreviations f days from sowing to flowering - P mean photoperiod - P _c critical photoperiod - P _ce ceiling photoperiod - T mean temperature - T _b base temperature - T _o optimum temperature - SDP short-day plant     

On‐farm diagnosis and management of iron chlorosis in groundnut

Abstract

Iron (Fe) chlorosis is a major nutritional constraint to groundnut (Arachis hypogaea L.) productivity in many parts of the world. On‐farm research was conducted at a Fe‐chlorotic site to evaluate the performance of three genotypes (TMV‐2, ICGS‐11, and ICGV‐86031), three fertilizer practices [no fertilizer control, fanners practice (125: 200: 0 kg NPK ha^?1), recommended practice (20: 50: 30 kg NPK ha^?1)], and two Fe treatments (non‐sprayed control and foliar FeSO₄ sprays) for their effect on Fe‐chlorosis and haulm and pod yields. These treatments were tested in a strip‐split plot design with four replicates. Results revealed that TMV‐2 and ICGS‐11 were susceptible to Fe‐chlorosis and produced significantly smaller haulm and pod yield, whereas, ICGV‐8603 1 was tolerant to Fe‐chlorosis. Farmer's fertilizer practice had the highest incidence of Fe‐chlorosis. Extractable Fe and chlorophyll content in the fresh leaves were the best indices of Fe‐status and were significantly (P<0.01) correlated with visual chlorosis ratings. Foliar application of FeSO₄ (0.5 w/ v) was effective in correcting Fe‐chlorosis and increased pod yield by about 30 to 40% in susceptible genotypes. These results suggests that use of tolerant genotypes such as ICGV‐86031 or foliar application of FeSO₄ in susceptible genotypes such as TMV‐2 and ICGS‐11 in combination with recommended fertilizer levels is an effective management package for alleviating Fe‐chlorosis in groundnut.     

Inheritance of time to flowering in cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis> (L.) Walp.)

Time to flowering and maturity is an important adaptive feature in annual crops, including cowpeas (Vigna unguiculata (L.) Walp.). In West and Central Africa, photoperiod is the most important environmental variable affecting time to flowering in cowpea. The inheritance of time from sowing to flowering (f) in cowpeas was studied by crossing a photoperiod-sensitive genotype Kanannnado to a photoperiod-insensitive variety IT97D-941-1. Sufficient seed of F₁, F₂, F₃ and backcross populations were generated. The parental, F₁, F₂, F₃ and the backcross populations were screened for f under long natural days (mean daylength 13.4 h per day) in the field and the parents, F₁, F₂ and backcross populations under short day (10 h per day) conditions. The result of the screening showed that photoperiod in the field was long enough to delay flowering of photoperiod-sensitive genotypes. Photoperiod-sensitivity was found to be partially dominant to insensitivity. Frequency distribution of the trait in the various populations indicated quantitative inheritance. Additive (d) and additive × dominance (j) interactions were the most important gene actions conditioning time to flowering. A narrow sense heritability of 86% was estimated for this trait. This will result in 26 days gain in time to flowering with 5% selection intensity from the F₂ to F₃ generation. At least seven major gene pairs, with an average delay of 6 days each, were estimated to control time to flowering in this cross.     

Improving participatory varietal selection processes: participatory varietal selection and the role of informal seed diffusion mechanisms for upland rice in Ghana

This paper considers the process of Participatory Varietal Selection (PVS) and presents approaches and ideas based on PVS activities conducted on upland rice throughout Ghana between 1997 and 2003. In particular the role of informal seed systems in PVS is investigated and implications for PVS design are identified. PVS programmes were conducted in two main agroecological zones, Forest and Savannah, with 1,578 and 1,143 mm of annual rainfall, respectively, and between 40 and 100 varieties tested at each site. In the Savannah zone IR12979-24-1 was officially released and in the Forest zone IDSA 85 was widely accepted by farmers. Two surveys were conducted in an area of the Forest zone to study mechanisms of spread. Here small amounts (1–2 kg) of seed of selected varieties had been given to 94 farmers. In 2002, 37% of 2,289 farmers in communities surveyed had already grown a PVS variety and had obtained seed via informal mechanisms from other farmers, i.e. through gift, exchange or purchase. A modified approach for PVS is presented which enables important issues identified in the paper to be accommodated. These issues include: utilising existing seed spread mechanisms; facilitating formal release of acceptable varieties; assessing post-harvest traits, and; the need for PVS to be an ongoing and sustainable process.     

Inheritance of duration from sowing to first flowering in pigeonpea

Duration from sowing to flowering is the most important trait influencing adaptation in pigeon pea (Cajanus cajan), but the inheritance of this trait has not been elucidated clearly. Crosses were made between two early (60 to 70d) and one late (160 to 170d) flowering pigeonpea genotype and F₁, F₂ and BC₁ populations produced. These populations, comprising 60 to 100 parents, 30 F₁, 400F₂ and 40 to 50 BC₁ plants, were grown under natural (mean13.4 hd^-1) and artificially extended (to 15 hd^-1) daylength and duration from sowing to first flowering recorded. Genetic analysis of the segregation ratios, supported by Chi-square tests, indicated that the duration from sowing to flowering in each of the crosses was controlled by two genes assorting independently and with predominantly additive quantitative effects. The segregation patterns were most clearly defined in the 15 hd^-1 daylength. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development and application of an indirect competitive enzyme-linked immunoassay for aflatoxin m(1) in milk and milk-based confectionery

High-titer rabbit polyclonal antibodies to aflatoxin M(1) (AFM1) were produced by utilizing AFM1-bovine serum albumin (BSA) conjugate as an immunogen. An indirect competitive enzyme-linked immunosorbent assay was standardized for estimating AFM1 in milk and milk products. To avoid the influence of interfering substances present in the milk samples, it was necessary to prepare AFM1 standards in methanol extracts of certified reference material (CRM) not containing detectable AFM1 (< 0.05 ng/g). The reliability of the procedure was assessed by using CRM with AFM1 concentrations of < 0.5 and 0.76 ng/g. Also, assays of milk samples mixed with AFM1 ranging in concentration between 0.5 and 50 ng/L gave recoveries of > 93%. The relative cross-reactivity with aflatoxins (AF) and ochratoxin A, assessed as the amount of AFM1 necessary to cause 50% inhibition of binding, was 5% for AFB1 and much less for AFB2, AFG1, and AFG2; there was no reaction with ochratoxin A. AFM1 contamination was measured in retail milk and milk products collected from rural and periurban areas in Andhra Pradesh, India. Of 280 milk samples tested, 146 were found to contain < 0.5 ng/mL of AFM1; in 80 samples it varied from 0.6 to 15 ng/mL, in 42 samples from 16 to 30 ng/mL, and in 12 samples from 31 to 48 ng/mL. Most of the milk samples that contained high AFM1 concentrations were obtained from periurban locations. The results revealed a significant exposure of humans to AFM1 levels in India and thus highlight the need for awareness of risk among milk producers and consumers.     

Methodological approach for predicting and mapping the phenological adaptation of tropical maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) using multi-environment trials

Background

The phenological development of the maize crop from emergence through flowering to maturity, usually expressed as a rate (i.e. 1/duration), is largely controlled by temperature in the tropics. Maize plant phenological responses vary between varieties and quantifying these responses can help in predicting the timing and duration of critical periods for crop growth that affect the quality and quantity of seed. We used routine multi-environment trials data of diverse tropical maize varieties to: (1) fit 82 temperature dependent phenology models and select the best model for an individual variety, (2) develop a spatial framework that uses the phenology model to predict at landscape level the length of the vegetative and reproductive phases of diverse varieties of maize in different agro-ecologies. Multi-environment trial data of 22 maize varieties from 16 trials in Kenya, Ethiopia, and Sudan was analyzed and the Levenberg–Marquardt algorithm combined with statistical criteria was applied to determine the best temperature-dependent model.

Results

The Briere model, which is not often used in plant phenology, provided the best fit, with observed and predicted days to flowering showing good agreement. Linking the model with temperature and scaling out through mapping gave the duration from emergence to maturity of different maize varieties in areas where maize could potentially be grown.

Conclusion

The methodology and framework used in the study provides an opportunity to develop tools that enhance farmers’ ability to predict stages of maize development for efficient crop management decisions and assessment of climate change impacts. This methodology could contribute to increase maize production if used to identify varieties with desired maturity for a specific agro-ecology in in the targeted regions.

     

Polymorphism of the Melatonin Receptor Genes and its Relationship with Seasonal Reproduction in the Gulin Ma Goat Breed

Melatonin is thought to be the main molecule that transmits the signal of seasonal change to the neuroendocrine system in seasonal breeding species. Melatonin exerts its effects through specific melatonin receptors, MTNR1A and MTNR1B. In the present study, six native goat breeds in China and one introduced goat breed were analysed to investigate the relationship between the genetic polymorphism of receptor genes and seasonal reproduction. Sequencing results showed that there were five polymorphic mutations in the MTNR1A gene and two in the MTNR1B gene. In the MTNR1A gene, genotypes AA, AB and BB for 424C>T and genotypes CC, CD and DD for 589C>A were observed in these goat breeds. In all six native goat breeds, only genotype AA was detected. In the MTNR1B gene, genotypes EE, EF and FF for 1179G>A and genotypes GG, GH and HH for 1529A>G were detected. However, in Gulin Ma goats, the genotypes EE and HH were not found. Moreover, the base of G at position 1179 and A at position 1529 were linked (By Arlequin ver 3.1, Zoological Institute, Berne, Switzerland, http://cmpg.unibe.ch/software/arlequin3 ,D′ = 0.7496, r² = 0.4421, χ² = 489.8679, p = 0.000). Among these mutations, no amino acid change was found in MTNR1A, while both of the mutations in MTNR1B gene caused amino acid changes of R222H and S339G, respectively. The structural analysis showed that the R222H mutation occurred in the first amino acid residue of the third cytoplasmic loop, and the S339G mutation was located in the carboxyl terminus of the protein. In terms of seasonal breeding, all the genotypes we detected showed a similar kidding frequency distribution trend with a higher frequency in May–August than in January–April and in September–December. This suggests that the relationship between the polymorphisms in the MTNR1A and MTNR1B genes and seasonal breeding could not be established.