ABSTRACT
During the winter and spring of 2021, the root-knot nematodes were extracted from samples of galled roots of potted American pitcher plants (Sarracenia sp.). Samples were collected from a botanical garden nursery in Los Angeles County, California. The root-knot nematode was identified by molecular methods as Meloidogyne haplanaria. In the USA, M. haplanaria was initially found in Texas, and subsequently reported from Arkansas and Florida. Molecular characterization of the Californian M. haplanaria isolate was done using the analysis of the D2-D3 of 28S rRNA, ITS rRNA, mitochondrial l-rRNA, COI, and nad5 gene sequences. Some rRNA gene clusters of M. haplanaria were similar with those of M. arenaria. Possible hybridization events within mitotic parthenogenetic root-knot nematodes are discussed. This study confirmed that reliable diagnostics of M. haplanaria should be based on mtDNA sequence analysis. This is a first report of M. haplanaria from Sarracenia sp. and California. Consequently, this nematode was considered to be eradicated from this botanical garden nursery and the State of California.
ABSTRACT
A total of 33 corn hybrids were evaluated in a series of greenhouse and field trials to determine if they differed in resistance to either Meloidogyne incognita race 3 or M. arenaria race 1. Reproduction of M. incognita race 3 and M. arenaria race 1 on the hybrids was also compared. Reproduction of M. arenaria differed among corn hybrids after 58 to 65 days in greenhouse experiments; however, reproduction was similar among hybrids in the field experiment. No hybrids were consistently resistant to M. incognita. Two isolates of M. arenaria and two of M. incognita were evaluated in the greenhouse trials, and no evidence of isolate-dependent resistance was observed. Meloidogyne incognita reproduced better than M. arenaria on the hybrids in this study. A survey of 102 corn fields from 11 counties throughout southern Georgia was conducted to determine the relative frequency of M. incognita and M. arenaria. Meloidogyne species were found in 34 of the fields surveyed, and 93.9% of these were identified as M. incognita. The frequency of occurrence of M. incognita was 99.6% if the previous crop was cotton and 84.6% if the previous crop was peanut. Pratylenchus spp. were extracted from all intact corn root systems examined.
ABSTRACT
Previous reports of crop losses to plant-parasitic nematodes have relied on published results of survey data based on certain commodities, including tobacco, peanuts, cotton, and soybean. Reports on crop-loss assessment by land-grant universities and many commodity groups generally are no longer available, with the exception of the University of Georgia, the Beltwide Cotton Conference, and selected groups concerned with soybean. The Society of Nematologists Extension Committee contacted extension personnel in 49 U.S. states for information on estimated crop losses caused by plant-parasitic nematodes in major crops for the year 1994. Included in this paper are survey results from 35 states on various crops including corn, cotton, soybean, peanut, wheat, rice, sugarcane, sorghum, tobacco, numerous vegetable crops, fruit and nut crops, and golf greens. The data are reported systematically by state and include the estimated loss, hectarage of production, source of information, nematode species or taxon when available, and crop value. The major genera of phytoparasitic nematodes reported to cause crop losses were Heterodera, Hoplolaimus, Meloidogyne, Pratylenchus, Rotylenchulus, and Xiphinema.
ABSTRACT
Inheritance of resistance to the peanut root-knot nematode (Meloidogyne arenaria (Neal) Chitwood race 1) was investigated in the flue-cured tobacco cv. Speight G 28 and the breeding lines 81-RL-2K and SA 1214. The genetic relationship of this resistance in Speight G 28 to the resistance of the same cultivar to races 1 and 3 of M. incognita was also studied. Crosses were made between the root-knot nematode-susceptible flue-cured tobacco cv. NC 2326 and the three resistant genotypes. Parental, F1, F2 and backcross generations (BC1P1, BC1P2) were grown for each cross in randomized complete block designs with five replications in the greenhouse. Data indicated that resistance to M. arenaria race 1 in the three resistance sources is conditioned by a single dominant gene, but this resistance is partial compared to that for M. incognita races 1 and 3. Further, resistance to races 1 and 3 of M. incognita and resistance to M. arenaria race 1 in cv. Speight G 28 appear to be controlled by the same gene. These results, combined with the absence of segregation in the F2 populations of the crosses between resistant parents 81-RL-2K × SA 1214, 81-RL-2K × Speight G 28, and SA 1214 × Speight G 28, suggest allelism of resistance among these genotypes.
ABSTRACT
Reproduction ofMeloidogyne incognita and M. arenaria was determined on 25 commercial tropical corn hybrids in greenhouse studies. Soil around corn seedlings was infested with 3,000 eggs/plant. Reproduction was quantified from counts of egg masses on roots stained with phloxine B 60 days after soil infestation. All of the tropical hybrids were susceptible to M. incognita and M. arenaria. Egg mass indices (0-5 scale) ranged from 3.4 to 4.2 and from 3.4 to 4.1 for M. incognita and M. arenaria, respectively.
ABSTRACT
The effect of temperature (10, 20, 25, 30, and 35 C) on attachment and development of Pasteuria penetrans on Meloidogyne arenaria race 1 was elevated in growth chambers. The greatest attachment rate of endospores of P. penetrans occurred on second-stage juveniles at 30 C. The bacterium developed more quickly within its host at 30 and 35 C than at 25 C or below. The development of the bacterium within the nematode female was divided into nine recognizable life stages, which ranged from early vegetative thalli to mature sporangia. Mature sporangium was the predominant life stage observed after 35, 40, 81, and 116 days at 35, 30, 25, and 20 C, respectively. The body width and length of M. arenaria females infected with P. penetrans were smaller initially than the same dimensions in uninfected females, but became considerably larger over time at 25, 30, and 35 C. This isolate of P. penetrans also parasitized and completed its life cycle in males of M. arenaria.
ABSTRACT
A microplot study on the influence of cropping sequences with peanut in summer and bare fallowed or cover crops of rye or vetch in winter on the population development of Pasteuria penetrans was initiated in the spring of 1987. The number of spores of P. penetrans attached per second-stage juvenile of Meloidogyne arenaria race 1 increased from 0.11 in the fall of 1987 to 7.6, 8.6, and 3.6 in the fall of 1989 in the rye, vetch, and fallowed plots, respectively. Higher (P
ABSTRACT
Aggressiveness and reproduction differed among four geographical populations of M. arenaria on six soybean cultivars in field microplots. These differences were consistent over 3 years. The populations did not differ in virulence; i.e., population by cultivar interactions were not significant. Perineal pattern morphology, the North Carolina differential host test, chromosome counts of immature oocytes, and esterase phenotypes confirmed that the four populations were M. arenaria. Three populations were host race 2 and one population was host race 1.
ABSTRACT
The distribution of Meloidogyne spp. was determined in the Piedmont and Coastal Plains soybean production areas of South Carolina. Meloidogyne arenaria, M. incognita, and M. javanica were found in six of seven counties surveyed, with some populations consisting of two or more species. Because M. arenaria populations did not reproduce on peanut (Arachis hypogaea cv. Florunner), they were designated as Host Race 2. Severity of root galling, shoot and root growth, seed yield, and nematode reproduction were examined in fields infested with M. arenaria at Govan and Pelion, South Carolina, using soybean cultivars differing in host suitability to M. arenaria. When different responses in shoot and root growth, seed yield, and nematode reproduction in the two locations were found, soil influences were examined in duplicate field microplot experiments. Soybean growth was affected more by soil influences than by nematode populations; however, the two M. arenaria populations differed in amount of galling and rate of reproduction.
ABSTRACT
The host suitability of 64 commercial corn hybrids for a Meloidogyne arenaria race 2 population and a M. incognita race 4 population was determined in greenhouse experiments. 'Northrup King 508' and 'Pioneer Brand 3147' maintained M. arenaria below and at the initial population level, respectively, indicating that these hybrids are relatively poor hosts for this species. RF values (final egg number/initial egg number) of the hybrids for M. arenaria ranged from 0.8 for Northrup King 508 to 42.3 for 'Pioneer Brand XC941'. All hybrids were excellent hosts for M. incognita with RF values ranging from 20.7 for 'Sunbelt 1860' to 49.5 for Pioneer Brand XC941.