Euphytica

An almond breeding program was initiated in 1966 to develop improved cultivars for arid conditions with irrigation. Nut and kernel traits were evaluated for almond parents and progenies. Highly significant parent/progeny correlation coefficients (0.7–0.9) were found for shell hardness, percentage of kernel, in-shell (nut) and kernel weight, kernel length and width, as well as kernel color and outer shell retention. Double kernels and kernel thickness had low parent/progeny correlation coefficients. Shell hardness and percent kernel were highly correlated, as were shell hardness and outer shell retention, percent kernel and outer shell retention, and kernel width and nut weight. All but two of the evaluated traits (kernel thickness and percent doubles) appear to be highly heritable with mostly additive gene action, although some degree of dominance appeared to be involved in percent kernel, shell hardness and percent doubles.

Benzyladenine (BA) at concentrations from 33–2000 mg/l caused development of adventitious shoots on subsequent leaves of sugarbeet plants when sprayed once onto cotyledon-stage seedlings. Cultivar EL44 produced more adventitious shoots and greater fresh weight reduction in response to BA treatment than cultivar EL40. Related anomalies caused by BA included dissected leaves, and bumps and rods on petioles.

A study was made of the seed production characters of replicated single plants of two Aberystwyth varieties, S.170 tall fescue and S.48 timothy, and estimates were made of the total genetic variation and the heritability of each character. Six-plant selections were made from each of the two varieties, and performance trials indicated that seed yield had been increased by 20% in tall fescue and 47% in timothy. As indicated by the measurements on single plants, increases in seed weight per inflorescence were almost wholly responsible for the increase in seed yield, with the number of inflorescences remaining unaltered in the two new selections. The mean inflorescence size of both selections was similar to that of the two varieties, but floret fertility and 1000-seed weight were significantly increased. In S.48 timothy there was also an improvement in the facility with which seed could be threshed from the mature inflorescence.

Genetic response in hop to fungal pathogen infection has been evaluated at the chromosomal level through QTL analyses but very little information exists on the expression of genes during infection periods. Raw GBS reads and phenotypic data from a previously published QTL analysis along with a newly assembled PacBio-derived hop reference genome were used to re-evaluate resistance to races v4/v6 of powdery mildew (PM; Podosphaera humuli). QTL analyses revealed two tightly linked regions of association on a single linkage group. The three SNP markers most tightly linked to PM resistance (found on contig 000559F) were observed downstream from a putative R-gene locus for powdery mildew resistance. This 230 kb region contained a series of seven putative R-genes surrounded by seven putative peroxidase-3 genes downstream and seven putative glucan endo-1,3-beta-glucosidase upstream and an expressed F-box domain protein. RNAseq data showed all putative R-genes along with all putative glucan endo-1,3-beta-glucosidase genes were expressed under diseased conditions, while none of the peroxidase genes were expressed. The second region contained three SNPs found on contig 002916F next to two putative R-genes. RNAseq data showed complex expression of exons contained in putative isoforms of R-genes. This preliminary information will prove valuable information for development of precise markers located either within or next to genes responsible for race v4/v6 PM resistance.

Giai đoạn sinh sản của cây có hoa rất nhạy cảm với các tác động của nhiệt độ cao. Nhiệt độ cao là yếu tố chính ảnh hưởng đến khả năng sống của hạt phấn ở bông upland (Gossypium hirsutum). Mục tiêu của nghiên cứu này là xác định mối quan hệ giữa tỷ lệ nảy mầm hạt phấn bông và nhiệt độ bằng cách đánh giá sự nảy mầm của hạt phấn của bốn giống bông upland in vitro ở các nhiệt độ khác nhau trong giai đoạn ra hoa. Kết quả cho thấy tỷ lệ nảy mầm hạt phấn in vitro có liên quan đến nhiệt độ nuôi cấy trong quá trình nảy mầm và nhiệt độ trong quá trình phát triển bông non. Nhiệt độ cao ảnh hưởng đến sự phát triển và nảy mầm của hạt phấn, và khả năng chịu nhiệt độ cao khác nhau giữa các giống bông. Tỷ lệ nảy mầm hạt phấn giảm nhanh chóng khi nhiệt độ nuôi cấy thay đổi từ 30 đến 39 °C. Nhiệt độ nuôi cấy 35 °C có thể là nhiệt độ quan trọng đối với sự chuyển đổi khả năng sống của hạt phấn và có thể được sử dụng để sàng lọc các giống bông có hạt phấn có khả năng chịu nhiệt độ cao. Trước giai đoạn nhiệt độ cao, những giống có tỷ lệ giảm tỷ lệ nảy mầm hạt phấn dưới 41% ở 35 °C so với tỷ lệ ở 30 °C có thể được coi là giống chịu nhiệt độ cao, và những giống có tỷ lệ giảm tỷ lệ nảy mầm hạt phấn lớn hơn 41% có thể được coi là giống nhạy cảm. Stress nhiệt độ cao đối với sự nảy mầm hạt phấn in vitro lớn hơn 30 °C, và stress nhiệt độ cao cho sự phát triển bông non có thể lớn hơn 33 °C. Sự giữ quả có ý nghĩa đáng kể; nó có tương quan tích cực với tỷ lệ nảy mầm hạt phấn và tương quan âm với nhiệt độ trong giai đoạn nhiệt độ cao. Nghiên cứu này đã cung cấp một phương pháp để sàng lọc nhanh chóng các giống (dòng) có hạt phấn chịu nhiệt độ cao trong chương trình chọn giống bông upland.

The appearance of bracts through the surface of the cauliflower curd had a heritability estimate of 0.73 ± 0.10 based on the regression of progeny on parent when grown under field conditions. When curds were taken from field grown plants and aseptically cultured, their bracting characteristics were enhanced. It is advocated that a two-tier system of selection, firstly in the field and then in culture, would increase the likelihood of breeding bract free cauliflowers.

Most commercial citrus fruit species and cultivars are inter- and intra-specific hybrids. Conventional hybridization in citrus is largely handicapped by apomixis and long juvenility. As an alternative, somatic hybridization via protoplast fusion has been employed to create novel citrus germplasm. Witches' broom disease of lime (WBDL) emerged in Oman during the 1970s, which has been spreading to the neighboring countries. The disease is extremely destructive. A possible solution to the WBDL problem is to develop resistant hybrids. Resistance is available among the citrus relatives of lime i.e., sweet orange. Somatic hybrids combining sweet orange with lime have been produced but the fruit characteristics are different from lime. Herein, we report the development of somatic hybrids between a progenitor of lime (Citrus micrantha) and sweet orange (Citrus sinensis) in efforts to recreate a lime-like fruit using sweet orange as a donor of disease resistance gene(s). Successful somatic hybridization was verified by ploidy analyses using flow cytometry and RAPD analyses. This is the first report of using a progenitor species in somatic hybridization experiments in efforts to resynthesize an improved lime.