Use of corn height to improve the relationship between active optical sensor readings and yield estimates

Early in-season loss of N continues to be a problem in corn (Zea mays L.). One method to improve N use efficiency is fertilizing based on in-season crop foliage sensors. The objective of this study was to evaluate two ground-based, active-optical (GBAO) sensors and explore the use of corn height with sensor readings for improving relationships with corn yield. Two GBAO sensors (GreenSeeker^® (GS), Trimble, Sunnydale, CA, USA; and Holland Crop Circle (CC) ACS 470 Sensor^®, Holland Scientific, Lincoln, NE, USA) were used within 30 established corn N-rate trials in North Dakota at the V6 and V12 growth stages in 2011 and 2012. Corn height was recorded manually at the date of sensor data collection. At the V6 growth stage, the GS relationship to yield and the INSEY (in-season estimate of yield) value was improved when the sensor reading was multiplied times corn height. At the V12 stage, using the GS, the INSEY relationship with yield was also generally increased when height was considered. The CC-based red/near-infrared INSEY relationship with yield was similar to the GS INSEY. The CC-based red edge/near infrared INSEY relationship was increased with height only at the first sensor date, but not with the second. The second CC-based sensor–INSEY relationship with yield was maximized using sensor reading only. Segregating the 30 site data set into sites with high clay surface textures and sites with medium texture improved all INSEY relationships compared to pooling all sites. Relationships between INSEY and corn yield at no-till sites were significant at the V12 stage in the wetter 2011 growing season, but not at the V6 stage either year, nor at the V12 stage in the very dry 2012 season. In the high clay and medium textured soils at the V6 stage, corn height improved the relationship between INSEY and yield often enough to suggest that incorporating corn height into an algorithm for yield prediction would strengthen yield prediction, and thus improve N rate decisions.     

Genotypic effects of sorghum accessions on fecundity of sorghum head bug,Calocoris angustatus Lethiery

Summary Sorghum head bug (Calocoris angustatus Leth.) (Hemiptera: Miridae) is an important pest of grain sorghum in India. We studied the fecundity of head bug females reared for one to three generations on head bug-resistant and head bug-susceptible genotypes during the 1988 and 1989 rainy and 1988–89 post-rainy seasons. Head bug population increase was lower for the first, second and/or third generation when the bugs were reared on IS 2761, IS 19955, IS 14334, IS 23748, IS 16357, IS 17610, and IS 21444 compared with the susceptible controls CSH 1, CSH 5, and CSH 9. These genotypes also suffered a low grain damage (damage rating (DR) 5) (except IS 2761) compared with the susceptible controls (DR>6). A marginal decrease in fecundity was observed when the bugs were reared on IS 2761, IS 14334, IS 16357, IS 20740 and IS 17610 and then transferred to the susceptible control, CSH 1. Sorghum genotypes having lower increase in bug population across generations, suffering low grain damage, and showing adverse effects on fecundity can be used in breeding for resistance to head bugs.     

Effect of long-term manuring and fertilizers on carbon pools,soil structure,and sustainability under different cropping systems in wet-temperate zone of northwest Himalayas

We investigated C management index (CMI; an indicator of sustainability of a management system and is based on total and labile C) and soil aggregation in medium-textured soils (silt loam and silty clay loam) under different cropping systems as follows: maize-wheat (M-W), rice-wheat (R-W), soybean-wheat (S-W), Guinea grass, and Setaria grass. Field experiments were 6–32 years long and were located in the wet-temperate zone of northwest Himalayas. The plant nutrients were applied through chemical fertilizers (urea, superphosphate, and muriate of potash) with or without organic materials (FYM, wheat straw, and Lantana spp.). The content of total C (C_T), labile C (C_L), CMI, mean weight diameter (MWD), and aggregate porosity varied significantly under different cropping systems. The range was 1.59 (R-W)–4.29% (Setaria) for C_T, 1.23 (R-W)–3.89 mg/kg (Guinea grass) for C_L, 52.09 (R-W)–129.77 (Guinea grass) for CMI, 0.90 (R-W)–5.09 (Guinea grass) for MWD, and 41.5 (R-W)–56.8% (S-W) for aggregate porosity. Aggregate porosity was highest (56.8%) under S-W, followed by grasses (50.1–51.2%), and M/R-W (41.5–50.0%). As per these data, (a) continuous use of N alone as urea lowered soil sustainability over control (no fertilizers); (b) use of NPK at recommended rates improved soil productivity over control; (c) the NPK + organic amendments further improved soil sustainability; and (d) the sustainability under different cropping systems followed the order: perennial grasses > soybean-wheat > maize-wheat > rice-wheat.     

Environmental factors influence the expression of resistance to sorghum midge, Stenodiplosis sorghicola

Host plant resistance is an effective means of controlling sorghum midge (Stenodiplosis sorghicola). We studied the influence of environmental factors on expression of resistance to sorghum midge in three midge-resistant and two midge-susceptible genotypes. Midge-resistant lines AF 28, ICSV 197, and TAM 2566 suffered 8.8 to 17.3% damage across seven so wings compared to 25.6%damage in ICSV 112, and 69.4% damage in CSH 5. Susceptibility of the midge-resistant lines (AF 28, ICSV 197, and TAM 2566) decreased with an increase in open pan evaporation, maximum and minimum temperatures, and solar radiation; while the midge-susceptible lines (ICSV 112 and CSH 5) showed a poor interaction with these factors. Midge damage in ICSV 197 showed a negative correlation with minimum temperature and relative humidity and positive correlation with sunshine hours,while the reverse was true for CSH 5. Grain growth rate between 0 and 3 days after anthesis was lower in crops sown on 1st October, when AF 28 and ICSV 197 suffered maximum midge damage. Maximum and minimum temperatures and maximum relative humidity influenced the moisture content of the grain, grain growth rate, and sorghum midge damage. There was considerable variation in genotype × environment interaction for expression of resistance to sorghum midge,and the implications of these results have been discussed in relation to development of sorghum cultivars with resistance to this insect. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mango explant browning: Effect of ontogenic age,mycorrhization and pre-treatments

The in vitro performance of mango shoot culture is delimited by several factors, of which explant necrosis and media browning are considered as major constraints for successful exploitation of such an important commercial crop. Our results showed that source of explants had a significant effect on the performance of in vitro cultures of mango. The variations in survival of explants collected from glasshouse grown seedlings and field-grown stock plants indicated towards differences between their physiological/ontogenic age. Though, chronologically, both are young, the glasshouse grown shoots are ontogenetically younger and; therefore, responded better over field-grown shoots. Improved performance of explants harvested from mycorrhizal plants suggests integration of mycorrhizal biotechnology with tissue culture biotechnology in order to achieve better results as mycorrhiza being a well-known stress alleviator may help explants mitigate in vitro stresses. Furthermore, shoot tip explants of field-grown ‘Amrapali’ mango was assayed for their browning propensity at pre- and post-culture stages. Status of different bio-chemicals such as in vivo phenol, in vitro phenol exudation, phenylalanine ammonia lyase, peroxidase and polyphenol oxidase as affected by various pre-treatments were estimated to establish the relationship of these bio-chemicals with necrosis of mango shoot cultures. The different pre-treatments comprised etiolation of newly emerged shoots (5–7 days old) of stock plants using black polythene for 7 days, etiolation treatment + agitation of explants in antioxidant solution (antioxidants: ascorbic acid at 100 mg l⁻¹ + citric acid at 50 mg l⁻¹), etiolation treatment + agitation of explants in polyvinylpyrrolidone solution (PVP) at 0.2% and non-etiolated control. Of these, explants treated with PVP proved to be superior to other treatments with regards to explant necrosis percentage as such explants exhibited least activities of phenols and oxidative enzymes. Correlation studies indicated existence of high positive correlation between explant necrosis and these bio-chemicals.     

Bread wheat cultivar PBW 343 carries residual additive resistance against virulent stripe rust pathotype

With continuous outbreaks of stripe rust (Puccinia striiformis f. sp. tritici) epidemics and rapid breakdown of deployed resistance in bread wheat (Triticum aestivum L.) cultivars in North West Plains Zone (NWPZ) in India warrant knowledge and deployment of new and durable sources of resistance to stripe rust. Bread wheat cultivar PBW 343, until recently the most widely cultivated wheat variety in India, is now highly susceptible to stripe rust (score 9 on a 1–9 scale), whereas PBW 621 (score 5.05–5.65) and HD 2967 (score 5.40–6.20) show low levels of resistance. We conducted an experiment, spanning three crop seasons (2013–2014 to 2015–2016), in which parental lines, F₁ and F₂ populations, F₃ and F₄ families from two bread wheat crosses, PBW 621/PBW 343 and HD 2967/PBW 343 were generated and evaluated for stripe rust resistance against a virulent pathotype. While the F₁ revealed partial dominance, the segregation pattern for stripe rust resistance in F₂ and F₃ showed transgressive segregation for resistance in both crosses. Chi-square analysis indicated that resistant segregants possessed two genes, one contributed by PBW 621 or HD 2967 (depending on the cross) and the other, unexpectedly but obviously, came from the most susceptible cultivar, PBW 343. Possible genetic mechanisms for this residual resistance and implications for breeding programs are discussed.     

Characterization of Fusarium population associated with wilt of jojoba in Israel

Fusarium wilt, caused by Fusarium oxysporum, is a major disease of jojoba, causing serious economic losses. This study was aimed at characterizing the Fusarium populations associated with jojoba in Israel. Fifty Fusarium isolates used in this study included 23 isolates from the 1990s (“past”) and 27 recently isolated (“recent”). All the isolates were characterized by arbitrarily primed (ap)-PCR and 16 representatives were additionally delineated using multilocus (tef1, rpb1, rpb2) phylogeny and evaluated for their pathogenic potential. Consequently, 88% of the isolates were identified and characterized to the F. oxysporum species complex. The remaining 12% grouped within the F. fujikuroi, F. solani, and F. redolens species complexes. Variations in the infection rate (16.7%–100%), disease symptoms (0.08–1.25, on a scale of 0–3), and fungal colonization index (0.67–2.17, on a scale of 0–4) were observed within the tested isolates, with no significant differences between the past and recent isolates. The representative isolates were assigned to 11 groups based on ap-PCR. Pathogenicity tests showed that isolates from Groups II, IV, and V were the most aggressive, whereas isolates from Groups III, VIII, and IX were the least aggressive. Among the tested isolates, F. oxysporum sensu lato was the most aggressive, followed by F. proliferatum, while F. nygamai was the least aggressive. This study demonstrates the complexity and genetic diversity of Fusarium wilt on jojoba in Israel, indicating possible multiple introductions of infected germplasm into the country.     

Non-structural protein 3A for differentiation of foot-and-mouth disease infected and vaccinated animals in Haryana (India)

There are severe international trade restrictions on foot-and-mouth disease (FMD) affected areas. Because of endemic nature of FMD, India started FMD control programme (FMD-CP) using mass vaccination in selected states including Haryana (year 2003). Although no significant incidence of the disease was reported after launching FMD-CP in the state but in order to participate in international trade of animal and animal products, veterinary authorities have to prove that there is no FMD virus (FMDV) circulation in the animal population, for which it is necessary to differentiate the FMD infected and vaccinated animals. For this purpose, an in-house indirect ELISA utilizing baculovirus-expressed FMDV non-structural protein (NSP) 3A was used to find evidence for virus circulation (prevalence of anti-NSP 3A-specific antibodies) by examining serum samples that were collected either before start of FMD-CP or after completion of third phase (Pre-4th) of vaccination in Haryana (India). A significant reduction (P < 0.01) in prevalence of anti-NSP 3A-specific antibodies (possibly carriers) was observed 2 years after launching FMD-CP in Haryana. However, in cattle the percentage of animals with anti-NSP 3A-specific antibodies was found to be significantly higher (P < 0.01) than buffalo, both before (P < 0.01) and after (P < 0.01) launching FMD-CP in the state. The findings of this study suggest that use of FMDV vaccine in cattle and buffaloes in endemic areas reduces virus circulation (carriers) in the vaccinated herds and that the current 3ANSP-ELISA can be successfully used to monitor the FMDV circulation in endemic areas.     

Race-specific genetics of resistance to black rot disease [Xanthomonas campestris pv. campestris (Xcc) (Pammel) Dowson] and the development of three random amplified polymorphic DNA markers in cauliflower

Summary

In order to understand the genetics of resistance to black rot disease caused by Xanthomonas campestris pv. campestris (Xcc) (Pammel) Dowson in cauliflower (Brassica oleracea var. botrytis L.) and to identify random amplified polymorphic DNA (RAPD) markers that segregate with the resistance genes, susceptible (‘Pusa Himjyoti’, female parent) and resistant (‘BR-161’, pollen parent) plants were crossed. Six generations of plants (30 P₁, 30 P₂,30 F₁, 120 F₂, 90 B₁, and 90 B₂) were evaluated for the presence or absence of black rot disease in a randomised block design with three replications. The pattern of segregation of resistance was tested by the χ² test at the 5% level of significance. All F₁ progeny plants were resistant, and the segregation of resistant and susceptible plants in the F₂ and two backcross generations (B₁ and B₂) showed that a single dominant gene caused resistance to the black rot pathogen in ‘BR-161’. Three polymorphic RAPD markers (OPO-04₈₃₃, OPAW-20₂₅₃₈, and OPG-25₆₂₅) were found by bulk segregant analysis, which produced unique amplicons 833 bp, 2,538 bp, and 625 bp in length, respectively. These markers were associated in coupling phase to the resistance allele. Best fit ratios of 3:1 (resistant:susceptible) in the F₂ plants with the three RAPD markers, suggested that the markers were linked to the single gene controlling black rot resistance. These markers will be useful to identify more closely-linked markers and to develop black rot-resistant hybrid cauliflower varieties.