Prediction and Mapping of the Impact of Winter Temperature on the Development of Phytophthora cinnamomi-Induced Cankers on Red and Pedunculate Oak in France

ABSTRACT Phytophthora cinnamomi is the causal agent of a perennial canker that develops on the lower bole on northern red oak and pedunculate oak. The disease has a limited range in Europe, being reported only in southwest France. This limited distribution is probably linked to the susceptibility of P. cinnamomi to frost. A model was developed in previous work to estimate the impact of temperatures of <0 degrees C on the winter survival of P. cinnamomi in trunk cortical tissues and on the subsequent development of cankers. In this article, we report the use of this model to simulate canker development in 503 locations across France during a 30-year period. The predicted canker extension decreased sharply when the median P. cinnamomi winter survival index decreased from 0.95 to 0.65, with cankers that poorly developed when the median survival index was lower than 0.5 to 0.6. The actual incidence of the disease in 192 stands located across southwest France was compared with that of the model outputs. Both presence of disease in stands and frequency of cankered trees in infected stands, but not canker size on infected trees, were strongly related to the median P. cinnamomi survival index. No disease was present in stands with median survival index lower than 0.65, and the frequency of cankered trees in infected stands remained very low in stands with a median survival index between 0.65 and 0.70. Aspect was an additional factor explaining disease incidence, while the effect of elevation was likely due to its effect on winter temperatures. Maps of winter suitability to P. cinnamomi-induced cankers on oaks in France are presented.     

Genome-Wide Association Study of Nitrogen Use Efficiency and Agronomic Traits in Upland Rice

Genome-wide association study (GWAS) was performed for 16 agronomic traits including nitrogen use efficiency (NUE) and yield-related components using a panel of 190 mainly japonica rice varieties and a set of 38 390 single nucleotide polymorphism (SNP) markers. This panel was evaluated under rainfed upland conditions in Madagascar in two consecutive cropping seasons with two contrasted nitrogen input levels. Using another set of five grain traits, we identified previously known genes (GW5, GS3, Awn1 and Glabrous1), thus validating the pertinence and accuracy of our datasets for GWAS. A total of 369 significant associations were detected between SNPs and agronomic traits, gathered into 46 distinct haplotype groups and 28 isolated markers. Few association signals were identified for the complex quantitative trait NUE, however, larger number of quantitative trait loci (QTLs) were detected for its component traits, with 10 and 2 association signals for nitrogen utilization efficiency and nitrogen uptake efficiency, respectively. Several detected association signals co-localized with genes involved in nitrogen transport or nitrogen remobilization within 100 kb. The present study thus confirmed the potential of GWAS to identify candidate genes and new loci associated with agronomic traits. However, because of the quantitative and complex nature of NUE-related traits, GWAS might have not captured a large number of QTLs with limited effects.     

The mechanism of genetic control for low soil nitrogen (N) tolerance in common beans (Phaseolus vulgaris L.)

The study was conducted to determine the mode of inheritance and the genetic mechanisms associated with bean nitrogen use efficiency under low soil nitrogen. Eight widely grown and well adapted low soil N tolerant lines (CAL143, CIM9314-36, and AFR708) and non-tolerant varieties (E5, E8, GLP-2, CAL96, and SCAM80-CM/15) were crossed in a half diallel mating design. The parents and their F₁ generations were evaluated under low soil N and moderate soil N conditions. Significant genetic differences were observed for basal root length, root dry weight, nodule numbers, leaf area and grain yield for both N conditions. Inheritance of the traits associated with better performance under low soil N was found to be under both additive fixable and non-fixable genetic effects. Genotypes that had well-developed basal root systems performed better than those with less developed basal roots. F₁ hybrids from crosses between low N tolerant and non-tolerant parents performed better under nitrogen stressed conditions compared with those between susceptible parents. Hybrids involving CAL143 as one of the parents showed high levels of tolerance to low soil nitrogen conditions. Among parents, CAL143 showed the best performance for basal root length, root dry weight, nodule numbers, leaf area, and grain yield. This parent had highly significant GCA effects for the traits under both N conditions, except basal root length which was significant at Kabete and non-significant leaf area at Thika. The results show that CAL143 would be a good parent to use in a low soil N bean breeding program.     

Effect of pre-partum feed supplementation on post-partum ovarian activity,milk production and calf growth of small holder dairy Cattle in Cameroon

Tropical Animal Health and Production - Seventy-two cows were selected for an on-farm study on the effect of feed supplementation before calving on milk production, ovarian activity and calf growth...     

The potential for Fusarium oxysporum f. sp. fragariae,cause of fusarium wilt of strawberry,to colonize organic matter in soil and persist through anaerobic soil disinfestation

Fusarium wilt of strawberry, caused by Fusarium oxysporum f. sp. fragariae, is a disease of primary concern for strawberry production in many countries. Crop rotation and anaerobic soil disinfestation (ASD) have gained recent interest for their potential to contribute to management of this disease. Both techniques involve incorporation of organic matter into soil, which may be utilized by strains of Fusarium that are competitive saprophytes. We show that F. oxysporum f. sp. fragariae can colonize strawberry, lettuce, raspberry, and broccoli leaf tissues, which are sources of organic matter generated during crop rotation. This pathogen increased in soil population density during ASD treatments that did not become anaerobic, possibly as a result of growth on the organic amendment. However, significant population decreases were observed after ASD treatment when at least 100,000 cumulative reduced mV hours occurred in a 14-day experiment. Post-ASD abundance of F. oxysporum f. sp. fragariae in soil was negatively correlated with cumulative reduced mV hours. The only treatment that consistently caused disinfestation was exposed to a maximum temperature of 22 °C, which indicates there is potential for developing effective ASD treatments in the cool climates where strawberries are grown. Awareness that F. oxysporum f. sp. fragariae can act as a competitive soil saprophyte should be further investigated for its potential to alter disease outcomes where organic amendments are applied.     

Effect of cow parity and synchronization method with PGF2α on conception rates of Bos indicus cows in Cameroon

The objective of this work was to evaluate the effect of two synchronization methods with prostaglandins F2α (PGF2α) on heifers and multiparous cows. Fourty-three Bos indicus cows (white and Red Fulani) were divided into four groups in a two-by-two factorial structure, parity x method of synchronization. The synchronization methods consisted of a two-dose regime which involved injection of animals on day 0 with PGF2α (Lutalyse) at 5 ml per cow intramuscularly. On day 11, the injection was repeated at the same dosage. On day 14 (72 h after the second injection), a fixed-time artificial insemination (AI) was done. On day 15 (96 h after the second injection), a second insemination was done. The one-and-a-half-dose regime consisted of an injection similar to the first treatment mentioned above on day 0. Thereafter, cows were observed for heat, and anyone showing heat was inseminated. A second dose was given on day 11 to all animals not having shown any heat. A fixed-time AI was done on days 14 and 15. Blood samples were collected on the day 0 of insemination for each cow while day 11 and day 21 after insemination. Progesterone was analysed by means of standard ELISA progesterone kits to determine its profiles after insemination. Results show no evidence of the effect of treatments on conception rates (P?>?0.05). Similarly, heifers and multiparous cows had similar conception rates (P?>?0.05). Between 3 weeks and 3 months of pregnancy, there was a loss of embryos of 28 % in heifers and 20 % in multiparous cows, but the difference between the two groups was not significant (P?>?0.05). It recommended that farmers do not synchronize animals with poor body condition score (BCS). They should also monitor weight gains of heifers, remove them from the herd when they have been mixed with young growing bulls and put them in a breeding herd. The two-dose regime is better to be used in areas where the inseminator cannot easily be available.

     

Mode of inheritance of common bean (Phaseolus vulgaris L.) traits for tolerance to low soil phosphorus (P)

Low soil phosphorus (P) has been singled out as a major constraint leading to perpetually low bean (Phaseolus vulgaris L.) grain yield far below the expected yield potential. In developing countries beans are mainly produced by small-scale farmers who have little capacity to use inorganic fertilizers to replenish their soils. Yet bean production contributes significantly to their income and provides a cheap source of protein to rural and urban populations. The genetics of inheritance of the traits conferring low soil P tolerance is not well understood. The identification and understanding of the mode of inheritance of the traits for P-efficiency in bean will go along way in boosting bean yields through development of varieties adapted to low soil P. The objective of this study was to determine the inheritance of the traits conferring adaptation to low soil P, for the important large seeded red mottled bean market class. Three parents with known tolerance to low soil P were crossed with five adapted but non-tolerant genotypes in an 8 × 8 half diallel mating scheme. The resulting F₁ seeds were evaluated under medium and low soil P conditions at two locations. Both general combining ability (GCA) and specific combining ability (SCA) variances were highly significant (P ≤ 0.01) for all five characters studied except SCA variance for root dry weight at one location. The magnitude of GCA variance was up to twelve times higher than the SCA variance. The GCA:SCA ratio varied from 0.62 to 0.96 for the characters studied. The additive genetic variance was more important than the dominance variance for tolerance to low soil P.