Distinguishing Sichuan Walnut Cultivars and Examining Their Relationships with Juglans regia and J. sigillata by FISH, Early-Fruiting Gene Analysis, and SSR Analysis

Abstract

Walnuts are economically important tree species in Sichuan Province (China) that provide heathy nuts. Fluorescence in situ hybridization (FISH) and analyses of an early-fruiting gene fragment and simple sequence repeats (SSRs) were used to distinguish Sichuan walnut cultivars and examine their relationships with Juglans regia L. and Juglans sigillata Dode. Thirty-four small chromosomes were counted in four Sichuan walnut cultivars. In the four cultivars, 5S rDNA was located in the proximal regions of two chromosomes (5 and 6), while (AG 3 T 3) 3 was located at both ends of each chromosome. The existence of the signal at both chromosome ends ensured accurate chromosome counts. 5S rDNA and (AG 3 T 3) 3 were not effective in identifying Sichuan walnut cultivars. Evolutionary analysis involving 32 early-fruiting nucleotide sequences from Sichuan walnut materials were performed with the maximum likelihood method. There were a total of 602 positions. All positions with gaps and missing data were eliminated, resulting in a final dataset of 562 positions. The ML tree with the highest log likelihood (−1607.82) revealed two obvious groups: one including materials of J. regia, which fruits 1 year after grafting, and another including materials of J. sigillata, which fruits >3 years after grafting. The early-fruiting gene fragment divided 22 walnut materials (10 walnut cultivars and 12 walnut accessions) into two groups, indicating that it was somewhat effective for distinguishing Sichuan walnut cultivars. Furthermore, 22 SSR loci were revealed to identify nine walnut cultivars. Eight cultivars were exclusively discerned by one SSR locus each: Chuanzao 1 [CUJRB307 (116) or CUJRA206a (182)], Chuanzao 2 [JSI-73 (154)], Shuangzao [CUJRB103a (123), CUJRB218 (144), JSI-71 (146), or CUJRA206a (176)], Shimianju [ZMZ11 (138)], Meigupao [CUJRB218 (149), CUJRB103a (151), or CUJRA206a (190)], Muzhilinhe [CUJRB220 (136), ZMZ11 (147), CUJRC310 (156), or JSI-73 (166)], Maerkang [CUJRA124 (154), CUJRB218 (159), or CUJRA123 (182)], Yanyuanzao [CUJRA124 (150) or CUJRA206a (192)]. The Shuling cultivar was identified by the combination of

Oligo-FISH Can Identify Chromosomes and Distinguish Hippophaë rhamnoides L. Taxa

“…The chromosome size that we reported (0.89–3.03 μm) is within the range specified by previous studies on Hippophaë taxa (0.77–5.2 μm). Several chromosome sizes of other woody plants have been published: 1.05–1.81 μm in L. lucidum , 1.12–2.06 μm in F. pennsylvanica , 1.50–2.32 μm in S. oblata [ 29 ], 0.97–2.16 μm in J. regia [ 31 ], 1.23–2.34 μm in Z. armatum [ 34 ], 1.07–2.41 μm in Ch. campanulatus [ 30 ], 1.82–2.85 μm in B. diaphana [ 28 ], 1.18–3.0 μm in H. mutabilis [ 32 ], 1–4 μm in Citrus species [ 39 ], and 4.03–7.21 μm in P. concolor [ 33 ].…”

“…(AG 3 T 3 ) 3 , a classic chromosome end marker, is typically located in the distal region of the chromosome in H. mutabilis [ 32 ], J. regia , J. sigillata [ 31 ], F. pennsylvanica , S. oblata , L. lucidum , L. × vicaryi [ 28 ], B. diaphana , and B. soulieana [ 28 ]. Other similar types of (T x A y G z ) n [ 49 ] have also been identified at each chromosome end in the woody plants C. sinensis × P. trifoliata [ 23 ], Citrus clementina Hort.…”

“…[ 28 ], Fraxinus pennsylvanica Marsh., Syringa oblata Ait., Ligustrum lucidum Lindl., Ligustrum × vicaryi Rehder [ 29 ], Chimonanthus campanulatus R.H. Chang & C.S. Din [ 30 ], Juglan regia L. and Juglans sigillata Dode [ 31 ], and Hibiscus mutabilis L. [ 32 ]. The probe of the 5S rDNA fragment 5′-TCAGAACTCCGAAGTTAAGCGTGCTTGGGCGAGGTAGTAC-3′ was designed and developed in Piptanthus concolor Harrow ex Craib [ 33 ], Zanthoxylum armatum Candelle [ 34 ], B. diaphana and B. soulieana [ 28 ], F. pennsylvanica , S. oblata , L. lucidum , L. × vicaryi [ 29 ], Ch.…”

“…The probe of the 5S rDNA fragment 5′-TCAGAACTCCGAAGTTAAGCGTGCTTGGGCGAGGTAGTAC-3′ was designed and developed in Piptanthus concolor Harrow ex Craib [ 33 ], Zanthoxylum armatum Candelle [ 34 ], B. diaphana and B. soulieana [ 28 ], F. pennsylvanica , S. oblata , L. lucidum , L. × vicaryi [ 29 ], Ch. campanulatus [ 30 ], J. regia and J. sigillata [ 31 ], and H. mutabilis [ 32 ]. The probe of the (TTG) 6 trinucleotide repeat sequence 5′-TTGTTGTTGTTGTTGTTG-3′ was designed and developed in Avena L. species [ 35 ], F. pennsylvanica , S. oblata , L. lucidum , and L. × vicaryi [ 29 ].…”

Genetic Diversity and Structure of Persian Walnut (Juglans regia L.) in Pakistan: Implications for Conservation

“…The common walnut (Juglans regia L.; Juglandaceae) is a monoecious, wind pollinated, fruit tree with animal-based seeds dispersed. It is self-compatible but achieves a high rate of cross-pollination [1,2], mostly favoring protandry but sometimes protogyny, and usually has a diploid genome karyotype of 2n = 32 [3][4][5][6], although a karyotype of 2n = 34 has been found in one study [7]. Economically, J. regia is valued for its nutritious and medicinal nuts as well as high-quality timber [8,9].…”