Effects of Water Stress on Vegetative and Reproductive Traits of Three Commercial Cotton Varieties in Field Conditions in Central Iran

Backgroundwater scarcity is one of the most important factors that restricts crop production specially, cotton which must planted in areas without cold temperature limitation. Most of such area in Iran encounters drought events, hot temperatures and high atmospheric evaporative demand. So, understanding of stress severity and cultivar responses will help to better management of crop in stress conditions. Our previous study showed that cultivar responses in view of some physiological and morphological aspects were highly different in water stress condition. In this study we focused on yield formatting traits.Results Three cotton commercial varieties; Khorshid, Khordad and Varamin studied in sever, mild and without water stress. In normal condition zero type cultivar, the khorshid, produced the highest seed cotton yield. Varamin cultivar had more and longer sympodial branches which could raise it’s yield. Also, Varamin cultivar’s seed cotton yield was higher than the others (3617 kg -1 ha compared with 2477 and 3060 for khordad and khorshid, respectively). Khorshid was superior to the others at sever water stress.ConclusionSeed cotton yield showed high correlation whit boll number and boll weight and vegetative aspects such as plant height, node number and sympodial branches number. Management for developing more sympodial branches results in higher bud and flower and will increase the yield. Totally, we recommend Khorshid and Varamin cultivars for normal condition and Khorshid for sever stress conditions.

Susceptibility of Avocado Fruit to Scirtothrips aurantii Faure (Thysanoptera: Thripidae) and Wind Scarring Damage in Limpopo and KwaZulu-Natal Provinces of South Africa

In South Africa, the avocado (Persea americana) is an important fruit, grown primarily for export and contributing ZAR 1.75 billion to the gross domestic product of the country. As an export driven industry, optimising exportable avocado fruit volume is a primary concern. Wind induced abrasion and damage by thrips (Thysanoptera: Thripidae), through their feeding on avocado fruit results in corky tissue development (scarring) and making the fruit unsuitable for export. The study aimed to determine the economic losses caused by these agents as well as assess different cultivar responses to scarring damage. Across cultivars, the 1.49% revenue annually due to Scirtothrips aurantii downgrading (3.86% loss factor), translating to ZAR 34.90 million (US$2.39 million). Packhouse study results showed that both thrips and wind abrasion damage accounted for 30% scarring damage, a loss factor of 13.72% and a combined revenue loss of 5.57%. The cultivar ‘Pinkerton’ showed the greatest susceptibility to scarring damage by both wind and S. aurantii whilst the cultivar ‘Carmen®-Hass’ showed a natural predisposition to higher levels of thrips damage. The presence of macadamia trees near avocado trees predisposes avocado fruit to S. aurantii damage.

Effect of Single and Combined Inoculations of Potato Plants with Four Fusarium Species on Wilt Severity, Plant Growth, and Production

Potato (Solanum tuberosum L.) Fusarium wilt is an increasingly serious disease in many potato-growing regions worldwide and notably in Tunisia. Fusarium sambucinum, F. oxysporum, F. solani, and F. graminearum are the main causal agents with F. oxysporum being the most aggressive on plants. Co-infection with this Fusarium species complex is frequently observed. Cultivar responses to different pathogen mixtures can give additional information on the relative aggressiveness of the different complexes. This study may lead to a better understanding of how interactions between the four Fusarium species may affect disease incidence and severity. Interactions between these Fusarium species was evaluated using single and combined inoculations (15 different Fusraium inocula) onto potato the two cultivars Spunta and Oceania. The tested inocula were evaluated for their effects on leaf yellowing and necrosis, vascular discoloration severity, potato growth and production. Necrosis severity noted 75 days post-planting induced by three different inocula C2-1 (F. sambucinum + F. solani), C2-2 (F. solani + F. oxysporum), and C3-3 (F. sambuinum+F. oxysporum +F. graminearum) were found to be the highly aggressive inoculation treatments. Overall, all mixed inocula including F. sambucinum showed increased aggressiveness levels. The two cultivars exhibited differential response to the different tested Fusarium mixtures and behaved in the majority as sensitive to moderately sensitive to C1-1, C1- 4, C2-1, C2-2, C2-3, C2-4, C2-5, C2-6, C3-1, C3-3, C3-4 and C4 treatments. This study clearly demonstrated that Fusarium wilt of potato is expected to be more severe when more than one Fusarium species is present. The relative predominance of F. sambucinum may reflect its competitive potential in mixture and its significant involvement in potato Fusarium wilt severity.

Rice Cultivar Response to Florpyrauxifen-Benzyl When Applied with Imazethapyr and a Cytochrome P450 Inhibitor

Understanding cultivar responses to a new herbicide is crucial to determining appropriate herbicide use and management practices. Florpyrauxifen-benzyl is a new rice herbicide developed to control troublesome weeds in rice production. Little research has been conducted to characterize rice cultivar responses to florpyrauxifen-benzyl, and thus, a field experiment was conducted at the Pine Tree Research Station (PTRS) in 2017 and 2018 and at the Rice Research and Extension Center (RREC) in 2018 to determine rice cultivar tolerance to florpyrauxifen-benzyl as influenced by herbicide rate, the addition of imazethapyr, and rice growth stage. Another experiment was conducted in 2018 at PTRS and RREC to assess crop response when florpyrauxifen-benzyl at different rates is applied with and without malathion, a known cytochrome P450 inhibitor. Three cultivars were evaluated in both experiments: a long-grain variety “CL111,” a medium-grain variety “CL272,” and a long-grain hybrid “CLXL745.” Injury in the first experiment was higher when florpyrauxifen-benzyl was applied at 60 g ae ha−1 than at the labeled rate of 30 g ha−1, with the most injury being 10% when averaged over growth stage at the time of application. Generally, applications made at the 3-leaf growth stage resulted in the most injury; however, this injury was at most 14%. Additionally, there was no reduction in grain yield for any cultivar, indicating florpyrauxifen-benzyl can be used safely in conjunction with imazethapyr in imidazolinone-resistant rice. In the second experiment, there was no more than 10% injury and no reduction in grain yield, with the addition of malathion not causing an increase in rice injury. Results from these experiments indicate florpyrauxifen-benzyl can be mixed with imazethapyr and the addition of malathion will not lead to increased risk for injury to rice.

Adaptation patterns of sixteen alfalfa (Medicago sativa L.) cultivars across contrasting environments of Algeria and implications for the crop improvement

The additive main effects and multiplicative interaction analysis was applied to assess the genotype × environment interaction (GEI) effects and stability for 4-year dry matter yield (DMY) of 16 alfalfa (Medicago sativa L.) cultivars of diversified geographic origin grown in four Algerian environments given by the combination of two water managements (rainfed and irrigated) and two evaluation sites, viz. the sub-humid location of Alger and the semi-arid, salinity-affected site of Hmadna. The analysis of variance (ANOVA) revealed significant variation among cultivars and environments (P<0.001). The GEI was significant (P<0.001) and the environment main effect had greater influence than the genotype effect on long-term yield according to ANOVA. Rainfed conditions had 41.6% and 48.5% lower yield than the irrigated ones in Alger and Hmadna, respectively. Alfalfa cropping in the semiarid location caused lower DMY than in the sub-humid one (– 38.0% under irrigated and –45.2% under rainfed conditions) and a slightly lower persistence over the 4-year period. Outstanding environment-specific cultivar responses were observed, fully justifying the large GEI effects, although the Italian cultivar Sicilian ecotype had remarkable yield stability and good mean yield. The American variety Ameristand 801S and the Moroccan landrace Erfoud 1 were the most salt-tolerant cultivars. The evaluated germplasm, and particularly some exotic cultivars, could be used as parents to breed new varieties more adapted to drought and salinity in the Mediterranean basin.

Cucumber cultivar responses to two tetranychid mites, two-spotted spider mite and strawberry spider mite in greenhouses

Cultivating resistant host plants has been considered as an important strategy for sustainable pest management of mites. The current study was conducted to evaluate the response of 43 cucumber (Cucumis sativus L.) cultivars against two important tetranychid species, two-spotted spider mite (Tetranychus urticae Koch.) and strawberry spider mite (Tetranychus turkestani Ugarov & Nikolski). The experiment was implemented in a Randomized Complete Block design (RCB) with 43 treatments replicated 4 times in a greenhouse during 2015-2016. Two main evaluation criteria, cultivar injury rate (from 1 to 5) and number of eggs/female/day (EFD) on each cultivar, were used to compare responses. The results revealed that the highest number of eggs/female/day (EFD) for both mites was observed on Taha cultivar (9.0±0.40 and 9.5±0.28 for T. urticae and T. turkestani, respectively). The highest injury rate was also observed on this cultivar (4.8±0.26 and 5.0±0.0 for T. urticae and T. turkestani, respectively). In contrast, the lowest EFD number for T. urticae (2.8±0.47) and T. turkestani (2.5±0.28) was seen on Samer star and Davos cultivars, respectively. However, no host preference for egg-laying was observed on Iver and Samer star cultivars for T. turkestani. These two cultivars had the lowest injury level too (1.2±0.25 for Samer star and 1.5±0.28 for Negeen to T. urticae and T. turkestani, respectively). The obtained results demonstrated that Taha was the most susceptible cultivar colonized easily by both two tetranychid species. In contrast, Samer star and Negeen were the most resistant cultivars, strongly recommended for cultivation in greenhouses.

Assessment of Resistance in Potato Cultivars to Verticillium Wilt Caused by Verticillium dahliae and Verticillium nonalfalfae

Verticillium wilt caused by Verticillium spp., also called potato early dying disease, is one of the most serious soilborne diseases affecting potato production in China. The disease has been expanding into most potato production areas over the past few years. Information on host resistance against Verticillium wilt among the potato cultivars in China is scarce, but it is critical for sustainable management of the disease. This study, therefore, evaluated 30 commercially popular potato cultivars against Verticillium dahliae strain Vdp83 and Verticillium nonalfalfae strain Vnp24, two well-characterized strains causing Verticillium wilt of potato in China. Both strains were isolated from diseased potato plants, and they were previously proven to be highly virulent. Ten plants of each cultivar were inoculated with the V. dahliae strain and incubated on greenhouse benches. Symptoms were rated at weekly intervals, and the relative area under the disease progress curve was calculated. The experiment was repeated once, and nonparametric analysis was used to calculate the relative marginal effects and the corresponding confidence intervals. Five resistant cultivars and four susceptible cultivars identified from the analyses were then challenged with the V. nonalfalfae strain. Cultivar responses to V. nonalfalfae were like those exhibited against V. dahliae, except for one cultivar. This study showed that resistance among potato cultivars exists in China against Verticillium spp. and that the resistance to V. dahliae identified in potato is also effective against the other Verticillium species that cause Verticillium wilt with a few exceptions. Cultivars identified as resistant to Verticillium wilt can be deployed to manage the disease until the breeding programs develop new cultivars with resistance from the sources identified in this study.

Differences in Pathogenicity, Genetic Variability and Cultivar Responses among Isolates of Fusarium oxysporum from Strawberry in Australia

Variation in the virulence of Fusarium oxysporum f. sp. fragariae (Fof) strains is important when evaluating the resistance of plants to this fungus. Twenty-five isolates of F. oxysporum harvested from strawberry (Fragaria ×ananassa) plants growing in Australia were characterized using pathogenicity tests, vegetative compatibility groups (VCGs), and genetic analysis of translation elongation factor 1 alpha (EF-1α). The level of disease varied depending on isolate used, indicating heterogeneous populations of Fof. Two distinct VCGs were identified and corresponded to two of the 10 lineages identified by partial EF-1α. Using a subset of Fof isolates, resistance in eight cultivars ranged from highly resistant to highly susceptible, with some cultivar × isolate interaction. ‘Strawberry Festival’, ‘QHI Sugarbaby’, and ‘DPI Rubygem’ had high levels of resistance across all isolates. Isolates from Western Australia (WA) were genetically distinct from those from Queensland (QLD) and were more virulent to ‘Camarosa’, a major cultivar grown in WA.

UPLAND RICE CULTIVAR RESPONSES TO ROW SPACING AND WATER STRESS ACROSS MULTIPLE ENVIRONMENTS

SUMMARYUpland rice (Oryza sativa L., UR) could be an option under soybean–maize crop rotation system. However, the recommended row spacing for UR (0.30 m) is shorter than that recommended for soybean and corn (0.40 m), limiting the use of UR in this rotation. We hypothesize that cultivar adaptation to wider than recommended row spacing and local environmental conditions harbour significant potential for overcoming the yield constraints of wider row spacing. We evaluated the row spacing effects on rice grain yield and their components in UR cultivars grown under different water deficit conditions. The experiments were designed as a randomized block in a split–split-plot scheme with sites (the cities of Santo Antônio de Goiás, Porangatu and Formoso) as main plots, row spacing (0.25, 0.35, 0.45 and 0.55 m) as the subplots and UR cultivars (one old and two modern genotypes) as the sub-subplots. We found that, in the less stressful environments, the modern cultivars, BRSMG Curinga and BRS Primavera, presented the highest grain yield. By contrast, in environments with moderate to intense water stress, the traditional cultivar, Douradão, presented the best performance, regardless of row spacing used. We conclude that UR is a viable option for soybean–maize rotation systems, as the UR cultivars tested presented no noticeable yield losses when sown with the same row spacing used for soybean and maize crops (0.40 m). In terms of impact, it can lead to an increase in UR cropped area in Brazil, and decrease in dependence on flooded rice harvested in the south of the country.