Crops, Volume 1, Issue 3 (December 2021) – 6 articles

The brown planthopper, Nilaparvata lugens (Stål)[BPH], is a damaging pest of rice in Asia. Insecticides and rice varietal resistance are widely implemented BPH management practices. However, outbreaks of BPH have been linked to excessive insecticide use—challenging the compatibility of these two management practices. IR62 is a variety with resistance against BPH, the whitebacked planthopper, Sogatella furcifera Horváth [WBPH], and the green leafhopper, Nephotettix virescens (Distant)[GLH]. We compared BPH responses to IR62 and to the susceptible variety IR64 treated with buprofezin, carbofuran, cartap hydrochloride, cypermethrin, deltamethrin, fipronil, or thiamethoxam + chlorantraniliprole. In greenhouse bioassays, cypermethrin, fipronil and thiamethoxam + chlorantraniliprole reduced egg laying on both varieties, and, together with buprofezin, reduced nymph survival to zero. Buprofezin, carbofuran, and cartap hydrochloride stimulated egg laying, and carbofuran increased nymph biomass, but these effects were reduced on IR62. Planthopper populations were ten times higher on deltamethrin-treated rice than untreated rice in a screenhouse experiment. Host resistance failed to buffer against this insecticide-induced resurgence in BPH and WBPH. However, IR62 reduced the effect in GLH. Rice treated with cypermethrin and fipronil had reduced yields compared to untreated controls, suggesting possible phytotoxic effects. We found little evidence of synergies between the two management practices; but host resistance did buffer against the undesirable effects of some insecticides. Full article

Seedling vigor and regrowth ability are important traits for the forage production of winter wheat. The objectives of this study were to map quantitative trait loci (QTL) associated with seedling vigor and regrowth vigor traits using a genome-wide association mapping study (GWAS). Seedling vigor and regrowth vigor were evaluated with shoot length, the number of shoots per plant and shoot dry weight per plant 45 days after planting and 15 days after cutting. A large phenotypic variation was observed for all the traits studied. In total, 12 significant QTL for seedling vigor and 16 for regrowth vigor traits were detected on various chromosomes. Four QTL on chromosomes 2B, 4B, 5A and 7A for seedling vigor co-localized with QTL for regrowth vigor due to significant correlations between corresponding traits of the initial growth and regrowth. A BLAST search using DNA sequences of the significant loci revealed candidate genes playing roles in vegetative and reproductive development in different crop species. The QTL and single-nucleotide polymorphism (SNP) markers identified in this study will be further validated and used for marker-assisted selection of the traits during forage wheat breeding. Full article

Alfalfa (Medicago sativa L.) establishment failure is often attributed to autotoxicity when alfalfa is reseeded shortly after termination of the previous alfalfa stand, but renovation/rotation strategies for irrigated semiarid, subtropical environments have not been studied. Two identical studies were initiated at the New Mexico State University Rex E. Kirksey Agricultural Science Center at Tucumcari, NM, USA to compare continuous alfalfa (ALF), a single year of rotation to sorghum-sudangrass (SS1; Sorghum bicolor × S. sudanense (Piper) Stapf), two years of rotation with sorghum-sudangrass (SS2), and winter wheat forage (Triticum aestivum L.) followed by a single season of sorghum-sudangrass (WW/SS). Soil type and renovation/rotation strategy may influence soil fertility prior to replanting alfalfa, but soil fertility did not appear to influence alfalfa re-establishment or first production year yields. With a Test x Rotation interaction due to differences between tests for WW/SS for first production year yield after September alfalfa replanting, the main effect of Rotation was significant for yield (6.43AB, 5.3B0, 6.92A, and 3.54C Mg ha⁻¹ for ALF, SS1, SS2, and WW/SS, respectively; 5% LSD = 1.22). Alfalfa stand destruction and replanting with no intervening crop rotation may be feasible in sandy soils with irrigation in the semiarid, subtropical southwestern USA and similar environments. Full article

The genetic diversity of cultivated rice in farmers’ fields remains understudied in West Africa despite the importance of rice for food security in this region. In this study, we genotyped rice samples from Burkina Faso using the C6AIR SNP (Single Nucleotide Polymorphism) array (IRRI), including 27 registered cultivars and 50 rice samples collected in rice fields from three geographical zones in western Burkina Faso. Most of the registered cultivars clustered with the indica genetic group, except seven assigned to japonica and one admix. All but one of the rice samples from farmers’ fields belonged to the indica group. The other field sample, which unexpectedly clustered with the Aus genetic group, originated from a rainfed lowland site known to differ in terms of agronomic practices, and which revealed to be highly differentiated from the five other sites. Apart from this peculiar site, the rice grown in irrigated areas did not differ from rice sampled in rainfed lowlands. Finally, obtained genetic data confirmed the high frequency of one cultivar, in congruence with farmers’ interviews. We argue on the importance to document and preserve the high agro-biodiversity observed in rice from Burkina Faso as a prerequisite to face the current challenges of growing rice demand and global change. Full article

Treating plants with elevated carbon dioxide (eCO₂) can increase their drought tolerance. Increased atmospheric CO₂, a fundamental factor in climate change, may compensate for the drought-induced reduction in crop growth and yield. Basil, being moderately sensitive to drought stress (DS), experiences several morphological changes under DS. Thus, we designed an experiment that addresses how DS and different levels of CO₂ affect the overall morphological growth patterns during basil’s early and late-season growth. The experiment was conducted under four different growth conditions: two water treatments, (1) a full-strength Hoagland’s solution was added to the basil plants at 120% of the evapotranspiration each day, and (2) 50% of the full-strength Hoagland’s solution was added to basil plants for the drought treatment, alongside two levels of CO₂ application [ambient 420 ppm (aCO₂) and elevated 720 ppm (eCO₂)]). The DS had a severe impact on the morphological traits of the shoot and root systems. Compared to control, DS reduced the marketable fresh mass (FM) by 31.6% and 55.2% in the early and late stages of growth. FM was highest under control + eCO₂ (94.4–613.7 g) and lowest under DS + aCO₂ (67.9–275.5 g). Plant height under DS + aCO₂ and DS + eCO₂ reduced by 16.8% and 10.6% during the late season. On the other hand, dry mass percent (DM%) increased by 31.6% and 55.2% under DS + eCO₂ compared to control in the early and late stages of growth, respectively. This study suggested that eCO₂ during DS significantly impacts basil morphological traits compared to aCO₂. Besides, anthocyanin decreased by 10% in DS + aCO₂ and increased by 12.6% in DS + aCO₂ compared to control. Similarly, nitrogen balance index, a ratio of chlorophyll and flavonoids, was recorded to be the highest in DS + aCO₂ (40.8) compared to any other treatments. Overall, this study indicates that the suppression of basil’s morphophysiological traits by DS is more prominent in its later growth stage than in the earlier stages, and eCO₂ played an important role in alleviating the negative effect of DS by increasing the DM% by 55%. Full article

Colletotrichum sublineola is a casual pathogen of sorghum anthracnose. Sorghum pathologists often need to conduct evaluations for anthracnose resistance in large scale which are expensive and labor intensive. As a solution, an excised-leaf assay has been used, but whether or not leaf age, position or region affects pathogenicity scores has not previously been evaluated. Essentially, in an excised-leaf assay, is response to C. sublineola over all or part of a leaf blade identical? To get an answer, three sorghum and one Johnson grass cultivars were tested. The top five leaves were inoculated at the apex, mid-leaf and base of each leaf blade. Results show nearly no effect of leaf age to pathogenicity level within the top five leaves. Furthermore, in order to evaluate any protective role of leaf wax to C. sublineola, the wax was disrupted by simply wiping the leaf surface by a thumb, or as an alternative method, leaf surface tension was reduced by submerging leaves into 2% TWEEN 20 before inoculation. Compared to control, wiped leaves increased pathogenicity scores on the leaf blade and midrib in two of three sorghum cultivars, but 2% TWEEN 20-treated leaves had only minimal changes in pathogenicity level compared to controls. Full article